tag:theconversation.com,2011:/ca/topics/astrobiology-806/articlesAstrobiology – The Conversation2024-03-12T12:29:40Ztag:theconversation.com,2011:article/2076982024-03-12T12:29:40Z2024-03-12T12:29:40ZNASA’s search for life on Mars: a rocky road for its rovers, a long slog for scientists – and back on Earth, a battle of the budget<p>Is or was there life on Mars? That profound question is so complex that it will not be fully answered by the <a href="https://mars.nasa.gov/">two NASA rovers now exploring it</a>. </p>
<p>But because of the literal groundwork the rovers are performing, scientists are finally investigating, in-depth and in unprecedented detail, the planet’s evidence for life, known as its “<a href="https://astrobiology.nasa.gov/education/alp/what-is-a-biosignature/">biosignatures</a>.” This search is remarkably complicated, and in the case of Mars, it is spanning decades. </p>
<p><a href="https://geology.ufl.edu/people/faculty/dr-amy-j-williams-2/">As a geologist</a>, I have had the extraordinary opportunity to work on both the Curiosity and Perseverance rover missions. Yet as much as scientists are learning from them, it will take another robotic mission to figure out if Mars has ever hosted life. That mission will bring Martian rocks back to Earth for analysis. Then – hopefully – we will have an answer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photograph of the planet Mars, showing white caps and the reddish Martian surface." src="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=564&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=564&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=564&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=708&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=708&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578822/original/file-20240229-16-zmsstx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=708&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A photograph of Mars, the fourth planet from the Sun, taken by the Hubble Space Telescope in 2017.</span>
<span class="attribution"><a class="source" href="https://science.nasa.gov/image-detail/amf-gsfc_20171208_archive_e000019/">NASA</a></span>
</figcaption>
</figure>
<h2>From habitable to uninhabitable</h2>
<p>While so much remains mysterious about Mars, there is one thing I am confident about. Amid the thousands of pictures both rovers are taking, I’m quite sure no alien bears or meerkats will show up in any of them. Most scientists doubt the surface of Mars, or its near-surface, could currently sustain even single-celled organisms, much less complex forms of life. </p>
<p>Instead, the rovers are acting as extraterrestrial detectives, hunting for clues that life may have existed eons ago. That includes evidence of long-gone liquid surface water, life-sustaining minerals and organic molecules. To find this evidence, <a href="https://mars.nasa.gov/msl/home/">Curiosity</a> and <a href="https://mars.nasa.gov/mars2020/">Perseverance</a> are treading very different paths on Mars, more than 2,000 miles (3,200 kilometers) from each other. </p>
<p>These two rovers will help scientists answer some big questions: Did life ever exist on Mars? Could it exist today, perhaps deep under the surface? And would it be only microbial life, or is there any possibility it might be more complex? </p>
<p>The Mars of today is nothing like the <a href="https://www.nasa.gov/solar-system/nasa-funded-study-extends-period-when-mars-could-have-supported-life/#:%7E">Mars of several billion years ago</a>. In its infancy, Mars was far more Earth-like, with a thicker atmosphere, rivers, lakes, maybe even oceans of water, and the essential elements needed for life. But this period was cut short when Mars <a href="https://mgs-mager.gsfc.nasa.gov/#:%7E">lost its magnetic field</a> and nearly all of its atmosphere – now only 1% as dense as the Earth’s. </p>
<p>The change from habitable to uninhabitable took time, perhaps hundreds of millions of years; if life ever existed on Mars, it likely died out a few billion years ago. Gradually, Mars became the cold and dry desert that it is today, with a landscape comparable to <a href="https://www.alluringworld.com/mcmurdo-dry-valleys/">the dry valleys of Antarctica</a>, without glaciers and plant or animal life. The average Martian temperature is minus 80 degrees Fahrenheit (minus 62 degrees Celsius), and its meager atmosphere is nearly all carbon dioxide. </p>
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<a href="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The Perseverance rover, dusty and dirty, parked in a patch of Martian soil." src="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=692&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=692&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579676/original/file-20240304-28-76rhqs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=692&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Mars rover Perseverance has taken over 200,000 pictures, including this selfie from April, 2021.</span>
<span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/25790/perseverances-selfie-with-ingenuity/">NASA/JPL-Caltech/MSSS</a></span>
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</figure>
<h2>Early exploration</h2>
<p>Robotic exploration of the Martian surface began in the 1970s, when life-detection experiments on the <a href="https://mars.nasa.gov/mars-exploration/missions/viking-1-2/">Viking missions</a> failed to find any conclusive evidence for life. </p>
<p><a href="https://www.jpl.nasa.gov/missions/mars-pathfinder-sojourner-rover">Sojourner, the first rover</a>, landed in 1997 and demonstrated that a moving robot could perform experiments. In 2004, <a href="https://mars.nasa.gov/mer/">Spirit and Opportunity</a> followed; both found evidence that liquid water once existed on the Martian surface. </p>
<p>The Curiosity rover <a href="https://mars.nasa.gov/msl/home/">landed in 2012</a> and began ascending Mount Sharp, the 18,000-foot-high mountain located inside Gale crater. There is a reason why NASA chose it as an exploration site: The mountain’s rock layers show <a href="https://www.jpl.nasa.gov/news/mars-rover-views-spectacular-layered-rock-formations">a dramatic shift in climate</a>, from one with abundant liquid water to the dry environment of today. </p>
<p>So far, Curiosity has found evidence in several locations of past liquid water, minerals that may provide chemical energy, and intriguingly, a <a href="https://doi.org/10.1029/2021JE007107">variety of organic carbon molecules</a>. </p>
<p>While organic carbon is not itself alive, it is a building block <a href="https://www.nasa.gov/solar-system/nasas-curiosity-takes-inventory-of-key-life-ingredient-on-mars/">for all life as we know it</a>. Does its presence mean that life once existed on Mars?</p>
<p>Not necessarily. Organic carbon can be abiotic – that is, unrelated to a living organism. For example, maybe the organic carbon came from a <a href="https://www.livescience.com/tissint-meteorite-organic-compounds">meteorite that crashed on Mars</a>. And though the rovers carry wonderfully sophisticated instruments, they can’t definitively tell us if these organic molecules are related to past life on Mars.</p>
<p>But laboratories here on Earth likely can. By collecting rock and soil samples from the Martian surface, and then returning them to Earth for detailed analysis with our state-of-the-art instruments, scientists may finally have the answer to an age-old question.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/YPNVVDphQVc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">An animation of the proposed Mars Sample Return mission.</span></figcaption>
</figure>
<h2>Perseverance</h2>
<p>Enter Perseverance, NASA’s <a href="https://mars.nasa.gov/mars2020/">newest flagship mission to Mars</a>. For the past three years – it landed in February 2021 – Perseverance has been searching for signs of bygone microbial life in the rocks within Jezero crater, selected as the landing site because it once contained a large lake. </p>
<p>Perseverance is the first step of the <a href="https://mars.nasa.gov/msr/">Mars Sample Return</a> mission, an international effort to collect Martian rock and soil for return to Earth.</p>
<p>The instrument suite onboard Perseverance will help the science team choose the rocks that seem to promise the most scientific return. This will be a careful process; after all, there would be only <a href="https://mars.nasa.gov/msr/multimedia/videos/?v=523">30 seats on the ride back to Earth</a> for these geological samples.</p>
<h2>Budget woes</h2>
<p>NASA’s original plan called for returning those samples to Earth by 2033. But work on the mission – now estimated to cost between US$8 billion to $11 billion – has slowed <a href="https://www.cbsnews.com/losangeles/news/jpl-to-lay-off-more-than-500-employees/">due to budget cuts and layoffs</a>. The cuts are severe; a request for $949 million to fund the mission for fiscal 2024 <a href="https://www.latimes.com/science/story/2024-03-06/nasa-budget-deal-hope-for-mars-sample-return-mission-jpl">was trimmed to $300 million</a>, although efforts are underway to <a href="https://spacenews.com/congressional-letter-asks-white-house-to-reverse-msr-spending-cuts/">restore at least some of the funding</a>. </p>
<p>The Mars Sample Return mission is critical to better understand the potential for life beyond Earth. The science and the technology that will enable it are both novel and expensive. But if NASA discovers life once existed on Mars – even if it’s by finding a microbe dead for a billion years – that will tell scientists that life is not a fluke one-time event that only happened on Earth, but a more common phenomenon that could occur on many planets.</p>
<p>That knowledge would revolutionize the way human beings see ourselves and our place in the universe. There is far more to this endeavor than just returning some rocks.</p><img src="https://counter.theconversation.com/content/207698/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amy J. Williams receives funding from NASA Participating Scientist grants associated with the Mars 2020 Perseverance rover and the Mars Science Laboratory Curiosity rover. </span></em></p>Determining whether or not life exists on another planet is an extraordinarily complicated – and expensive – scientific endeavor.Amy J. Williams, Assistant Professor of Geology, University of FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2168532024-02-05T13:30:30Z2024-02-05T13:30:30ZStudying lake deposits in Idaho could give scientists insight into ancient traces of life on Mars<figure><img src="https://images.theconversation.com/files/568753/original/file-20240110-30-i5trcc.JPG?ixlib=rb-1.1.0&rect=23%2C398%2C3128%2C1343&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists have been studying the Clarkia site for nearly five decades.</span> <span class="attribution"><span class="source">Robert Patalano</span></span></figcaption></figure><p>Does life exist elsewhere in the universe? If so, how do scientists search for and identify it? Finding life beyond Earth is extremely difficult, partly because other planets are so far away and partly because we are not sure what to look for.</p>
<p>Yet, astrobiologists have learned a lot about <a href="https://science.nasa.gov/astrobiology/">how to find life</a> in extraterrestrial environments, mainly by studying how and when the early Earth became livable.</p>
<p>While research teams at NASA are <a href="https://mars.nasa.gov/mars2020/mission/overview/">directly combing</a> the surface of Mars for signs of life, our <a href="https://news.bryant.edu/there-life-red-planet-faculty-earns-funding-explore-theory-earth">interdisciplinary research group</a> is <a href="https://news.bryant.edu/mars-mind-bryant-students-earn-funding-nasa-ri-space-grant-consortium">using a site here on Earth</a> to approximate ancient environmental conditions on Mars. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rock face with several blocky layers of rock, in different stripes of color. The top layers are a darker clay, while the bottom layers are a lighter volcanic ash." src="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568752/original/file-20240110-18-1v7yda.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A close-up view of the Clarkia site where you can see lacustrine clay and volcanic ash layers. This site represents Mars in our work.</span>
<span class="attribution"><span class="source">Taylor Vahey</span></span>
</figcaption>
</figure>
<p>Contained within northern Idaho’s <a href="https://doi.org/10.1130/G48901.1">Clarkia Middle Miocene Fossil Site</a> are sediments that preserve some of Earth’s most diverse biological marker molecules, or <a href="https://doi.org/10.1016/j.epsl.2008.07.012">biomarkers</a>. These are remains of past life that offer glimpses into Earth’s history.</p>
<h2>An ancient lake</h2>
<p>About 16 million years ago, a lava flow in what would one day become Clarkia, Idaho, dammed a local drainage system and created a deep lake in a <a href="https://archive.org/details/latecenozoichist0000unse/page/424/mode/2up">narrow, steep-sided valley</a>. Although the lake has since dried up, weathering, erosion and <a href="https://www.facebook.com/p/Fossil-Bowl-100063724775941/">human activity</a> have exposed sediments of the former lake bed.</p>
<p>For nearly five decades, research teams like ours – being led by <a href="https://www.radcliffe.harvard.edu/people/hong-yang">Dr. Hong Yang</a> and <a href="https://www.bryant.edu/academics/faculty/leng-qin">Dr. Qin Leng</a> – have used <a href="https://doi.org/10.7717/peerj.4880">fossil remains</a> and <a href="https://doi.org/10.1016/0146-6380(95)80001-8">biogeochemistry</a> to reconstruct past environments of the Clarkia Miocene Lake region. </p>
<p>The lake’s depth created the <a href="https://www.jstor.org/stable/1303276">perfect conditions</a> for protecting microbial, plant and animal remains that fell to the lake’s bottom. In fact, the sediments are so well preserved that some of the fossilized leaves still show their autumn colors from when they sank into the water millions of years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A reddish brown long, thin leaf shown embedded on a piece of smooth sediment." src="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568751/original/file-20240110-15-2y3q3p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A fossil magnolia leaf showing fall (reddish) colors. This leaf likely fell off a tree in the fall once the trees paused photosynthesis for the winter and sank to the bottom of the lake, where it was buried. The leaf retained its fall coloring for 16 million years, though once being dug up and exposed to air, it quickly oxidized and lost its color.</span>
<span class="attribution"><span class="source">Robert Patalano</span></span>
</figcaption>
</figure>
<p>Today, ancient lake beds on Earth are becoming <a href="https://doi.org/10.1146/annurev-earth-053018-060332">important settings</a> for learning about habitable environments on other planets. </p>
<h2>Biological marker molecules</h2>
<p>Clarkia’s lake sediments <a href="https://doi.org/10.1016/0146-6380(94)90045-0">contain a suite</a> of ancient biomarkers. These compounds, or classes of compounds, can reveal how organisms and their <a href="https://doi.org/10.1016/j.quascirev.2011.07.009">environments functioned</a> in the past.</p>
<p>Since the discovery of the <a href="https://www.idahogeology.org/pub/Information_Circulars/IC-33.pdf">Clarkia fossil site in 1972</a>, multiple research teams have used various <a href="https://doi.org/10.1016/S0146-6380(02)00212-7">cutting-edge technologies to analyze</a> different biomarkers. </p>
<p>Some of those found at Clarkia <a href="https://doi.org/10.1073/pnas.90.6.2246">include lignin</a>, which is the structural support tissue of plants, <a href="https://doi.org/10.1016/S0146-6380(00)00107-8">lipids like fats and waxes</a>, and possibly <a href="https://doi.org/10.1038/344656a0">DNA and amino acids</a>.</p>
<p>Understanding the origins, history and environmental factors that have allowed these biosignatures to stay so well preserved at Clarkia may also allow our team to predict the potential of organic matter preservation in ancient lake deposits on Mars.</p>
<h2>Studying life signatures on Mars</h2>
<p>In 2021, the <a href="https://mars.nasa.gov/mars2020/">Mars Perseverance Rover</a> landed on top of lake deposits in Mars’ <a href="https://doi.org/10.1126/science.abl4051">Jezero Crater</a>. Jezero is a meteorite impact crater believed to have once been flooded with water and home to an ancient river delta. Microbial life may have lived in Jezero’s crater lake, and their biomarkers might be found in lake bed sediments today. Perseverance has been drilling into the crater’s surface to collect samples that could contain ancient signs of life, with the intent of <a href="https://mars.nasa.gov/msr/#Facts">returning the samples to Earth in 2033</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C4977%2C2799&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's rendition of the Perseverence rover, made of metal with six small wheels, a camera and a robotic arm." src="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&rect=14%2C7%2C4977%2C2799&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547616/original/file-20230911-26-nc2bk5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Perseverance Rover is collecting samples to learn more about Mars’ environment.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/MarsLanding/c835b14b3e6645d7a0cd46558745752b/photo?Query=mars%20rover&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=530&currentItemNo=11&vs=true">NASA/JPL-Caltech via AP</a></span>
</figcaption>
</figure>
<p>Clarkia has many similarities to the Jezero Crater. Both Clarkia and Jezero Crater have ancient <a href="https://doi.org/10.1006/icar.2000.6530">lake deposits</a> derived from silica-rich, <a href="https://doi.org/10.1029/2017JE005478">basaltic rock</a> that formed under <a href="https://doi.org/10.1016/j.gloplacha.2022.103737">a climate with</a> higher temperatures, high humidity and a carbon dioxide-rich atmosphere. </p>
<p>At Clarkia, these conditions preserved microbial biomarkers in the ancient lake. Similar settings could have <a href="https://doi.org/10.1029/2012JE004115">formed lakes</a> on the surface of Mars. </p>
<p>The samples <a href="https://mars.nasa.gov/mars-rock-samples/#23">Perseverance is collecting</a> contain the geologic and climate history of the Jezero Crater landing site and may even contain preserved biomarkers of ancient life.</p>
<p>While Perseverance continues its mission, our group is <a href="https://agu.confex.com/agu/fm23/meetingapp.cgi/Paper/1367388">establishing criteria</a> for biomolecular authentication. That means we are developing ways to figure out whether ancient biomarkers from Earth, and hopefully Mars, are true echoes of life – rather than recent contamination or molecules from nonliving sources.</p>
<p>To do so, we are studying biomarkers from Clarkia’s fossil leaves and sediments and developing laboratory experiments using <a href="https://spaceresourcetech.com/collections/regolith-simulants">Martian simulants</a>. This material simulates the chemical and physical properties of Jezero Crater’s lake sediments.</p>
<p>By deciphering the sources, history and preservation of biomarkers connected with Clarkia’s ancient lake deposits, we hope to develop new strategies for studying the Perseverance Rover samples once they are back on Earth.</p><img src="https://counter.theconversation.com/content/216853/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Patalano receives funding from the NASA Rhode Island Space Grant Program. </span></em></p>While NASA rovers on the surface of Mars look for hints of life, researchers back on Earth are studying ‘echoes of life’ from ancient basins – hoping that the two sites might be similar.Robert Patalano, Lecturer of Biological and Biomedical Sciences, Bryant UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2166392023-11-09T19:09:59Z2023-11-09T19:09:59ZA new theory linking evolution and physics has scientists baffled – but is it solving a problem that doesn’t exist?<figure><img src="https://images.theconversation.com/files/558544/original/file-20231109-17-qp5bsl.jpg?ixlib=rb-1.1.0&rect=10%2C42%2C7130%2C4710&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/leafless-tree-with-water-droplets-TYnHpsuAkBg">Tim Johnson / Unsplash</a></span></figcaption></figure><p>In October, a paper titled “<a href="https://www.nature.com/articles/s41586-023-06600-9">Assembly theory explains and quantifies selection and evolution</a>” appeared in the top science journal Nature. The authors – a team led by Lee Cronin at the University of Glasgow and Sara Walker at Arizona State University – claim their theory is an “interface between physics and biology” which explains how complex biological forms can evolve.</p>
<p>The paper provoked strong responses. On the one hand were headlines like “<a href="https://www.sciencealert.com/assembly-theory-bold-new-theory-of-everything-could-unite-physics-and-evolution">Bold New ‘Theory of Everything’ Could Unite Physics And Evolution</a>”.</p>
<p>On the other were reactions from scientists. One evolutionary biologist <a href="https://twitter.com/baym/status/1710815658890432679">tweeted</a> “after multiple reads I still have absolutely no idea what [this paper] is doing”. Another <a href="https://twitter.com/Irishpalaeo/status/1712450672476512424">said</a> “I read the paper and I feel more confused […] I think reading that paper has made me forget my own name.”</p>
<p>As a biologist who studies evolution, I felt I had to read the paper myself. Was assembly theory really the radical new paradigm its authors suggested? Or was it the “<a href="https://twitter.com/AdamRutherford/status/1711160807453569404">abject wankwaffle</a>” its critics decried?</p>
<h2>Hackle-raising claims</h2>
<p>When I sat down to read the paper, the very first sentence of the abstract had my hackles up: </p>
<blockquote>
<p>Scientists have grappled with reconciling biological evolution with the immutable laws of the Universe defined by physics.</p>
</blockquote>
<p>I had no idea we scientists grappled with this. No biologist I know has a problem with the laws of physics or sees any problem with reconciling them with evolution. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/life-modern-physics-cant-explain-it-but-our-new-theory-which-says-time-is-fundamental-might-203129">Life: modern physics can't explain it – but our new theory, which says time is fundamental, might</a>
</strong>
</em>
</p>
<hr>
<p>The abstract goes on to note that the laws of physics do not predict “life’s origin, evolution and the development of human culture and technology”, and claims we need a “new approach” to understand “how diverse, open-ended forms can emerge from physics without an inherent design blueprint”.</p>
<p>The complaint that biological evolution seems incompatible with the laws of physics, taken with the use of loaded terms like “design blueprint”, is reminiscent of creationist arguments against evolution. No wonder the blood pressure of evolutionary biologists was spiking.</p>
<p>In the words of <a href="https://www.nature.com/articles/s41586-023-06600-9#comment-6296992737">one Nature commenter</a>: “Why so many creationist tropes in the first few sentences?”</p>
<h2>Biology and physics</h2>
<p>Before I go further, I should note that I may, along with some of scientists quoted above, not fully understand the aim of the paper. But I have problems with what I do understand of it. </p>
<p>First of all, the claim that evolution is at odds with the immutable laws of physics does not seem to be supported. </p>
<p>The paper says “the open-ended generation of novelty does not fit cleanly in the paradigmatic frameworks of either biology or physics”, which doesn’t seem to make much sense. </p>
<figure class="align-center ">
<img alt="A microscope photo of fluorescent cells" src="https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558547/original/file-20231109-15-kojsc4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Is there a conflict between biology and physics that needs to be explained?</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/a-close-up-of-a-cell-phone-case-sIqWYiNLiJU">National Cancer Institute / Unsplash</a></span>
</figcaption>
</figure>
<p>In the paradigm of biology, we understand there is a variation in biological forms through genetic drift, mutation and selection. Does this <em>need</em> to “fit the paradigm of physics”, as long as it doesn’t break any laws of physics?</p>
<p>Another troubling statement: “To comprehend how diverse, open-ended forms can emerge from physics without an inherent design blueprint, a new approach to understanding and quantifying selection is necessary.” </p>
<p>Is it? One of the tenets of evolutionary theory is that there is no “teleology” – no goal or aimed-for endpoint – in the process. So how could there be a “design blueprint”? Why would its absence need to be explained?</p>
<h2>Putting numbers on the odds of evolution</h2>
<p>So what is assembly theory trying to do? <a href="https://twitter.com/leecronin/status/1711356692720501103">According to Cronin</a>, it “aims to explain selection & evolution before biology”; as such its goal is a theory that unifies inert and living matter and seeks to explain their complexity or otherwise, in the same way.</p>
<p>The paper itself says it is a “framework that does not alter the laws of physics, but redefines the concept of an ‘object’ on which these laws act”. </p>
<blockquote>
<p>[Assembly theory] conceptualizes objects not as point particles, but as entities defined by their possible formation histories. This allows objects to show evidence of selection, within well-defined boundaries of individuals or selected units. </p>
</blockquote>
<p>The “object” in assembly theory is then what “laws of physics” act on. For any object, we can calculate its “assembly index”, a number that measures how complex the object would be to make. </p>
<p>Any object that is both abundant and has a high assembly index is unlikely to have arisen by chance, so it must be a product of evolution and selection. This, in itself, is neither problematic nor new – apart from this calculated “index”.</p>
<p>How do we figure out that assembly index? We count the number of steps it would take to build a molecule, say, or a bodily organ, or a whole organism. The higher the index, the more likely it is to have evolved. </p>
<p>So assembly theory is an attempt to quantify the complexity of something and the likelihood of it having evolved. </p>
<h2>A problem that doesn’t exist?</h2>
<p>Is this useful? It’s hard to say. </p>
<p>For one thing, it implies there is only one pathway to produce a complicated (high assembly index) object such as a biochemical molecule, which is simply not the case.</p>
<p>Also, as <a href="https://twitter.com/professor_dave/status/1710914156612710503">another scientist pointed out</a>: </p>
<blockquote>
<p>it’s obvious that if a molecule is complex and there are lots of copies of it, then it likely emerged from some process of evolution. And most chemists could spot such cases without the need for assembly theory. Although trying to put numbers on it is very neat.</p>
</blockquote>
<p>My own feeling is that this is a poorly written paper, as evidenced by the inability of many biologists to understand what it is trying to do, and much of the negative reaction to the work springs from the hard-to-follow framing and use of phrases that echo creationist talking points. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/physics-has-long-failed-to-explain-life-but-were-testing-a-groundbreaking-new-theory-in-the-lab-215636">Physics has long failed to explain life – but we're testing a groundbreaking new theory in the lab</a>
</strong>
</em>
</p>
<hr>
<p>As for assembly theory itself, it seems to have been <a href="https://www.quantamagazine.org/a-new-theory-for-the-assembly-of-life-in-the-universe-20230504/">developed</a> in the course of Cronin and Walker’s efforts to find a general way to <a href="https://www.nature.com/articles/s41467-021-23258-x">recognise signs of life on alien planets</a>, and even <a href="https://www.mdpi.com/1099-4300/24/7/884">create artificial life</a>. And perhaps, in those contexts, it may prove useful.</p>
<p>However, as a sweeping new paradigm aiming to unify evolution and physics, assembly theory appears – to me and many others – to be addressing a problem that does not exist.</p><img src="https://counter.theconversation.com/content/216639/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Bateman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>‘Assembly theory’ aims to explain evolution without biology. Is it a dazzling breakthrough or an attempt to answer questions nobody asked?Bill Bateman, Associate professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146142023-10-24T12:22:02Z2023-10-24T12:22:02ZSpace rocks and asteroid dust are pricey, but these aren’t the most expensive materials used in science<figure><img src="https://images.theconversation.com/files/552576/original/file-20231006-23-aam2il.jpg?ixlib=rb-1.1.0&rect=0%2C34%2C5751%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Meteorites can get pricey, but they're not the most expensive material. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/FranceMeteoriteAuction/e075e1b22656489db39610bafb0682af/photo?Query=meteorites&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=341&currentItemNo=5&vs=true">AP Photo/Thibault Camus</a></span></figcaption></figure><p>After a journey of seven years and nearly 4 billion miles, <a href="https://science.nasa.gov/mission/osiris-rex">NASA’s OSIRIS-REx</a> <a href="https://www.space.com/osiris-rex-asteroid-samples-land-houston">spacecraft landed</a> gently in the Utah desert on the morning of Sept. 24, 2023, with a precious payload. <a href="https://science.nasa.gov/mission/osiris-rex">The spacecraft</a> brought back a sample from the asteroid Bennu.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's illustration of a gray metallic spacecraft hovering above the dark surface of an asteroid, with an arm that reaches down to the surface." src="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">OSIRIS-REx collected a sample from the asteroid Bennu.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/20c047ec48f74f6995ffad6b0f54422c?ext=true">NASA/Goddard Space Flight Center via AP</a></span>
</figcaption>
</figure>
<p>Roughly half a pound of material collected from the <a href="https://science.nasa.gov/solar-system/asteroids/101955-bennu/facts/">85 million-ton asteroid</a> (77.6 billion kg) will help scientists learn about the <a href="https://solarsystem.nasa.gov/missions/osiris-rex/in-depth/">formation of the solar system</a>, including whether <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/101955-bennu/in-depth/">asteroids like Bennu</a> include the chemical ingredients for life.</p>
