tag:theconversation.com,2011:/fr/topics/alien-life-13652/articlesAlien life – The Conversation2024-03-04T16:15:33Ztag:theconversation.com,2011:article/2250022024-03-04T16:15:33Z2024-03-04T16:15:33ZJupiter’s moon Europa produces less oxygen than we thought – it may affect our chances of finding life there<figure><img src="https://images.theconversation.com/files/579561/original/file-20240304-24-hmeyeg.jpeg?ixlib=rb-1.1.0&rect=20%2C0%2C1976%2C1000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Europa seen in true colour (left) and false colour (right).</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>Jupiter’s icy moon Europa has long been thought of as one of the most habitable worlds in the Solar System. Now the Juno mission to Jupiter has directly sampled its atmosphere in detail for the first time. The results, <a href="https://www.nature.com/articles/s41550-024-02206-x">published in Nature Astronomy</a>, show that Europa’s icy surface produces less oxygen than we thought.</p>
<p>There are plenty of reasons to be excited about the possibility of finding microbial life on Europa. Evidence from the Galileo mission has shown that the moon <a href="https://pubmed.ncbi.nlm.nih.gov/9450749/">has an ocean</a> below its icy surface containing about twice the amount of water as Earth’s oceans. Also, models derived from Europa data show that its ocean floor is in contact with rock, enabling chemical water-rock interactions that <a href="https://theconversation.com/nasa-considers-sending-swimming-robots-to-habitable-ocean-worlds-of-the-solar-system-186228">produce energy</a>, making it the prime candidate for life.</p>
<p>Telescope observations, meanwhile, reveal a weak, <a href="https://europa.nasa.gov/news/18/hubble-finds-oxygen-atmosphere-on-jupiters-moon-europa/">oxygen-rich atmosphere</a>. It also looks as though <a href="https://www.nasa.gov/news-release/nasas-hubble-spots-possible-water-plumes-erupting-on-jupiters-moon-europa/">plumes of water erupt</a> intermittently from the ocean. And there is some evidence of the presence of <a href="https://europa.nasa.gov/why-europa/ingredients-for-life/#:%7E:text=NASA%2FJPL%2DCaltech-,Europa's%20surface%20is%20blasted%20by%20radiation%20from%20Jupiter.,in%20Europa's%20extremely%20tenuous%20atmosphere.">basic chemical elements</a> on the surface – including carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur – used by life on Earth. Some of these could seep down into the water from the atmosphere and surface.</p>
<p>The heating of Europa and its ocean is partly thanks to the moon’s orbit around Jupiter, which produces tidal forces to heat an otherwise frigid environment. </p>
<p>Although Europa boasts three basic ingredients for life – water, the right chemical elements and a source of heat – we don’t yet know if there has been enough time for life to develop.</p>
<figure class="align-center ">
<img alt="Plumes seen on Europa." src="https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=506&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=506&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=506&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=636&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=636&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579569/original/file-20240304-16-u47ybe.png?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">Plumes seen on Europa.</span>
<span class="attribution"><span class="source">Nasa</span></span>
</figcaption>
</figure>
<p>The other prime candidate in our solar system is Mars, the Rosalind Franklin rover’s target in 2028. Life <a href="https://theconversation.com/perseverance-mars-rover-how-to-prove-whether-theres-life-on-the-red-planet-154982">might have started on Mars</a> at the same time as it did on Earth, but then probably stopped due to climate change. </p>
<p>A third candidate is Saturn’s moon Enceladus where the Cassini-Huygens mission discovered plumes of water from a sub-surface salty ocean, <a href="https://www.nature.com/articles/s41586-023-05987-9">also in contact with rock</a> at the ocean’s floor. </p>
<p>Titan is the closest runner up in fourth place, <a href="https://iopscience.iop.org/article/10.3847/2041-8213/aa7851">with its thick atmosphere</a> of organic compounds including hydrocarbon and tholins, born in the high atmosphere. These then float down to the surface coating it with ingredients for life.</p>
<h2>Losing oxygen</h2>
<p>The Juno mission boasts <a href="https://ui.adsabs.harvard.edu/abs/2017SSRv..213..547M/abstract">the best charged particle instruments</a> sent to Jupiter so far. It can measure the energy, direction and composition of charged particles on the surface. Similar instruments at Saturn and Titan <a href="https://uwaterloo.ca/chem13-news-magazine/february-2017/chemistry/what-earth-are-tholins">found tholins</a> (a type of organic substance) there. But they also measured particles that suggested atmospheres at Saturn’s moons Rhea and Dione, in addition to those at Titan and Enceladus.</p>
<p>These particles are known as <a href="https://www.sciencedirect.com/topics/physics-and-astronomy/pickup-ions">pickup ions</a>. Planetary atmospheres consist of neutral particles, but the top of an atmosphere becomes “ionised” (meaning it loses electrons) in sunlight and via collisions with other particles, forming ions (charged atoms that have lost electrons) and free electrons. </p>
<p>When a plasma – a charged gas making up the fourth state of matter beyond solid, liquid and gas – flows past an atmosphere with newly formed ions, it disturbs the atmosphere with electric fields which can accelerate the new ions – the first part of an ion pickup process. </p>
<p>These pickup ions then spiral around the planet’s magnetic field and are usually lost from the atmosphere, while some hit the surface and are absorbed. The pickup process has rid the Martian atmosphere of particles after the red planet’s magnetic field was lost 3.8 billion years ago.</p>
<p>Europa also has a pickup process. The new measurements show the telltale signs of pickup molecular oxygen and hydrogen ions from the surface and atmosphere. Some of these escape from Europa, whereas some hit the icy surface enhancing the amount of oxygen at and under the surface. </p>
<p>This confirms that oxygen and hydrogen are indeed the main constituents of Europa’s atmosphere – in agreement with remote observations. However, the measurements imply that the amount of oxygen being produced – released by the surface to the atmosphere – is only about 12kg per second, at the lower end of earlier estimates from about 5kg to 1,100 kg per second. </p>
<p>This would indicate that the surface suffers very little erosion. The measurements indicate that this may amount to only 1.5cm of Europa’s surface per million years, which is less than we had thought. So Europa is constantly losing oxygen due to pickup processes, with only a small amount of additional oxygen being released from the surface to replenish it and ending up back on the surface.</p>
<p>So what does that mean for its chances of hosting life? Some of the oxygen trapped in the surface may find its way to the subsurface ocean to nourish any life there. But based on the study’s estimate of the overall loss of oxygen, this should be less than the 0.3kg-300kg per second estimated earlier. </p>
<p>It remains to be seen whether this rate, recorded on 29, September 2022, is usual. Perhaps it is not representative of the overall oxygen on the moon. It may be that the eruption of plumes, orbital position and upstream conditions increase and decrease the rate at certain times, respectively.</p>
<p>Nasa’s <a href="https://www.jpl.nasa.gov/missions/europa-clipper">Europa Clipper mission</a>, to be launched later this year, and the Juice mission which will make two flybys of Europa on its way to orbit Ganymede, will be able to follow up these measurements, and provide much more information on Europa’s habitability.</p><img src="https://counter.theconversation.com/content/225002/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Coates receives funding from STFC and UKSA (UK). </span></em></p>Only about 12kg of oxygen is produced per second on Europa, which is on the lower side of previous estimates from about 5kg to 1,100 kg per second.Andrew Coates, Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2186582023-12-06T15:53:37Z2023-12-06T15:53:37ZUFOs: how astronomers are searching the sky for alien probes near Earth<p>There has been increased interest in unidentified flying objects (UFOs) ever since the Pentagon’s <a href="https://www.dni.gov/files/ODNI/documents/assessments/Prelimary-Assessment-UAP-20210625.pdf">2021 report</a> revealed what appears to be anomalous objects in US airspace, dubbed unidentified aerial phenomena (UAP). Fast forward to 2023, and Nasa <a href="https://www.nasa.gov/news-release/update-nasa-shares-uap-independent-study-report-names-director/">has already formed a panel</a> to investigate the reports and <a href="https://www.nytimes.com/2023/09/14/science/nasa-ufo-uap-report.html">appointed a director </a> for UAP research. </p>
<p>A <a href="https://www.aaro.mil/">newly founded Pentagon desk</a> has also released <a href="https://globalnews.ca/news/9746110/metallic-flying-orbs-nasa-pentagon-panel-ufos-uaps/">footage of mysterious metallic orbs</a>. What is perhaps most remarkable is that David Grusch, a former intelligence officer, testified under oath before the US Congress, stating that he had interviewed around 40 people involved <a href="https://thedebrief.org/intelligence-officials-say-u-s-has-retrieved-non-human-craft/">in secret programmes dealing with crashed UFOs</a>.</p>
<p>I am interested in searching the sky for alien, physical objects which may one day tell us whether we are alone in the galaxy. Consider this: within our own Milky Way galaxy, there are 40 billion Earth-sized, potentially habitable planets. </p>
<p>Human ingenuity has enabled us to engineer and launch probes like Voyager and Pioneer, capable of reaching the closest stars. We’ve initiated efforts such as the <a href="https://breakthroughinitiatives.org/initiative/3">Breakthrough Starshot programme</a> which aims to reach nearby star Alpha Centauri in just a few decades by exploring innovative propulsion methods. <a href="https://www.nature.com/articles/nature02884">Sending a probe may be more economical</a> than sending out radio or laser communication if there is no need to hurry.</p>
<p>If humans can send a probe to another star, why couldn’t another civilisation send a probe to our Solar System? Such a probe could make it to the <a href="https://arxiv.org/abs/1808.07024">main asteroid belt</a> and <a href="https://earthsky.org/space/alien-lurker-probes-co-orbital-asteroids-earth/">lurk on an asteroid</a>. </p>
<p>Or, it could make its way to the Earth, entering our atmosphere. If observed, it would be branded as a “UFO”. A civilisation capable of producing and sending probes could dispatch millions of them on exploratory missions throughout our galaxy.</p>
<p>Some may argue that such probes could only exist if they adhere to the laws of physics and engineering as we understand them today. However, humanity is a relatively young civilisation, and our knowledge is constantly evolving. </p>
<p>While humans have dreamt of flying for millennia as we gazed at the skies, it has only been 120 years since the Wright brothers achieved the first powered flight. That’s about as long ago as Albert Einstein published his theory of special relativity.</p>
<p>Is it really so difficult to imagine that a civilisation that is hundreds of thousands years older than ours might have learned more about the laws of physics or developed <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7514271/">a few more engineering tricks</a>?</p>
<p>If a civilisation <a href="https://theconversation.com/seti-why-extraterrestrial-intelligence-is-more-likely-to-be-artificial-than-biological-169966">were to evolve into artificial intelligence (AI)</a>, it might survive for millions of years. This could mean it would casually regard slow to a neighbouring star as nothing more than a leisurely stroll.</p>
<p>That said, few astronomers felt impressed by the <a href="https://www.youtube.com/watch?v=rO_M0hLlJ-Q">US Navy videos</a> or government reports. We need significantly better evidence and data than what has been presented so far.</p>
<h2>Unveiling UFOs</h2>
<p>How can we test whether there are extra terrestrial probes near Earth, and whether they can be tied to the possible UFO phenomenon? There are many options. Analysing materials from potentially crashed UFOs could give irrefutable proof. This <a href="https://www.sciencedirect.com/science/article/abs/pii/S0376042121000907?fr=RR-2&ref=pdf_download&rr=8303a873ba1235b9">would require state-of-the-art techniques</a> to determine if these wrecks exhibit exotic or distinctly different characteristics of manufacture.</p>