<p>NASA’s mission was budgeted at <a href="https://www.asteroidmission.org/qa/">US$800 million</a> and will end up costing around <a href="https://www.planetary.org/space-policy/cost-of-osiris-rex">$1.16 billion</a> for <a href="https://www.nasa.gov/news-release/nasas-first-asteroid-sample-has-landed-now-secure-in-clean-room/">just under 9 ounces of sample</a> (255 g). But is this the most expensive material known? Not even close.</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">professor of astronomy</a>. I use Moon and Mars rocks in my teaching and have a modest collection of meteorites. I marvel at the fact that I can hold in my hand something that is billions of years old from billions of miles away.</p>
<h2>The cost of sample return</h2>
<p>A handful of asteroid works out to $132 million <a href="https://www.hoodmwr.com/things-that-weigh-around-1-ounce/">per ounce</a>, or $4.7 million per gram. That’s about 70,000 times the <a href="https://goldprice.org/">price of gold</a>, which has been in the range of $1,800 to $2,000 per ounce ($60 to $70 per gram) for the past few years.</p>
<p>The first extraterrestrial material returned to Earth came from the Apollo program. Between 1969 and 1972, six Apollo missions brought back 842 pounds (382 kg) of <a href="https://curator.jsc.nasa.gov/lunar/">lunar samples</a>.</p>
<p>The <a href="https://www.planetary.org/space-policy/cost-of-apollo">total price tag</a> for the Apollo program, adjusted for inflation, was $257 billion. These Moon rocks were a relative bargain at $19 million per ounce ($674 thousand per gram), and of course Apollo had additional value in demonstrating technologies for human spaceflight. </p>
<p>NASA is planning to bring samples back from Mars in the early 2030s to see if any contain traces of ancient life. The <a href="https://mars.nasa.gov/msr/">Mars Sample Return</a> mission aims to return <a href="https://www.universetoday.com/161264/we-can-only-bring-30-samples-of-mars-back-to-earth-how-do-we-decide/">30 sample tubes</a> with a <a href="https://downloads.regulations.gov/NASA-2022-0002-0002/attachment_5.pdf">total weight of a pound</a> (450 g). The <a href="https://science.nasa.gov/mission/mars-2020-perseverance">Perseverance rover</a> has already <a href="https://www.universetoday.com/160109/perseverance-is-building-up-a-big-collection-of-mars-samples/">cached 10 of these samples</a>. </p>
<p>However, <a href="https://www.science.org/content/article/mars-sample-return-got-new-price-tag-it-s-big">costs have grown</a> because the mission is complex, involving multiple robots and spacecraft. Bringing back the samples could run $11 billion, putting their cost at $690 million per ounce ($24 million per gram), five times the unit cost of the Bennu samples.</p>
<h2>Some space rocks are free</h2>
<p>Some space rocks cost nothing. Almost 50 tons of free samples from the solar system <a href="https://science.nasa.gov/solar-system/meteors-meteorites/">rain down on the Earth</a> every day. Most burn up in the atmosphere, but if they reach the ground <a href="https://www.amnh.org/explore/news-blogs/on-exhibit-posts/meteor-meteorite-asteroid">they’re called meteorites</a>, and most of those come from asteroids. </p>
<p><a href="https://www.nhm.ac.uk/discover/types-of-meteorites.html">Meteorites can get costly</a> because it can be difficult to recognize and retrieve them. Rocks all look similar unless you’re a geology expert. </p>
<p>Most meteorites are stony, <a href="https://www.britannica.com/science/chondrite">called chondrites</a>, and they can be bought online for as little as $15 per ounce (50 cents per gram). Chondrites differ from normal rocks in containing <a href="https://www.amnh.org/exhibitions/permanent/meteorites/origins-of-the-solar-system/chondrules">round grains called chondrules</a> that formed as molten droplets in space at the birth of the solar system 4.5 billion years ago.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A meteorite that looks like a long gray rock with dark gray veins running across it." src="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=305&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=305&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=305&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=384&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=384&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=384&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A chondrite from the Viñales meteorite, which originated from the asteroid belt between Mars and Jupiter.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ordinary_chondrite_%28Vi%C3%B1ales_Meteorite%29_15.jpg">Ser Amantio di Nicolao/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p><a href="https://aerolite.org/shop/iron-meteorites/">Iron meteorites</a> are distinguished by a dark crust, caused by melting of the surface as they come through the atmosphere, and an internal pattern of long metallic crystals. They cost $50 per ounce ($1.77 per gram) or even higher. <a href="https://geology.com/meteorites/value-of-meteorites.shtml">Pallasites</a> are stony-iron meteorites laced with the mineral olivine. When cut and polished, they have a translucent yellow-green color and can cost over $1,000 per ounce ($35 per gram).</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A brown-gray meteorite that's roughly circular with textured ridges" src="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An iron meteorite.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Odessa_%28iron%29_meteorite.jpg">Llez/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>More than a few meteorites have reached us from the Moon and Mars. Close to 600 have been recognized as <a href="https://sites.wustl.edu/meteoritesite/items/lunar-meteorites/">coming from the Moon</a>, and <a href="https://www.catawiki.com/en/stories/4683-10-most-expensive-meteorites-ever-offered-up-on-earth">the largest</a>, weighing 4 pounds (1.8 kg), sold for a price that works out to be about $4,700 per ounce ($166 per gram). </p>
<p>About 175 meteorites are identified as <a href="https://www2.jpl.nasa.gov/snc/">having come from Mars</a>. <a href="https://aerolite.org/shop/mars-meteorites/">Buying one</a> would cost about $11,000 per ounce ($388 per gram). </p>
<p>Researchers can figure out <a href="https://science.nasa.gov/solar-system/meteors-meteorites/facts/">where meteorites come from</a> by using their landing trajectories to project their paths back to the asteroid belt or comparing their composition with different classes of asteroids. Experts can tell where Moon and Mars rocks come from by their geology and mineralogy.</p>
<p>The limitation of these “free” samples is that there is no way to know where on the Moon or Mars they came from, which limits their scientific usefulness. Also, they start to get contaminated as soon as they land on Earth, so it’s hard to tell if any microbes within them are extraterrestrial.</p>
<h2>Expensive elements and minerals</h2>
<p>Some elements and minerals are expensive because they’re scarce. Simple <a href="http://www.leonland.de/elements_by_price/en/list">elements in the periodic table</a> have low prices. Per ounce, carbon costs one-third of a cent, iron costs 1 cent, aluminum costs 56 cents, and even mercury is less than a dollar (per 100 grams, carbon costs $2.40, iron costs less than a cent and alumnium costs 19 cents). Silver is $14 per ounce (50 cents per gram), and gold, $1,900 per ounce ($67 per gram). </p>
<p><a href="https://alansfactoryoutlet.com/how-much-do-elements-cost-the-price-of-75-elements-per-kilogram/">Seven radioactive elements</a> are extremely rare in nature and so difficult to create in the lab that they eclipse the price of NASA’s Mars Sample Return. Polonium-209, the most expensive of these, costs $1.4 trillion per ounce ($49 billion per gram).</p>
<p>Gemstones can be expensive, too. <a href="https://www.gemsociety.org/article/emerald-jewelry-and-gemstone-information/">High-quality emeralds</a> are 10 times the <a href="https://goldprice.org/">price of gold</a>, and <a href="https://ajediam.com/diamond-prices/white-natural-diamond/">white diamonds</a> are 100 times the price of gold. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A circular white diamond sitting on a white surface." src="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=727&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=727&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=727&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=914&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=914&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=914&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">High-quality white diamonds can cost millions of dollars.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/eeaab33d812a487ebfd2e5a76a25eb03?ext=true">AP Photo/Mary Altaffer</a></span>
</figcaption>
</figure>
<p>Some diamonds have a boron impurity that gives them a <a href="https://www.diamonds.pro/education/blue/">vivid blue hue</a>. They’re found in only a handful of mines worldwide, and at <a href="https://www.usatoday.com/story/money/2022/04/28/worlds-largest-blue-diamond-sells/9567999002/">$550 million per ounce</a> ($19 million per gram) they rival the cost of the upcoming Mars samples – an ounce is 142 carats, but very few gems are that large. </p>
<p>The <a href="https://www.sciencealert.com/scientists-create-world-s-most-expensive-material-valued-at-145-million-per-gram">most expensive synthetic material</a> is a tiny spherical “cage” of carbon with a nitrogen atom trapped inside. The atom inside the cage is extremely stable, so can be used for timekeeping. <a href="https://arstechnica.com/science/2015/12/oxford-company-now-selling-endohedral-fullerenes-priced-at-110-million-per-gram/">Endohedral fullerenes</a> are made of carbon material that may be used to create extremely accurate atomic clocks. They can cost $4 billion per ounce ($141 million per gram).</p>
<h2>Most expensive of all</h2>
<p><a href="https://www.livescience.com/32387-what-is-antimatter.html">Antimatter</a> occurs in nature, but it’s exceptionally rare because any time an antiparticle is created it quickly annihilates with a particle and produces radiation. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7MkfMGzMcf8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">At CERN’s ‘antimatter factory,’ scientists create antimatter in very small quantities.</span></figcaption>
</figure>
<p>The <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2010.0026">particle accelerator at CERN</a> can produces 10 million antiprotons per minute. That sounds like a lot, but <a href="https://archive.ph/6RUrA">at that rate</a> it would take billions of years and cost a billion billion (10<sup>18</sup>) dollars to generate an ounce (3.5 x 10<sup>16</sup> dollars per gram). </p>
<p><a href="https://www.newscientist.com/article/mg24232342-600-how-star-treks-warp-drives-touch-on-one-of-physics-biggest-mysteries/">Warp drives</a> as envisaged by “Star Trek,” which are powered by matter-antimatter annihilation, will have to wait.</p><img src="https://counter.theconversation.com/content/214614/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation. </span></em></p>Some space rocks you can get for free – if you know how to identify them. Rarer materials cost more, and the asteroid sample NASA just brought back has a high price tag.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2133942023-09-13T13:57:15Z2023-09-13T13:57:15ZPossible hints of life found on distant planet – how excited should we be?<figure><img src="https://images.theconversation.com/files/547762/original/file-20230912-19-lzosd4.jpeg?ixlib=rb-1.1.0&rect=5%2C0%2C3811%2C2160&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The exoplanet K2-18b might host a water ocean.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">Credits: Illustration: NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)</a></span></figcaption></figure><p>Data from the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a> (JWST) has shown that an exoplanet around a star in the constellation Leo has some of the chemical markers that, on Earth, are associated with living organisms. But these are vague indications. So how likely is it that this exoplanet harbours alien life?</p>
<p>Exoplanets are worlds that orbit stars other than the Sun. The planet in question is named <a href="http://www.exoplanetkyoto.org/exohtml/K2-18.html">K2-18b</a>. It’s so named because it was the first planet found to orbit the red dwarf star K2-18. There is a K2-18c as well – the second planet to be discovered. The star itself is dimmer and cooler than the Sun, meaning that, to get the same level of light as we do on Earth, the planet would need to be much closer to its star than we are. </p>
<p>The system is roughly 124 light years away, which is close in astronomical terms. So what are conditions like on this exoplanet? This is a difficult question to answer. We have telescopes and techniques powerful enough to tell us what the star is like, and how far away the exoplanet is, but we can’t capture direct images of the planet. We can work out a few basics, however. </p>
<p>Working out how much light hits K2-18b is important for assessing the planet’s potential for life. K2-18b orbits closer to its star than Earth does: it’s at roughly 16% of the distance from Earth to the Sun. Another measurement we need is the star’s power output: the total amount of energy it radiates per second. K2-18’s power output is 2.3% that of the Sun. </p>
<p>Using geometry, we can work out that K2-18b receives about 1.22 kilowatts (kW) in solar power per square metre. <a href="https://www.sws.bom.gov.au/Educational/2/1/12">This is similar</a> to the 1.36 kW of incoming light we receive on Earth. Although there’s less energy coming from K2-18, it evens out because the planet is closer. So far, so good. However, the incoming light calculation doesn’t take into account clouds or how reflective the planet’s surface is.</p>
<figure class="align-center ">
<img alt="JWST" src="https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548036/original/file-20230913-19-odwob3.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of the James Webb Space Telescope (JWST).</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/ames/webb">NASA</a></span>
</figcaption>
</figure>
<p>When we consider life on other planets, a popular term to use is the <a href="https://exoplanets.nasa.gov/search-for-life/habitable-zone/">habitable zone</a>, which means that at an average surface temperature, water will be in a liquid state – as this condition is considered essential for life. In 2019, the Hubble Space Telescope determined that K2-18b showed signs of <a href="https://www.nature.com/articles/s41550-019-0878-9#change-history">water vapour</a>, suggesting that liquid water would be present on the surface. It is currently thought that there are large oceans on the planet.</p>
<p>This caused a ripple of excitement at the time, but without further evidence it was just an interesting result. Now we have reports that JWST has identified carbon dioxide, methane and – possibly – the compound dimethyl sulfide (DMS) <a href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">in the atmosphere</a>. The tentative detection of DMS is significant because it is only produced on Earth by <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dimethyl-sulfide">algae</a>. We currently know of no way it can be naturally produced without a life-form.</p>
<h2>Is there life on K2-18b?</h2>
<p>All these indications seem to suggest that K2-18b might be the place to go to find alien life. It is not quite as simple as that, though, as we have no idea how accurate the results are. The method used to determine what is in the atmosphere of an exoplanet involves light from a different source (usually a star or galaxy) passing through the edge of the atmosphere that is then observed by us. Any chemical compounds will <a href="https://webbtelescope.org/contents/media/images/01FEE26XVSM851DHPVCE1KB4S2">absorb light in specific wavelengths</a> which can then be identified. </p>
<p>Imagine it as looking at a light bulb through a glass tumbler. You can see through it perfectly when empty. If you fill it with water, you can still see through pretty well, but there are some optical effects and colouration, which are the equivalent of hydrogen and dust clouds in space. Now imagine you poured in red food dye – this might be the equivalent of the main chemical constituent in a planet’s atmosphere. </p>
<p>But most atmospheres are made up of many chemicals. The equivalent of looking for any one of them would be like pouring 50 – likely many more – coloured food dyes, in different amounts, into your tumbler and trying to identify how much of one particular colour is present. It is an incredibly difficult task with plenty of room for subjective assessment and errors. In addition, the light going through the atmosphere contains a signal of the star’s chemical constituents – further complicating the analysis.</p>
<figure class="align-center ">
<img alt="Atmospheric composition of K2-18 b." src="https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547763/original/file-20230912-17-ds12z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The chemical composition of K2-18b’s atmosphere.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">Credits: Illustration: NASA, CSA, ESA, R. Crawford (STScI), J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)</a></span>
</figcaption>
</figure>
<p>Only a few years ago there was a surge of interest in <a href="https://www.nytimes.com/2020/09/14/science/venus-life-clouds.html">whether life existed on Venus</a>, as observations had indicated the presence of phosphine gas, which can be produced by microbes. </p>
<p>However, this finding was later successfully refuted by <a href="https://arxiv.org/pdf/2010.09761.pdf">several studies</a>. If there can be confusion about what is in the atmosphere of a planet that’s just next door, in astronomical terms, it’s easy to see why analysing a planet that’s many times further away is a difficult task.</p>
<h2>What can we take from this?</h2>
<p>The chances of life on exoplanet K2-18b are low but not impossible. These results will likely not change anybody’s opinions or beliefs about extraterrestrial life. Instead, they do demonstrate the advancing ability to look into worlds that are not our own and find more information. </p>
<figure class="align-center ">
<img alt="Rho Ophiuchi" src="https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548021/original/file-20230913-21-su4cro.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">JWST image of Rho Ophiuchi, the closest star-forming region to Earth.</span>
<span class="attribution"><a class="source" href="https://webbtelescope.org/contents/media/images/2023/128/01H449193V5Q4Q6GFBKXAZ3S03?news=true">NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI)</a></span>
</figcaption>
</figure>
<p>The power of JWST is not only in producing incredible pictures, but in providing <a href="https://webbtelescope.org/contents/news-releases/2023/news-2023-103.html">more detailed</a> and accurate data on celestial objects themselves. Knowing which exoplanets host water and which do not could provide information on how the Earth formed. </p>
<p>Studying the atmospheres of gas giant exoplanets can inform the study of similar worlds in the Solar System, such as Jupiter and Saturn. And identifying levels of CO2 indicates how an extreme greenhouse effect might affect a planet. This is the real power of studying the composition of planetary atmospheres.</p><img src="https://counter.theconversation.com/content/213394/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Whittaker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The results are intriguing, but analysing the atmospheres of exoplanets is no easy task.Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2131042023-09-11T15:42:17Z2023-09-11T15:42:17ZHow to prove you’ve discovered alien life – new research<figure><img src="https://images.theconversation.com/files/547466/original/file-20230911-28-wkdmi6.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C498%2C498&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In 2021, scientists thought they had discovered phosphine in the clouds of Venus.</span> <span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA00270">NASA</a></span></figcaption></figure><p>In the past few decades, <a href="https://www.businessinsider.com/times-scientists-thought-they-discovered-extraterrestrial-alien-life-signs-2023-2?r=US&IR=T">several phenomena</a> have led to excited speculation in the scientific community that they might indeed be indications that there is extraterrestrial life. It will no doubt happen again. </p>
<p>Recently, two very different examples sparked excitement. In 2017, it was the mystery interstellar object <a href="https://theconversation.com/evidence-of-aliens-what-to-make-of-research-and-reporting-on-oumuamua-our-visitor-from-space-106711">‘Oumuamua</a>. And in 2021, it was the <a href="https://theconversation.com/venus-could-it-really-harbour-life-new-study-springs-a-surprise-145981">possible discovery of the gas phosphine</a> in the clouds of Venus.</p>
<p>In both cases, it seemed possible that the phenomenon indicated some kind of extraterrestrial biological source. Notably, physicist Avi Loeb from Harvard University <a href="https://theconversation.com/has-earth-been-visited-by-an-alien-spaceship-harvard-professor-avi-loeb-vs-everybody-else-155509">argued in favour</a> of the oddly shaped ‘Oumuamua being an alien spaceship. </p>
<p>And phosphine in the atmosphere of a rocky planet is <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2018.1954">proposed to be</a> a strong signature for life, as it is continuously produced by microbes on Earth. </p>
<p>These are just two of the latest cases of a long list of examples of such initially promising phenomena. But although a few of the examples are still controversial, most have turned out to have other explanations (it wasn’t aliens).</p>
<p>So how can we be sure we’ve come to the right conclusion for something as subtle as the presence of a certain gas or a strange looking space rock? In our new paper <a href="https://www.liebertpub.com/doi/abs/10.1089/ast.2022.0084">published in the journal Astrobiology</a>, we have proposed a technique for reliably evaluating such evidence. </p>
<p>The word “possible” is strange, with a rather unfortunate degree of flexibility. There’s a sense in which it is possible that I’ll meet King Charles III today, but at the same time it is extraordinarily unlikely. </p>
<p>Many shouts of: “It might be aliens!” should be interpreted in this (strained) sense. By contrast, we often use the word “might” to express something that has high probability, as in “it might snow today.”</p>
<p>The concept of possibility incorporates these extremes, and everything in-between. Newspapers might capitalise on this flexibility with a cheeky headline that appears to indicate that something is a bit more exciting than it actually is. But the scientific world needs to express itself with rigour, transparently conveying the degree of confidence justified by the evidence.</p>
<p>Some would turn to <a href="https://theconversation.com/ufos-how-to-calculate-the-odds-that-an-alien-spaceship-has-been-spotted-162269">Bayes’ Theorem</a>, a common statistical formula, which gives the probability (Pr) of something, given some evidence. </p>
<p>One could, optimistically, input the available evidence into the Bayes formula, and achieve as output a number between 0 and 1 (where 0.5 is a 50:50 chance that a signal is produced by aliens). But the Bayesian approach doesn’t really help when it comes to extraterrestrial life. </p>
<figure class="align-center ">
<img alt="Image of the Bayesian formula." src="https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=79&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=79&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=79&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=100&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=100&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404772/original/file-20210607-23-2oywyc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=100&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Bayesian formula for alien evidence, produced by Anders Sandberg, University of Oxford.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>For example, it requires an input for the prior probability that aliens exist. And intuitions about that vary dramatically (estimates for the number of inhabited planets in our galaxy <a href="https://www.forbes.com/sites/jamiecartereurope/2021/06/23/there-is-only-one-other-planet-in-our-galaxy-that-could-be-earth-like-say-scientists/">range from one to billions</a>). </p>
<p>It also requires a value for the probability of the phenomenon in question occurring naturally – not caused by aliens. For some kinds of “biosignatures” (such as a dinosaur skeleton) we know that the probability of it occurring without life is incredibly low. But for many others (say, a particular blend of gases) we don’t know much at all. </p>
<figure class="align-center ">
<img alt="Diagram of how much possibility space we have explored." src="https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=310&fit=crop&dpr=1 600w, https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=310&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=310&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=389&fit=crop&dpr=1 754w, https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=389&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/546969/original/file-20230907-20-2t155l.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=389&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How much of the relevant possibility space have we explored?</span>
<span class="attribution"><span class="source">Peter Vickers</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Here one meets with <a href="https://global.oup.com/academic/product/exceeding-our-grasp-9780195174083?cc=gb&lang=en&">the problem of “unconceived alternatives”</a>. Put simply: we may know too little about alternative sources of the phenomenon. Perhaps we just haven’t explored the space of possible causes of the relevant phenomenon very much. </p>
<p>After all, humans have only carried out a limited amount of rigorous research – we don’t know about every single process that could produce a certain gas in an atmosphere.</p>
<h2>New approaches</h2>
<p>In 2021, a Nasa-affiliated group <a href="https://www.nature.com/articles/s41586-021-03804-9.epdf?sharing_token=aMvAzNSKTDpeQ_Lx50lBO9RgN0jAjWel9jnR3ZoTv0OiHZ7kRMaxJS4ikXfsEfuhWNXQC4W7SsC52JCjUDnSSqLC5BhXbWxxUcFJQ3KnlmY6LAuQF02dgmfPAEQqFuQhHT7iq8uOqnhGqUWJGAFWKU9xwVrg8ofZtBSQm0hNMoQ%3D">published a paper</a> setting out the Confidence of Life Detection (CoLD) framework, designed to solve this problem.</p>
<p>It recommends seven steps to verifying a discovery, from ruling out contamination to getting follow-up observations of a predicted biological signal in the same region.</p>
<p>Unfortunately, the problem of unconceived alternatives remains a serious challenge. Level 4 in the framework requires that “all known non-biological sources of signal” are shown to be implausible. But this only starts to mean something when the relevant space of different possibilities has been thoroughly explored. </p>
<p>Our new paper, published by the group <a href="https://www.durham.ac.uk/research/institutes-and-centres/humanities-engaging-science-society/research/eurica-project-leverhulme/">Exploring Uncertainty and Risk in Contemporary Astrobiology</a> (EURiCA), has come up with another proposal.</p>
<p>Or, rather, it is an idea borrowed from another context. For many years, it has been imperative for the Intergovernmental Panel on Climate Change (IPCC) to be clear on how confident they are concerning a great many propositions about climate change. </p>
<p>In order to express their degree of confidence, <a href="https://www.ipcc.ch/site/assets/uploads/2017/08/AR5_Uncertainty_Guidance_Note.pdf">a framework has been in place</a> for more than 20 years now, which combines the quantity and quality of the evidence with the degree to which experts agree (the degree of consensus, if any). While this has been robustly challenged, it has stood the test of time in the face of extraordinary scrutiny and the highest possible stakes. </p>
<p>This same framework could be used in the context of discovering extraterrestrial life. A dedicated team of experts would make a judgement based not only on their assessment of the scientific evidence (X-axis in image above), but also the extent of agreement across the community (Y-axis). </p>
<p>So the worst assessment would have low agreement among experts and limited evidence while the best would have high agreement and robust evidence. </p>
<p>What of unconceived alternatives? The community of experts will only agree that purported evidence for life is “robust” if the relevant possibilities have been thoroughly explored. If they haven’t, there’s a good chance some other explanation will turn up in the long run. </p>
<p>Astrobiologists mustn’t limit their research to the study of the signatures of life. They must also carefully investigate the possible ways that non-biological processes might mimic those same signatures. </p>
<p>Only when we know that, might we finally be able to say, “This time, it really could be aliens.”</p><img src="https://counter.theconversation.com/content/213104/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Vickers receives funding from Leverhulme Trust Research Project Grant (RPG-2021-274).</span></em></p><p class="fine-print"><em><span>Sean McMahon receives funding from Leverhulme Trust Research Project Grant (RPG-2021-274) and the Royal Society of Edinburgh grant #1918.</span></em></p>Alien hunters should learn from the Intergovernmental Panel on Climate Change (IPCC).Peter Vickers, Professor in Philosophy of Science, Durham UniversitySean McMahon, Chancellor's Fellow in Astrobiology, The University of EdinburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2008292023-03-05T19:19:56Z2023-03-05T19:19:56ZWhat are the best conditions for life? Exploring the multiverse can help us find out<figure><img src="https://images.theconversation.com/files/513318/original/file-20230303-18-ugje3l.jpeg?ixlib=rb-1.1.0&rect=12%2C0%2C4013%2C3024&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Israel Pina / Unsplash</span></span></figcaption></figure><p>Is our universe all there is, or could there be more? Is our universe just one of a countless multitude, all together in an all-encompassing multiverse? </p>
<p>And if there are other universes, what would they be like? Could they be habitable?</p>
<p>This might feel like speculation heaped upon speculation, but it’s not as crazy as you might think. </p>
<p>My colleagues and I have been exploring what other parts of the multiverse might be like – and what these hypothetical neighbouring universes can tell us about the conditions that make life possible, and how they arise.</p>
<h2>What-if universes</h2>
<p>Some physicists <a href="https://www.space.com/25100-multiverse-cosmic-inflation-gravitational-waves.html">contend</a> that a burst of rapid expansion at the cosmic dawn known as inflation makes some form of multiverse inevitable. Our universe would really just be one of many. </p>
<p>In this theory, each new universe crystallises out of the seething background of inflation, imprinted with its own unique mix of physical laws.</p>
<p>If physical laws similar to ours govern these other universes, then we can come to grips with them. Well, at least in theory. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513319/original/file-20230303-14-sdad7i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The history of our universe. Other universes with slightly different laws of physics may also have crystallised from the early period of inflation.</span>
<span class="attribution"><a class="source" href="http://map.gsfc.nasa.gov/media/060915/index.html">NASA</a></span>
</figcaption>
</figure>
<p>Within our universe, physics is governed by rules that tell us how things should interact with each other, and constants of nature, such as the speed of light, that dictate the strengths of these interactions. So, we can imagine hypothetical “what-if” universes where we change these properties and explore the consequences within mathematical equations.</p>
<p>This might sound simple, but the rules we tinker with are the fundamental makeup of the universe. If we imagine a universe where, say, the electron is a hundred times heavier than in our universe, then what would its consequences be for stars, planets and even life?</p>
<h2>What does life need?</h2>
<p>We recently tackled this question in a series of papers where we considered habitability across the multiverse. Of course, habitability is a complex concept, but we think life requires a few choice ingredients to get going.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-multiverse-is-huge-in-pop-culture-right-now-but-what-is-it-and-does-it-really-exist-181781">The multiverse is huge in pop culture right now – but what is it, and does it really exist?</a>
</strong>
</em>
</p>
<hr>
<p>Complexity is one of those ingredients. For life on Earth, that complexity comes from the elements of the periodic table, which can be mixed and arranged into a myriad of different molecules. We are living molecular machines. </p>
<p>But a stable environment and a steady flow of energy are also essential. It is no surprise that Earthly life began on the surface of a rocky planet, with an abundance of chemical elements, bathed in the light of a long-lived stable star.</p>
<h2>Tweaking the fundamental forces</h2>
<p>Do similar environments exist across the extent of the multiverse? We started our theoretical exploration by considering the <a href="https://www.mdpi.com/2218-1997/8/12/651">abundance of chemical elements</a>. </p>
<p>In our universe, other than primordial hydrogen and helium that were formed in the Big Bang, all elements arise through the lives of stars. They are either generated through the nuclear reactions in stellar cores, or in the supreme violence of supernovae, when a massive star tears itself apart at the end of its life.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-are-lucky-to-live-in-a-universe-made-for-us-46988">We are lucky to live in a universe made for us</a>
</strong>
</em>
</p>
<hr>
<p>All these processes are governed by the four fundamental forces in the universe. Gravity squeezes the stellar core, driving it to immense temperatures and densities. Electromagnetism tries to force atomic nuclei apart, but if they can get close enough, the strong nuclear force can bind them into a new element. Even the weak nuclear force, which can flip a proton into a neutron, plays an important role in the ignition of the stellar furnace.</p>
<p>The masses of the fundamental particles, such as electrons and quarks, can also play a pivotal role. </p>
<p>So, to explore these hypothetical universes, we have many dials we can adjust. The changes to the fundamental universe flow through to the rest of physics.</p>
<h2>The carbon–oxygen balance</h2>
<p>To tackle the immense complexity of this problem, we chopped the various pieces of physics into manageable chunks: <a href="https://www.mdpi.com/2218-1997/9/1/4">stars and atmospheres</a>, <a href="https://www.mdpi.com/2218-1997/9/1/2">planets and plate tectonics</a>, the <a href="https://www.mdpi.com/2218-1997/9/1/42">origins of life</a>, and more. And then we pinned the chunks together to tell an overall story about habitability across the multiverse.</p>
<p>A complex picture emerges. Some factors can strongly influence the habitability of a universe. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-a-planet-need-plate-tectonics-to-develop-life-61303">Does a planet need plate tectonics to develop life?</a>
</strong>
</em>
</p>
<hr>
<p>For example, the ratio of carbon to oxygen, something set by a particular chain of nuclear reactions in the heart of a star, appears to be particularly important. </p>
<p>Straying too far from the value in our universe, where there are roughly equal amounts of the two elements, results in environments where it would be extremely difficult for life to emerge and thrive. </p>
<p>But the abundance of other elements appears to be less important. As long as they are stable, which does depend on the balance of the fundamental forces, they can play a pivotal role in the building blocks of life.</p>
<h2>More complexity to explore</h2>
<p>We have only been able to take a broad-brush approach to unravel habitability across the multiverse, sampling the space of possibilities in very discrete steps. </p>
<p>Furthermore, to make the problem manageable, we had to take several theoretical shortcuts and approximations. So we are only at the first stage of understanding the conditions for life across the multiverse.</p>
<p>In the next steps, the full complexity of alternative physics of other universes needs to be considered. We will need to understand the influence of the fundamental forces at the small scale and extrapolate it to the large scale, onto the formation of stars and eventually planets. </p>
<h2>A word of caution</h2>
<p>The notion of a multiverse is still only a hypothesis, an idea that has yet to be tested. In truth, we don’t yet know if it is an idea that <em>can</em> be tested. </p>
<p>And we don’t know if the physical laws could be different across the multiverse and, if they are, just how different they could be. </p>
<p>We may be at the start of a journey that will reveal our ultimate place within infinity – or we may be heading for a scientific dead end.</p><img src="https://counter.theconversation.com/content/200829/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Geraint Lewis receives funding from Australian Research Council. </span></em></p>Some physicists think we live in a multiverse, surrounded by universes not quite like our own. What does that mean for life?Geraint Lewis, Professor of Astrophysics, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2003382023-02-22T01:59:36Z2023-02-22T01:59:36ZThere could be alien life on Mars, but will our rovers be able to find it?<figure><img src="https://images.theconversation.com/files/511377/original/file-20230221-946-yjfk13.jpg?ixlib=rb-1.1.0&rect=0%2C187%2C4032%2C2158&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists think Mars rovers may have some blind spots when it comes to finding signs of life. </span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Robotic rovers are currently exploring the surface of Mars. Part of a rover’s mission is to survey the planet for signs of life. There might be nothing to find – but what if there is, and the rovers just can’t “see” it?</p>
<p>New research published today in <a href="https://doi.org/10.1038/s41467-023-36172-1">Nature Communications</a> suggests the rovers’ current equipment might not actually be up to the task of finding evidence of life. </p>
<p>As an extreme environment microbiologist, the challenges of searching for life where it seems near-impossible are familiar to me. </p>
<p>In astrobiology, we study the diversity of life in sites on Earth with environmental or physical features that resemble regions already described on Mars. We call these terrestrial environments “Mars analogue” sites.</p>
<h2>Limits of detection</h2>
<p>The new research, led by Armando Azua-Bustos at the Center for Astrobiology in Madrid, tested the sophisticated instruments currently in use by NASA’s Curiosity and Perseverance rovers – as well as some newer lab equipment planned for future analysis – in the Mars analogue of the Atacama Desert. </p>
<figure class="align-center ">
<img alt="A red, dusty, barren landscape, with a medium size rock formation. One scientist is climing the rock. Another is crouched at its base." src="https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511268/original/file-20230221-26-ixl70u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Scientists take samples from the Atacama Desert’s arid soil.</span>
<span class="attribution"><span class="source">Armando Azua-Bustos/Centro de Astrobiología</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Azua-Bustos and colleagues found the rovers’ testbed equipment – tools for analysing samples in the field – had limited ability to detect the traces of life we might expect to find on the red planet. They were able to detect the mineral components of the samples, but were not always able to detect organic molecules.</p>
<p>In my team’s case, our Mars analogue sites are the cold and hyper-arid deserts of the Dry Valleys and Windmill Islands in Antarctica.</p>
<p>In both of these sites, life exists despite extreme pressures. Finding evidence of life is challenging, given the harsh conditions and the scarcity of microbial life present. </p>
<p>First, we must define the biological and physical boundaries of life existing (and being detected) in analogue “extreme” environments. Then we need to develop tools to identify the “biosignatures” for life. These include organic molecules like lipids, nucleic acids and proteins. Finally, we determine how sensitive tools need to be to detect those biosignatures, on Earth and also Mars. This tells us the limits of our detection.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Y7eF-mjXkLU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Traces of life are scarce in the Atacama Desert.</span></figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/perseverance-the-mars-rover-searching-for-ancient-life-and-the-aussie-scientists-who-helped-build-it-141590">Perseverance: the Mars rover searching for ancient life, and the Aussie scientists who helped build it</a>
</strong>
</em>
</p>
<hr>
<h2>The search for a dark microbiome</h2>
<p>In my field of extreme microbiology, “microbial dark matter” is when the majority of microscopic organisms in a sample have not been isolated and/or characterised. To identify them, we require next-generation sequencing <strong>need to define</strong>. Azua-Bustos’s team go one step further, proposing a “dark microbiome” which contains potentially relic, extinct Earth species.</p>
<p>Azua-Bustos’s team found sophisticated laboratory techniques could detect a dark microbiome in the Atacama Desert’s Martian-like hyper-arid soil samples. However, the rovers’ current equipment wouldn’t be able to detect it on Mars. </p>
<p>In samples with such scarce biomass, we use highly sensitive laboratory methods to detect microbial life, including gene sequencing and visualising cells using microscopic analysis. Prototypes for genome sequencing in the field are being developed, but they do not have the sensitivity needed for low biomass samples – yet.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511372/original/file-20230221-26-9xc7jp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Professor Belinda Ferrari in Antarctica.</span>
<span class="attribution"><span class="source">Dr Eden Zhang</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/there-is-water-on-mars-but-what-does-this-mean-for-life-48310">There is water on Mars, but what does this mean for life?</a>
</strong>
</em>
</p>
<hr>
<h2>Different planet, different rules</h2>
<p>The search for life on other planets also relies on our understanding of what life would need to exist, with the <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0020302">simplest list</a> being energy, carbon and liquid water. </p>
<p>On Earth, most organisms use photosynthesis to harness energy from sunlight. This process requires water, which is almost totally unavailable in dry desert environments like Antarctica and the Atacama Desert – and, most likely, Mars. We think a process we dubbed “atmospheric chemosynthesis” could be filling this gap.</p>
<p>My team first discovered atmospheric chemosynthesis in the cold desert soils of Antarctica. In this overlooked metabolic process, bacteria literally “<a href="https://www.nature.com/articles/nature25014">live on thin air</a>” by consuming trace levels of hydrogen and carbon monoxide gas from the atmosphere. </p>
<figure class="align-center ">
<img alt="A photo of the vast, barren Antarctic landscape. There is a cloudless blue sky, ice, ocean in the far distance, and a very tiny hut visible in the mid distance." src="https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=345&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=345&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=345&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=434&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=434&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511374/original/file-20230221-26-1zucql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=434&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antarctica is one of the few places on Earth with permafrost similar to areas on Mars.</span>
<span class="attribution"><span class="source">Dr Belinda Ferrari</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We think dry desert microbiomes may rely on this process for energy as well as water, which is a byproduct of the process. Ecosystems like the ones we’ve found in Antarctica now offer one of the most <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2021.0066">promising ecological models</a> in the search for Martian life. </p>
<p>We now believe there is potential for life in the ice-cemented subsurface of Mars. My team – alongside collaborators at NASA and the University of Pretoria – <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2021.0066">plan to investigate</a> this in Antarctica’s University Valley, by defining the environmental limits to energy, metabolic water and carbon production via trace gas consumption. </p>
<figure class="align-center ">
<img alt="A human in a red coat looks tiny, crouching in front of enormous reddish rock formations that have ice in between." src="https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/511563/original/file-20230222-20-sivq4n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">University Valley has a layer of dry permafrost soil overlaying ice-rich permanently frozen ground. Some Martian environments have similar features.</span>
<span class="attribution"><span class="source">Jackie Goordial/McGill University</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/discovery-of-microbe-rich-groundwater-in-antarctica-guides-search-for-life-in-space-40931">Discovery of microbe-rich groundwater in Antarctica guides search for life in space</a>
</strong>
</em>
</p>
<hr>
<h2>We won’t find what we can’t define</h2>
<p>Our new knowledge of target biosignatures and the level of sensitivity needed to detect them will be critical when designing or optimising future instrumentation to be deployed on missions aimed at finding life. </p>
<p>The goal of future missions to Mars, including the <a href="https://www.researchgate.net/publication/236125178_The_Icebreaker_Life_Mission_to_Mars_A_Search_for_Biomolecular_Evidence_for_Life">Icebreaker Life</a> mission planned for 2026, is to search for evidence of life. The Icebreaker Life will sample ice-cemented ground, similar to Antarctic dry permafrost, and if it detects signs of life, a Mars Sample Return mission would be a high priority.</p>
<p>Returning samples to Earth for laboratory analysis is risky. As we found with our Antarctic soil samples, challenges can include contamination, preservation of cold temperatures during transport, and the need for specialist quarantine laboratories, to analyse samples without destroying them. </p>
<p>But as Asua-Bustos suggests, bringing samples to Earth for detailed lab analyses may be the only sure way to detect – or rule out – the presence (or past presence) of life.</p><img src="https://counter.theconversation.com/content/200338/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Belinda Ferrari receives funding from the Australian Research Council. While not directly related to this article her previous funding has led to new research questions on the habitability of Mars.</span></em></p>Our Mars rovers might not be sensitive enough to detect signs of life. But lessons from Antarctica might make future missions more successful.Belinda Ferrari, Professor of Microbiology, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1848282022-07-14T12:34:04Z2022-07-14T12:34:04ZTo search for alien life, astronomers will look for clues in the atmospheres of distant planets – and the James Webb Space Telescope just proved it’s possible to do so<figure><img src="https://images.theconversation.com/files/473980/original/file-20220713-20-g1f04j.png?ixlib=rb-1.1.0&rect=34%2C116%2C691%2C572&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">TRAPPIST-1e is a rocky exoplanet in the habitable zone of a star 40 light-years from Earth and may have water and clouds, as depicted in this artist's impression.</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:TRAPPIST-1e_artist_impression_2018.png#/media/File:TRAPPIST-1e_artist_impression_2018.png">NASA/JPL-Caltech/Wikimedia Commons</a></span></figcaption></figure><p>The ingredients for life are <a href="https://doi.org/10.1073/pnas.98.3.805">spread throughout the universe</a>. While Earth is the only known place in the universe with life, detecting life beyond Earth is a <a href="https://www.planetary.org/articles/the-2020-astrophysics-decadal-survey-guide">major goal</a> of <a href="https://www.planetary.org/space-policy/what-is-the-decadal-survey">modern astronomy</a> and <a href="https://www.planetary.org/space-policy/what-is-the-decadal-survey">planetary science</a>.</p>
<p>We are two scientists who study <a href="https://scholar.google.com/citations?user=2SCIYjIAAAAJ&hl=en&oi=ao">exoplanets</a> and <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en&oi=ao">astrobiology</a>. Thanks in large part to next-generation telescopes like James Webb, researchers like us will soon be able to measure the chemical makeup of atmospheres of planets around other stars. The hope is that one or more of these planets will have a chemical signature of life.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing green bands around stars." src="https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473981/original/file-20220713-24-ei1562.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are many known exoplanets in habitable zones – orbits not too close to a star that the water boils off but not so far that the planet is frozen solid – as marked in green for both the solar system and Kepler-186 star system with its planets labeled b, c, d, e and f.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Kepler186f-ComparisonGraphic-20140417_improved.jpg#/media/File:Kepler186f-ComparisonGraphic-20140417_improved.jpg">NASA Ames/SETI Institute/JPL-Caltech/Wikimedia Commons</a></span>
</figcaption>
</figure>
<h2>Habitable exoplanets</h2>
<p>Life <a href="https://doi.org/10.1073/pnas.1816535115">might exist in the solar system</a> where there is liquid water – like the subsurface aquifers on Mars or in the oceans of Jupiter’s moon Europa. However, searching for life in these places is incredibly difficult, as they are hard to reach and detecting life would require sending a probe to return physical samples.</p>
<p>Many astronomers believe there’s a <a href="https://exoplanets.nasa.gov/news/1675/life-in-the-universe-what-are-the-odds/">good chance that life exists on planets orbiting other stars</a>, and it’s possible that’s where <a href="https://doi.org/10.1016/j.actaastro.2022.03.019">life will first be found</a>.</p>
<p>Theoretical calculations suggest that there are around <a href="https://www.technologyreview.com/2020/11/06/1011784/half-milky-way-sun-like-stars-home-earth-like-planets-kepler-gaia-habitable-life/">300 million potentially habitable planets</a> in the Milky Way galaxy alone and <a href="https://doi.org/10.3847/1538-3881/abc418">several habitable Earth-sized planets</a> within only 30 light-years of Earth – essentially humanity’s galactic neighbors. So far, astronomers have <a href="https://exoplanets.nasa.gov/">discovered over 5,000 exoplanets</a>, including hundreds of potentially habitable ones, using <a href="https://sci.esa.int/web/exoplanets/-/60655-detection-methods">indirect methods</a> that measure how a planet affects its nearby star. These measurements can give astronomers information on the mass and size of an exoplanet, but not much else.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing two lines each with two peaks in the blue and red wavelengths." src="https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473983/original/file-20220713-17654-sd7qoy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Every material absorbs certain wavelengths of light, as shown in this diagram depicting the wavelengths of light absorbed most easily by different types of chlorophyll.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Chlorophyll_ab_spectra-en.svg#/media/File:Chlorophyll_ab_spectra-en.svg">Daniele Pugliesi/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Looking for biosignatures</h2>
<p>To detect life on a distant planet, astrobiologists will study starlight that has <a href="https://doi.org/10.1089/ast.2017.1729">interacted with a planet’s surface or atmosphere</a>. If the atmosphere or surface was transformed by life, the light may carry a clue, called a “biosignature.”</p>
<p>For the first half of its existence, Earth sported an atmosphere without oxygen, even though it hosted simple, single-celled life. Earth’s biosignature was very faint during this early era. That changed abruptly <a href="https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change">2.4 billion years ago</a> when a new family of algae evolved. The algae used a process of photosynthesis that produces free oxygen – oxygen that isn’t chemically bonded to any other element. From that time on, Earth’s oxygen-filled atmosphere has left a strong and easily detectable biosignature on light that passes through it.</p>
<p>When light bounces off the surface of a material or passes through a gas, certain wavelengths of the light are more likely to remain trapped in the gas or material’s surface than others. This selective trapping of wavelengths of light is why objects are different colors. Leaves are green because chlorophyll is particularly good at absorbing light in the red and blue wavelengths. As light hits a leaf, the red and blue wavelengths are absorbed, leaving mostly green light to bounce back into your eyes.</p>
<p>The pattern of missing light is determined by the specific composition of the material the light interacts with. Because of this, astronomers can learn something about the composition of an exoplanet’s atmosphere or surface by, in essence, measuring the specific color of light that comes from a planet. </p>
<p>This method can be used to recognize the presence of certain atmospheric gases that are associated with life – such as oxygen or methane – because these gasses leave very specific signatures in light. It could also be used to detect peculiar colors on the surface of a planet. On Earth, for example, the chlorophyll and other pigments plants and algae use for photosynthesis capture specific wavelengths of light. These pigments <a href="https://doi.org/10.1073/pnas.1304213111">produce characteristic colors</a> that can be detected by using a sensitive infrared camera. If you were to see this color reflecting off the surface of a distant planet, it would potentially signify the presence of chlorophyll.</p>
<h2>Telescopes in space and on Earth</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A giant gold mirror in a lab." src="https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473985/original/file-20220713-17654-d5rtyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The James Webb Space Telescope is the first telescope able to detect chemical signatures from exoplanets, but it is limited in its capabilities.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:JWST_Full_Mirror.jpg#/media/File:JWST_Full_Mirror.jpg">NASA/Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>It takes an incredibly powerful telescope to detect these subtle changes to the light coming from a potentially habitable exoplanet. For now, the only telescope capable of such a feat is the new <a href="http://jwst.nasa.gov/">James Webb Space Telescope</a>. As it <a href="https://blogs.nasa.gov/webb/2022/07/11/nasas-webb-telescope-is-now-fully-ready-for-science/">began science operations</a> in July 2022, James Webb took a reading of the spectrum of the <a href="https://www.nytimes.com/2022/07/12/science/wasp-96b-exoplanet-webb-telescope.html">gas giant exoplanet WASP-96b</a>. The spectrum showed the presence of water and clouds, but a planet as large and hot as WASP-96b is unlikely to host life.</p>
<p>However, this early data shows that James Webb is capable of detecting faint chemical signatures in light coming from exoplanets. In the coming months, Webb is set to turn its mirrors toward <a href="https://www.space.com/42512-trappist-1-planet-could-host-life.html">TRAPPIST-1e</a>, a potentially habitable Earth-sized planet a mere 39 light-years from Earth.</p>
<p>Webb can look for biosignatures by studying planets as they pass in front of their host stars and capturing <a href="https://www.physics.uu.se/research/astronomy-and-space-physics/research/planets/exoplanet-atmospheres/">starlight that filters through the planet’s atmosphere</a>. But Webb was not designed to search for life, so the telescope is only able to scrutinize a few of the nearest potentially habitable worlds. It also can only detect changes to <a href="https://doi.org/10.3847/1538-3881/ab21e0">atmospheric levels of carbon dioxide, methane and water vapor</a>. While certain combinations of these gasses <a href="https://doi.org/10.1038/s41550-021-01579-7">may suggest life</a>, Webb is not able to detect the presence of unbonded oxygen, which is the strongest signal for life.</p>
<p>Leading concepts for future, even more powerful, space telescopes include plans to block the bright light of a planet’s host star to reveal starlight reflected back from the planet. This idea is similar to using your hand to block sunlight to better see something in the distance. Future space telescopes could use small, internal masks or large, external, umbrella-like spacecraft to do this. Once the starlight is blocked, it becomes much easier to study light bouncing off a planet.</p>
<p>There are also three enormous, ground-based telescopes currently under construction that will be able to search for biosignatures: the <a href="http://gmto.org/">Giant Magellen Telescope</a>, the <a href="https://www.tmt.org/">Thirty Meter Telescope</a> and the <a href="https://www.eso.org/sci/facilities/eelt/">European Extremely Large Telescope</a>. Each is far more powerful than existing telescopes on Earth, and despite the handicap of Earth’s atmosphere distorting starlight, these telescopes might be able to probe the atmospheres of the closest worlds for oxygen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cow and its calf standing in a field." src="https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=511&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=511&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473982/original/file-20220713-12-4xssot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=511&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Animals, including cows, produce methane, but so do many geologic processes.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Cows_eating_grass_(42882305160).jpg#/media/File:Cows_eating_grass_(42882305160).jpg">Jernej Furman/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Is it biology or geology?</h2>
<p>Even using the most powerful telescopes of the coming decades, astrobiologists will only be able to detect strong biosignatures produced by worlds that have been completely transformed by life.</p>
<p>Unfortunately, most gases released by terrestrial life can also be produced by nonbiological processes – cows and volcanoes both release methane. Photosynthesis produces oxygen, but sunlight does, too, when it splits water molecules into oxygen and hydrogen. There is a <a href="https://doi.org/10.1089/ast.2017.1727">good chance astronomers will detect some false positives</a> when looking for distant life. To help rule out false positives, astronomers will need to understand a planet of interest well enough to understand whether its <a href="https://doi.org/10.1089/ast.2017.1737">geologic or atmospheric processes could mimic a biosignature</a>. </p>
<p>The next generation of exoplanet studies has the potential to pass the bar of the <a href="https://quoteinvestigator.com/2021/12/05/extraordinary/">extraordinary evidence</a> needed to prove the existence of life. The first data release from the James Webb Space Telescope gives us a sense of the exciting progress that’s coming soon.</p><img src="https://counter.theconversation.com/content/184828/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Daniel Apai receives funding from NASA and the Gordon and Betty Moore Foundation.</span></em></p>Life on Earth has dramatically changed the chemistry of the planet. Astronomers will measure light that bounces off distant planets to look for similar clues that they host life.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaDaniel Apai, Professor of Astronomy and Planetary Sciences, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1555092021-02-18T14:50:16Z2021-02-18T14:50:16ZHas Earth been visited by an alien spaceship? Harvard professor Avi Loeb vs everybody else<figure><img src="https://images.theconversation.com/files/384998/original/file-20210218-16-8c2xlv.jpg?ixlib=rb-1.1.0&rect=0%2C26%2C2522%2C1619&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's impression of 'Oumuamua.</span> <span class="attribution"><span class="source"> ESO/M. Kornmesser </span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>A highly unusual object <a href="http://www.ifa.hawaii.edu/info/press-releases/interstellar/">was spotted</a> travelling through the solar system in 2017. Given a Hawaiian name,ʻOumuamua, it was small and elongated – a few hundred metres by a few tens of meters, travelling at a speed fast enough to escape the Sun’s gravity and move into interstellar space.</p>