<p>Obtaining such exotic samples, if they indeed exist, may prove challenging – they are rumoured to be <a href="https://nypost.com/2021/04/30/former-sen-harry-reid-thinks-lockheed-martin-may-have-ufo-fragments/">in the hands of private companies</a>. But <a href="https://www.democrats.senate.gov/newsroom/press-releases/schumer-rounds-introduce-new-legislation-to-declassify-government-records-related-to-unidentified-anomalous-phenomena-and-ufos_modeled-after-jfk-assassination-records-collection-act--as-an-amendment-to-ndaa">newly proposed legislation</a> might offer a solution to that problem in United States by mandating that all artificial materials from any non-human intelligence be surrendered to the US government.</p>
<p>In the projects I lead, we are searching for artificial non-human objects by <a href="https://www.sciencedirect.com/science/article/pii/S0094576522000480">looking for short light flashes</a> in the night sky. Short flashes typically occur when a flat, highly reflective surface — such as a mirror or glass — reflects sunlight. It could, however, also result from an artificial object emitting its own internal light.</p>
<p>Such short light flashes sometimes repeat and follow a straight line as the object tumbles in space during its orbit around the Earth. This is why satellites often appear as repeating light flashes in images. </p>
<p>Historical photographic plates taken before the launch of Sputnik 1 in 1957 <a href="https://earthsky.org/space/9-weird-transients-palomar-observatory-1950/">have revealed</a> the presence of nine light sources (transients) that appear and vanish within an hour in a small image, defying <a href="https://www.nature.com/articles/s41598-021-92162-7">astronomical explanations</a>. In some cases, the transient light sources <a href="https://arxiv.org/abs/2204.06091">are even aligned</a>, just like when short flashes come from moving objects. </p>
<figure class="align-center ">
<img alt="Image of the three disappearing stars." src="https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=234&fit=crop&dpr=1 600w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=234&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=234&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=294&fit=crop&dpr=1 754w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=294&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/563920/original/file-20231206-23-e5jplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=294&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The three disappearing stars.</span>
<span class="attribution"><a class="source" href="https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad3422/7457759">[Edited, higher-resolution version of Fig 2 in paper by Solano et al. (2023)(https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stad3422/7457759)]</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The <a href="https://www.universetoday.com/163820/in-1952-a-group-of-three-stars-vanished-astronomers-still-cant-find-them/">most recent finding</a> of this kind shows three bright stars in an image dated July 19, 1952 (coincidentally, the same time as the famous <a href="https://en.wikipedia.org/wiki/1952_Washington,_D.C.,_UFO_incident">Washington UFO flyovers</a>). The three stars were never seen again.</p>
<p>Searching for alien probes in the modern night sky presents a serious but necessary challenge. A new research programme, <a href="https://thedebrief.org/a-new-era-of-optical-seti-the-search-for-artificial-objects-of-non-human-origin/">known as ExoProbe</a>, searches for short light flashes from potential alien objects with the help of multiple telescopes. </p>
<p>To verify the authenticity of each flash, it must be observed in at least two different telescopes. Since these telescopes are separated by hundreds of kilometres, any light flash caused by an object within the inner Solar System enables the measurement of parallax — the apparent shift in the position of an object as seen from two different points — and the calculation of the distance to the object. </p>
<p>The ExoProbe project also uses its own methods to filter out light flashes from the millions of space debris fragments and thousands of satellites cluttering the sky. By adding a telescope taking real-time spectra (the wavelength distributions of the light) of the objects in a wide field, you can analyse the transients before they vanish into nothingness.</p>
<p>Finally, increasing the number of telescopes further enhances accuracy in measuring parallax and determining the actual three dimensional location of the object. Ultimately, the goal is to identify any potential alien object and bring it back to Earth for further study. </p>
<p>Some 60 years of searches for extraterrestrial civilisations in the radio frequencies have yielded no candidates whatsoever. We find ourselves at a moment in time when new paths must be explored. That means we can finally focus our attention closer to home. Regardless of the outcome, this journey is certainly an homage to our insatiable curiosity.</p><img src="https://counter.theconversation.com/content/218658/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Beatriz Villarroel receives funding from a private donor for the ExoProbe project.</span></em></p>Several scientific projects are aiming to investigate UFO sightings.Beatriz Villarroel, Assistant professor of Physics, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2185062023-12-05T12:39:02Z2023-12-05T12:39:02ZSeti: how we’re searching for alien life at previously unexplored frequencies<figure><img src="https://images.theconversation.com/files/563420/original/file-20231204-30-rxc98b.png?ixlib=rb-1.1.0&rect=26%2C98%2C2000%2C1814&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>Is there life beyond Earth? The question has turned out to be one of the hardest to answer in science. Despite the seemingly boundless expanse of the universe, which implies there’s potential for abundant life, the vast distances between stars render the search akin to locating a needle in a cosmic haystack.</p>
<p>The <a href="http://seti.berkeley.edu/.">Search for Extraterrestrial Intelligence (Seti)</a> constitutes a branch of astronomy dedicated to finding extraterrestrial life by searching for unusual signals, dubbed technosignatures. The identification of a technosignature wouldn’t just signify the existence of life, but specifically point to the presence of intelligent life using advanced technology.</p>
<p>That said, 60 years of searches have so far come up short. But now my colleagues at <a href="https://breakthroughinitiatives.org/">Breakthrough Listen</a> and I have <a href="https://www.tcd.ie/physics/news-events/news/2022/astrophysicists-scan-the-galaxy-for-signs-of-life/">started investigating</a> a previously unexplored range of frequencies. </p>
<p>Seti makes the assumption that extraterrestrial civilisations might rely on technology in a similar way to people on Earth, such as using cell phones, satellites or radar.</p>
<p>Since a significant portion of such technology generates signals that are prominently detectable in radio frequencies, focusing on these wavelengths serves as a logical starting point in the quest for potential extraterrestrial intelligence. </p>
<p>Previous technosignature surveys have included only the radio frequency band above 600 MHz, leaving lower frequencies virtually unexplored. That’s despite the fact that everyday communication services such as air traffic control, marine emergency broadcasting and FM radio stations all emit this type of low-frequency radiation on Earth.</p>
<p>The reason it hasn’t been explored is that telescopes that operate at these frequencies are rather new. And lower-frequency radio waves have less energy, meaning they can be more challenging to detect.</p>
<p>In our <a href="https://iopscience.iop.org/article/10.3847/1538-3881/acf9f5">concluded survey</a>, we ventured into these frequencies for the first time ever.</p>
<p>The <a href="https://www.ucl.ac.uk/astrophysics/research/cosmology/lofar-low-frequency-array#:%7E:text=The%20LOw%20Frequency%20ARray%20is,for%20a%20multi%2Duser%20operation.">Low Frequency Array (Lofar)</a> is the world’s most sensitive low-frequency telescope, operating from 10-250 MHz. It’s composed of 52 radio telescopes with more on the way, spread across Europe. These telescopes can reach a high resolution when used in unison. </p>
<figure class="align-center ">
<img alt="Radio telescope at Birr, Ireland." src="https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&rect=114%2C76%2C4993%2C2711&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562423/original/file-20231129-21-y3a68g.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Radio telescope at Birr, Ireland.</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>Our survey, however, only made use of two of these stations: <a href="https://lofar.ie/">one situated in Birr</a>, Ireland, and <a href="https://www.chalmers.se/en/infrastructure/oso/telescopes-and-instruments/radio-astronomy-facilities/lofar/">the other</a> in Onsala, Sweden. We surveyed 44 planets orbiting other stars than our Sun that had been identified by Nasa’s <a href="https://tess.mit.edu/">Transiting Exoplanet Survey Satellite</a>. Over the course of two summers, we scanned these planets at 110 to 190 MHz with our two telescopes.</p>
<p>Initially, this doesn’t seem like a large amount of targets, but low-frequency observation boasts a major advantage in having large fields of view compared with their higher-frequency siblings. That’s because the area of the sky covered decreases with higher frequencies. </p>
<p>In the case of Lofar, we covered 5.27 square degrees of the sky for each pointing of our telescopes. This culminated in 36,000 targets per telecope pointing – or more than 1,600,000 targets in total, when you check what other stars are nearby and include their planets as well.</p>
<h2>Interfering signals</h2>
<p>Searching for technosignatures from space introduces a significant challenge — the same technosignatures are ubiquitous on Earth. This presents an obstacle as the telescopes in these searches boast sensitivity levels that can detect signals, such as a phone call, from halfway across the Solar System. </p>
<p>Consequently, the data collected is inundated with thousands of signals originating from Earth, posing a considerable difficulty in isolating and identifying signals that could be of extraterrestrial origin. The need to sift through this extensive and noisy dataset adds a layer of complexity to the search.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=502&fit=crop&dpr=1 600w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=502&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=502&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=631&fit=crop&dpr=1 754w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=631&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/562422/original/file-20231129-15-tobzas.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=631&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Overview of the stars searched for technosignatures by Lofar in our Milky Way.</span>
<span class="attribution"><span class="source">Owen Johnson</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We came up with an innovative approach to mitigating such radio frequency interference, called the “coincidence rejection” method. This takes into account the local radio emissions at each of our telescopes. For example, if I am using the telephone close to the telescope in Ireland to call my supervisor, that same call won’t appear in the data in Sweden, and vice versa (mainly because the telescope isn’t pointing in our direction, it’s pointing at an exoplanet candidate).</p>
<p>So, we decided to only include signatures in the dataset if they exhibited a simultaneous presence at both stations, suggesting they come from outside Earth.</p>
<p>In this way, we whittled down thousands of candidate signals to zero. This means we didn’t find any signs of intelligent life with our search, but we have only just started – and there are likely to be an enormous number of Earth-like planets out there. Knowing that the coincidence rejection method works with a high success rate may be key to helping us discover life at one of these planets in the future.</p>
<p>There are many ways forward for technosignature searches at low frequencies. Currently, there is a <a href="https://nenufar.obs-nancay.fr/en/homepage-en/">sister survey (Nenufar)</a> being carried out on that operates at 30-85 MHz. Along with this, further Lofar observations will increase the volume of the survey by a factor of ten over the course of the coming year. The collected data is also used for investigating astronomical objects known as pulsars, fast radio bursts, radio exoplanets and more.</p>
<p>Thankfully, we’re only at the start of a long journey. I have no doubt that many wondrous things will be found. And if we’re lucky, we may reap the biggest reward of all: some company in the cosmos.</p><img src="https://counter.theconversation.com/content/218506/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Owen Johnson receives funding from the Breakthrough Prize Foundation. </span></em></p>Previous searches for extraterrestrial life have included only the radio band above 600 MHz, leaving lower frequencies virtually unexplored.Owen Johnson, PhD Candidate of Astrophysics, Trinity College DublinLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2160372023-10-20T15:24:19Z2023-10-20T15:24:19ZCarl Sagan detected life on Earth 30 years ago – here’s how his experiment is helping us search for alien species today<figure><img src="https://images.theconversation.com/files/554817/original/file-20231019-24-ktzu5b.jpeg?ixlib=rb-1.1.0&rect=0%2C88%2C494%2C415&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Earth and Moon as seen by the Galileo spacecraft from a distance of 6 million km away.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>It’s been 30 years since a group of scientists led by <a href="https://science.nasa.gov/people/carl-sagan/">Carl Sagan</a> found <a href="https://www.nature.com/articles/365715a0">evidence</a> for life on Earth using data from instruments on board the Nasa <a href="https://science.nasa.gov/mission/galileo/">Galileo</a> robotic spacecraft. Yes, you read that correctly. Among his many pearls of wisdom, Sagan was famous for saying that science is more than a body of knowledge – it is a way of thinking.</p>
<p>In other words, how humans go about the business of discovering new knowledge is at least as important as the knowledge itself. In this vein, the study was an example of a “control experiment” – a critical part of the scientific method. This can involve asking whether a given study or method of analysis is capable of finding evidence for something we already know. </p>
<p>Suppose one were to fly past Earth in an alien spacecraft with the same instruments on board as Galileo had. If we knew nothing else about Earth, would we be able to unambiguously detect life here, using nothing but these instruments (which wouldn’t be optimised to find it)? If not, what would that say about our ability to detect life anywhere else? </p>
<p>Galileo launched in October 1989 on a six-year flight to Jupiter. However, Galileo had to first make several orbits of the inner Solar System, making close flybys of Earth and Venus, in order to pick up enough speed to reach Jupiter. </p>
<p>In the mid-2000s, scientists took samples of dirt from the Mars-like environment of Chile’s Atacama desert on Earth, which is <a href="https://new.nsf.gov/news/microbes-mars">known to contain</a> microbial life. They then used similar experiments as those used on the NASA Viking spacecraft (which aimed to detect life on Mars when they landed there in the <a href="https://www.nasa.gov/history/45-years-ago-viking-1-touches-down-on-mars/">1970s</a>) to see if life could be found in Atacama. </p>
<p>They failed – the implication being that had the Viking spacecraft landed on Earth in the Atacama Desert, and performed the same experiments as they did on Mars, they might well have <a href="https://www.space.com/3038-martian-life-evaded-detection-viking-landers.html">missed</a> signatures for life, even though it is known to be present. </p>
<h2>Galileo results</h2>
<p>Galileo was kitted out with a variety of instruments designed to study the atmosphere and space environment of Jupiter and its moons. These included imaging cameras, spectrometers (which break down light by wavelength) and a radio experiment.</p>
<p>Importantly, the authors of the study did not presume any characteristics of life on Earth <em>ab initio</em> (from the beginning), but attempted to derive their conclusions just from the data. The near infra-red mapping spectrometer (NIMS) instrument detected gaseous water distributed throughout the terrestrial atmosphere, ice at the poles and large expanses of liquid water “of oceanic dimensions”. It also recorded temperatures ranging from -30°C to +18°C. </p>
<figure class="align-center ">
<img alt="Image taken by the Galileo spacecraft at a distance of 2.4 million km." src="https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C498%2C498&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554815/original/file-20231019-29-7ie95h.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">Can you see us? Galileo image.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Evidence for life? Not yet. The study concluded that the detection of liquid water and a water weather system was a <a href="https://math.stackexchange.com/questions/1110111/necessary-but-not-sufficient-in-logic">necessary, but not sufficient</a> argument. </p>
<p>NIMS also detected high concentrations of oxygen and methane in the Earth’s atmosphere, as compared to other known planets. Both of these are highly reactive gases that would rapidly react with other chemicals and dissipate in a short period of time. The only way for such concentrations of these species to be upheld were if they were continuously replenished by some means – again suggesting, but not proving, life. Other instruments on the spacecraft detected the presence of an ozone layer, shielding the surface from damaging UV radiation from the Sun. </p>
<p>One might imagine that a simple look through the camera might be enough to spot life. But the images showed oceans, deserts, clouds, ice and darker regions in South America which, only with prior knowledge, we know of course to be rain forests. However, once combined with more spectrometry, a distinct absorption of red light was found to overlay the darker regions, which the study concluded was “strongly suggestive” of light being absorbed by photosynthetic plant life. No minerals were known to absorb light in exactly this fashion. </p>
<p>The highest resolution images taken, as dictated by the flyby geometry, were of the deserts of central Australia and the ice sheets of Antarctica. Hence none of the images taken showed cities or clear examples of agriculture. The spacecraft also flew by the planet at closest approach during the daytime, so lights from cities at night were not visible either. </p>
<p>Of greater interest though was Galileo’s <a href="https://pds-ppi.igpp.ucla.edu/data/GO-A-PWS-2-REFDR-GSAFULL-V1.0/DOCUMENT/PWS/PWS.PDF">plasma wave radio experiment</a>. The cosmos is full of natural radio emission, however most of it is broadband. That is to say, the emission from a given natural source occurs across many frequencies. Artificial radio sources, by contrast, are produced in a narrow band: an everyday example is the meticulous tuning of an analogue radio required to find a station amidst the static.</p>
<p>An example of natural radio emission from aurora in Saturn’s atmosphere can be heard below. The frequency changes rapidly – unlike a radio station.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6nxLXvqLp50?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Galileo detected consistent narrowband radio emission from Earth at fixed frequencies. The study concluded this could only have come from a technological civilisation, and would only be detectable within the last century. If our alien spacecraft had made the same flyby of Earth at any time in the few billion years prior to the 20th century then it would have seen no definitive evidence of a civilisation on Earth at all. </p>
<p>It is perhaps no surprise then that, as yet, no evidence for extra-terrestrial life has been found. Even a spacecraft flying within a few thousand kilometres of human civilisation on Earth is not guaranteed to detect it. Control experiments like this are therefore critical in informing the search for life elsewhere. </p>
<p>In the present era, humanity has now discovered over 5,000 planets around other stars, and we have even detected the presence of water <a href="https://www.nature.com/articles/s41550-019-0878-9">in the atmospheres</a> of some planets. Sagan’s experiment shows this is not enough by itself.</p>
<p>A strong case for life elsewhere will likely require a combination of mutually supporting evidence, such as light absorption by photosynthesis-like processes, narrowband radio emission, modest temperatures and weather and chemical traces in the atmosphere which are hard to explain by non-biological means. As we move into the era of instruments such as the <a href="https://webb.nasa.gov/">James Webb space telescope</a>, Sagan’s experiment remains as informative now as it was 30 years ago.</p><img src="https://counter.theconversation.com/content/216037/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gareth Dorrian 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>Control experiments are critical in informing the search for alien life.Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of BirminghamLicensed 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/2134582023-09-13T07:13:57Z2023-09-13T07:13:57ZSigns of life? Why astronomers are excited about carbon dioxide and methane in the atmosphere of an alien world<figure><img src="https://images.theconversation.com/files/547922/original/file-20230913-23-zphpi7.jpeg?ixlib=rb-1.1.0&rect=28%2C5%2C3805%2C2149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA / CSA / ESA / J. Olmsted (STScI) / Science: N. Madhusudhan (Cambridge University)</span></span></figcaption></figure><p>Are we alone? This question is nearly as old as humanity itself. Today, this question in astronomy focuses on finding life beyond our planet. Are we, as a species, and as a planet, alone? Or is there life somewhere else?</p>
<p>Usually the question inspires visions of weird, green versions of humans. However, life is more than just us: animals, fish, plants and even bacteria are all the kinds of things we seek signs of in space.</p>
<p>One thing about life on Earth is that it leaves traces in the chemical makeup of the atmosphere. So traces like that, which are visible from a long way away, are something we look for when we’re hunting aliens. </p>
<p>Scientists in the United Kingdom and the United States <a href="https://arxiv.org/abs/2309.05566">have just reported</a> some very interesting chemical traces in the atmosphere of a planet called K2-18b, which is about 124 light-years from Earth. In particular, they may have detected a substance which on Earth is only produced by living things. </p>
<h2>Meet exoplanet K2-18b</h2>
<p>K2-18b is an interesting exoplanet – a planet that orbits another star. Discovered in 2015 by the Kepler Space Telescope’s K2 mission, it is a type of planet called a sub-Neptune. As you probably guessed, these are smaller than Neptune in our own Solar System.</p>
<p>The planet is about eight and a half times heavier than Earth, and orbits a type of star called a red dwarf, which is much cooler than our Sun. However, K2-18b orbits much closer to its star than Neptune does – in what we call the habitable zone. This is the area that is not too hot and not too cold, where liquid water can exist (instead of freezing to ice or boiling into steam).</p>
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Read more:
<a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">To 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</a>
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<p>Earth is what is called a rocky planet (for obvious reasons), but sub-Neptunes are gas planets, with much larger atmospheres containing lots of hydrogen and helium. Their atmosphere can also contain other elements.</p>
<p>Which brings us to the excitement around K2-18b. </p>
<h2>How to fingerprint an atmosphere</h2>
<p>The planet was first discovered by the Kepler Space Telescope, which was monitoring distant stars and hoping for planets to pass in front of them. When a planet does pass between us and a star, the star becomes momentarily dimmer – which is what tells us a planet is there.</p>
<p>By measuring how big the dip in brightness is, how long it takes for the planet to pass in front of the star, and how often it happens, we can work out the size and orbit of the planet. This technique is great at finding planets, but it doesn’t tell us about their atmospheres – which is a key piece of information to understand if they hold life or are habitable.</p>
<p>NASA’s James Webb Space Telescope – the big space telescope launched at the end of 2021 – has now observed and measured the atmosphere of this exoplanet. </p>