<p>I was at a meeting when the discovery of ʻOumuamua was announced, and a friend immediately said to me, “So how long before somebody claims it’s a spaceship?” It seems that whenever astronomers discover anything unusual, somebody claims it must be aliens.</p>
<p>Nearly all scientists believe that ʻOumuamua probably originates from outside the solar system. It is an <a href="https://theconversation.com/comet-or-asteroid-mysterious-oumuamua-shows-why-we-may-need-a-new-classification-system-99083">asteroid- or comet-like object</a> that has left another star and travelled through interstellar space - we saw it as it zipped by us. But not everyone agrees. <a href="https://www.cfa.harvard.edu/%7Eloeb/">Avi Loeb</a>, a Harvard professor of astronomy, <a href="https://www.scientificamerican.com/article/astronomer-avi-loeb-says-aliens-have-visited-and-hes-not-kidding1/">suggested in a recent book</a> that it is indeed an alien spaceship. But how feasible is this? And how come most scientists disagree with the claim?</p>
<p>Researchers estimate that the Milky Way should contain around 100 million billion billion comets and asteroids ejected from other planetary systems, and that one of these <a href="https://academic.oup.com/mnrasl/article/478/1/L49/4925005">should pass through our solar system</a> every year or so. So it makes sense that ‘Oumuamua could be one of these. We <a href="https://www.nasa.gov/feature/interstellar-comet-borisov-reveals-its-chemistry-and-possible-origins/">spotted another last year</a> – “Borisov” – which suggests they are as common as we predict.</p>
<p>What made ʻOumuamua particularly interesting was that it didn’t follow the orbit you would expect – its trajectory shows it has some extra “non-gravitational force” acting on it. This is not too unusual. The pressure of solar radiation or gas or particles driven out as an object warms up close to the Sun can give extra force, and <a href="https://ui.adsabs.harvard.edu/abs/2018Natur.559..223M/abstract">we see this with comets all the time</a>. </p>
<p>Experts on comets and the solar system <a href="https://theconversation.com/mysterious-alien-cigar-asteroid-is-actually-an-interstellar-lump-of-ice-not-a-space-ship-89322">have explored</a> various explanations for this. Given this was a small, dark object passing us very quickly before disappearing, the images we were able to get weren’t wonderful, and so it is difficult to be sure.</p>
<figure class="align-right ">
<img alt="Image of Avi Loeb." src="https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=769&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=769&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=769&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=966&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=966&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385002/original/file-20210218-26-3o0bqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=966&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Avi Loeb.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Loeb, however, believes that ʻOumuamua is an alien spaceship, powered by a “light sail” – a method for propelling a spacecraft using radiation pressure exerted by the Sun on huge mirrors. He argues the non-gravitational acceleration is a sign of “deliberate” manoeuvring. This argument seems largely to be based on the fact that ʻOumuamua lacks a fuzzy envelope (“coma”) and a comet-like tail, which are usual signatures of comets undergoing non-gravitational acceleration (although jets from particular spots cannot be ruled out).</p>
<h2>Sanity checks</h2>
<p>He may or may not be right, and there is no way of proving or disproving this idea. But claims like this, especially from experienced scientists are disliked by the scientific community for many reasons.</p>
<p>If we decide that anything slightly odd that we don’t understand completely in astronomy could be aliens, then we have a lot of potential evidence for aliens – there is an awful lot <a href="https://theconversation.com/cosmology-is-in-crisis-but-not-for-the-reason-you-may-think-52349">we don’t understand</a>. To stop ourselves jumping to weird and wonderful conclusions every time we come across something strange, science has several sanity checks.</p>
<p>One is <a href="https://plato.stanford.edu/entries/simplicity/">Occam’s razor</a>, which tells us to look for the simplest solutions that raise the fewest new questions. Is this a natural object of the type that we suspect to be extremely common in the Milky Way, or is it aliens? Aliens raise a whole set of supplementary questions (who, why, from where?) which means Occam’s razor tells us to reject it, at least until all simpler explanations are exhausted. </p>
<p>Another sanity check is <a href="https://bigthink.com/personal-growth/how-the-sagan-standard-can-help-you-make-better-decisions?rebelltitem=1#rebelltitem1">the general rule</a> that “extraordinary claims require extraordinary evidence”. A not quite completely understood acceleration is not extraordinary evidence, as there are many plausible explanations for it.</p>
<p>Yet another check is the often sluggish but usually reliable peer-review system, in which scientists publish their findings in scientific journals where their claims can be assessed and critiqued by experts in their field.</p>
<h2>Alien research</h2>
<p>This doesn’t mean that we shouldn’t look for aliens. A lot of time and money is being devoted to researching them. For astronomers who are interested in the proper science of aliens, there is “astrobiology” – the science of looking for life outside Earth based on signs of biological activity. On February 18, Nasa’s Perseverance rover will land on Mars and look for molecules <a href="https://theconversation.com/perseverance-mars-rover-how-to-prove-whether-theres-life-on-the-red-planet-154982">which may include such signatures</a>, for example. Other interesting targets are the moons of Jupiter and Saturn.</p>
<figure class="align-center ">
<img alt="Image of Jupiter's moon Europa." src="https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385003/original/file-20210218-20-4b4aaw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jupiter’s moon Europa may harbour simple life in its internal ocean.</span>
<span class="attribution"><span class="source">NASA/JPL/DLR</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In the next five years, we will also <a href="https://exoplanets.nasa.gov/search-for-life/can-we-find-life/">have the technology</a> to search for alien life on planets around other stars (exoplanets). Both the <a href="https://theconversation.com/how-hubbles-successor-will-give-us-a-glimpse-into-the-very-first-galaxies-45970">James Webb Space Telescope</a> (due to launch in 2021), and the <a href="https://www.eso.org/sci/facilities/eelt/">European Extremely Large Telescope</a> (due for first light in 2025) will analyse exoplanet atmospheres in detail, searching for signs of life. For example, the oxygen in the Earth’s atmosphere is there because life constantly produces it. Meanwhile, <a href="https://theconversation.com/seti-new-signal-excites-alien-hunters-heres-how-we-could-find-out-if-its-real-152498">the Search for Extraterrestrial Intelligence (Seti)</a> initiative has been scanning the skies with radio telescopes for decades in search of messages from intelligent aliens. </p>
<p>Signs of alien life would be an amazing discovery. But when we do find such evidence, we want to be sure it is good. To be as sure as we can be, we need to present our arguments to other experts in the field to examine and critique, follow the scientific method which, in its slow and plodding way, gets us there in the end. </p>
<p>This would give us much more reliable evidence than claims from somebody with a book to sell. It is quite possible, in the next five to ten years, that somebody will announce that they have found good evidence for alien life. But rest assured this isn’t it.</p><img src="https://counter.theconversation.com/content/155509/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Goodwin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There’s a good reason why so many scientists disagree with claims that Earth has been visited by aliens.Simon Goodwin, Professor of Theoretical Astrophysics, University of SheffieldLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1549822021-02-16T10:38:40Z2021-02-16T10:38:40ZPerseverance Mars rover: how to prove whether there’s life on the red planet<figure><img src="https://images.theconversation.com/files/384291/original/file-20210215-19-s5qrjf.jpg?ixlib=rb-1.1.0&rect=23%2C21%2C1573%2C876&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Perseverance in action.</span> <span class="attribution"><span class="source">NASA/JPL-Caltech</span></span></figcaption></figure><p>We’ll soon be able to properly start asking the question: “Are we alone in the universe?” Nasa’s next major mission, the <a href="https://mars.nasa.gov/mars2020/">Mars 2020 Perseverance rover</a>, will land on the surface on <a href="https://youtu.be/tITni_HY1Bk">February 18</a>. Following a <a href="https://theconversation.com/mars-perseverance-rover-set-for-nail-biting-landing-heres-the-rocket-science-154886">complex landing procedure</a>, it will get started on one of its main goals – searching for life on Mars. </p>
<p>The rover has two ways of gathering samples. It can either analyse them with its <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/">on-board laboratory</a> or it can <a href="https://theconversation.com/bringing-mars-rocks-back-to-earth-perseverance-rover-lands-on-feb-18-a-lead-scientist-explains-the-tech-and-goals-153851">save them for return</a> to Earth by future missions. But what exactly is it looking for, and what would it need to find to convince us that there is indeed past or present life? </p>
<p>If the landing is successful, this will be the first mission <a href="https://mars.nasa.gov/mars-exploration/missions/viking-1-2/">in decades</a> to actively search for direct evidence of life on Mars. This life – if it exists – will most likely take the form of extinct microbes. </p>
<p>We have recently found some tantalising hints at the possibility for current life in the <a href="https://theconversation.com/methane-on-mars-a-new-discovery-or-just-a-lot-of-hot-air-114656">form of methane gas</a> in the atmosphere. On Earth, a large percentage of methane in the atmosphere is produced by biological processes. This means that methane could be considered a biological signature. But it can also be readily produced by geological processes, so it is not proof of life. </p>
<figure class="align-center ">
<img alt="Diagram showin different ways methane could end up in Mars' atmosphere." src="https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384231/original/file-20210215-23-1f81efk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Are living organisms producing methane on Mars?</span>
<span class="attribution"><span class="source">Nasa</span></span>
</figcaption>
</figure>
<p>There are many molecules that are only made by terrestrial biology, such as <a href="https://www.britannica.com/science/isoprene">isoprene</a> or DNA. So finding something like those would allow us to move toward the conclusion that life exists or existed on Mars. If Perseverance does find such molecules, we will have the harder job of proving it was native to Mars and not a microbial hitchhiker from Earth. To help us work that out, the rover will first run “control experiments” with no sample. If the molecules are there in these experiments, they are likely to be terrestrial contamination on the rover itself.</p>
<h2>Sophisticated instruments</h2>
<p>That said, if we find molecules that are not readily produced by standard chemical reactions on Mars, we might be onto something biologically alien. One of the instruments that will be used to search for biosignatures on Mars is <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/sherloc/">SHERLOC</a> (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals). It will use an ultraviolet laser light to probe samples from a safe distance of about 5cm. This way it reduces the chance of contaminating the samples while measuring the reflected light for evidence of biological molecules. </p>
<p>This works because each molecule type reflects the light in a unique way, allowing us to determine with a high degree of certainty that we have found something like <a href="https://en.wikipedia.org/wiki/Amino_acid">amino acids</a> (which build proteins) or <a href="https://en.wikipedia.org/wiki/Lipid">lipids</a> (which build cell walls). These molecules are known to persist in the environment after other biological molecules like DNA have been broken down and are no longer detectable. </p>
<p>Perseverance will also carry the <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/supercam/">SuperCam</a> instrument, which can shoot a laser to a distance of around seven metres. It can analyse the resulting dust cloud for evidence of rock types that could preserve clues to past life. This helps narrow down locations that might be best to investigate more fully without having to take the time to drive to them.</p>
<figure class="align-center ">
<img alt="Artist's impression showing the rover on Mars with sample tubes around it on the ground." src="https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/384233/original/file-20210215-23-16mg383.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The rover will store rock and soil samples in sealed tubes on the planet’s surface for future missions to retrieve.</span>
<span class="attribution"><span class="source">Nasa/JPL-Caltech</span></span>
</figcaption>
</figure>
<p>Rock samples from a depth of around 5cm will also be collected and stored in sealed containers for a future mission to collect. The analysis we can conduct on Earth is many times more precise and detailed than the instruments we can send to Mars. Plus we can do multiple kinds of analysis in multiple labs around the world, allowing for better overall results. For example, if evidence for extinct life is suspected to be preserved in a sample, we could use <a href="https://theconversation.com/startling-images-show-strange-and-beautiful-science-up-close-25129">electron microscopy</a> (which uses electrons rather than light to probe a sample) to try and see if it contains <a href="https://www.newscientist.com/article/2217747-fossilised-microbes-from-3-5-billion-years-ago-are-oldest-yet-found/">fossilised microbial cells</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/could-invisible-aliens-really-exist-among-us-an-astrobiologist-explains-129419">Could invisible aliens really exist among us? An astrobiologist explains</a>
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<p>All of this depends on our very narrow understanding of what life is. We only know about one kind of life – the terrestrial kind. Our experiments are searching for life within our current knowledge. It is always possible that life beyond our current understanding exists, perhaps silicon-based rather than carbon-based. Perseverance isn’t likely to detect such life even if it’s thriving on Mars.</p>
<p>Unless something gets up and moves in front of the camera, obtaining conclusive evidence likely be a long process, especially while we wait to analyse those cached samples. If we find even a hint of evidence for life, the next steps will be to detect it with multiple analytical techniques, show that it isn’t contamination from Earth and work out whether the evidence make sense in the context of the environment and data from the other instruments. </p>
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Read more:
<a href="https://theconversation.com/our-rover-could-discover-life-on-mars-heres-what-it-would-take-to-prove-it-89625">Our rover could discover life on Mars – here's what it would take to prove it</a>
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<p>Any evidence for life will have to go through the rigorous scientific process of testing, re-testing and peer review. What’s more, Perseverance is only conducting analysis in <a href="https://en.wikipedia.org/wiki/Jezero_(crater)">one crater</a> on Mars. </p>
<p>But other missions in the search for life, including the European Space Agency’s <a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars">Rosalind Franklin rover</a>, aren’t far behind. Excitingly, Rosalind Franklin will be the first to drill up to 2m under the harsh, freezing Martian surface. If there is any current life on Mars, we might be more likely to find it deeper below the surface, which is constantly bombarded with <a href="https://theconversation.com/mars-mission-how-increasing-levels-of-space-radiation-may-halt-human-visitors-94052">harmful radiation</a>.</p>
<p><em>You can hear more about the three Mars missions arriving at the red planet in February in the first episode of our new podcast, <a href="https://theconversation.com/uk/topics/the-conversation-weekly-98901">The Conversation Weekly</a> – the world explained by experts. Subscribe wherever you get your podcasts.</em></p>
<iframe src="https://player.acast.com/60087127b9687759d637bade/episodes/a-big-month-for-mars?theme=default&cover=1&latest=1" frameborder="0" width="100%" height="110px" allow="autoplay"></iframe><img src="https://counter.theconversation.com/content/154982/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samantha Rolfe does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Methane gas in the atmosphere is a tantalising hint suggesting that life could exists on Mars.Samantha Rolfe, Lecturer in Astrobiology and Principal Technical Officer at Bayfordbury Observatory, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1481472020-10-19T12:23:41Z2020-10-19T12:23:41ZNASA’s OSIRIS-REx will land on an asteroid to bring home rocks and dust – if it can avoid Mt. Doom<figure><img src="https://images.theconversation.com/files/363991/original/file-20201016-13-oev830.png?ixlib=rb-1.1.0&rect=0%2C0%2C2902%2C1475&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This artist's rendering shows OSIRIS-REx spacecraft descending toward asteroid Bennu to collect a sample of the asteroid’s surface.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/thumbnails/image/updatedtagpose.png">NASA/Goddard/University of Arizona</a></span></figcaption></figure><p>Imagine parallel parking a 15-passenger van into just two to three parking spaces surrounded by two-story boulders. On Oct. 20, a University of Arizona-led NASA mission 16 years in the making will attempt the astronomical equivalent more than 200 million miles away. </p>
<p>A NASA mission called <a href="https://www.asteroidmission.org/objectives/">OSIRIS-REx</a> will soon attempt to touch the surface of an asteroid and collect loose rubble. </p>
<p>OSIRIS-REx is the United States’ first asteroid sample return mission, aiming to collect and carry a pristine, unaltered sample from an asteroid back to Earth for scientific study. The spacecraft will attempt to touch the surface of the asteroid Bennu, which is hurtling through space at 63,000 miles per hour. If all goes according to plan, the spacecraft will deploy an 11-foot-long robotic arm called TAGSAM – Touch-and-Go Sample Acquisition Mechanism – and spend about 10 seconds collecting at least two ounces of loose rubble from the asteroid. The spacecraft, monitored remotely by a team of scientists and engineers, will then stow away the sample and begin its return to Earth, scheduled for 2023.</p>
<p>You can watch this sample collection “Touch-And-Go” maneuver Oct. 20 at 5 p.m. EDT/ 2 p.m. PDT on NASA Television and the agency’s <a href="https://www.nasa.gov/nasalive">website</a>.</p>
<p><a href="https://research.arizona.edu/about/leadership">As senior vice president for research and innovation</a> at UArizona and a mechanical engineer with a long career in space systems engineering, I believe this milestone for OSIRIS-REx captures perfectly the spirit of research and innovation, the careful balance of problem-solving and perseverance, of obstacle and opportunity. </p>
<h2>What Bennu can teach us</h2>
<p>In 2004, Michael Drake, then head of the <a href="https://www.lpl.arizona.edu">UArizona Lunar and Planetary Laboratory</a>; his protégé, <a href="https://www.lpl.arizona.edu/faculty/lauretta">Dante Lauretta</a>, then a UArizona assistant professor of planetary science; and experts from Lockheed Martin and NASA discussed the very earliest concept of the OSIRIS-REx mission and what it might achieve.</p>
<p>Asteroids are relics of the earliest materials that formed our solar system, and studying such a sample might allow scientists to answer fundamental questions about the origins of the solar system. Further, <a href="https://www.asteroidmission.org/why-bennu/">Bennu</a> is a near-Earth asteroid with possible risk of impacting the Earth in the late 2100s, so the mission also is exploring ways in which such a collision might be avoided. </p>
<p>Perhaps, though, the most ambitious goal of the OSIRIS-REx mission is resource identification – the “RI” in OSIRIS. This means, essentially, mapping the chemical properties of Bennu to learn, among other things, about the potential for mining asteroids to produce rocket fuel – a notion which, in 2004, was far ahead of its time.</p>
<p>NASA selected UArizona to lead the mission in 2011, with Drake at the helm. Lauretta, a first-generation college student and UArizona alumnus, took over when Drake died that year and continues to lead OSIRIS-REx today. He would unquestionably make his predecessor proud.</p>
<p>While OSIRIS-REx is the first NASA mission to attempt to collect a sample from an asteroid, the scientific and technological knowledge requisite of such a mission is the result of decades of prior exploration. In the early 1990s, <a href="https://solarsystem.nasa.gov/missions/galileo/overview/">NASA’s Galileo</a> flew past the asteroids <a href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA00332">Gaspra and Ida</a>. <a href="https://solarsystem.nasa.gov/missions/near-shoemaker/in-depth/">NEAR Shoemaker</a> was the first human-made object to orbit and land on an asteroid. Before heading for the dwarf planet Ceres in 2012, NASA’s <a href="https://solarsystem.nasa.gov/missions/dawn/overview/">Dawn spacecraft</a> orbited and mapped extensively the <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/4-vesta/in-depth/">asteroid Vesta</a>. </p>
<p>And perhaps most significantly, in 2010, the Japanese counterpart of NASA, JAXA, returned to Earth a small amount of dust from an asteroid via its Hayabusa spacecraft. Early last year, <a href="https://www.hayabusa2.jaxa.jp/en/">JAXA’s Hayabusa 2</a> landed on and successfully collected <a href="https://theconversation.com/touching-the-asteroid-ryugu-revealed-secrets-of-its-surface-and-changing-orbit-137852">a sample from the asteroid Ryugu</a>. The spacecraft will return to Earth in December of this year. It has been a privilege and an absolute delight to observe and learn from the accomplishments of our colleagues in Japan.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/hFP3eqRgsus?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">OSIRIS-REx is a NASA mission to explore near-Earth asteroid Bennu and return a sample to Earth.</span></figcaption>
</figure>
<h2>Navigating the unexpected</h2>
<p>OSIRIS-REx launched from Cape Canaveral, Florida, on Sept. 8, 2016, and arrived at Bennu in December 2018. In the months leading up to this moment, its team of scientists and engineers has remotely conducted two rehearsals, getting very near to Bennu without touching it. </p>
<p>When the OSIRIS-REx team selected Bennu as its target, it suspected and hoped that the asteroid’s surface would look something like a sandy beach. But the scientific process – and nature itself – is full of surprises, some challenging, all wondrous. As the OSIRIS-REx spacecraft approached Bennu, its suite of high-resolution cameras beamed hundreds of photos of the asteroid back to Earth, revealing not a beachlike surface, but a rugged, boulder-strewn landscape.</p>
<p>This was not exactly in the plan.</p>
<p>The team pored over these images for months, searching for a site both wide enough for a spacecraft the size of a large passenger van to touch down and maneuver without hitting a boulder and containing material fine enough to provide loose rubble to collect. </p>
<p>On Dec. 12, 2019, the OSIRIS-REx team announced the chosen landing site: Nightingale. Nightingale is home to a relatively new crater the size of a tennis court. At its edge lies a boulder the size of a two-story building. The team, which includes hundreds of faculty, researchers and students from UArizona and several partner institutions, affectionately refers to this boulder as “Mount Doom.” </p>
<p>In one small section of Nightingale’s crater – the size of just a few parking spaces – the team identified loose rubble small enough for the OSIRIS-REx spacecraft to grab and carry away.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=280&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=280&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=280&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=352&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=352&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364000/original/file-20201016-19-1vmgkir.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=352&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This set of stereoscopic images provides a 3D view of the 170-foot (52-meter) boulder that juts from asteroid Bennu’s southern hemisphere and the rocky slopes that surround it. The image was created by stereo image processing scientists Brian May, who is also the lead guitarist for the rock band Queen, and Claudia Manzoni.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/goddard/2019/bennu-in-stereo">NASA/Goddard/University of Arizona</a></span>
</figcaption>
</figure>
<h2>Nothing ventured, nothing gained</h2>
<p>Things could go wrong on Oct. 20.</p>
<p><a href="https://doi.org/10.1038/d41586-020-02910-4">Aside from crashing into Mount Doom</a>, other less dramatic, more probable risks lurk. The TAGSAM collector head could land on a rock, perched at an angle, rather than flush against a flat surface of rubble, making its collection far less effective. Because the collector head can accommodate particles only the size of a nickel or smaller, there is also the risk of it being effectively “clogged” by something larger. In uncharted territory, things don’t always go according to plan.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>Nevertheless, we are optimistic. </p>
<p>The age-old adage rings true: Nothing ventured, nothing gained. We already have gained so much knowledge from the OSIRIS-REx mission, and we will continue exploring and problem solving with the same bold determination that has taken us so far.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/364001/original/file-20201016-21-1rf0fla.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This image shows the OSIRIS-REx spacecraft’s sampling arm – called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) – and asteroid Bennu during the mission’s checkpoint rehearsal.</span>
<span class="attribution"><a class="source" href="https://www.asteroidmission.org/20200414samcamcheckpoint/">NASA/Goddard/University of Arizona</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/148147/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizabeth Cantwell works for the University of Arizona as Chief Research Officer.</span></em></p>OSIRIS-REx will touch down on asteroid Bennu, collect a sample of the dust and begin its journey back to Earth, where scientists will study it, hoping to learn secrets of the solar system’s origin.Elizabeth Cantwell, Professor of Practice for Aerospace and Mechanical Engineering and Senior Vice President for Research & Innovation, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1467322020-09-28T15:05:29Z2020-09-28T15:05:29ZMars: mounting evidence for subglacial lakes, but could they really host life?<figure><img src="https://images.theconversation.com/files/360265/original/file-20200928-20-1qo7icm.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1397%2C785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There seems to be a network of underground bodies of liquid water at Mars' south pole.</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/news/news.php?feature=7200">NASA/JPL/Malin Space Science Systems</a></span></figcaption></figure><p>Venus <a href="https://theconversation.com/venus-could-it-really-harbour-life-new-study-springs-a-surprise-145981">may harbour life</a> some 50km above its surface, we learned a couple of weeks ago. Now a new paper, <a href="https://www.nature.com/articles/s41550-020-1200-6">published in Nature Astronomy</a>, reveals that the best place for life on Mars might be more than a kilometre <em>below</em> its surface, where an entire network of subglacial lakes has been discovered.</p>
<p>Mars was not always so cold and dry as it is now. There are abundant signs that water flowed across its surface in the distant past, but today you’d struggle to find even any crevices that you could call moist.</p>
<p>There is nevertheless plenty of water on Mars today, but it’s virtually all frozen, so not much use for life. Even in places where the noon-time temperature creeps above freezing, <a href="https://theconversation.com/nasa-streaks-of-salt-on-mars-mean-flowing-water-and-raise-new-hopes-of-finding-life-48182">surface signs of liquid water</a> are frustratingly rare. This is because the atmospheric pressure on Mars is too slight to confine water in its liquid state, so ice usually
turns directly into vapour when heated.</p>
<h2>Lakes beneath ice</h2>
<p>It is beginning to look as if the most favourable place for liquid water on Mars is beneath its vast south polar ice cap. On Earth, such lakes began to be <a href="http://www.antarcticglaciers.org/glacier-processes/glacial-lakes/subglacial-lakes/">discovered in Antarctica</a> in the 1970s, where nearly 400 are now known. Most of these have been found by “radio echo sounding” (essentially radar), in which equipment on a survey aircraft emits radio pulses. </p>
<p>Part of the signal reflects back from the ice surface, but some is reflected from further below – especially strongly where there is a boundary between ice and underlying liquid water. Antarctica’s largest subglacial lake is Lake Vostok – which is 240km long, 50km wide and hundreds of metres deep – located 4km below the surface.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Radar image of Lake Vostok below the Antarctic ice." src="https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359439/original/file-20200922-20-1uzlet7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Radar satellite image revealing Lake Vostok below the Antarctic ice. The area shown is about 300km across.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Indications of similar lakes below the southern polar ice cap of Mars were <a href="https://theconversation.com/discovered-a-huge-liquid-water-lake-beneath-the-southern-pole-of-mars-100523">first suggested</a> by radar reflections 1.5km below the ice surface in a region named Ultimi Scopuli. These were detected between May 2012 and December 2015 by <a href="https://mars.nasa.gov/express/mission/sc_science_marsis01.html">MARSIS</a> (Mars Advanced Radar for Subsurface and Ionosphere Sounding), an instrument carried by the European Space Agency’s <a href="https://sci.esa.int/web/mars-express/">Mars Express</a> that has been orbiting the planet since 2003. </p>
<figure class="align-center ">
<img alt="Image of Ultimi Scopuli, a region of Mars’s south polar ice cap." src="https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359455/original/file-20200922-20-625wz7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A 4km wide area in Ultimi Scopuli: strange ice texture gives no clue as to presence of liquid water 1.5km below.</span>
<span class="attribution"><span class="source">NASA/JPL/University of Arizona</span></span>
</figcaption>
</figure>
<p>The new study of MARSIS data using signal processing techniques that take account of both the intensity and the sharpness (“acuity”) of the reflections has demonstrated that the previously detected region does indeed mark the top of a liquid body. This is the Ultimi Scopuli subglacial lake, and there seem also to be smaller patches of liquid nearby in the 250km by 300km area covered by the survey. The authors suggest that the liquid bodies consist of hypersaline solutions, in which high concentrations of salts are dissolved in water. </p>
<p>They point out that salts of calcium, magnesium, sodium and potassium are known to be ubiquitous in the martian soil, and that dissolved salts could help to explain how subglacial lakes on Mars can remain liquid despite the low temperature at the base of the ice cap. The weight of the overlying ice would supply the pressure necessary to keep the water in liquid state rather than turning to vapour.</p>
<h2>Life in subglacial lakes?</h2>
<p>Lake Vostok is touted as a <a href="https://theconversation.com/first-direct-evidence-of-microbial-life-under-1km-of-antarctic-ice-30695">possible habitat for life</a> that has been isolated from the Earth’s surface for millions of years, and as an analogue for proposed environments habitable by microbes (and possibly more complex organisms) in the internal oceans of icy moons such as Jupiter’s <a href="https://theconversation.com/new-water-plumes-from-jupiters-moon-europa-raise-hopes-of-detecting-microbial-life-66019">Europa</a> and Saturn’s <a href="https://theconversation.com/nasa-saturn-moon-enceladus-is-able-to-host-life-its-time-for-a-new-mission-76102">Enceladus</a>.</p>
<figure class="align-center ">
<img alt="The white ice cap at the south pole of Mars, seen from space." src="https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=343&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=343&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=343&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=431&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=431&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359858/original/file-20200924-25-kki0ri.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=431&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mars’s south polar ice cap as seen by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/centers/ames/multimedia/images/2005/marscap.html">NASA</a></span>
</figcaption>
</figure>
<p>Although hypersaline water would give microbes a place to live below Mars’ south polar cap, without an energy (food) source of some kind they could not survive. Chemical reactions between water and rock might release some energy but probably not enough; it would help if there was an occasional volcanic eruption, or at least hot spring, feeding into lake. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-on-earth-could-live-in-a-salt-water-lake-on-mars-an-expert-explains-101148">What on Earth could live in a salt water lake on Mars? An expert explains</a>
</strong>
</em>
</p>
<hr>
<p>We lack evidence of this on Mars, unlike on Europa and Enceladus. Although the new findings make Mars even more interesting than before, they haven’t advanced its ranking in the <a href="https://theconversation.com/water-water-everywhere-where-to-drink-in-the-solar-system-46153">list of solar system bodies</a> most likely to host life.</p>
<p>That said, the salty water could act as a <a href="https://theconversation.com/what-on-earth-could-live-in-a-salt-water-lake-on-mars-an-expert-explains-101148">preservation chamber</a> – helping us find alien organisms that are now extinct but once <a href="https://www.youtube.com/watch?time_continue=56&v=SIkvVQrOpMM&feature=emb_logo">came to Mars</a> from other parts of the solar system.</p><img src="https://counter.theconversation.com/content/146732/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Rothery is Professor of Planetary Geosciences at the Open University. He is co-leader of the European Space Agency's Mercury Surface and Composition Working Group, and a Co-Investigator on MIXS (Mercury Imaging X-ray Spectrometer) that is now on its way to Mercury on board the European Space Agency's Mercury orbiter BepiColombo. He has received funding from the UK Space Agency and the Science & Technology Facilities Council for work related to Mercury and BepiColombo, and is currently funded by the European Commission under its Horizon 2020 programme for work on planetary geological mapping (776276 Planmap). He is author of Planet Mercury - from Pale Pink Dot to Dynamic World (Springer, 2015), Moons: A Very Short Introduction (Oxford University Press, 2015) and Planets: A Very Short Introduction (Oxford University Press, 2010). He is Educator on the Open University's free learning Badged Open Course (BOC) on Moons and its equivalent FutureLearn Moons MOOC, and chair of the Open University's level 2 course on Planetary Science and the Search for Life.</span></em></p>New findings boost chances of finding life on Mars, but there are better candidates in the solar system.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1465332020-09-25T12:23:59Z2020-09-25T12:23:59ZAncient microbial life used arsenic to thrive in a world without oxygen<figure><img src="https://images.theconversation.com/files/359871/original/file-20200924-18-13kp7nk.jpg?ixlib=rb-1.1.0&rect=71%2C29%2C1374%2C727&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Purple microbial mats offer clues to how ancient life functioned. </span> <span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Billions of years ago, life on Earth was mostly just large slimy mats of microbes living in shallow water. Sometimes, these microbial communities made carbonate minerals that over many years cemented together to become <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/stromatolite">layered limestone rocks called stromatolites</a>. They are the oldest evidence of life on Earth. But the fossils don’t tell researchers the details of how they formed.</p>
<p>Today, most life is supported by oxygen. But these microbial mats existed for a billion years <a href="https://en.wikipedia.org/wiki/Great_Oxidation_Event">before oxygen was present in the atmosphere</a>. So what did life use instead? </p>
<p>Our team of <a href="https://scholar.google.com/citations?user=Ikl5sOsAAAAJ&hl=en&oi=sra">geologists</a>, <a href="https://scholar.google.com/citations?hl=en&user=dST-ijMAAAAJ">physicists</a> and <a href="https://scholar.google.com/citations?hl=en&user=Wx6rafEAAAAJ">biologists</a> had found hints in fossilized stromatolites that arsenic was the chemical of choice for ancient photosynthesis and respiration. But modern-day versions of these microbial communities still live on Earth today. Perhaps one of these used arsenic and could offer proof for our theory?</p>
<p>So we joined a surveying expedition of Chilean and Argentinian scientists to look for living stromatolites in the extreme conditions of the High Andes. In a small stream deep in the <a href="https://www.livescience.com/64752-atacama-desert.html">Atacama Desert</a>, we found a big surprise. The bottom of the channel was bright purple and made of stromatolite-building microbial mats that thrive in the complete absence of oxygen. Just as the clues we’d found in ancient fossils suggested, these mats use two different forms of arsenic to perform photosynthesis and respiration. Our discovery offers the strongest evidence yet for how the oldest life on Earth survived in a pre-oxygen world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing how arsenic can function in place of oxygen in photosynthesis and respiration." src="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359873/original/file-20200924-22-zzmnx4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Modern organisms make oxygen during photosynthesis and use it in respiration, but other elements, like arsenic, shown here as As, can work too.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Christophe Dupraz, Anthony Bouton, Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Turning sunlight into energy</h2>
<p>For the last 2.4 billion years, photosynthetic organisms like plants and <a href="https://ucmp.berkeley.edu/bacteria/cyanointro.html">blue-green cyanobacteria</a> have used sunlight, water and carbon dioxide to make oxygen and organic matter. In doing this, they turn energy from the Sun into energy to be used by life. Other organisms breathe in oxygen as they digest organic carbon, gaining energy for their respiration in the process.</p>
<p>Microbes in the ancient world also captured energy from sunlight, but their primitive machinery <a href="https://en.wikipedia.org/wiki/Oxygen_evolution">could not make oxygen from water</a> or use oxygen for respiration. They needed another chemical to do this.</p>
<p>From a biochemical perspective, there are only a few possible candidates: iron, sulfur, hydrogen or arsenic. A lack of evidence in the fossil record and minuscule amounts of some of these chemicals <a href="https://link.springer.com/referenceworkentry/10.1007%2F978-3-662-44185-5_1275">in the primordial soup</a> suggests neither iron, sulfur nor hydrogen would be likely candidates for the earliest form of photosynthesis. That leaves arsenic.</p>
<p>In 2014, our team found the first clue that stromatolites were produced by arsenic-assisted photosynthesis and respiration. We collected pieces of <a href="http://pilbara.mq.edu.au/wiki/Stromatolites">2.72-billion-year-old stromatolites</a> from the pre-oxygen world by drilling into an ancient reefs in <a href="https://www.abc.net.au/news/science/2017-05-10/early-life-on-land-in-3.5bn-year-old-hot-spring-in-pilbara/8497594">the Outback of Australia</a>. We then took these samples to France and cut them into thin slivers. <a href="https://www.synchrotron-soleil.fr/en/beamlines/nanoscopium">By measuring the X-rays that came off these samples when we bombarded them with photons</a>, we made a map of the chemical elements in the sample. If two kinds of arsenic are present in the map, then it is a sign that life was using arsenic for photosynthesis and respiration. In these relics of ancient life we found lots of both forms of arsenic, but not iron or sulfur.</p>
<p>This was tantalizing, but we wanted more proof: a modern analog to help prove our arsenic theory. No researchers had ever found a microbial mat community living in a place completely free of oxygen, but if we found one, it could help explain how the first stromatolites formed when our planet’s oceans and atmosphere were lacking oxygen.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Pieter Visscher using a field gear to measure the chemical make up of the purple microbial mats." src="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=468&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=468&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359872/original/file-20200924-17-z7a471.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=468&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Samples taken from the microbial mats had high levels of arsenic and lithium, but no oxygen.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">D’Angelo Duran</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Modern microbes, ancient analogs</h2>
<p>The Atacama Desert in Chile is the driest place on Earth, flanked by volcanoes and exposed to extremely high UV radiation. It’s not too different from how the Earth looked 3 billion years ago and not exactly supportive of life as we know it. Here – with the help of a team that spanned four continents and seven countries – we found what we were looking for. </p>
<p>Or destination was Laguna La Brava, a very salty shallow lake deep into the harsh desert. A shallow stream, fed by a volcanic groundwater spring, led into the lake. The streambed was a unique, deep purple color. The color came from a microbial mat, thriving quite happily in waters that contained unusually high amounts of arsenic, sulfur and lithium, but missing one important element – oxygen.</p>
<p>Could these slimy purple blobs offer answers to an ancient question?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A purple and brown clump of microbes sitting on a white background." src="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359874/original/file-20200924-14-117qz8m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A piece of the microbial mats living at the bottom of the oxygen-free stream.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We cut a piece of the mat and looked for evidence of minerals. A drop of acid made the minerals fizz – carbonates! – this microbe community was forming stromatolites. So our team went to work, camping out at the site for days at a time. </p>
<p>We measured the chemistry of the water and the mat with our field equipment during day and night, summer and winter. Not once did we find oxygen, and back in the laboratory we confirmed that sulfur and arsenic were abundant. Looking through the microscope, we saw purple photosynthetic bacteria, but oxygen-producing cyanobacteria were eerily absent. We had also collected DNA samples from the mat and found genes for arsenic metabolism. </p>
<p>In the lab, we mixed up microbes from the mat, added arsenic and exposed the mix to sunlight. Photosynthesis was happening. The microbes used both arsenic and sulfur, but preferred the arsenic. When we added a minuscule amount of organic matter, a different arsenic compound was used for respiration and preferred over sulfur.</p>
<p>[<em>You’re too busy to read everything. We get it. That’s why we’ve got a weekly newsletter.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybusy">Sign up for good Sunday reading.</a> ]</p>
<p>All that was left was to show that the two types of arsenic could be detected in the modern stromatolites. We went back to France, and using an X-ray emission technique made chemical maps from the Chilean samples. Every experiment we performed supported the <a href="https://doi.org/10.1038/s43247-020-00025-2">presence of a vigorous arsenic cycle</a> in the absence of oxygen in this unique modern stromatolite. This validates, beyond doubt, the idea that the fossil Australian samples that we studied in 2014 held evidence of an active arsenic cycle in deep time on our young planet. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The large lake of Laguna La Brava with active volcanoes behind at sunset." src="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359875/original/file-20200924-16-s5sknw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Laguna La Brava is closer to the Martian environment than most places on Earth.</span>
<span class="attribution"><a class="source" href="https://marinesciences.uconn.edu/person/pieter-visscher/">Pieter Visscher</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Answers on Earth, leads for Mars</h2>
<p>The harsh conditions of the Atacama are so similar to Martian and early Earth environments that <a href="https://www.sciencealert.com/life-rebounds-after-eternity-without-water-earth-s-driest-places-atacama-desert-microbes-mars">NASA scientists and astrobiologists turn to the Atacama</a> to answer questions about how life began on our planet, and how it might start elsewhere. The arsenic-cycling mats we discovered at Laguna La Brava offer strong clues to some of the most fundamental questions about life.</p>
<p>On board the Mars 2020 Perseverance rover that is currently hurtling through space is an instrument that can observe elements using the <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/pixl/">exact same process we used to make our element maps</a>. Perhaps it will discover that arsenic is abundant in layered rocks on Mars, suggesting that life on Mars also used arsenic. For over a billion years, it did so on Earth. Under the harshest conditions life finds a way, and it is that way <a href="https://doi.org/10.1038/s43247-020-00025-2">we are trying to understand</a>.</p><img src="https://counter.theconversation.com/content/146533/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pieter Visscher receives funding from the National Science Foundation, NASA Exobiology (USA), UBFC-ISITE program (France)</span></em></p><p class="fine-print"><em><span>Brendan Paul Burns and Kimberley L. Gallagher do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>How ancient microbes survived in a world without oxygen has been a mystery. Scientists discovered a living microbial mat that uses arsenic instead of oxygen for photosynthesis and respiration.Pieter Visscher, Professor of Marine Sciences, University of ConnecticutBrendan Paul Burns, Senior Lecturer, UNSW SydneyKimberley L. Gallagher, Adjunct Professor of Chemistry, Quinnipiac UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1461852020-09-18T12:07:59Z2020-09-18T12:07:59ZThe detection of phosphine in Venus’ clouds is a big deal – here’s how we can find out if it’s a sign of life<figure><img src="https://images.theconversation.com/files/358693/original/file-20200917-16-6y1m7g.png?ixlib=rb-1.1.0&rect=93%2C1%2C1005%2C671&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A radar mosaic image of Venus.</span> <span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/stellar_items/image_files/3_feature_1600x900_venus.jpg">NASA.gov</a></span></figcaption></figure><p>On Sept. 14, 2020, a new planet was added to the list of potentially habitable worlds in the Solar System: Venus. </p>
<p><a href="https://en.wikipedia.org/wiki/Phosphine">Phosphine</a>, a toxic gas made up of one phosphorus and three hydrogen atoms (PH₃), <a href="https://news.mit.edu/2019/phosphine-aliens-stink-1218">commonly produced by organic life forms</a> but otherwise difficult to make on rocky planets, <a href="https://doi.org/10.1038/s41550-020-1174-4">was discovered in the middle layer of the Venus atmosphere.</a> This raises the tantalizing possibility that something is alive on our planetary neighbor. With this discovery, Venus joins the exalted ranks of Mars and the icy moons Enceladus and Europa among planetary bodies where life may once have existed, or perhaps might even still do so today.</p>
<p>I’m a planetary scientist and something of a <a href="https://twitter.com/ThePlanetaryGuy/status/1306052714074443776?s=20">Venus evangelical</a>. This discovery is one of the most exciting made about Venus in a very long time — and opens up a new set of possibilities for further exploration in search of life in the Solar System. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Venus as seen in the infrared by the Japanese Akatsuki spacecraft. The warm colors are from the hot lower atmosphere glowing through the cooler cloud layers above. Image credit: JAXA/ISAS/DARTS/Damia Bouic.</span>
<span class="attribution"><a class="source" href="https://planetary.s3.amazonaws.com/web/assets/pictures/20180113_ir2_20160927_090331_226_l2b_v10_PRGB.jpg">JAXA/ISAS/DARTS/Damia Bouic</a></span>
</figcaption>
</figure>
<h2>Atmospheric mysteries</h2>
<p>First, it’s critical to point out that this detection does not mean that astronomers have found alien life in the clouds of Venus. Far from it, in fact. </p>
<p>Although the discovery team identified phosphine at Venus <a href="https://alma-telescope.jp/en/news/press/venus-202009">with two different telescopes</a>, helping to confirm the initial detection, phosphine gas can result from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity. </p>
<p>However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than those processes are capable of generating, allowing the team to <a href="http://astrobiology.com/2020/09/phosphine-on-venus-cannot-be-explained-by-conventional-processes.html">rule out</a> numerous inorganic possibilities. But our understanding of the chemistry of Venus’ atmosphere is sorely lacking: Only a handful of missions have plunged through the inhospitable, <a href="https://solarsystem.nasa.gov/planets/venus/overview/">carbon dioxide-dominated atmosphere</a> to take samples among the global layer of <a href="https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Acid_clouds_and_lightning">sulfuric acid clouds</a>.</p>
<p>So we planetary scientists are faced with two possibilities: Either there is some sort of life in the Venus clouds, generating phosphine, or there is unexplained and unexpected chemistry taking place there. How do we find out which it is?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A model of the Soviet Vega 1 spacecraft at the Udvar-Hazy Center, Dulles International Airport. Vega 1 carried a balloon to Venus on its way to visit Halley’s Comet in 1985.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/5/52/Vega_model_-_Udvar-Hazy_Center.JPG">Daderot</a></span>
</figcaption>
</figure>
<p>First and foremost, we need more information about the abundance of PH₃ in the Venus atmosphere, and we can learn something about this from Earth. Just as the discovery team did, existing telescopes capable of detecting phosphine around Venus can be used for follow-up observations, to both definitively confirm the initial finding and figure out if the amount of PH₃ in the atmosphere changes with time. In parallel, there is now a huge opportunity to carry out lab work to better understand the types of chemical reactions that might be possible on Venus — for which we have <a href="https://twitter.com/PlanetDr/status/1306308300397596672?s=20">very limited information</a> at present.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antennas of the Atacama Large Millimeter/submillimeter Array telescope, on the Chajnantor Plateau in the Chilean Andes. The telescope was used to confirm the initial detection of phosphine in Venus’ atmosphere.</span>
<span class="attribution"><a class="source" href="https://cdn.eso.org/images/screen/ann13016a.jpg">ESO/C. Malin.</a></span>
</figcaption>
</figure>
<h2>Once more unto the breach</h2>
<p>But measurements on and from Earth can take us only so far. To really get to the heart of this mystery, <a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">we need to go back to Venus</a>. Spacecraft equipped with spectrometers that can detect phosphine from orbit could be dispatched to the second planet with the express purpose of characterizing where, and how much, of this gas is there. Because spacecraft <a href="https://en.wikipedia.org/wiki/Pioneer_Venus_Orbiter">can survive for many years in Venus’ orbit</a>, we could obtain continuous observations with a dedicated orbiter over a much longer period than with telescopes on Earth.</p>
<p>But even orbital data can’t tell us the whole story. To fully get a handle on what’s happening at Venus, we have to actually get into the atmosphere. <a href="https://solarsystem.nasa.gov/resources/2197/aerial-platforms-for-the-scientific-exploration-of-venus/">And that’s where aerial platforms come in</a>. Capable of operating above much of the acidic cloud layer – where the temperature and pressure are almost Earthlike – for potentially months at a time, balloons or <a href="https://www.northropgrumman.com/vamp/">flying wings</a> could take detailed atmospheric composition measurements there. These craft could even carry the kinds of instruments <a href="https://www.lpi.usra.edu/opag/meetings/apr2019/presentations/Schulte.pdf">being developed to look for life on Europa</a>. At that point, humanity might finally be able to definitively tell if we share our Solar System with Venusian life.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1827&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1827&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1827&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=2296&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=2296&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=2296&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A concept for an aerial platform at Venus. Two connected balloons could take turns to inflate, allowing the balloon to control the altitude at which it floats. An instrument package would then hang from below the balloons.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/resources/detail_files/2197_Venus_Aerial_Platforms_Final_Report_Summary_Report_10_25_2018-1.jpg">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>A new dawn for Venus exploration?</h2>
<p>Thirty-one years have elapsed since the United States last sent a dedicated mission to Venus. That could soon change as NASA considers two of four missions in the late 2020s targeting Venus. One, called <a href="https://science.jpl.nasa.gov/projects/VERITAS/">VERITAS</a>, would carry a powerful radar to peer through the thick clouds and return unprecedented high-resolution images of the surface. The other, <a href="https://www.nasa.gov/feature/goddard/2020/nasa-goddard-team-selected-to-design-concept-for-probe-of-mysterious-venus-atmosphere">DAVINCI+</a>, would plunge through the atmosphere, sampling the air as it descended, perhaps even able to sniff any phosphine present. NASA plans to pick at least one mission in April 2021.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p><a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">I have argued before for a return to Venus</a>, and will continue to do so. Even without this latest scientific discovery, Venus is a compelling exploration target, with tantalizing evidence that the planet <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">once had oceans</a> and perhaps even suffered a hellish fate at the hands of <a href="https://eos.org/research-spotlights/how-long-was-venus-habitable">its own volcanic eruptions</a>. </p>
<p>But with the detection of a <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2018.1954?journalCode=ast">potential biomarker</a> in Venus’ atmosphere, we now have yet another major reason to return to the world ancient Greek astronomers called Phosphorus — a name for Venus that, it turns out, is wonderfully prescient.</p><img src="https://counter.theconversation.com/content/146185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul K. Byrne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>News that Venus may harbor life has swept the globe. So how do we find out for sure? A planetary scientist explains what’s next.Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1460932020-09-14T19:50:32Z2020-09-14T19:50:32ZLife on Venus? Traces of phosphine may be a sign of biological activity<figure><img src="https://images.theconversation.com/files/357810/original/file-20200914-14-hd6f47.jpg?ixlib=rb-1.1.0&rect=6%2C18%2C1376%2C1364&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">JAXA / ISAS / DARTS / Damia Bouic</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The discovery that the atmosphere of Venus absorbs a precise frequency of microwave radiation has just <a href="https://doi.org/10.1038/s41550-020-1174-4">turned planetary science on its head</a>. An international team of scientists used radio telescopes in Hawaii and Chile to find signs that the clouds on Earth’s neighbouring planet contain tiny quantities of a molecule called phosphine.</p>
<p>Phosphine is a compound made from phosphorus and hydrogen, and on Earth its only natural source is tiny microbes that live in oxygen-free environments. It’s too early to say whether phosphine is also a sign of life on Venus – but no other explanation so far proposed seems to fit. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ePoDG00VydE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows how methane was detected in the atmosphere of Mars. The process is the same for finding phosphine on Venus.</span></figcaption>
</figure>
<h2>What makes an atmosphere?</h2>
<p>The molecular makeup of a planet’s atmosphere normally depends on what its parent star is made of, the planet’s position in its star’s system, and the chemical and geological processes that take place given these conditions. </p>
<p>There is phosphine in the atmospheres of Jupiter and Saturn, for example, but there it’s not a sign of life. Scientists think it is formed in the deep atmosphere at high pressures and temperatures, then dredged into the upper atmosphere by a strong convection current. </p>
<p>Although phosphine quickly breaks down into phosphorus and hydrogen in the top clouds of these planets, enough lingers – 4.8 parts per million – to be observable. The phosphorus may be what gives clouds on Jupiter a reddish tinge.</p>
<p>Things are different on a rocky planet like Venus. The new research has found fainter traces of phosphine in the atmosphere, at 20 parts per billion. </p>
<p>Lightning, clouds, volcanoes and meteorite impacts might all produce some phosphine, but not enough to counter the rapid destruction of the compound in Venus’s highly oxidising atmosphere. The researchers considered all the chemical processes they could think of on Venus, but none could explain the concentration of phosphine. What’s left? </p>
<p>On Earth, phosphine is only produced by microbial life (and by various industrial processes) – and the concentration in our atmosphere is in the parts per trillion range. The much higher concentration on Venus cannot be ignored. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-asked-astronomers-are-we-alone-in-the-universe-the-answer-was-surprisingly-consistent-132088">We asked astronomers: are we alone in the Universe? The answer was surprisingly consistent</a>
</strong>