<p>The telescope did this by measuring the colour of light so finely, it can detect traces of specific atoms and molecules. This process, called spectroscopy, is like measuring the fingerprint of elements. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing the absorption of different wavelengths of light by the atmosphere of K2-18b, and which wavelengths correspond to different substances in the atmosphere." src="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547994/original/file-20230913-15-44y44s.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"></a>
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<span class="caption">The atmosphere of the exoplanet K2-18b showed strong signs of methane and carbon dioxide, as well as a weak indication of dimethyl sulfide.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-dioxide-in-atmosphere-of-k2-18b">NASA / CSA / ESA / R. Crawford (STScI) / J. Olmsted (STScI) / N. Madhusudhan (Cambridge University)</a></span>
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<p>Each element and molecule has its own colour signature. If you can look at the colour signature, you can do a bit of detective work, and work out what elements or compounds are in the planet.</p>
<p>While the planet does not have its own light, astronomers waited for when K2-18b passed in front of its star, and measured the starlight as it went through the planet’s atmosphere, allowing the team to detect fingerprints of substances in the atmosphere.</p>
<h2>Alien marine farts?</h2>
<p>The new study found a lot of carbon dioxide and methane. This is interesting as this is like what is found on Earth, Mars, and Venus in our Solar System – rather than Neptune.</p>
<p>However, it also found a small amount of dimethyl sulfide. Dimethyl sulfide is an interesting molecule, made up of carbon, hydrogen, and sulfur.</p>
<p>On Earth, it’s generally a bit smelly. But it’s also closely linked to life.</p>
<p>The only process we know that creates dimethyl sulfide on our planet is life. In particular, marine life and plankton emit it in the form of flatulence.</p>
<p>So yes, scientists are excited by the potential idea of alien marine farts. If it is real. And linked to life.</p>
<h2>The search continues</h2>
<p>While on Earth, dimethyl sulfide is linked to life, on other planets it may somehow be related to geological or chemical processes.</p>
<p>After all, K2-18b is something like Neptune – a planet we do not really know a lot about. Just last month, researchers discovered that <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103523002440">clouds on Neptune are strongly linked</a> to the Sun’s 11-year cycle of activity. We have a lot to learn about planets and their atmospheres.</p>
<p>Also, the measurement of dimethyl sulfide is very subtle – not nearly as strong as the carbon dioxide and methane. This means more detailed measurements, to improve the strength of the signal, are required. </p>
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<a href="https://theconversation.com/the-webb-telescope-has-released-its-very-first-exoplanet-image-heres-what-we-can-learn-from-it-189876">The Webb telescope has released its very first exoplanet image – here's what we can learn from it</a>
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<p>Other telescopes may need to join the effort. Instruments on the Very Large Telescope in Chile are able to measure the atmospheres of planets around other stars – as is a new instrument called Veloce on the Anglo Australian Telescope at Siding Spring Observatory in Australia.</p>
<p>And new space telescopes, like Europe’s PLATO which is under construction, will also help us get a better look at alien atmospheres.</p>
<p>So while the signs of dimethyl sulfide on K2-18b may not be linked to life, they are still an exciting prospect. There is plenty more to explore.</p><img src="https://counter.theconversation.com/content/213458/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brad E Tucker receives funding from the Australian Research Council and Australian Capital Territory Government. </span></em></p>The James Webb Space Telescope has detected key carbon-bearing molecules on the potential ocean world K2-18b, including tantalising hints of a substance produced by tiny plankton on Earth.Brad E Tucker, Astrophysicist/Cosmologist, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2109552023-08-04T12:30:01Z2023-08-04T12:30:01ZAre we alone in the universe? 4 essential reads on potential contact with aliens<figure><img src="https://images.theconversation.com/files/541095/original/file-20230803-27-wa23kr.jpg?ixlib=rb-1.1.0&rect=39%2C0%2C8694%2C5617&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UFOs usually have non-extraterrestrial origins, but many have urged the government to be more transparent about UFO data. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/long-exposure-of-andromeda-galaxy-royalty-free-image/1455373371?phrase=space&adppopup=true">Westend61/Westend61 via Getty Images</a></span></figcaption></figure><p>The House subcommittee on National Security, the Border, and Foreign Affairs <a href="https://www.c-span.org/video/?529499-1/hearing-unidentified-aerial-phenomena">met in July 2023 to discuss</a> affairs so foreign that they may not even be of this world. During the meeting, several military officers testified that unidentified anomalous phenomena – the government’s name for UFOs – <a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">pose a threat</a> to national security. </p>
<p>Their testimony may have <a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">raised eyebrows in the chamber</a>, but there’s still no public physical evidence of extraterrestrial life. In fact, most UFO sightings <a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">have earthly explanations</a>, from tricks of the light to weather balloons. </p>
<p>Whether or not these testimonials hold any grains of truth, some scholars argue that simply by listening for signs of extraterrestrials, we’re already <a href="https://theconversation.com/first-contact-with-aliens-could-end-in-colonization-and-genocide-if-we-dont-learn-from-history-207793">engaging in the first phase of contact</a> with alien life. </p>
<p>These four articles from our archives dive into what went down during the subcommittee hearing, why perceived UFO sightings usually have human explanations, and how humanity can learn from history when it comes to engaging with extraterrestrials. </p>
<h2>1. Whistleblower allegations</h2>
<p>The most interesting testimony of the July 26 subcommittee hearing came from ex-Air Force Intelligence Officer David Grusch, who <a href="https://oversight.house.gov/wp-content/uploads/2023/07/Dave_G_HOC_Speech_FINAL_For_Trans.pdf">claimed that</a> the U.S. has nonhuman biological material recovered from a UFO crash site. The Pentagon has <a href="https://abcnews.go.com/Politics/house-oversight-plans-ufo-hearing-after-unconfirmed-claims/story?id=99899883">denied this claim</a>, and it has <a href="https://abcnews.go.com/Politics/house-oversight-plans-ufo-hearing-after-unconfirmed-claims/story?id=99899883">denied the existence of any program</a> designed to retrieve and reverse-engineer crashed UFOs. </p>
<p>All witnesses at the hearing advocated for more government transparency around reports of UFOs. Intelligence agencies and the Pentagon currently steward this data, most of which <a href="https://www.newsnationnow.com/space/ufo/pentagon-blocks-lawmakers-ufo-data-uap-hearing/">is not public</a>. While having access to more data may help understand what’s going on, as the University of Arizona’s <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">Chris Impey</a> put it, “the gold standard is physical evidence.”</p>
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<a href="https://theconversation.com/whistleblower-calls-for-government-transparency-as-congress-digs-for-the-truth-about-ufos-210435">Whistleblower calls for government transparency as Congress digs for the truth about UFOs</a>
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<h2>2. Sociological explanations</h2>
<p>Again, while no physical evidence has been made public, anyone surfing the internet can see plenty of alleged UFO videos, photos and stories. <a href="https://scholar.google.com/citations?user=ZEQu09wAAAAJ&hl=en">Barry Markovsky</a>, from the University of South Carolina, is a sociologist of shared beliefs and misconceptions who explained why UFOs seem to <a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">captivate the public</a> every few years.</p>
<p>People want explanations <a href="https://thedecisionlab.com/biases/ambiguity-effect">for ambiguous situations</a>, and they’re easily influenced by others. Social media enables a concept called <a href="https://doi.org/10.31269/triplec.v3i2.21">bottom-up social diffusion</a>. Say one user posts a blurry video claiming it depicts a UFO. It’s easy for that user’s network to see and repost the video and so on, until it goes viral. Then, when organized institutions like news outlets or government sources publish UFO-related information, that’s called <a href="https://doi.org/10.31269/triplec.v3i2.21">top-down social diffusion</a>. </p>
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<a href="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two circle-and-line graphics, the left showing several circles connected to one another with lines, while the right shows one circle at the top connecting several other circles" src="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=284&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=284&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=284&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=357&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=357&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=357&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The left image shows bottom-up diffusion, in which information spreads from person to person. The right shows top-down diffusion, in which information spreads from one authority.</span>
<span class="attribution"><span class="source">Barry Markovsky</span></span>
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<p>“Diffusion processes can combine into self-reinforcing loops. Mass media spreads UFO content and piques worldwide interest in UFOs. More people aim their cameras at the skies, creating more opportunities to capture and share odd-looking content,” Markovsky wrote. “Poorly documented UFO pics and videos spread on social media, leading media outlets to grab and republish the most intriguing. Whistleblowers emerge periodically, fanning the flames with claims of secret evidence.”</p>
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<a href="https://theconversation.com/why-people-tend-to-believe-ufos-are-extraterrestrial-208403">Why people tend to believe UFOs are extraterrestrial</a>
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<h2>3. Signature detection</h2>
<p>While UFOs might have traction on social media, it’s likely that the first trace of extraterrestrial life won’t come from a crashed alien spaceship. Instead, scientists could potentially <a href="https://theconversation.com/signatures-of-alien-technology-could-be-how-humanity-first-finds-extraterrestrial-life-191054">pick up signals</a> like radio waves or pollution from some distant galaxy that might indicate extraterrestrial technology. </p>
<p>The <a href="https://www.seti.org/">Search for Extraterrestrial Intelligence</a> is a group of scientists all working on the search for extraterrestrial life. Part of what they do is listen for these “<a href="https://doi.org/10.1017/S1473550419000284">technosignatures</a>”.</p>
<p>As two astronomers who work on the Search for Extraterrestrial Intelligence, Penn State’s <a href="https://sites.psu.edu/macyhuston/">Macy Huston</a> and <a href="https://sites.psu.edu/astrowright/">Jason Wright</a> wrote about how humans often <a href="https://www.doi.org/10.1126/science.199.4327.377">unintentionally broadcast signals</a> like radio waves into space. In theory, extraterrestrial civilizations could be doing the same thing – and if scientists can pick up on these signals, they might have their first hints at alien life. </p>
<p>“However, this approach assumes that extraterrestrial civilizations <a href="https://www.universetoday.com/149513/beyond-fermis-paradox-xvii-what-is-the-seti-paradox-hypothesis/">want to communicate</a> with other technologically advanced life,” Huston and Wright explained. “Humans very rarely send targeted signals into space, and some scholars argue that intelligent species may <a href="https://theconversation.com/blasting-out-earths-location-with-the-hope-of-reaching-aliens-is-a-controversial-idea-two-teams-of-scientists-are-doing-it-anyway-182036">purposefully avoid broadcasting</a> out their locations. This search for signals that no one may be sending is called <a href="https://doi.org/10.48550/arXiv.physics/0611283">the SETI Paradox</a>.” </p>