</em>
</p>
<hr>
<h2>Signs of life?</h2>
<p>To determine whether the phosphine on Venus is really produced by life, chemists and geologists will be trying to identify other reactions and processes that could be alternative explanations. </p>
<p>Meanwhile, biologists will be trying to better understand the microbes that live in Venus-like conditions on Earth – high temperatures, high acidity, and high levels of carbon dioxide – and also ones that produce phosphine. </p>
<p>When Earth microbes produce phosphine, they do it via an “anaerobic” process, which means it happens where no oxygen is present. It has been observed in places such as activated sludge and sewage treatment plants, but the exact collection of microbes and processes is not well understood. </p>
<p>Biologists will also be trying to work out whether the microbes on Earth that produce phosphine could conceivably do it under the harsh Venusian conditions. If there is some biological process producing phosphine on Venus, it may be a form of “life” very different from what we know on Earth.</p>
<p>Searches for life beyond Earth have often skipped over Venus, because its surface temperature is around 500°C and the atmospheric pressure is almost 100 times greater than on Earth. Conditions are <a href="https://www.liebertpub.com/doi/10.1089/ast.2017.1783">more hospitable for life</a> as we know it about 50 kilometres off the ground, although there are still vast clouds of sulfuric acid to deal with.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-idea-of-alien-life-now-seems-inevitable-and-possibly-imminent-115643">Why the idea of alien life now seems inevitable and possibly imminent</a>
</strong>
</em>
</p>
<hr>
<h2>Molecular barcodes</h2>
<p>The researchers found the phosphine using spectroscopy, which is the study of how light interacts with molecules. When sunlight passes through Venus’s atmosphere, each molecule absorbs very specific colours of this light. </p>
<p>Using telescopes on Earth, we can take this light and split it into a massive rainbow. Each type of molecule present in Venus’ atmosphere produces a distinctive pattern of dark absorption lines in this rainbow, like an identifying barcode. </p>
<figure class="align-center ">
<img alt="A rainbow image of stripes fading from red through the visible spectrum to blue, with narrow black lines." src="https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The full visible spectrum of sunlight, showing the dark ‘barcodes’ that indicate the presence of different atoms and molecules.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/390/the-solar-spectrum/">N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF</a></span>
</figcaption>
</figure>
<p>This barcode is not always strongest in visible light. Sometimes it can only be detected in the parts of the electromagnetic spectrum that are invisible to the human eye, such as UV rays, microwave, radio waves and infrared. </p>
<p>The barcode of carbon dioxide, for example, is most evident in the infrared region of the spectrum. </p>
<p>While phosphine on Jupiter was first detected in infrared, for Venus observations astronomers used radio telescopes: the <a href="https://www.almaobservatory.org/en/home/">Atacama Large Millimeter/submillimeter Array</a> (ALMA) and <a href="https://www.eaobservatory.org/jcmt/about-jcmt/">James Clerk Maxwell Telescope</a> (JCMT), which can detect the barcode of phosphine in millimetre wavelengths.</p>
<h2>New barcodes, new discoveries</h2>
<p>The discovery of phosphine on Venus relied not only on new observations, but also a more detailed knowledge of the compound’s barcode. Accurately predicting the barcode of phosphine across all relevant frequencies took <a href="http://www.tampa.phys.ucl.ac.uk/ftp/eThesis/ClaraSousaSilva2015.pdf">the whole PhD</a> of astrochemist Clara Sousa-Silva in the <a href="https://www.ucl.ac.uk/exoplanets/research/spectroscopy-exoplanets">ExoMol group</a> at University College London in 2015. </p>
<p>She used computational quantum chemistry – basically putting her molecule into a computer and solving the equations that describe its behaviour – to predict the strength of the barcode at different colours. She then tuned her model using available experimental data before making the <a href="https://arxiv.org/abs/1410.2917">16.8 billion lines of phosphine’s barcode</a> available to astronomers. </p>
<p>Sousa-Silva originally thought her data would be used to study Jupiter and Saturn, as well as weird stars and distant “hot Jupiter” exoplanets. </p>
<p>More recently, she led the detailed consideration of <a href="https://arxiv.org/abs/1910.05224">phosphine as a biosignature</a> – a molecule whose presence implies life. This analysis demonstrated that, on small rocky exoplanets, phosphine should not be present in observable concentrations unless there was life there as well. </p>
<p>But she no doubt wouldn’t have dreamed of a phone call from an astronomer who has discovered phosphine on our nearest planetary neighbour. With phosphine on Venus, we won’t be limited to speculating and looking for molecular barcodes. We will be able to send probes there and hunt for the microbes directly.</p><img src="https://counter.theconversation.com/content/146093/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The discovery of phosphine in the acidic clouds of Venus can’t be explained by any known chemical or geological processes.Laura McKemmish, Lecturer, UNSW SydneyBrendan Paul Burns, Senior Lecturer, UNSW SydneyLucyna Kedziora-Chudczer, Program Manager / Adjunct Research Fellow, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1294192020-01-10T15:21:37Z2020-01-10T15:21:37ZCould invisible aliens really exist among us? An astrobiologist explains<figure><img src="https://images.theconversation.com/files/309424/original/file-20200110-97140-1rwkigh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">They probably won't look anything like this.</span> <span class="attribution"><span class="source">Martina Badini/Shutterstock</span></span></figcaption></figure><p>Life is pretty easy to recognise. It moves, it grows, it eats, it excretes, it reproduces. Simple. In biology, researchers often use the acronym “<a href="https://basicbiology.net/biology-101/mrs-gren">MRSGREN</a>” to describe it. It stands for movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. </p>
<p>But <a href="https://www.imperial.ac.uk/news/168110/former-astronaut-helen-sharman-finds-space/">Helen Sharman</a>, Britain’s first astronaut and a chemist at Imperial College London, recently said that alien lifeforms that are impossible to spot <a href="https://www.theguardian.com/lifeandstyle/2020/jan/05/astronaut-helen-sharman-this-much-i-know">may be living among us</a>. How could that be possible?</p>
<p>While life may be easy to recognise, it’s actually notoriously difficult to define and has had scientists and philosophers in debate for centuries – if not millennia. For example, a 3D printer can reproduce itself, but we wouldn’t call it alive. On the other hand, a mule is famously sterile, but we would never say it doesn’t live.</p>
<p>As nobody can agree, there are more than <a href="http://www.bbc.com/earth/story/20170101-there-are-over-100-definitions-for-life-and-all-are-wrong">100 definitions</a> of what life is. An alternative <a href="https://www.sfu.ca/colloquium/PDC_Top/OoL/whatislife/Vikingmission.html">(but imperfect) approach</a> is describing life as “a self-sustaining chemical system capable of Darwinian evolution”, which works for many cases we want to describe.</p>
<p>The lack of definition is a huge problem when it comes to searching for life in space. Not being able to define life other than “we’ll know it when we see it” means we are truly limiting ourselves to geocentric, possibly even anthropocentric, ideas of what life looks like. When we think about aliens, we often picture a humanoid creature. But the <a href="https://www.seti.org/about-us/mission">intelligent life</a> we are searching for <a href="https://theconversation.com/alien-life-is-out-there-but-our-theories-are-probably-steering-us-away-from-it-124042">doesn’t have to be humanoid</a>. </p>
<h2>Life, but not as we know it</h2>
<p>Sharman says she believes aliens exist and “there’s no two ways about it”. Furthermore, <a href="https://www.theguardian.com/lifeandstyle/2020/jan/05/astronaut-helen-sharman-this-much-i-know">she wonders</a>: “Will they be like you and me, made up of carbon and nitrogen? Maybe not. It’s possible they’re here right now and we simply can’t see them.”</p>
<p>Such life would exist in a “<a href="https://www.astrobio.net/retrospections/a-shadow-biosphere/">shadow biosphere</a>”. By that, I don’t mean a ghost realm, but undiscovered creatures probably with a different biochemistry. This means we can’t study or even notice them because they are outside of our comprehension. Assuming it exists, such a shadow biosphere would probably be microscopic. </p>
<p>So why haven’t we found it? We have limited ways of studying the microscopic world as only a small percentage of microbes can be cultured in a lab. This may mean that there could indeed be many lifeforms we haven’t yet spotted. We do now have the ability to sequence the DNA of unculturable strains of microbes, but this can only detect life as we know it – that contain DNA.</p>
<p>If we find such a biosphere, however, it is unclear whether we should call it alien. That depends on whether we mean “of extraterrestrial origin” or simply “unfamiliar”.</p>
<h2>Silicon-based life</h2>
<p>A popular suggestion for an alternative biochemistry is one based on silicon rather than carbon. It makes sense, even from a geocentric point of view. Around 90% of the Earth is made up of silicon, iron, magnesium and oxygen, which means there’s lots to go around for building potential life.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/309425/original/file-20200110-97149-1c3ngac.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of a silicon-based life form.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/inorganic-mycelium-life-parallel-world-silicon-1215536761">Zita</a></span>
</figcaption>
</figure>
<p>Silicon is <a href="https://www.teachastronomy.com/textbook/Life-On-Earth/Silicon-versus-Carbon/">similar to carbon</a>, it has four electrons available for creating bonds with other atoms. But silicon is heavier, with 14 protons (protons make up the atomic nucleus with neutrons) compared to the six in the carbon nucleus. While carbon can create strong double and triple bonds to form long chains useful for many functions, such as building cell walls, it is much harder for silicon. It struggles to create strong bonds, so long-chain molecules are much less stable. </p>
<p>What’s more, common silicon compounds, such as silicon dioxide (or silica), are generally solid at terrestrial temperatures and insoluble in water. Compare this to highly soluble carbon dioxide, for example, and we see that carbon is more flexible and provides many more molecular possibilities.</p>
<p>Life on Earth is fundamentally different from the bulk composition of the Earth. Another argument against a silicon-based shadow biosphere is that too much silicon is locked up in rocks. In fact, the chemical composition of life on Earth has an approximate correlation with the chemical composition of the sun, with 98% of atoms in biology consisting of hydrogen, oxygen and carbon. So if there were viable silicon lifeforms here, they may have evolved elsewhere.</p>
<p>That said, there are arguments in favour of silicon-based life on Earth. Nature is adaptable. A few years ago, scientists at Caltech managed to breed a bacterial protein that created bonds with silicon – essentially <a href="http://astrobio.net/news-exclusive/possibility-silicon-based-life-grows/">bringing silicon to life</a>. So even though silicon is inflexible compared with carbon, it could perhaps find ways to assemble into living organisms, potentially including carbon.</p>
<p>And when it comes to other places in space, such as Saturn’s moon <a href="https://theconversation.com/saturns-moon-titan-may-harbour-simple-life-forms-and-reveal-how-organisms-first-formed-on-earth-81527">Titan</a> or planets orbiting other stars, we certainly can’t rule out the possibility of silicon-based life.</p>
<p>To find it, we have to somehow think outside of the terrestrial biology box and figure out ways of recognising lifeforms that are fundamentally different from the carbon-based form. There are plenty of experiments testing out these alternative biochemistries, such as the one from Caltech. </p>
<p>Regardless of the belief held by many that life exists elsewhere in the universe, we have no evidence for that. So it is important to consider all life as precious, no matter its size, quantity or location. The Earth <a href="https://theconversation.com/climate-explained-what-each-of-us-can-do-to-reduce-our-carbon-footprint-123851">supports</a> the only known life in the universe. So no matter what form life elsewhere in the solar system or universe may take, we have to make sure we protect it from harmful contamination – whether it is terrestrial life or alien lifeforms.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/elon-musks-starship-may-be-more-moral-catastrophe-than-bold-step-in-space-exploration-124450">Elon Musk’s Starship may be more moral catastrophe than bold step in space exploration</a>
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<p>So could aliens be among us? I don’t believe that we have been visited by a life form with the technology to travel across the vast distances of space. But we do have evidence for life-forming, carbon-based molecules having arrived on Earth on <a href="https://theconversation.com/did-comets-kick-start-life-on-earth-chemists-find-missing-piece-of-puzzle-57369">meteorites</a>, so the evidence certainly doesn’t rule out the same possibility for more unfamiliar life forms.</p><img src="https://counter.theconversation.com/content/129419/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samantha Rolfe does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Earth may be crawling with undiscovered creatures with a different biochemistry to life as we know it.Samantha Rolfe, Lecturer in Astrobiology and Principal Technical Officer at Bayfordbury Observatory, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1203342019-07-15T19:41:39Z2019-07-15T19:41:39ZCurious Kids: can people live in space?<figure><img src="https://images.theconversation.com/files/284012/original/file-20190714-173376-1dokasd.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4256%2C2803&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People do live outside Earth – on the International Space Station! But humans have had to find a way to make the conditions there more like what we’re used to at home.
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasamarshall/4546245011/in/photolist-7VJGfF-fnfXki-qidpLg-cQ4xgm-QFJZnr-eCNmV7-eMrbRX-RzmRGN-2aRYg19-qMprds-23YVfdZ-eAoEY9-fppfqr-USqpb5-TDyYaB-UUeTAo-BNNHi9-5XvyCU-TjCQCK-4QGxZ3-5HtSZ6-UT9d6s-93e8zz-LgAp9o-eAkuqt-dCgq6q-591ALd-rn1Ffx-TtP2JP-Q3bxeP-dTbik6-77KW8j-9pa7R9-dWfxVJ-3baA-NARDGE-bfry6c-cCTs3j-nbMFb1-28Z35yZ-56zpvR-SsjkLu-NJnPqo-5D6PN6-e9MSUr-RG1NCz-dwGjKv-naFfE3-7dikES-DJhqxZ">Flickr/NASA's Marshall Space Flight Center</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Can people live outside Earth? – Holly, age 7, Toowoomba.</strong></p>
</blockquote>
<hr>
<p>That’s a great question, Holly. The short answer is yes, but it’s really, really difficult.</p>
<p>Humans are great at living in tough places. Even before we developed modern technology, we had spread out to live in all of Earth’s continents – from the really cold areas in North America, Europe and Asia, to the hottest parts of Australia. But there are still lots of places on Earth humans can’t normally survive – like underneath the ocean, or at the South Pole.</p>
<p>Those places are dangerous – without protection, you would die in seconds or minutes. But, thanks to modern technology, we’ve worked out how to live there. People can live for months at a time under the oceans, or down at the icy South Pole. </p>
<p>How do they manage it? Well, they find a way to make the conditions there more like what we’re used to at home.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-is-the-sun-orange-when-white-stars-are-the-hottest-120216">Curious Kids: why is the Sun orange when white stars are the hottest?</a>
</strong>
</em>
</p>
<hr>
<p>To live underwater, people build submarines. They’re warm and dry inside – perfect conditions for people to live in. People take food, oxygen and water with them into submarines, and use electricity to power lights and heaters. In other words, they change a cold, dark and dangerous place (deep beneath the ocean) into something like a home.</p>
<p>We do the same at the South Pole. We build special buildings, and dig tunnels, and make them warm and dry. The people who live there take food and water with them, and there’s extra heating so people don’t freeze in the Antarctic winds and ice.</p>
<p>But you can’t live in these cold, dark places forever. Humans don’t cope well if they don’t get enough sunlight, so they do need to get back to “normal life” after a while. And it’s really expensive to bring all the food, water, air and energy to these places.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/283979/original/file-20190714-173355-17gdet5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People live at the Amundsen-Scott South Pole Station all year around - even during the six month long Antarctic night!</span>
<span class="attribution"><span class="source">Mradyfist at English Wikipedia</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-plants-could-grow-in-the-goldilocks-zone-of-space-76918">Curious Kids: What plants could grow in the Goldilocks zone of space?</a>
</strong>
</em>
</p>
<hr>
<h2>Life in space</h2>
<p>Space is very dangerous – and without protection, people would not be able to survive there. In space, there’s no air – so you couldn’t breathe. It’s cold – so you’d freeze. And there’s lots of nasty radiation (from the Sun, and from the rest of the Universe), so you’d get really, really bad sunburn. But despite all that, we have people living in space all the time!</p>
<p>There’s this amazing place orbiting the Earth called the International Space Station – and there are people who live there, all day, every day. You can sometimes even see it from your back yard, on a clear night!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284014/original/file-20190715-173360-e2rsyh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">That white line is the International Space Station passing overhead. This picture was taken using a photographer’s trick called ‘long exposure’ which makes the space station show up as a white line in the night sky.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/atbaker/7932888640/in/photolist-d618q5-2fAKJNv-qr1yCz-huATMM-q8egXH-V8beBq-6UuDmQ-95WKej-9pzSDn-ShHRup-bAc1Qv-9aTExb-7eo7Jo-bmiANe-2dveumo-bmtjYS-nDTTLH-ftL8gm-dkegkp-ogmfdt-oqQtKu-aBP3J4-9fn3ab-7VJGfF-qidpLg-8zmcuA-7vp7d1-cQ4xgm-dbA8EN-kCmUA8-ebXpJb-b4mf3x-ejnPj2-fyGDUA-ogHV6Q-8dquHT-nUktq9-9cRJNU-e89jGp-odRdNH-eR5YnB-dTbik6-77KW8j-jbBnNb-9pa7R9-3baA-NARDGE-bfry6c-cCTs3j-dfNgCw">Flickr/Adam Baker</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=481&fit=crop&dpr=1 754w, https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=481&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/283977/original/file-20190714-173342-1h9chec.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=481&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This is what the International Space Station looks like, close up.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:International_Space_Station_after_undocking_of_STS-132.jpg">NASA/Crew of STS-132 [Public domain]</a></span>
</figcaption>
</figure>
<p>The space station is like a submarine built especially for space. A giant tin can, filled with air, and kept nice and warm – not too hot, and not too cold. It protects the astronauts from the cold of space, gives them air to breathe, and protects them from all that nasty radiation. We send up regular shipments of food and drink – everything they need to survive.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284010/original/file-20190714-173334-1khrm6o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Here’s an astronaut on a space walk outside the International Space Station.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasamarshall/10964570005/in/photolist-hGUhEr-b3Mqy2-dTY2Kz-8aE4iy-eaHfPn-7Vgz8v-doRZct-6JpCJn-ehT8Yu-aMeHai-osq6Bz-obm6mJ-mh6bRX-duZzwh-er2DTN-cydn2j-k22WqN-fZieCr-8ANQgx-9VipVu-8zRDxu-i9SuEK-a1Vbxu-kyqeFi-higDYa-nHg8Q5-gE167S-ogup12-Lt2no8-6PpwUE-7FHpsL-9hmzCa-Yvd4oZ-7YkUXQ-qndcGF-9oYa8K-fBQZfn-aFeh9K-WSf3An-fNWQTQ-9bAN7N-8EvcNt-biScG4-kASrb8-eadNr2-8F6JgF-nBXuN5-6Fwtn2-b9b9yB-816Wau">NASA's Marshall Space Flight Center</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In other words – we’ve found a way to let people live outside Earth, and we do it by making the place we want to live just like home. Again, though, it’s not safe for people to live their forever, and <a href="https://theconversation.com/curious-kids-do-astronauts-get-space-sick-when-they-travel-from-earth-to-the-international-space-station-82888">being in space for a long time isn’t good for your body</a>.</p>
<p>If people ever get to live on Mars, or on the Moon – or other places in the Solar system (and beyond) – it will be because we have found a way to make those places nice, safe and a bit more like home.</p>
<p>Whilst living on the Moon or Mars sounds like science fiction, people are talking seriously about doing just that in the future. It would be very dangerous, and really expensive. But who knows what the future holds?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-astronauts-get-space-sick-when-they-travel-from-earth-to-the-international-space-station-82888">Curious Kids: Do astronauts get space sick when they travel from Earth to the International Space Station?</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
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<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em> <em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/120334/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonti Horner does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The short answer is yes, but it’s really, really difficult.Jonti Horner, Professor (Astrophysics), University of Southern QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1094372019-01-13T09:22:03Z2019-01-13T09:22:03ZSpace subjects that will get the world’s attention in 2019 - and beyond<figure><img src="https://images.theconversation.com/files/252808/original/file-20190108-32121-14h86ms.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scale models of rockets at China Aerospace Science and Technology Corporation's booth at the International Astronautical Congress.</span> <span class="attribution"><span class="source">FOCKE STRANGMANN/EPA</span></span></figcaption></figure><p>The first few days of 2019 brought remarkable news from outer space. On January 1 NASA’s New Horizons space probe made the most distant planetary flyby ever, and <a href="https://www.wired.com/story/new-horizons-first-photos-ultima-thule/">captured images</a> of a small object 4 billion miles away from earth. The following day, China landed its Chang'e 4 rover, named Jade Rabbit 2, on the <a href="https://theconversation.com/china-lands-on-the-far-side-of-moon-here-is-the-science-behind-the-mission-108566">far side of the moon</a> – another first.</p>
<p>This suggests that 2019 will be a big year for all things related to space; a suggestion borne out by developments at the International Astronautical Federation’s <a href="http://www.iafastro.org/events/iac/">International Astronautical Congress</a> which I attended. The event is held each year during the first week of October to commemorate the launch of Sputnik on 4 October 1957, which started the space age.</p>
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Read more:
<a href="https://theconversation.com/sixty-years-after-sputnik-taking-stock-and-looking-to-the-future-85017">Sixty years after Sputnik: taking stock and looking to the future</a>
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<p>The 2018 congress was held in Bremen, Germany, and attended by the world’s space agencies, private space companies, engineers, and spaceflight fans. In the past decade, a number of interesting trends have emerged at this congress. </p>
<p>These include which countries are emerging as space powers; what topics get people talking; and what concerns experts have about humanity’s ongoing attempts to become a “multi-planet species” that can live on other planets.</p>
<p>Here are the <a href="http://www.summerschool.uct.ac.za/spaceflight_past_present_future">space subjects</a> that are likely to capture the world’s attention in the coming years.</p>
<h2>Wider reach, new players</h2>
<p>First, it’s clear from attendance figures at the congress that the space industry and countries’ interest in all matters inter-planetary is growing. About 2000 people attended the 2011 congress in Cape Town, South Africa; there were more than 6000 delegates at the 2018 event.</p>
<p>Second, the proportion of delegates and presenters who are women has increased significantly. Women now comprise about one-fifth of all who attend, reflecting their breakthrough into the engineering disciplines.</p>
<p>Third, Chinese researchers are prominent in their numbers compared to a decade ago. These are not only from China’s national space agency. They also come from private Chinese space companies that are offering to launch satellites. The Chang'e launch and landing is an indication, too, that China is now among the leading space powers.</p>
<p>Interestingly, the United Arab Emirates’ space agency’s 2018 exhibition stand was bigger than that of the USA’s NASA. This suggests that oil-rich Middle Eastern states today show space growth and interest.</p>
<h2>Hot topics</h2>
<p>There were a number of hot topics up for discussion at the congress. These included space tourism – panels on the subject were well attended. Part of the attraction is probably simply that Elon Musk is an expert at grabbing headlines. His <a href="https://www.spacex.com/">company website</a> includes paintings of a future Martian town. But he’s not the only one pushing for humans to travel in space; Jeff Bezos’ <a href="https://www.blueorigin.com/">Blue Origin</a> is also a major player.</p>
<p>Musk takes things a step further by suggesting that humans will, in the next decades, start living on other planets. He <a href="https://www.businessinsider.com/elon-musk-spacex-mars-plan-timeline-2018-10?IR=T">advocates that</a>, at 26 month intervals, 100 000 people should emigrate to Mars and construct pressurised towns on that planet.</p>
<p>His hope is that they will fly to Mars on SpaceX’s proposed Big Falcon Rocket. Building a fleet of such rockets will certainly provide plenty of business for his company. It won’t be cheap transport: Musk <a href="https://bigthink.com/technology-innovation/elon-musk-cost-spacex-ticket">plans</a> to offer tickets at around US$200 000 each. </p>
<p>Another perennial topic, <a href="https://www.astrobio.net/">astrobiology</a> – finding life on another planet – was also on the agenda. This idea comes with many potential pitfalls. Contamination is among them.</p>
<p>All space agencies adhere to the international protocols against “<a href="https://www.nasa.gov/feature/new-report-addresses-limiting-interplanetary-contamination-during-human-missions">forward contamination</a>”. That is, inadvertently spreading earth germs to another planet or moon. This would prevent subsequent explorers from knowing if the presence of earth bacteria was due to contamination, or if earth’s bacteria are naturally spread through the solar system as suggested by a theory called <a href="https://helix.northwestern.edu/article/origin-life-panspermia-theory">panspermia</a>.</p>
<p>The reverse problem is “backward contamination”: inadvertently returning to earth carrying some extra-terrestrial microbes. We would have no natural antibodies or resistance to defend ourselves from even fatal illnesses. The fate of entire Khoikhoi clans who were <a href="https://www.sahistory.org.za/dated-event/smallpox-epidemic-strikes-cape">wiped out</a> by smallpox infections, to which they had no natural resistance, is merely one historical example warning us, out of many.</p>
<p>Astrobiology discussions threw up another topic that’s engaged intellectuals and science fiction writers for over a century: finding intelligent life on another planet or moon. </p>
<p>The International Institute of Space Law and the International Academy for Astronautics have already proposed a <a href="https://www.seti.org/protocols-eti-signal-detection">set of protocols</a> to guide our responses after the detection of extra-terrestrial intelligent life but, so far, no state has passed those into law.</p>
<h2>Space junk and asteroids</h2>
<p>“Planetary protection” was also a big issue. That is, how can we protect the Earth from another hit by an asteroid such as the one which led to the extinction of the dinosaurs? Proposed solutions range from knocking an earth-bound asteroid off-course by a nuclear explosion, to nudging it away by utilising long-term thrust forces.</p>
<p>And there is growing concern over <a href="https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-orbital-debris-58.html">space debris</a>: the thousands of fragments of spacecraft, rockets, and defunct satellites orbiting around us. Due to their high speeds – up to eight kilometres per second – a piece of debris the size of a bullet would have more than the impact of a grenade.</p>
<p>This has led to calls for space traffic management, modelled on current air traffic management. Already the International Space station, and some other satellites, carry the propellants needed to enable them to take evasive manoeuvres whenever needed to avoid head-on collisions with some other orbiting object.</p><img src="https://counter.theconversation.com/content/109437/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Keith Gottschalk is a member of the South African Space Association, the British Interplanetary Society, and the Planetary Society.</span></em></p>The space industry and global interest in all matters inter-planetary is growing.Keith Gottschalk, Political Scientist, University of the Western CapeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1011482018-09-06T10:31:01Z2018-09-06T10:31:01ZWhat on Earth could live in a salt water lake on Mars? An expert explains<figure><img src="https://images.theconversation.com/files/231080/original/file-20180808-1652-1qkdol3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The south polar cap of Mars is hiding a subsurface lake, according to new research.