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<a href="https://theconversation.com/signatures-of-alien-technology-could-be-how-humanity-first-finds-extraterrestrial-life-191054">Signatures of alien technology could be how humanity first finds extraterrestrial life</a>
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<h2>4. Ethical considerations</h2>
<p>While the Search for Extraterrestrial Intelligence hasn’t yet detected any extraterrestrial technosignatures, a <a href="https://escholarship.org/uc/item/2sq6f3b0">working group of interdisciplinary scholars</a> in Indigenous studies argued that the act of listening for these signals may already count as engaging in first contact with extraterrestrial life.</p>
<p>The Indigenous studies working group argued that first contact may not be just one event – rather, you can think of it as a <a href="https://doi.org/10.1177/2514848619862191">long phase</a> that begins with listening and planning. Listening can be an act of surveillance, and with that comes ethical considerations. </p>
<p>But research groups like the Search for Extraterrestrial Intelligence don’t often include perspectives from the humanities, even though there are many histories of first contact between groups of people here on Earth to draw from. </p>
<p>James Cook’s 1768 voyage to Oceania, for example, was planned as scientific exploration. But its <a href="https://doi.org/10.17953/aicrj.45.1.lempert">legacy of genocide</a> still affects the Indigenous people of Australia and New Zealand today. </p>
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<figcaption><span class="caption">This BBC video describes the modern ramifications of Captain James Cook’s colonial legacy in New Zealand.</span></figcaption>
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<p>“The initial domino of a public ET message, or recovered bodies or ships, could initiate <a href="https://doi.org/10.1098/rsta.2010.0236">cascading events</a>, including military actions, corporate resource mining and perhaps even geopolitical reorganizing,” wrote <a href="https://www.wacd.ucla.edu/people/faculty/david-shorter">David Shorter</a>, <a href="https://www.bowdoin.edu/profiles/faculty/wlempert/index.html">William Lempert</a> and <a href="https://kimtallbear.com/">Kim Tallbear</a>. “No one can know for sure <a href="https://theconversation.com/is-your-religion-ready-to-meet-et-32541">how engagement with extraterrestrials would go</a>, though it’s better to consider cautionary tales from Earth’s own history sooner rather than later.”</p>
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Read more:
<a href="https://theconversation.com/first-contact-with-aliens-could-end-in-colonization-and-genocide-if-we-dont-learn-from-history-207793">First contact with aliens could end in colonization and genocide if we don't learn from history</a>
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<p><em>Editor’s note: This story is a roundup of articles from The Conversation’s archives.</em></p><img src="https://counter.theconversation.com/content/210955/count.gif" alt="The Conversation" width="1" height="1" />
Whistleblower allegations that the government possesses UFOs may not be backed up by public physical evidence, but some argue that listening for extraterrestrial life is the first phase of contact.Mary Magnuson, Assistant Science EditorLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2084032023-07-17T12:26:25Z2023-07-17T12:26:25ZWhy people tend to believe UFOs are extraterrestrial<figure><img src="https://images.theconversation.com/files/536674/original/file-20230710-27-qxl8co.jpg?ixlib=rb-1.1.0&rect=63%2C0%2C7071%2C4657&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Photos claiming to be UFO evidence are often doctored or otherwise ambiguous. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/in-flight-above-urban-park-royalty-free-image/BD0513-001?phrase=ufos&adppopup=true">Ray Massey/The Image Bank via Getty Images</a></span></figcaption></figure><p>Most of us still call them UFOs – unidentified flying objects. NASA <a href="https://www.nasa.gov/feature/nasa-announces-unidentified-aerial-phenomena-study-team-members/">recently adopted</a> the term “unidentified anomalous phenomena,” or UAP. Either way, every few years popular claims resurface that these things are not of our world, or that the <a href="https://thedebrief.org/intelligence-officials-say-u-s-has-retrieved-non-human-craft/">U.S. government has some stored away</a>.</p>
<p>I’m <a href="https://scholar.google.com/citations?user=ZEQu09wAAAAJ&hl=en">a sociologist</a> who focuses on the interplay between individuals and groups, especially concerning shared beliefs and misconceptions. As for why UFOs and their alleged occupants enthrall the public, I’ve found that normal human perceptual and social processes explain UFO buzz as much as anything up in the sky. </p>
<h2>Historical context</h2>
<p>Like political scandals and high-waisted jeans, UFOs trend in and out of collective awareness but never fully disappear. <a href="https://abcnews.go.com/Technology/ufos-exist-americans-national-geographic-survey/story?id=16661311">Thirty years of polling</a> find that <a href="https://www.pewresearch.org/short-reads/2021/06/30/most-americans-believe-in-intelligent-life-beyond-earth-few-see-ufos-as-a-major-national-security-threat/">25%-50% of surveyed Americans</a> believe at least some UFOs are alien spacecraft. Today in the U.S., over <a href="https://news.gallup.com/poll/353420/larger-minority-says-ufos-alien-spacecraft.aspx">100 million adults</a> think our galactic neighbors pay us visits.</p>
<p>It wasn’t always so. Linking objects in the sky with visiting extraterrestrials has risen in popularity only in the <a href="https://theconversation.com/from-flying-boats-to-secret-soviet-weapons-to-alien-visitors-a-brief-cultural-history-of-ufos-164128">past 75 years</a>. Some of this is probably market-driven. Early UFO stories boosted newspaper and magazine sales, and today they are reliable <a href="https://kipac.stanford.edu/highlights/aliens-could-be-out-there-dont-trust-clickbait">clickbait</a> online. </p>
<p>In 1980, a popular book called “<a href="https://archive.org/details/roswellincident00berl">The Roswell Incident</a>” by Charles Berlitz and William L. Moore described an alleged flying saucer crash and government cover-up 33 years prior near Roswell, New Mexico. The only evidence ever to emerge from this story was a small string of downed weather balloons. Nevertheless, the book coincided with a <a href="https://www.washingtonpost.com/history/2022/07/08/roswell-flying-saucer-ufo/">resurgence of interest</a> in UFOs. From there, a steady stream of UFO-themed <a href="https://tvshowpilot.com/fun-posts/best-alien-tv-shows/">TV shows</a>, <a href="https://www.imdb.com/list/ls041828914/">films</a>, and <a href="https://screenrant.com/netflix-ufo-documentaries-best-greatest/">pseudo-documentaries</a> has fueled public interest. Perhaps inevitably, <a href="https://www.press.jhu.edu/books/title/12893/conspiracy">conspiracy theories</a> about government cover-ups have risen in parallel.</p>
<p>Some UFO cases inevitably remain unresolved. But despite <a href="https://theconversation.com/why-is-the-pentagon-interested-in-ufos-116714">the growing interest</a>, multiple <a href="https://www.af.mil/The-Roswell-Report/">investigations</a> have found <a href="https://www.washingtonpost.com/magazine/2021/08/11/stop-ufo-mania-no-evidence-of-aliens/">no evidence</a> that UFOs are of extraterrestrial origin – other than the occasional meteor or misidentification of <a href="https://www.nasa.gov/vision/universe/watchtheskies/03may_maximumvenus.html">Venus</a>. </p>
<p>But the U.S. Navy’s 2017 <a href="https://www.nytimes.com/2017/12/16/us/politics/pentagon-program-ufo-harry-reid.html">Gimbal video</a> continues to appear in the media. It shows strange <a href="https://www.youtube.com/watch?v=2TumprpOwHY&ab_channel=ABCNews">objects filmed by fighter jets</a>, often interpreted as evidence of alien spacecraft. And in June 2023, an otherwise credible Air Force veteran and former intelligence officer made the <a href="https://thedebrief.org/intelligence-officials-say-u-s-has-retrieved-non-human-craft/">stunning claim</a> that the U.S. government is storing numerous downed alien spacecraft and their dead occupants. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2TumprpOwHY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">UFO videos released by the U.S. Navy, often taken as evidence of alien spaceships.</span></figcaption>
</figure>
<h2>Human factors contributing to UFO beliefs</h2>
<p>Only a small percentage of UFO believers are <a href="https://news.gallup.com/vault/190592/gallup-vault-eyewitnesses-flying-saucers.aspx">eyewitnesses</a>. The rest base their opinions on eerie images and videos strewn across both social media and traditional mass media. There are astronomical and biological reasons to be <a href="https://www.bloomsbury.com/us/skeptic-encyclopedia-of-pseudoscience-2-volumes-9781576076538/">skeptical</a> of UFO claims. But less often discussed are the psychological and social factors that bring them to the popular forefront.</p>
<p>Many people would love to know whether or not <a href="https://exoplanets.nasa.gov/news/1675/life-in-the-universe-what-are-the-odds/">we’re alone in the universe</a>. But so far, the evidence on UFO origins is ambiguous at best. Being <a href="https://thedecisionlab.com/biases/ambiguity-effect">averse to ambiguity</a>, people want answers. However, being highly motivated to find those answers can <a href="https://doi.org/10.1037/0033-2909.108.3.480">bias judgments</a>. People are more likely to accept weak evidence or fall prey to optical illusions if they support preexisting beliefs. </p>
<p>For example, in the 2017 Navy video, the UFO appears as a cylindrical aircraft moving rapidly over the background, rotating and darting in a manner unlike any terrestrial machine. <a href="https://www.skeptic.com/reading_room/gimbal-video-genuine-ufo-or-camera-artifact/">Science writer Mick West’s analysis</a> challenged this interpretation using data displayed on the tracking screen and some basic geometry. He explained how the movements attributed to the blurry UFO are an illusion. They stem from the plane’s trajectory relative to the object, the quick adjustments of the belly-mounted camera, and misperceptions based on our tendency to assume cameras and backgrounds are stationary.</p>
<p>West found the UFO’s flight characteristics were more like a bird’s or <a href="https://amuedge.com/beyond-ufos-what-are-navy-pilots-seeing-in-the-skies/">a weather balloon’s</a> than an acrobatic interstellar spacecraft. But the illusion is compelling, especially with the Navy’s still deeming the object unidentified.</p>
<p><a href="https://www.youtube.com/watch?v=AvhMMhW-JN0&t=249s&ab_channel=MickWest">West also addressed</a> the former intelligence officer’s <a href="https://thedebrief.org/intelligence-officials-say-u-s-has-retrieved-non-human-craft/">claim that the U.S. government possesses crashed UFOs</a> and dead aliens. He emphasized caution, given the whistleblower’s only evidence was that people he trusted told him they’d seen the alien artifacts. West noted we’ve <a href="https://bigthink.com/13-8/military-whistleblowers-ufos-70-years/">heard this sort of thing before</a>, along with promises that the proof will soon be revealed. But it never comes.</p>
<p>Anyone, including pilots and intelligence officers, can be socially influenced to see things that aren’t there. Research shows that hearing from others who claim to have seen something extraordinary is enough to <a href="https://www.jstor.org/stable/10.1525/sop.2001.44.1.21">induce similar judgments</a>. The effect is heightened when the influencers are numerous or higher in status. Even recognized experts aren’t immune from <a href="https://www.bbc.com/news/av/world-us-canada-65771398">misjudging unfamiliar images</a> obtained under unusual conditions.</p>
<h2>Group factors contributing to UFO beliefs</h2>
<p>“Pics or it didn’t happen” is a <a href="https://www.theguardian.com/news/2015/feb/26/pics-or-it-didnt-happen-mantra-instagram-era-facebook-twitter">popular expression</a> on social media. True to form, users are posting countless shaky images and videos of UFOs. Usually they’re nondescript lights in the sky captured on cellphone cameras. But they can <a href="https://www.feedough.com/why-things-go-viral/">go viral on social media</a> and reach millions of users. With no higher authority or organization propelling the content, social scientists call this a bottom-up <a href="https://doi.org/10.1146/annurev.soc.24.1.265">social diffusion</a> process.</p>
<p>In contrast, top-down diffusion occurs when information emanates from centralized agents or organizations. In the case of UFOs, sources have included social institutions like <a href="https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104590/unidentified-flying-objects-and-air-force-project-blue-book/">the military</a>, individuals with large public platforms like <a href="https://thehill.com/homenews/4062715-us-has-downplayed-the-number-of-ufo-sightings-senator-hawley/">U.S. senators</a>, and major media outlets like <a href="https://www.cbsnews.com/news/ufo-military-intelligence-60-minutes-2021-08-29/">CBS</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two circle-and-line graphics, the left showing several circles connected to one another with lines, while the right shows one circle at the top connecting several other circles" src="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=284&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=284&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=284&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=357&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=357&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536695/original/file-20230710-15-14kf6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=357&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 left image shows bottom-up diffusion, in which information spreads from person to person. The right shows top-down, in which information spreads from one authority.</span>
<span class="attribution"><span class="source">Barry Markovsky</span></span>
</figcaption>
</figure>
<p>Amateur organizations also promote active personal involvement for many thousands of members, <a href="https://mufon.com/">the Mutual UFO Network</a> being among the oldest and largest. But as Sharon A. Hill points out in her book “<a href="https://mcfarlandbooks.com/product/scientifical-americans/">Scientifical Americans</a>,” these groups apply questionable standards, spread misinformation and garner little respect within mainstream scientific communities.</p>
<p>Top-down and bottom-up <a href="https://doi.org/10.31269/triplec.v3i2.21">diffusion processes</a> can combine into <a href="https://qz.com/1714598/information-feedback-loops-make-social-media-more-dangerous">self-reinforcing loops</a>. Mass media spreads UFO content and piques worldwide interest in UFOs. More people aim their cameras at the skies, creating more opportunities to capture and share odd-looking content. Poorly documented UFO pics and videos spread on social media, <a href="https://www.cbc.ca/radio/asithappens/as-it-happens-the-monday-edition-1.6065136/why-this-ufo-video-analyst-doesn-t-buy-the-hype-around-the-pentagon-report-1.6065138">leading media outlets</a> to grab and republish the most intriguing. Whistleblowers emerge periodically, fanning the flames with claims of secret evidence.</p>
<p>Despite the hoopla, nothing ever comes of it.</p>
<p>For a <a href="https://theconversation.com/are-we-alone-the-question-is-worthy-of-serious-scientific-study-98843">scientist familiar with the issues</a>, skepticism that UFOs carry alien beings is wholly separate from the <a href="https://www.space.com/25219-drake-equation.html">prospect of intelligent life</a> elsewhere in the universe. Scientists engaged in the <a href="https://www.seti.org/">search for extraterrestrial intelligence</a> have a number of ongoing research projects designed to detect signs of extraterrestrial life. If intelligent life is out there, they’ll likely be the first to know. </p>
<p>As astronomer <a href="https://www.simonandschuster.com/books/Contact/Carl-Sagan/9781501197987">Carl Sagan wrote</a>, “The universe is a pretty big place. If it’s just us, seems like an awful waste of space.”</p><img src="https://counter.theconversation.com/content/208403/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Barry Markovsky 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>While UFO videos might seem compelling, they’re rarely backed up with evidence. A sociologist explains why claims of alien life gain traction through both social and mass media every few years.Barry Markovsky, Distinguished Professor Emeritus of Sociology, University of South CarolinaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2091012023-07-07T14:12:35Z2023-07-07T14:12:35ZPhysicist who found spherical meteor fragments claims they may come from an alien spaceship – here’s what to make of it<figure><img src="https://images.theconversation.com/files/536320/original/file-20230707-25-qnitc7.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6586%2C2997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anybody out there?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-space-galaxy-stars-universe-filled-1995429968">Triff/Shutterstock</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Avi Loeb, a physicist from Harvard University in the US, <a href="https://www.independent.co.uk/news/world/americas/avi-loeb-interstellar-object-aliens-b2369534.html">has recovered</a> 50 tiny spherical iron fragments from the bottom of the Pacific Ocean that he claims may be material from an interstellar alien spaceship. </p>
<p>Loeb is linking his finding with the passage of a fireball in January 2014. The meteor was observed by sensors of the US Department of Defense that track all objects entering the Earth’s atmosphere. It was recorded as travelling faster than most meteors and eventually broke up over the South Pacific Ocean near Papua New Guinea. </p>
<p>Data on the object is held by Nasa’s <a href="https://cneos.jpl.nasa.gov/">Centre for Near Earth Object Studies</a> (CNEOS). The meteor’s official name is CNEOS 20140108, and is also referred to as IM1 (for interstellar meteor).</p>
<figure class="align-center ">
<img alt="Loeb next to image of spherule" src="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Loeb next to image of spherule.</span>
<span class="attribution"><span class="source">NewsNation/Youtube</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>There is a very large scientific leap from observing a fireball to claiming it is an alien spaceship. What is the evidence on which Loeb bases the claim? And how likely is it to be true? </p>
<h2>‘Oumuamua, an interstellar comet</h2>
<p>We have already had at least one visitor from interstellar space - the comet <a href="https://theconversation.com/discovery-of-cigar-shaped-asteroid-from-outer-space-could-help-unveil-secrets-of-extrasolar-worlds-87873">'Oumuamua</a>. The appearance of 1I/2017U1, the official name for 'Oumuamua, was certainly an unusual event. The object was observed in 2017 as it was leaving the Solar System. Its <a href="https://legacy.ifa.hawaii.edu/info/press-releases/interstellar/interstellar_orbit.pdf">trajectory</a> is different from the near-circular orbits of the planets and elliptical orbits of comets.</p>
<p>The comet’s path was traced back, with scientists discovering that it had come from well beyond the outermost fringes of the Solar System. Scientists were excited but also intrigued - although its shape was not captured on camera, the way that light reflected from it as it rotated suggested that it had an odd shape like a cigar when viewed side-on or a plate when viewed from the top.</p>
<figure class="align-center ">
<img alt="'Oumuamua" src="https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&rect=42%2C22%2C1235%2C768&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?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">‘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>In a thoughtful <a href="https://blogs.scientificamerican.com/observations/how-to-search-for-dead-cosmic-civilizations/">article written in 2018</a>, Loeb speculated that 'Oumuamua might be artificial, rather than natural in origin – the product of an alien civilisation. He suggested that we should keep searching for interstellar debris in the Solar System. </p>
<p>In pursuit of such debris, Loeb’s team interrogated the CNEOS database, looking for objects with unusual orbital characteristics. That’s when they found CNEOS 20140108 and, based on its high velocity, suggested it was an <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac8eac/pdf">interstellar meteor</a> – giving it the more manageable name of IM1. </p>
<p>Modelling the path of the fireball, Loeb identified a specific area of the South Pacific where he believed debris from IM1 would be deposited. Following a dredging operation in the area with a powerful magnet, he now claims to have found <a href="https://www.independent.co.uk/news/world/americas/avi-loeb-interstellar-object-aliens-b2369534.html">material from IM1</a>.</p>
<p>But what are the chances that he has found genuine interstellar debris at all, never mind a spaceship?</p>
<h2>Cosmic spherules?</h2>
<p>The metallic spherules that have been recovered are each about half a millimetre in diameter. It isn’t impossible for them to be of extraterrestrial origin: several previous expeditions have recovered spherules from space from the seabed.</p>
<p>The first expedition to find such samples was HMS Challenger in 1872-76. Material dredged from the ocean floor <a href="https://www.nhm.ac.uk/content/dam/nhmwww/discover/challenger/challenger-6-two-column.jpg.thumb.768.768.jpg">contained</a> many metallic droplets, described at the time, quite accurately, as “cosmic spherules”. Droplets from space are spherical because they solidify from molten material torn from the surface of meteorites as they traverse the atmosphere.</p>
<p>Subsequent expeditions throughout the 20th century have also found cosmic spherules at the bottom of the ocean, but it has become harder to identify them. This is because, in the 150 years since the Challenger expedition, the amount of pollution has increased on Earth. </p>
<p>In 1872, the industrial revolution was in its infancy in Europe and practically non-existent in the southern hemisphere. Hence pollution such as “fly ash” (waste from burning coal) and particles from vehicles was minimal. Many of these pollutants are also spherical in appearance and metallic in composition.</p>
<p>Today, products from industrial processes and vehicles are everywhere. So, without an actual analysis of the composition of the spherules and a comparison with analyses of meteorites (and common terrestrial pollutants), it is not possible to identify any as extraterrestrial.</p>
<h2>Interstellar?</h2>
<p>But Loeb doesn’t just think the material is from space, he thinks it is from interstellar space – arguing <a href="https://www.dailymail.co.uk/sciencetech/article-12243125/Harvards-Avi-Loeb-says-50-microscopic-spherules-recovered-Pacific-alien-probe.html">“this could be the first time humans put their hands on interstellar material”</a>. </p>
<p>This is simply not true. We have an abundance of interstellar material on Earth. Some of it is almost certainly on the ocean floor, but not in the form collected by Loeb. </p>
<p>The interstellar material to which I am referring comes in several different varieties. It is well known by astronomers that the interstellar medium - the space between stars - is not empty, but contains several different molecules, many of which are organic (made up of chains or rings of carbon). A portion of these molecules got mixed into the region of space where the Solar System was starting to form. </p>
<p>Stars themselves have also contributed material to the interstellar medium, as they evolved or exploded as supernovas. Some of this material comes as tiny diamonds or sapphires - rare mementoes of stars that lived and died before the Sun was born. These grains became part of the dust cloud that collapsed to form the Solar System, and were eventually carried to Earth in meteorites.</p>
<h2>Alien spacecraft?</h2>
<p>Loeb’s evidence for an extraterrestrial source for the material – never mind an interstellar origin – is rather shaky. He has found metallic spherules. For me (and many others) to accept that these spherules are extraterrestrial, I’d need firm analytical evidence. What is their composition? What is their age? Can we rule out terrestrial pollutants? Can we rule out debris from extraterrestrial material from within the Solar System? </p>
<p>The first question, about composition, has been answered: analysis of the spherules shows them to be <a href="https://www.dailymail.co.uk/sciencetech/article-12259813/EXCL-Harvard-scientists-say-UFO-crashed-ocean-2014-appears-artificial-origin.html">mainly iron with a few trace metals</a>.</p>
<p>We know meteors from our Solar System contain iron and nickel, echoing the relative abundances of these metals in the Sun. But the spherules apparently contain “negligible” amounts of nickel - thus indicating that they are almost certainly not from meteors within the Solar System. This does not, however, prove they are interstellar - it merely makes it more likely that they’re terrestrial pollutants.</p>