</span> <span class="attribution"><span class="source">NASA/JPL/MSSS</span></span></figcaption></figure><p>Tantalising <a href="http://science.sciencemag.org/content/361/6401/490">new evidence</a> has suggested that there may be <a href="https://theconversation.com/discovered-a-huge-liquid-water-lake-beneath-the-southern-pole-of-mars-100523">a salty lake</a> below a glacier on Mars. While brine at freezing temperatures does not sound like the most hospitable of environments, it is difficult to resist pondering whether organic life could survive – or even make some kind of living – there. </p>
<p>But what sort of life form could it be? As Mars was once a far more watery place, it may indeed be harbouring some ancient life form – either fossilised or alive. It is also possible that microbes from Earth have accidentally contaminated the planet during past space exploration missions, and not implausible that they now reside in the lake. </p>
<p>We are unlikely to find bigger animals in the lake though. There are some insects, fish and other organisms on Earth that are capable of life at subzero temperatures. Mars, however, lacks the food webs needed to sustain higher organisms. By contrast, many microorganisms are capable of inhabiting hostile environments even when no other organisms are present.</p>
<p>We know from research on Earth that many microbes can survive in brine. One recent study revealed that communities of such “halophilic microbes”, organisms <a href="https://doi.org/10.1093/femsre/fuy026">adapted to live at high salt levels</a>, are diverse and rich in biomass – even when saturated with sodium chloride (table salt).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235039/original/file-20180905-45139-1g96isd.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Orange-coloured halophilic algae <em>Dunaliella salina</em> within sea salt.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Many terrestrial halophiles are tough – highly tolerant of ultraviolet light and low temperatures. Some are capable of cellular breathing in the absence of oxygen. Certain halophilic microbes – including the fungus <a href="https://en.wikipedia.org/wiki/Aspergillus_penicillioides"><em>Aspergillus penicillioides</em></a>, the bacterium <a href="https://en.wikipedia.org/wiki/Halanaerobium_hydrogenoformans">Halanaerobium</a> and methane-producing organisms known as <a href="https://en.wikipedia.org/wiki/Archaea">archaea</a> – may be able to survive in a martian brine. </p>
<h2>Low temperature</h2>
<p>The main barrier to life is likely to be the prohibitively low temperature (about -70ºC). Yet the temperatures experienced on Mars are actually less cold than those used in freezers on Earth to preserve microbial cells or other biological material in a dormant yet viable condition (-70ºC to -80ºC). What’s more, some salts can actually prevent brines from freezing even at temperatures as low as those expected in the martian lake. It is therefore beyond doubt that some microbial systems could be preserved (and probably survive) on Mars. </p>
<p>Indeed, we know that microbes can survive long periods <a href="https://www.ncbi.nlm.nih.gov/pubmed/12713469">in a dormant condition</a> – even without liquid water. We are still not sure how long, but probably thousands of years and <a href="http://www.pnas.org/content/104/36/14401">maybe much longer</a>. <a href="http://www.pnas.org/content/109/10/4008">Plants</a> and <a href="https://link.springer.com/article/10.1134%2FS0012496618030079">animals</a> such as roundworms – which are more vulnerable to damage than some microbes – have been revived from permafrost after remaining frozen for about 30,000 to 42,000 years on Earth. </p>
<p>Microbes have also been recovered from fluids inside ancient salt crystals. And fossilised cells of some of the first life on Earth have been <a href="http://rstb.royalsocietypublishing.org/content/361/1474/1857.figures-only">preserved in ancient rocks</a> – including those associated with salts.</p>
<h2>Types of salt</h2>
<p>What is more tricky to demonstrate is that cells can be active under martian conditions. Liquid water is essential for microbial function, and bodies of water on Earth that support populations of cells can vary enormously in scale – from oceans or lakes to thin films of water molecules invisible to the naked eye.</p>
<p>Salt helps determine whether microbial activity can take place in the water. The proportion of water molecules within a solution is the called the <a href="http://mypchem.com/myp9/htm/RMM_&_moles.htm">relative molar fraction</a> of water – also referred to as “water activity”. This parameter can dictate whether life is plausible at a specific location and time. All microorganisms have an optimum value for water activity, and a minimum value at which their metabolic activity stops (this varies greatly, depending on the microbe and environmental conditions). </p>
<p>The types of salt and nutrients dissolved in water affect water activity. Some dissolved materials both dilute water molecules and hold on to them via chemical bonds, sometimes preventing cells being able to access them. The chemical nature of dissolved compounds can therefore determine whether proteins, membranes and other systems that life depends on retain sufficient stability and flexibility to remain intact and functional.</p>
<p>Whereas brines dominated by sodium chloride are by far the most commonly occurring on Earth, <a href="https://www.ebi.ac.uk/chebi/searchId.do?chebiId=35175">sulfate salts</a> were common on ancient Mars, and are still prevalent today. But we can’t be sure whether it is this type of salt that is present in the lake on Mars. If it is, it may be bad news for microbes. One study has found that brines containing sulfate salts can actually have a higher ionic strength (a measure of electric charge of a salt solution) <a href="https://doi.org/10.1089/ast.2015.1432">than those found on Earth</a>, which can make them less habitable. The exact mechanism underlying this, however, remains unclear. </p>
<p>Other types of salt, including magnesium chloride and perchlorates, enhance the <a href="https://doi.org/10.1073/pnas.1000557107">flexibility of biological molecules</a> at subzero temperatures and so boost cellular metabolism. Such salts, which are known as “chaotropic”, can <a href="https://doi.org/10.1016/j.copbio.2015.02.010">enable growth of microbes</a> at much lower temperatures than usual. The presence of other organic substances that are chaotropic – including glycerol, alcohols and fructose – can <a href="https://doi.org/10.1111/1462-2920.13530">also boost cellular metabolism</a> under [hostile conditions], such as at <a href="https://doi.org/10.1016/j.copbio.2015.02.010">low temperature</a> or low <a href="https://doi.org/10.1111/1462-2920.13530">water activity</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/231078/original/file-20180808-191019-105wncv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Red Planet welcomes ExoMars - south pole visible.</span>
<span class="attribution"><span class="source">ESA</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>So brines are complex and, while we do know much about the biophysical limits for life on Earth, little is known about the stress biology of the overwhelming majority of terrestrial microbes. If a subglacial salty lake on Mars is confirmed, we will first have to determine what salts are there in order to know more about implications for cellular life. </p>
<h2>Preservation chamber?</h2>
<p>So from what we know of life on Earth, low water activity, salts, chaotropic conditions and temperatures around -70ºC can each act to preserve life. But being preserved is not exactly the same as being alive and kicking. The known limits for growth on Earth lie in the range -15ºC to -20ºC for the most-resilient microbial species. The limits for cellular metabolism lie somewhere in the range -20ºC to -40ºC. That means there is no terrestrial microbe thus far identified that could retain cellular function under the conditions that generally occur on Mars.</p>
<p>If terrestrial microbes are indeed present in the martian environment, they may well be alive yet inactive, and are likely to have the potential to resume activity once the local temperature increases to a biologically permissive level. And once there is active life on Mars, it is logical to assume that there will also be evolution of that life taking place.</p>
<p>A subglacial saline martian lake is, in reality, more likely to act as a preservation chamber than a cradle of life. Nevertheless, it is still extremely exciting news – making the lake a perfect target for future space missions designed to search for the signs of ancient life.</p><img src="https://counter.theconversation.com/content/101148/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John E. Hallsworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Studies from our own planet shed light on whether there could be life in a subglacial lake on Mars.John E. Hallsworth, Lecturer of Environmental Microbiology, Queen's University BelfastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1008972018-08-01T18:01:11Z2018-08-01T18:01:11ZExoplanets: how we used chemistry to identify the worlds most likely to host life<figure><img src="https://images.theconversation.com/files/230230/original/file-20180801-136649-892cyt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Kepler 452-b is looking like a good candidate for having evolved life.</span> <span class="attribution"><span class="source"> NASA Ames/JPL-Caltech/T. Pyl</span></span></figcaption></figure><p>Are we alone in the universe? This question has been with us for thousands of years, but it is only now that science is on the cusp of providing a real answer. We now know of dozens of rocky planets orbiting stars other than our sun where, for all we know, life might exist. And soon, with the launch of the <a href="https://theconversation.com/how-hubbles-successor-will-give-us-a-glimpse-into-the-very-first-galaxies-45970">James Webb Space Telescope</a>, we will have the first chance to peer into the atmospheres of some of these worlds. </p>
<p>But what should we look for? In our new study, <a href="http://advances.sciencemag.org/content/4/8/eaar3302">published in Science Advances</a>, we identify combinations of planetary temperature and light conditions sufficient to give rise to the building blocks of life.</p>
<p>We started with what we know. On Earth, photosynthesis – the process through which plants make energy – has transformed our atmosphere from one rich in carbon dioxide to one rich in molecular oxygen. That’s because plants transform carbon dioxide and water into sugars and oxygen using sunlight.</p>
<p>The presence of molecular oxygen may therefore indicate the presence of life, <a href="https://www.ncbi.nlm.nih.gov/pubmed/12469366">especially if it is observed alongside methane</a> (plants and bacteria can produce methane). If we found carbon dioxide and methane along with the complete absence of carbon monoxide, this <a href="http://advances.sciencemag.org/content/4/1/eaao5747">may also be a sign of life</a> on other planets. This is because, as far as we know, there are ways that life can release lots of methane in a carbon dioxide rich atmosphere without also making lots of carbon monoxide.</p>
<p>There may be other possibilities, too – scientists are looking through all possible small molecules to <a href="https://www.liebertpub.com/doi/abs/10.1089/ast.2015.1404">identify biosignatures</a> that we haven’t thought of yet.</p>
<h2>The problem with ‘habitable zones’</h2>
<p>But even if we knew exactly what to look for, where should we look? It is impossible to scan the entire cosmos for life. We have to look at individual systems, a handful at a time. </p>
<p>To be able to host life, an exoplanet needs to be the right distance from a star for liquid water to stably exist on its surface. The zone in which this criterion is satisfied is called the “<a href="https://theconversation.com/the-five-most-earth-like-exoplanets-so-far-50669">habitable zone</a>”. If we took a vial of life and dumped it on the surface of a planet in this zone, it could survive. So these planets are a good place to start looking.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/230205/original/file-20180801-136646-1uipmz4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This artist’s impression shows a sunset seen from the super-Earth Gliese 667 Cc, in its star’s habitable zone.</span>
<span class="attribution"><span class="source">ESO/L. Calçada</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>However, this does not address the question of whether life could arise there on its own. Life as we know it requires a variety of molecular structures that perform various functions within the cell. These include DNA, RNA, proteins and cell membranes, which are made up of relatively simple building blocks (lipids, nucleotides and amino acids). For a long time it was a mystery where those building blocks came from, but recently there have been major breakthroughs in determining how they arose on the surface of the early Earth. </p>
<p>For example, shining ultraviolet light on hydrogen cyanide (a chemical compound that exists in nature) in water, along with an negatively charged ion (an atom or molecule that has gained electrons) such as bisulfite, <a href="https://www.liebertpub.com/doi/abs/10.1089/ast.2017.1770">leads to simple sugars</a>.</p>
<p>Hydrogen cyanide is abundant in the “protoplanetary disks” which form solar systems and in comets, and <a href="https://www.nature.com/articles/s41598-017-06489-1">can be formed on a planet’s surface by impact</a>. The bisulfite on Earth probably developed from sulphur dioxide from volcanoes being absorbed into water – something that could also happen on exoplanets. </p>
<p>In certain environments, <a href="https://www.nature.com/articles/s41467-018-04147-2">with the right conditions</a>, hydrogen cyanide and a negatively charged ion can lead to the formation of many of life’s building blocks selectively and <a href="https://www.ncbi.nlm.nih.gov/pubmed/25803468">at large concentrations</a>. But the reactions depend on having the right amount of UV light. In the absence of light, these same molecules – hydrogen cyanide and bisulfite – slowly react to form products that do not lead to the building blocks of life. </p>
<h2>Origin of life zone</h2>
<p>The speed of these reactions in the light and in the dark can both be measured in the lab – and that’s what we did in our new study. Comparing these speeds allowed us to delineate an “abiogenesis zone” (abiogenesis means “origin of life”) – the region at the right distance from a star for chemistry in the light to outcompete the chemistry in the dark. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/230207/original/file-20180801-136673-1y1mz8i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">James Webb telescope.</span>
<span class="attribution"><span class="source">Pixabay</span></span>
</figcaption>
</figure>
<p>For stars like our sun, the abiogenesis zone overlaps with the habitable zone. But for cooler stars, the story is more complicated. When cool stars are inactive, the abiogenesis zone is too close to the star to overlap with the habitable zone. But cool stars can also be very active, producing large and frequent flares. Are these flares sufficient to drive the chemistry that leads to life’s building blocks? It may be possible, but much more work needs to be done to confidently identify planets around them as suitable for life. </p>
<p>We cross referenced our results with a catalogue of known exoplanets that are classified to be in the habitable zone to identify those that are primed for life. We found two candidates. <a href="https://theconversation.com/exoplanet-kepler-452b-offers-a-glimpse-into-the-future-fate-of-our-earth-45144">Kepler-452b</a> is the smallest exoplanet we know that resides definitively located in both the habitable and abiogenesis zones. Exoplanet <a href="https://www.space.com/24129-kepler-62e.html">Kepler-62e</a> may also be in the abiogenesis zone, but it is not as likely to be rocky. </p>
<p>Sadly both of these exoplanets are too far away for the James Webb telescope to investigate. While we didn’t find any exoplanets nearby in both the habitable and abiogenesis zones, we are discovering such worlds at breathtaking speed – with several thousands discovered already. So it may not be long until we do. For example, the <a href="https://tess.gsfc.nasa.gov/">Transiting Exoplanet Survey Satellite (TESS)</a> has a chance of finding more systems like Kepler-452b that are closer to home. Until then, we could also use the method to probe moons around giant gas planets within habitable zones to find out if they are primed for life.</p>
<p>Although this is exciting, it should be noted that it is very difficult to solve a problem on the basis of a single data point. Right now, Earth is the only data point we have for life. In the future, if we find multiple examples of life, concepts like the abiogenesis zone can be used to test the predictions of different origin of life theories and gain new insight about how life started on Earth and whether it could have started any other way. But of course it will be amazing enough simply to discover life somewhere outside our solar system.</p><img src="https://counter.theconversation.com/content/100897/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Rimmer receives funding from the Simons Foundation and the Kavli Foundation. </span></em></p>Life could have evolved on exoplanets Kepler-452b and Kepler-62e, according to a new study.Paul Rimmer, Research Associate of Astrophysics, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/979982018-06-11T10:09:57Z2018-06-11T10:09:57ZThe hunt for life on Mars: new findings on rock ‘chimneys’ could hold key to success<p>The search for life on Mars has taken a step forward with the NASA Curiosity rover’s <a href="http://science.sciencemag.org/content/360/6393/1096">discovery</a> of organic matter on the bottom of what was once a lake. <a href="https://theconversation.com/rover-detects-ancient-organic-material-on-mars-and-it-could-be-trace-of-past-life-97755">It may once</a> have been part of an alien life form or it might have a non-biological origin – either way this carbon would have provided a food source for any organic living thing in the vicinity. </p>
<p>The discovery adds extra intrigue to NASA’s search for extra-terrestrial life forms themselves. When hunting remotely with one car-sized machine, the question is where best to focus your efforts. It makes sense to look for the same types of places we expect to find fossilised microorganisms on Earth. This is complicated by the fact that these fossils are measured in microns – mere millionths of a metre. </p>
<p>The Curiosity rover looks for certain sedimentary rocks deposited near water, as it did for the latest discovery. This is based on the latest geological advice about the best prospects. Yet which rocks to prioritise is still a matter of some debate – and it’s a question that is just as relevant to geologists trying to unlock the secrets of our own ancient world. The Earth’s rocks and fossils are the nearest thing we have to time machines. </p>
<p>For a century or so, geologists focused on a type of rock called a stromatolite – devoting long hours to crawling around in awkward spaces trying to find them. Stromatolites occur mainly in shallow water and are layered on a millimetre scale. Many of them are undoubtedly built by slimy microbial “biofilms”, but to cut a long story short we now appreciate there is more than one way to make a stripy rock – and they don’t all involve microbes. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stromatolite city.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/31856336@N03/6188521133">Mike Beauregard</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>More recently geologists have become more interested in other types of rocks, including the “<a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/black-smoker">black smoker</a>” tube-type deposits formed by hot hydrothermal water being squeezed out of the Earth’s crust in the deep sea. Slightly easier to examine are similar chimney-like formations found in certain alkaline lakes around the world. </p>
<h2>Mono Lake</h2>
<p>One place on Earth where these chimneys occur is Mono Lake in California, a vast and beautiful stretch of water several hundred miles north of Los Angeles on the eastern slope of the Sierra Nevada mountains. In October 2014, our team obtained permission from the California State Parks to examine and sample some of the calcium carbonate chimneys that have formed there.</p>
<p>The rocks, which are frequently between two and three metres tall, are very young in geological terms, usually only tens of thousands of years old. But since first being <a href="https://books.google.co.uk/books/about/Quaternary_History_of_Mono_Valley_Califo.html?id=AE7nAAAAMAAJ&redir_esc=y">described</a> by the famous American geologist Israel Russell in 1889 they have proven an excellent natural laboratory for groups of scientists trying to understand how these structures came about. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=392&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=392&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=392&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=493&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=493&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221985/original/file-20180606-137295-11ddjcf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=493&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Exploration begins.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
</figcaption>
</figure>
<p>Before our visit, geologists were essentially divided about these chimneys. A group we might call “pure geochemists” <a href="https://www.sciencedirect.com/science/article/pii/001670379390339X">proposed</a> they were nothing to do with microbes, but produced by calcium-rich spring waters coming into contact with the alkaline lake, with its abundance of carbonate ions. </p>
<p>A smaller opposing camp <a href="http://archives.datapages.com/data/sepm/journals/v33-37/data/034/034002/0309.htm">agreed</a> it should be possible for these structures to emerge in the way that pure geochemists were suggesting. But they pointed out that, in the few recorded observations of carbonate rocks forming at the lake in the 19th and 20th centuries, some kind of biofilm did appear to have an influence. They also cited other studies that had shown that waterborne microbes called cyanobacteria did produce slimy substances that can accumulate calcium. </p>
<p>We went to Mono Lake to find out who was right. Our six-strong expedition divided into two factions: one looked for chimneys on the lake bottom using a research boat, while the other explored the famous “tufa towers” that rise up from the lake shore. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tufa towers on the shoreline.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
</figcaption>
</figure>
<p>The boat party toiled and cursed the astonishingly salty waters of the lake, while the shore party made steady progress with the invaluable assistance of local state park ranger, Dave Marquart. Their peace was interrupted only by a phone call from the stranded boaters requesting they urgently try to find someone with a four-wheel drive capable of pulling the boat back out of the water – luckily help was at hand. </p>
<p>One of the sites the shore party visited was in Marquart’s own back garden to the north-west of the lake. The rocks there were part of a set of ancient chimneys formed along a small tectonic fault. Their features suggested they had been built by microbes, but we needed to send them to a lab to be sure. </p>
<h2>Microbial ‘threads’</h2>
<p>Using an optical microscope, we were able to see dark thread-like structures entombed in slices of the rock. As we outline in our <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gbi.12292">new study</a> published in Geobiology, these “threads” are millions of fossilised photosynthesising cyanobacteria that once surrounded waters rising from a spring on the lake floor. </p>
<p>We sent the samples to Australia for further testing to establish whether the microbes played a key role in building the chimneys. This revealed surrounding patches of carbon and nitrogen, which we took to be fossilised cyanobacterial slime. This slime traps calcium and when it breaks down it creates calcium carbonate, entombing any living and dead cells in rock. </p>
<p>We found other ways in which this microbial slime had affected the fabric of the rock: grains of quartz and aluminosilicates that were clearly sand that had got stuck there, too. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Thread-like filaments in the Mono Lake rock.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
</figcaption>
</figure>
<p>In short, we found evidence that cyanobacteria formed tubular mats around rising spring water in the ancient Mono Lake – probably producing the majority of the resulting chimneys there, though there may be examples of “pure geochemistry” chimneys as well. This suggests that these rock formations do indeed represent a promising and fairly large target for exploring ancient or extra-terrestrial life. </p>
<p>They have the added advantage that the calcite rocks in question are geologically quite stable. This means the fossils could potentially be preserved for a very long time – easily hundreds of millions, quite plausibly billions of years. </p>
<p>To our knowledge no chimneys have been found on Mars yet, but they are not common on Earth and there is every chance that they have a Martian equivalent. There, and on other planets and moons, we should be looking for areas with conditions as similar as possible to where these chimneys exist on Earth – volcanic rocks where spring waters might once have risen through the bedrock into an alkaline lake. Without any question, NASA’s hunt for suitable rocks on the red planet should make finding them a high priority.</p><img src="https://counter.theconversation.com/content/97998/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Following NASA’s latest discovery of organic matter on the red planet, new findings in a salt lake in California could point to where to look for alien life.Alexander Brasier, Lecturer in Geology, University of AberdeenDavid Wacey, Australian Research Council Future Fellow, The University of Western AustraliaMike Rogerson, Senior Lecturer in Earth System Science, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/847422017-09-29T02:35:41Z2017-09-29T02:35:41ZWorries about spreading Earth microbes shouldn’t slow search for life on Mars<figure><img src="https://images.theconversation.com/files/188019/original/file-20170928-2939-1iwisqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Viking landers in the 1970s were the last to look directly for life on Mars.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/#/details-PIA00382.html">NASA/JPL</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>There may be no bigger question than whether we are alone in our solar system. As our spacecraft find new clues about the presence of liquid water now or in the past on Mars, the possibility of some kind of life there looks more likely. On Earth, water means life, and that’s why the exploration of Mars is guided by the idea of following the water.</p>
<p>But the search for life on Mars is paired with plenty of strong warnings about how we must sterilize our spacecraft to avoid contaminating our neighbor planet. How will we know what’s native Martian if we unintentionally seed the place with Earth organisms? A popular analogy points out that Europeans unknowingly brought smallpox to the New World, and they took home syphilis. Similarly, it is argued, our robotic explorations could contaminate Mars with terrestrial microorganisms.</p>
<p>As an astrobiologist who researches the environments of early Mars, I suggest these arguments are misleading. The current danger of contamination via unmanned robots is actually quite low. But contamination <a href="https://doi.org/10.1089/ast.2017.1703">will become unavoidable once astronauts get there</a>. <a href="https://www.nasa.gov/content/journey-to-mars-overview">NASA</a>, other agencies and the <a href="http://www.spacex.com/mars">private sector</a> hope to send <a href="https://www.nytimes.com/2017/09/28/science/elon-musk-mars.html">human missions to Mars by the 2030s</a>.</p>
<p>Space agencies have long prioritized preventing contamination over our hunt for life on Mars. Now is the time to reassess and update this strategy – before human beings get there and inevitably introduce Earth organisms despite our best efforts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/188026/original/file-20170928-1449-h7tdl9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microbiologists frequently collect swab samples from the floor of clean rooms during spacecraft assembly.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/#/details-PIA17368.html">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What planetary protection protocols do</h2>
<p>Arguments calling for extra caution have permeated Mars exploration strategies and led to the creation of specific guiding policies, known as <a href="https://planetaryprotection.nasa.gov/">planetary protection</a> protocols. </p>