<p>The most convincing evidence would be to measure an age for the spherules greater than that of the Sun - which would identify them as interstellar.</p>
<p>And that would be amazing, but it would not necessarily identify them as having an artificial, rather than natural origin. I am not sure what evidence would be sufficiently convincing for this - maybe the autograph of the alien engineer who built the spacecraft?</p><img src="https://counter.theconversation.com/content/209101/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady receives funding from the STFC and the UK Space Agency. She is Professor of Planetary and Space Sciences at the Open University, Chancellor of Liverpool Hope University and Senior Researcher at the Natural History Museum. She tweets as @MonicaGrady</span></em></p>There is a very large scientific leap from observing a fireball to claiming it as an alien spaceship.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2077142023-06-14T23:03:46Z2023-06-14T23:03:46ZFor the first time, astronomers have found life-supporting molecules called phosphates on Enceladus<figure><img src="https://images.theconversation.com/files/531898/original/file-20230614-22-z3g0a3.png?ixlib=rb-1.1.0&rect=742%2C233%2C3155%2C1760&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA/JPL/Space Science Institute</span></span></figcaption></figure><p>The search for habitable conditions beyond Earth has just become more interesting with the discovery of biologically available phosphorus from one of Saturn’s moons. Phosphorus is the most elusive of the six crucial elements needed for life.</p>
<p>In research <a href="https://doi.org/10.1038/s41586-023-05987-9">published today in Nature</a>, data from the Cassini spacecraft were used to find phosphorus compounds called phosphates in <a href="https://solarsystem.nasa.gov/news/13021/put-a-ring-on-it/">Saturn’s E ring</a> – one of the fainter outer rings of the planet.</p>
<p>These compounds likely came from the ice volcano (cryovolcano) plumes from the <a href="https://theconversation.com/waterworld-cassini-spots-the-motion-of-enceladuss-ocean-25069">sub-surface liquid water ocean</a> on Saturn’s moon Enceladus.</p>
<h2>A famous moon</h2>
<p>Enceladus seemed like a typical moon of Saturn until the Cassini spacecraft came to take a closer look. <a href="https://theconversation.com/a-look-back-at-cassinis-incredible-mission-to-saturn-before-its-final-plunge-into-the-planet-83226">Arriving at Saturn in 2005</a>, Cassini has been making <a href="https://solarsystem.nasa.gov/news/12892/cassini-10-years-at-saturn-top-10-discoveries/">discovery after discovery</a> that have catapulted Enceladus to one of the top places to look for life beyond Earth.</p>
<p>In particular, we learned Enceladus has a liquid water ocean beneath its icy surface, heated by gravitational tidal forcing – the kind of forcing that produces ocean tides on Earth.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=640&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=640&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=640&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=805&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=805&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531895/original/file-20230614-19-jl252o.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=805&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 process of organic compounds making their way onto ice grains emitted in plumes from Saturn’s moon Enceladus, where they were detected by NASA’s Cassini spacecraft.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech</span></span>
</figcaption>
</figure>
<p>This environment is tantalisingly similar to the <a href="https://theconversation.com/origins-of-life-new-evidence-first-cells-could-have-formed-at-the-bottom-of-the-ocean-126228">hydrothermal vents thought by some</a> to be the place where life may have originated on Earth. Such vents certainly host life on Earth today.</p>
<p>Most life on Earth ultimately relies on photosynthesis – generating energy from sunlight. Meanwhile, the ultimate energy source for any life on Enceladus would be the gravity of Saturn producing tides far stronger than the Moon produces on Earth, allowing a liquid water ocean despite the very cold -200°C ice crust surface.</p>
<h2>Easy sampling</h2>
<p>The Enceladus plumes have been called a “gimme” for efforts to sample the oceans of alien worlds. One wouldn’t need to land to collect a sample, nor to then launch to return it for analysis.</p>
<p>An obvious approach to sampling an ice volcano is to simply fly through it. However, this is difficult because the speed at which a space probe would encounter the plume would likely kill most organics.</p>
<p>Instead, the easiest approach is to examine the accumulation of ejected material from Enceladus in Saturn’s E ring, which is what the team did in this latest study. </p>
<p>Using this approach, researchers have previously discovered <a href="https://academic.oup.com/mnras/article/489/4/5231/5573821">complex organic molecules</a> <a href="https://www.nature.com/articles/s41586-018-0246-4">coming from Enceladus</a>. These findings confirmed that the watery environment on Enceladus supports complex chemistry involving nitrogen and oxygen.</p>
<p>However, until now we didn’t know about the availability of phosphorus on Enceladus; in many environments this element is locked in rocks.</p>
<h2>A crucial element</h2>
<p>The discovery of phosphates in Saturn’s E ring suggests phosphates could be available within the oceans of Enceladus at a concentration 100 times higher than in Earth’s oceans.</p>
<p>Phosphorus is crucial for life as we know it, partly because it is a key building block of DNA and RNA, molecules essential to all life on Earth. Phosphate is also vital for a number of other metabolic processes in all life. </p>
<p>Many of the essential components necessary for the emergence of life as we know it have thus been discovered on Enceladus. This puts it at or near the top of lists of places to search for life beyond Earth in our Solar System. </p>
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Read more:
<a href="https://theconversation.com/humans-are-still-hunting-for-aliens-heres-how-astronomers-are-looking-for-life-beyond-earth-197621">Humans are still hunting for aliens. Here's how astronomers are looking for life beyond Earth</a>
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<p>Nevertheless, this discovery is only the start of the story. For phosphate to form bonds with carbon – this type of bond is found in the backbone of DNA – we need specialised chemistry that’s very dependent on the environment.</p>
<p>We’ll need further study of the chemistry in and under the crust of Enceladus. But a future detection of organic phosphate compounds would be particularly interesting for the potential for life in the moon’s oceans.</p>
<h2>No ‘smoking gun’</h2>
<p>This research is reminiscent of the reported detection of <a href="https://theconversation.com/the-detection-of-phosphine-in-venus-clouds-is-a-big-deal-heres-how-we-can-find-out-if-its-a-sign-of-life-146185">phosphine on Venus</a> in September 2020, which was <a href="https://www.universetoday.com/158983/sofia-fails-to-find-phosphine-in-the-atmosphere-of-venus-but-the-debate-continues/">cast into doubt by later evidence</a>.</p>
<p>However, the detection method is quite different. On Venus the presence of phosphine was proposed by observing the atmosphere from Earth. The phosphates in this study were detected using an instrument orbiting Saturn called a mass spectrometer, which measured the mass of individual compounds found in the ice of the E ring.</p>
<p>To verify the analysis, the authors created a water solution on Earth very similar to the predicted Enceladus ocean.</p>
<p>That said, both detection methods carry a risk of misidentification, where a different molecule that’s not phosphine is actually responsible for the result. </p>
<p>It would be great to have a “smoking gun” for life beyond Earth, but realistically it will instead be a trickle of evidence that grows as we discover more about these environments. </p>
<p>The study published today is one more piece of evidence supporting the fact that Enceladus may be a great location in our search for extraterrestrial life. </p>
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<p><em>Acknowledgements: We thank Prof Steve Benner from The Foundation For Applied Molecular Evolution for his insight and contributions to this article.</em></p><img src="https://counter.theconversation.com/content/207714/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>Phosphorus is the most elusive element crucial for life as we know it – and we now have the first evidence there’s some available in the oceans of Enceladus.Laura McKemmish, Lecturer, UNSW SydneyAlbert Fahrenbach, Senior Lecturer, UNSW SydneyMartin Van Kranendonk, Professor and Director of the Australian Centre for Astrobiology, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2074562023-06-14T15:04:43Z2023-06-14T15:04:43ZAn element essential to life discovered on one of Saturn’s moons, raising hopes of finding alien microbes<figure><img src="https://images.theconversation.com/files/531159/original/file-20230609-25-9jhlr6.jpg?ixlib=rb-1.1.0&rect=17%2C19%2C974%2C358&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ice particles, with just a trace of phosphates, venting from near Enceladus's south pole, as imaged by Cassini in 2010.</span> <span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/jpeg/PIA17184.jpg">NASA/JPL-Caltech/Space Science Institute</a></span></figcaption></figure><p>Enceladus is the tiny moon of Saturn that seems to have it all. Its icy surface is intricately carved by ongoing geological processes. Its icy shell overlies an internal, liquid ocean. There, chemically charged warm water seeps out of the rocky core onto the ocean floor – potentially providing nourishment for microbial life.</p>
<p>Now, a new study, <a href="https://www.nature.com/articles/s41586-023-05987-9">published in Nature</a>, has uncovered more evidence. It presents the first proof that Enceladus’s ocean contains phosphorus, an element that is essential to life.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Cross-cutting ridges and grooves on the surface of Enceladus" src="https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531290/original/file-20230612-29-6bcdcp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&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 complicated history of fracturing of the icy crust is apparent in this 80 km wide view of the Samarkand Sulci region of Enceladus.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/Space Science Institute</span></span>
</figcaption>
</figure>
<p>The <a href="https://theconversation.com/bittersweet-feeling-as-cassini-mission-embarks-on-its-grand-finale-ahead-of-death-plunge-76670">Cassini spacecraft</a>, operated in orbit about Saturn 2004-17 by Nasa and the European Space Agency (Esa), found plumes of ice particles venting from cracks. These penetrate right through the icy shell so that the ocean water at the bottom of each crack is exposed to the vacuum of space, where the lack of confining pressure causes it to bubble and vaporise in the form of plumes. </p>
<p>These plumes provided samples of spray from Enceladus’s internal ocean that were scooped up for analysis by Cassini during several close fly-bys – a bonus that wasn’t anticipated when the mission was initially planned.</p>
<p>Particles analysed during these brief passages through the plumes demonstrated that the ice is contaminated by traces of <a href="https://theconversation.com/nasa-saturn-moon-enceladus-is-able-to-host-life-its-time-for-a-new-mission-76102">simple organic molecules as well as molecular hydrogen and tiny particles of silica</a>. Taken together, these indicate that chemical reactions between water and warm rock take place on the ocean floor, most probably at “<a href="https://oceanexplorer.noaa.gov/facts/mid-ocean-ridge.html">hydrothermal vents</a>” (a fissure releasing heated water) similar to those on Earth.</p>
<p>This is significant. It means Enceladus has all the ingredients for microbial life to sustain itself (in the absence of sunlight). It is in fact the setting considered most likely to have helped life on Earth begin. If it happened on Earth it could have happened inside Enceladus too.</p>
<h2>Missing link</h2>
<p>All life on Earth requires six essential elements: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur – known collectively by the scarcely pronounceable acronym CHNOPS. Five of these six essential elements were detected in Enceladus plume samples several years ago, but phosphorus had never been found. </p>