<p>Strict cleaning procedures are required on our spacecraft before they’re allowed to sample regions on Mars which could be a habitat for microorganisms, either native to Mars or brought there from Earth. These areas are labeled by the planetary protection offices as “<a href="https://www.nap.edu/catalog/21816/review-of-the-mepag-report-on-mars-special-regions">Special Regions</a>.”</p>
<p>The worry is that, otherwise, terrestrial invaders could jeopardize potential Mars life. They also could confound future researchers trying to distinguish between any indigenous Martian life forms and life that arrived as contamination from Earth via today’s spacecraft. </p>
<p>The sad consequence of these policies is that the multi-billion-dollar Mars spacecraft programs run by <a href="https://mars.nasa.gov/programmissions/overview/">space</a> <a href="http://exploration.esa.int/mars/44997-the-red-planet/">agencies</a> in the West have not proactively looked for life on the planet since the late 1970s.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/188014/original/file-20170928-1438-4xut2s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dr. Carl Sagan poses with a model of the Viking lander in Death Valley, California.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/images/151106main_image_feature_599_ys_full.jpg">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>That’s when NASA’s Viking landers made the only attempt ever to find life on Mars (or on any planet outside Earth, for that matter). They carried out specific biological experiments looking for evidence of microbial life. Since then, that incipient biological exploration has shifted to less ambitious geological surveys that try to demonstrate only that Mars was “<a href="https://mars.nasa.gov/msl/mission/science/objectives/">habitable</a>” in the past, meaning it had conditions that could likely support life.</p>
<p>Even worse, if a dedicated life-seeking spacecraft ever does get to Mars, planetary protection policies will allow it to search for life everywhere on the Martian surface, except in the very places we suspect life may exist: the Special Regions. The concern is that exploration could contaminate them with terrestrial microorganisms.</p>
<h2>Can Earth life make it on Mars?</h2>
<p>Consider again the Europeans who first journeyed to the New World and back. Yes, smallpox and syphilis traveled with them, between human populations, living inside warm bodies in temperate latitudes. But that situation is irrelevant to Mars exploration. Any analogy addressing possible biological exchange between Earth and Mars must consider the absolute contrast in the planets’ environments.</p>
<p>A more accurate analogy would be bringing 12 Asian tropical parrots to the Venezuelan rainforest. In 10 years we may very likely have an invasion of Asian parrots in South America. But if we bring the same 12 Asian parrots to Antarctica, in 10 hours we’ll have 12 dead parrots.</p>
<p>We’d assume that any indigenous life on Mars should be much better adapted to Martian stresses than Earth life is, and therefore would outcompete any possible terrestrial newcomers. Microorganisms on Earth have evolved to thrive in challenging environments like salt crusts in the Atacama desert or hydrothermal vents on the deep ocean floor. In the same way, we can imagine any potential Martian biosphere would have experienced enormous evolutionary pressure during billions of years to become expert in inhabiting <a href="http://online.liebertpub.com/doi/abs/10.1089/ast.2015.1380">Mars’ today environments</a>. The microorganisms hitchhiking on our spacecraft wouldn’t stand much of a chance against super-specialized Martians in their own territory.</p>
<p>So if Earth life cannot survive and, most importantly, reproduce on Mars, concerns going forward about our spacecraft contaminating Mars with terrestrial organisms are unwarranted. This would be the parrots-in-Antarctica scenario.</p>
<p>On the other hand, perhaps Earth microorganisms can, in fact, survive and create active microbial ecosystems on present-day Mars – the parrots-in-South America scenario. We can then presume that terrestrial microorganisms are already there, carried by any one of the dozens of spacecraft sent from Earth in the last decades, or by the natural exchange of rocks pulled out from one planet by a meteoritic impact and transported to the other. </p>
<p>In this case, protection protocols are overly cautious since contamination is already a fact.</p>
<h2>Technological reasons the protocols don’t make sense</h2>
<p>Another argument to soften planetary protection protocols hinges on the fact that current sterilization methods don’t actually “sterilize” our spacecraft, a feat engineers still don’t know how to accomplish definitively.</p>
<p>The cleaning procedures we use on our robots rely on pretty much the same stresses prevailing on the Martian surface: oxidizing chemicals and radiation. They end up killing only those microorganisms with no chance of surviving on Mars anyway. So current cleaning protocols are essentially conducting an artificial selection experiment, with the result that we carry to Mars only the most hardy microorganisms. This should put into question the whole cleaning procedure.</p>
<p>Further, technology has advanced enough that distinguishing between Earthlings and Martians is no longer a problem. If Martian life is biochemically similar to Earth life, we could sequence genomes of any organisms located. If they don’t match anything we know is on Earth, we can surmise it’s native to Mars. Then we could add Mars’ creatures to the tree of DNA-based life we already know, probably somewhere on its lower branches. And if it is different, we would be able to identify such differences based on its building blocks.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=473&fit=crop&dpr=1 600w, https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=473&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=473&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=594&fit=crop&dpr=1 754w, https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=594&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/188023/original/file-20170928-22252-1wes7l6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=594&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bacterial species <em>Tersicoccus phoenicis</em> is found in only two places: clean rooms in Florida and South America where spacecraft are assembled for launch.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/#/details-PIA17369.html">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Mars explorers have yet another technique to help differentiate between Earth and Mars life. The microbes <a href="https://doi.org/10.1089/ast.2012.0906">we know persist in clean spacecraft assembly rooms</a> provide an excellent control with which to monitor potential contamination. Any microorganism found in a Martian sample identical or highly similar to those present in the clean rooms would very likely indicate contamination – not indigenous life on Mars.</p>
<h2>The window is closing</h2>
<p>On top of all these reasons, it’s pointless to split hairs about current planetary protection guidelines as applied to today’s unmanned robots since human explorers are on the horizon. <a href="https://doi.org/10.1016/j.actaastro.2009.08.015">People would inevitably bring microbial hitchhikers with them</a>, because we cannot sterilize humans. Contamination risks between robotic and manned missions are simply not comparable. </p>
<p>Whether the microbes that fly with humans will be able to last on Mars is a separate question – though their survival is probably assured if they stay within a spacesuit or a human habitat engineered to preserve life. But no matter what, they’ll definitely be introduced to the Martian environment. Continuing to delay the astrobiological exploration of Mars now because we don’t want to contaminate the planet with microorganisms hiding in our spacecrafts isn’t logical considering astronauts (and their microbial stowaways) may arrive within two or three decades.</p>
<p>Prior to landing humans on Mars or bringing samples back to Earth, it makes sense to determine whether there is indigenous Martian life. What might robots or astronauts encounter there – and import to Earth? More knowledge now will increase the safety of Earth’s biosphere. After all, we still don’t know if returning samples could endanger humanity and the terrestrial biosphere. Perhaps reverse contamination should be our big concern.</p>
<p>The main goal of Mars exploration should be to try to find life on Mars and address the question of whether it is a separate genesis or shares a common ancestor with life on Earth. In the end, if Mars is lifeless, maybe we are alone in the universe; but if there is or was life on Mars, then there’s a zoo out there.</p><img src="https://counter.theconversation.com/content/84742/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alberto G. Fairén receives funding from the European Research Council.</span></em></p>Planetary protection protocols try to make sure we don’t seed places like Mars with life from our planet. An astrobiologist argues they’re misguided – especially with human astronauts on the horizon.Alberto G. Fairén, Research Scientist at Centro de Astrobiología, Spain, and Visiting Scientist in Astronomy, Cornell UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/818032017-09-15T10:21:37Z2017-09-15T10:21:37ZSeeds in space – how well can they survive harsh, non-Earth conditions?<figure><img src="https://images.theconversation.com/files/185909/original/file-20170913-18075-165yqah.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spend many months attached to the ISS and see how well you grow.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/research/experiments/1674.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Will we someday colonize space? Will our children visit other planets? To achieve goals like these, we’ll need to crack one crucial challenge: how to feed ourselves for long periods away from Earth.</p>
<p>A <a href="http://www.mars-one.com/faq/mission-to-mars/how-long-does-it-take-to-travel-to-mars">trip to Mars would take months</a>, and exploring the depths of the galaxy would take even longer. Provision of nutritious food for travelers is a significant obstacle. While stockpiling food is an option, storing enough to last many months strains weight and space limitations in spacecraft – and missions could easily outlast food shelf life. Growing food in space will be essential.</p>
<p>Essential – and not necessarily easy. The conditions in the vacuum of space are quite harsh compared to Earth. Seeds in space must be able to withstand large doses of ultraviolet and cosmic radiation, low pressure and microgravity. </p>
<p>Believe it or not, the first space travelers were seeds. In 1946, <a href="https://www.nasa.gov/pdf/449089main_White_Sands_Missile_Range_Fact_Sheet.pdf">NASA launched a V-2 rocket carrying maize</a> seeds to observe how they’d be affected by radiation. Since then, the scientific community has learned <a href="https://doi.org/10.1079/SSR200193">a great deal</a> about the effects of the space environment on seed <a href="https://doi.org/10.1016/j.asr.2011.05.017">germination</a>, <a href="https://doi.org/10.1016/0273-1177(86)90076-1">metabolism</a>, <a href="https://doi.org/10.1016/j.asr.2005.06.043">genetics</a>, <a href="http://journal.ashspublications.org/content/130/6/848.short">biochemistry</a> and even <a href="https://doi.org/10.1016/S0273-1177(03)00250-3">seed</a> <a href="https://doi.org/10.1016/j.actaastro.2006.09.009">production</a>. </p>
<p>Astrobiologists David Tepfer and Sydney Leach recently investigated <a href="https://doi.org/10.1089/ast.2015.1457">how seeds would do back on Earth</a> after spending extended periods on the International Space Station. The experiments they conducted on the <a href="https://www.nasa.gov/mission_pages/station/research/experiments/696.html">EXPOSE</a> <a href="https://www.nasa.gov/mission_pages/station/research/experiments/211.html">missions</a> were much longer than many other ISS seed experiments, and placed the seeds on the outside of the station, in the dead of space, rather than inside. The goal was to understand not only the effects of long-term radiation exposure, but a bit about the molecular mechanisms of those effects.</p>
<h2>Seeds have some defenses</h2>
<p>Seeds possess a couple of remarkable traits that Tepfer and Leach hypothesized would give these “model space travelers” a fighting chance.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=575&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=575&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=575&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=722&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=722&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185911/original/file-20170913-20280-41e1zd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=722&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Seeds protect their important insides with a strong external seed coat.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Dycotyledon_seed_diagram-en.svg">LadyofHats</a></span>
</figcaption>
</figure>
<p>First, they contain multiple copies of important genes – what scientists call redundancy. Genetic redundancy is common in flowering plants, especially food products such as <a href="https://www.sciencedaily.com/releases/2014/09/140930090636.htm">seedless watermelon and strawberries</a>. If one genetic copy is damaged, there’s still another available to do the job.</p>
<p>Secondly, seed coats contain chemicals called flavonoids that act as sunscreens, protecting the seed’s DNA from damage by ultraviolet (UV) light. On Earth, our planet’s atmosphere filters out some harmful UV light before it can reach us. But in space, there is no protective atmosphere.</p>
<p>Would these special features be enough to let the seeds survive or even thrive? To find out, Tepfer and Leach conducted a series of experiments – both outside the International Space Station and back on Earth – with tobacco, <em>Arabidopsis</em> (a flowering plant commonly used in research) and morning glory seeds. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=553&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=553&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185905/original/file-20170913-20310-w6bmrn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=553&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The EXPOSE-R experiment attached to the exterior of the International Space Station.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/expeditions/expedition26/russian_eva27.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Bombarded with energy</h2>
<p>Their EXPOSE-E experiment flew to the International Space Station (ISS) in 2008 and lasted 558 days – so just under two years.</p>
<p>They stored the seeds in a single layer on the outside of the ISS behind a special kind of glass that let in ultraviolet radiation only at wavelengths between 110 and 400 nanometers. DNA readily absorbs UV radiation in this wavelength range. A second, identical set of seeds was on the ISS, but shielded completely from UV radiation. The purpose of this experimental design was to observe the effects of UV radiation separately from other types of radiation <a href="https://www.space.com/32644-cosmic-rays.html">like cosmic rays</a> that are everywhere in space.</p>
<p>Tepfer and Leach chose tobacco and <em>Arabidopsis</em> seeds for EXPOSE-E because both have a redundant genome and therefore good odds for survival. They also included a genetically engineered variety of tobacco with an antibiotic resistance gene added; the plan was to later test this gene in bacteria and determine if there was any damage. In addition to normal <em>Arapidopsis</em>, they sent up two genetically modified strains of the plant that contained low and absent UV-protective chemicals in their seed coat. They also sent purified DNA and purified flavonoids. This gave the researchers a wide range of scenarios by which to understand the effects of space on the seeds.</p>
<p>A second ISS mission called EXPOSE-R included only the three types of <em>Arabidopsis</em> seeds. These received a little over double the dose of ultraviolet light because of the longer experiment time, 682 days. Lastly, researchers performed a ground experiment back in the lab that exposed <em>Arabidopsis</em>, tobacco and morning glory seeds to very high doses of UV light for only a month.</p>
<p>After all these various exposure conditions, it was time to see how well the seeds could grow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=410&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=410&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=410&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=515&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=515&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185907/original/file-20170913-20270-l4me1j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=515&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Expose-R experiment was equipped with three trays containing a variety of biological samples – including seeds.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/station/multimedia/exp18_eva2.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>What would researchers reap?</h2>
<p><a href="https://doi.org/10.1089/ast.2015.1457">When the seeds returned to Earth</a>, the researchers measured their germination rates – that is, how quickly the root emerged from the seed coat.</p>
<p>The seeds that had been shielded in the lab did the best, with more than 90 percent of them germinating. Next came the seeds that had been exposed to UV radiation for one month in the laboratory, with better than 80 percent germinating. </p>
<p>For the space-traveling seeds, more than 60 percent of the shielded seeds germinated. A mere 3 percent of space UV-exposed seeds did.</p>
<p>The 11 <em>Arabidopsis</em> plants that did grow from both the wild type and genetically engineered seeds did not survive once planted in soil. Tobacco plants, however, showed reduced growth but that growth rate recovered in subsequent generations. Tobacco has a much heartier seed coat and a more redundant genome, which may explain its apparent survival advantage.</p>
<p>When the researchers plugged the antibiotic resistance gene into bacteria, they found it was still functional after its trip to space. That finding suggests it’s not genetic damage that’s making these seeds less viable. Tepfer and Leach attributed the reduced germination rate to damage to other molecules in the seed besides DNA – such as proteins. A redundant genome or built-in DNA repair mechanisms weren’t going to overcome that damage, further explaining why the <em>Arabidopsis</em> plants didn’t survive transplanting.</p>
<p>In the ground experiments, the researchers found that radiation damage is dose-dependent – the more radiation the seeds received, the worse their germination rate.</p>
<p>These discoveries could inform future directions for research in space agriculture. Scientists may consider genetically engineering seeds to have added protection for the cellular machinery critical for protein synthesis, such as ribosomes. Future research will also need to explore further how seeds stored in space germinate in microgravity, rather than on Earth.</p>
<p>As researchers add to the knowledge of how space affects plants and their seeds, we can continue to make the strides necessary toward producing food in space. It will be a crucial step toward sustainable colonies that can survive beyond the comfortable confines of Earth’s biosphere.</p><img src="https://counter.theconversation.com/content/81803/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gina Riggio is affiliated with Blue Marble Space.</span></em></p>If you want to live on Mars, you’re going to need to grow food. Seeds are naturally equipped to handle challenging Earth environments, but how well can they survive what they’ll encounter off-planet?Gina Misra, Ph.D. Student in Cell and Molecular Biology, University of ArkansasLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/807002017-07-25T15:00:15Z2017-07-25T15:00:15ZWhy looking for aliens is good for society (even if there aren’t any)<figure><img src="https://images.theconversation.com/files/179468/original/file-20170724-6656-bbzr2o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The search for life elsewhere in the universe is one of the most compelling aspects of modern science. Given its scientific importance, significant resources are devoted to this young science of <a href="http://astrobiologysociety.org/">astrobiology</a>, ranging from rovers on Mars to telescopic observations of planets orbiting other stars. </p>
<p>The holy grail of all this activity would be the actual discovery of alien life, and such a discovery would likely have profound scientific and philosophical implications. But extraterrestrial life has not yet been discovered, and for all we know may not even exist. Fortunately, even if alien life is never discovered, all is not lost: simply searching for it <a href="https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/widening-perspectives-the-intellectual-and-social-benefits-of-astrobiology-regardless-of-whether-extraterrestrial-life-is-discovered-or-not/9657811BE831E32BE350CFE960B2087C">will yield valuable benefits for society</a>.</p>
<p>Why is this the case?</p>
<p>First, astrobiology is inherently multidisciplinary. To search for aliens requires a grasp of, at least, astronomy, biology, geology, and planetary science. Undergraduate courses in astrobiology need to cover elements of all these different disciplines, and postgraduate and postdoctoral astrobiology researchers likewise need to be familiar with most or all of them. </p>
<p>By forcing multiple scientific disciplines to interact, astrobiology is stimulating a partial reunification of the sciences. It is helping to move 21st-century science away from the extreme specialisation of today and back towards the more interdisciplinary outlook that prevailed in earlier times. </p>
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<img alt="" src="https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179466/original/file-20170724-28519-1uipio5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=426&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Earth rising above the surface of the moon, as seen from Apollo 8 in December 1968.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>By producing broadminded scientists, familiar with multiple aspects of the natural world, the study of astrobiology therefore enriches the whole scientific enterprise. It is from this cross-fertilization of ideas that future discoveries may be expected, and such discoveries will comprise a permanent legacy of astrobiology, even if they do not include the discovery of alien life.</p>
<p>It is also important to recognise that astrobiology is an incredibly open-ended endeavour. Searching for life in the universe takes us from extreme environments on Earth, to the plains and sub-surface of Mars, the icy satellites of the giant planets, and on to the all-but-infinite variety of planets orbiting other stars. And this search will continue regardless of whether life is actually discovered in any of these environments or not. The range of entirely novel environments opened to investigation will be essentially limitless, and so has the potential to be a never-ending source of scientific and intellectual stimulation.</p>
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<img alt="" src="https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179470/original/file-20170724-23039-ow0ro8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sand dunes near to Mars’ South Pole.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<h2>The cosmic perspective</h2>
<p>Beyond the more narrowly intellectual benefits of astrobiology are a range of wider societal benefits. These arise from the kinds of perspectives – cosmic in scale – that the study of astrobiology naturally promotes. </p>
<p>It is simply not possible to consider searching for life on Mars, or on a planet orbiting a distant star, without moving away from the narrow Earth-centric perspectives that dominate the social and political lives of most people most of the time. Today, the Earth is faced with global challenges that can only be met by increased international cooperation. Yet around the world, nationalistic and religious ideologies are acting to fragment humanity. At such a time, the growth of a unifying cosmic perspective is potentially of enormous importance.</p>
<p>In the early years of the space age, the then US ambassador to the United Nations, Adlai Stevenson, said of the world: “We can never again be a squabbling band of nations before the awful majesty of outer space.” Unfortunately, this perspective is yet to sink deeply into the popular consciousness. On the other hand, the wide public interest in the search for life elsewhere means that astrobiology can act as a powerful educational vehicle for the popularisation of this perspective.</p>
<p>Indeed, it is only by sending spacecraft out to explore the solar system, in large part for astrobiological purposes, that we can obtain images of our own planet that show it in its true cosmic setting.</p>
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<img alt="" src="https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=506&fit=crop&dpr=1 600w, https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=506&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=506&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=636&fit=crop&dpr=1 754w, https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=636&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/177896/original/file-20170712-19642-n0xtni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=636&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Earth photographed from the surface of Mars by the Mars Exploration Rover Spirit, March 2004.</span>
<span class="attribution"><span class="source">NASA/JPL/Cornell/Texas A&M</span></span>
</figcaption>
</figure>
<p>In addition, astrobiology provides an important evolutionary perspective on human affairs. It demands a sense of deep, or <a href="https://school.bighistoryproject.com/bhplive">big, history</a>. Because of this, many undergraduate astrobiology courses begin with an overview of the history of the universe. This begins with the Big Bang and moves successively through the origin of the chemical elements, the evolution of stars, galaxies, and planetary systems, the origin of life, and evolutionary history from the first cells to complex animals such as ourselves. Deep history like this helps us locate human affairs in the vastness of time, and therefore complements the cosmic perspective provided by space exploration.</p>
<h2>Political implications</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=740&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=740&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=740&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=930&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=930&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179465/original/file-20170724-23039-1jh765m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=930&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Alexander von Humboldt, 1843.</span>
</figcaption>
</figure>
<p>There is a well-known aphorism, widely attributed to the Prussian naturalist Alexander von Humboldt, to the effect that “the most dangerous worldview is the worldview of those who have not viewed the world”. Humboldt was presumably thinking about the mind-broadening potential of international travel. But familiarity with the cosmic and evolutionary perspectives provided by astrobiology, powerfully reinforced by actual views of the Earth from space, can surely also act to broaden minds in such a way as to make the world less fragmented and dangerous.</p>
<p>I think there is an important political implication inherent in this perspective: as an intelligent technological species, that now dominates the only known inhabited planet in the universe, humanity has a responsibility to develop international social and political institutions appropriate to managing the situation in which we find ourselves.</p>
<p>In concluding his monumental <a href="http://www.gutenberg.org/ebooks/45368">Outline of History</a> in 1925, HG Wells famously observed: “Human history becomes more and more a race between education and catastrophe.” Such an observation appears especially germane to the geopolitical situation today, where apparently irrational decisions, often made by governments (and indeed by entire populations) seemingly ignorant of broader perspectives, may indeed lead our planet to catastrophe.</p><img src="https://counter.theconversation.com/content/80700/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Crawford is also a Professor of Planetary Science and Astrobiology at Birkbeck, University of London. He is an advisor to the European Space Agency, Vice President of the Royal Astronomical Society, and on the Council of the Astrobiology Society of Britain. This article is based on a recent paper published in the International Journal of Astrobiology.</span></em></p>Even if alien life is never discovered, all is not lost.Ian Crawford, Visiting Research Associate in Astronomy, UCLLicensed as Creative Commons – attribution, no derivatives.