<p>Phosphorus is a vital ingredient, because it is needed for the phosphate groups (phosphorus plus oxygen) that link the long chains of <a href="https://www.genome.gov/genetics-glossary/Nucleic-Acids">nucleic acids</a> such as DNA and RNA that store genetic information. It also allows cells to store energy by means of molecules such as <a href="https://www.ncbi.nlm.nih.gov/books/NBK553175/">adenoside triphosphate</a> (ATP for short).</p>
<p>Of course, we don’t know for sure that life inside Enceladus (if it exists) is obliged to use nucleic acids or ATP. However, because the presence of phosphorus is essential for life as we know it, it makes Enceladus a more likely prospect now that we are certain that there is enough phosphorus available there.</p>
<figure class="align-center ">
<img alt="Against black space, a diffuse arc which is invisibly small icy particles scattering sunlight. A bright dot within the arc in Enceladus." src="https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531170/original/file-20230609-27-zq3ly3.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">
<figcaption>
<span class="caption">Enceladus, a tiny dot embedded in Saturn’s, E-ring.</span>
<span class="attribution"><span class="source">NASA/JPL/Space Science Institute</span></span>
</figcaption>
</figure>
<h2>Canny collecting</h2>
<p>The team found Enceladus’s phosphorus by avoiding the cluttered data collected during the Cassini’s frantically quick zooms through the plumes. Instead, they scoured sparser data accumulated in a more leisurely fashion by Cassini’s Cosmic Dust Analyzer during 15 periods between 2004 and 2008 while Cassini was travelling within one of Saturn’s rings: the “<a href="https://solarsystem.nasa.gov/news/13021/put-a-ring-on-it/">E-ring</a>”. Enceladus travels along this hoop as it orbits.</p>
<p>The E-ring hoop is more than 2,000km thick. About 30% of the ice particles emitted in Enceladus’ plumes end up there, as demonstrated by a <a href="https://webbtelescope.org/contents/media/images/2023/112/01GYJ7H5VSDMPRWX0R0Z6R87EC">recent image from the James Webb Space Telescope</a>, which is the only proof we have that the plumes were still active five years after <a href="https://theconversation.com/cassini-crashes-its-time-for-a-new-mission-to-explore-the-possibility-of-life-on-saturns-moons-84016">the end of the Cassini mission</a>.</p>
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<a href="https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531172/original/file-20230609-25-gy4g37.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"></a>
<figcaption>
<span class="caption">Lower left: The plume from Enceladus, imaged at a range of more than a billion km by the James Webb (JWST) telescope, accompanied by an artist’s impression.</span>
<span class="attribution"><span class="source">NASA, ESA, CSA, STScI, Leah Hustak (STScI)</span></span>
</figcaption>
</figure>
<p>Sorting through analyses of nearly a thousand ice particles, which are believed to represent frozen spray from Enceladus, the researchers found nine of them that contained phosphates. This may sound like a slim haul, but it is enough to demonstrate that Enceladus has more than enough dissolved phosphorus in its ocean to permit the functioning of life there.</p>
<p>Indeed, follow-up laboratory experiments suggest that the concentration of dissolved phosphorus in Enceladus’s ocean water may even be hundreds of times greater than in Earth’s oceans.</p>
<p>The team argue that their findings and associated modelling make it likely that any icy moon that grew further from the Sun than the Solar System’s “carbon dioxide snowline” – a location where temperatures during planetary formation were low enough for carbon dioxide to become ice – is likely to contain abundant phosphorus. This condition is met for icy moons at Saturn and beyond, but not at Jupiter. </p>
<p>Jupiter’s distance from the Sun places it beyond the “water-ice snowline” (where water becomes ice), but it is too close to the Sun, and hence too warm, to be beyond the carbon dioxide snowline.</p>
<p>So where does this leave Jupiter’s moon <a href="https://theconversation.com/new-water-plumes-from-jupiters-moon-europa-raise-hopes-of-detecting-microbial-life-66019">Europa</a>, a target for <a href="https://theconversation.com/europa-there-may-be-life-on-jupiters-moon-and-two-new-missions-will-pave-the-way-for-finding-it-122551">missions</a> due to arrive about ten years from now? </p>
<p>This moon has been widely touted as potentially able to support a more flourishing biosphere than Enceladus because of its larger size and greater store of chemical energy in its rocky interior. The team behind the new study are reticent on this, but their modelling suggests a phosphate concentration in Europa’s internal ocean about a thousand times less than at Enceladus. </p>
<p>To me, that is not a gamechanger, and we should continue to expect Europa to be habitable. But it would be reassuring to find some proof of phosphorus there too.</p>
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Read more:
<a href="https://theconversation.com/the-chemistry-that-could-feed-life-within-saturns-moon-enceladus-study-gives-clue-ahead-of-flyby-49683">The chemistry that could feed life within Saturn's moon Enceladus: study gives clue ahead of flyby</a>
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<img src="https://counter.theconversation.com/content/207456/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 from 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>Five out of the six essential elements required for life on Earth were known to exist on Enceladus. Now the sixth and final one has been found too.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1976212023-03-03T00:13:56Z2023-03-03T00:13:56ZHumans are still hunting for aliens. Here’s how astronomers are looking for life beyond Earth<figure><img src="https://images.theconversation.com/files/508029/original/file-20230203-12-uvmpl6.jpg?ixlib=rb-1.1.0&rect=302%2C315%2C4072%2C2733&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">zhengzaishuru/Shutterstock</span></span></figcaption></figure><p>We have long been fascinated with the idea of alien life. The earliest written record presenting the idea of “aliens” is seen in the satiric work of Assyrian writer <a href="https://blogs.scientificamerican.com/life-unbounded/the-first-alien/">Lucian of Samosata</a> dated to 200 AD.</p>
<p>In one novel, Lucian <a href="https://www.yorku.ca/inpar/lucian_true_tale.pdf">writes of a journey to the Moon</a> and the bizarre life he imagines living there – everything from three-headed vultures to fleas the size of elephants.</p>
<p>Now, 2,000 years later, we still write stories of epic adventures beyond Earth to meet otherworldly beings (<a href="https://www.britannica.com/topic/The-Hitchhikers-Guide-to-the-Galaxy-novel-by-Adams">Hitchhiker’s Guide</a>, anyone?). Stories like these entertain and inspire, and we are forever trying to find out if science fiction will become science fact.</p>
<h2>Not all alien life is the same</h2>
<p>When looking for life beyond Earth, we are faced with two possibilities. We might find basic microbial life hiding somewhere in our Solar System; or we will identify signals from intelligent life somewhere far away.</p>
<p>Unlike in <a href="https://www.britannica.com/topic/Star-Wars-film-series">Star Wars</a>, we’re not talking far, far away in another galaxy, but rather around other nearby stars. It is this second possibility which really excites me, and should excite you too. A detection of intelligent life would fundamentally change how we see ourselves in the Universe. </p>
<p>In the last 80 years, programs dedicated to the search for extraterrestrial intelligence (SETI) have worked tirelessly searching for cosmic “hellos” in the form of radio signals.</p>
<p>The reason we think any intelligent life would communicate via radio waves is due to the waves’ ability to travel vast distances through space, rarely interacting with the dust and gas in between stars. If anything out there is trying to communicate, it’s a pretty fair bet they would do it through radio waves. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=134&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=134&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=134&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=169&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=169&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505679/original/file-20230121-18-zi7kes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=169&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 three radio facilities used in the Breakthrough Listen Initiative. Left to Right: 100m Robert C. Byrd Green Bank Telescope, 64m Murriyang (Parkes) Radio Telescope, 64-antenna MeerKAT array.</span>
<span class="attribution"><span class="source">NRAO, CSIRO, MeerKAT</span></span>
</figcaption>
</figure>
<h2>Listening to the stars</h2>
<p>One of the most exciting searches to date is <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen</a>, the largest scientific research program dedicated to looking for evidence of intelligent life beyond Earth.</p>
<p>This is one of many projects funded by US-based Israeli entrepreneurs Julia and Yuri Milner, with some serious dollars attached. Over a ten-year period a total amount of <a href="https://breakthroughinitiatives.org/initiative/1">US$100 million</a> will be invested in this effort, and they have a mighty big task at hand. </p>
<p>Breakthrough Listen is currently targeting the closest one million stars in the hope of identifying any unnatural, alien-made radio signals. Using telescopes around the globe, from the 64-metre Murriyang Dish (Parkes) here in Australia, to the 64-antenna MeerKAT array in South Africa, the search is one of epic proportions. But it isn’t the only one. </p>
<p>Hiding away in the Cascade Mountains north of San Francisco sits the <a href="https://www.seti.org/ata">Allen Telescope Array</a>, the first radio telescope built from the ground up specifically for SETI use.</p>
<p>This unique facility is another exciting project, able to search for signals every day of the year. This project is currently upgrading the hardware and software on the original dish, including the ability to target several stars at once. This is a part of the non-profit research organisation, the SETI Institute.</p>
<h2>Space lasers!</h2>
<p>The SETI Institute is also looking for signals that would be best explained as “space lasers”.</p>
<p>Some astronomers hypothesise that intelligent beings might use massive lasers to communicate or even to propel spacecraft. This is because even here on Earth we’re investigating <a href="https://www.nasa.gov/feature/goddard/2022/the-future-of-laser-communications/">laser communication</a> and laser-propelled <a href="https://www.insidescience.org/news/new-light-sail-design-would-use-laser-beam-ride-space">light sails</a>.</p>
<p>To search for these mysterious flashes in the night sky, we need speciality instruments in locations around the globe, which are currently being developed and deployed. This is a research area I’m excited to watch progress and eagerly await results. </p>
<p>As of writing this article, sadly no alien laser signals have been found yet.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/do-aliens-exist-we-asked-five-experts-161811">Do aliens exist? We asked five experts</a>
</strong>
</em>
</p>
<hr>
<h2>Out there, somewhere</h2>
<p>It’s always interesting to ponder who or what might be living out in the Universe, but there is one problem we must overcome to meet or communicate with aliens. It’s the speed of light.</p>
<p>Everything we rely on to communicate via space requires light, and it can only travel so fast. This is where my optimism for finding intelligent life begins to fade. The Universe is big – <em>really</em> big.</p>
<p>To put it in perspective, humans started using radio waves to communicate across large distances in 1901. That <a href="https://ethw.org/Milestones:Reception_of_Transatlantic_Radio_Signals,_1901">first transatlantic signal</a> has only travelled 122 light years, reaching just 0.0000015% of the stars in our Milky Way.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a spiral galaxy with a box on the lower right corner centred on a tiny blue dot" src="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505680/original/file-20230121-16-884k8k.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"></a>
<figcaption>
<span class="caption">The little blue dot in the centre of the square is the current extent of human broadcasts just in our own galaxy.</span>
<span class="attribution"><a class="source" href="https://www.planetary.org/space-images/extent-of-human-radio-broadcasts">Adam Grossman/Nick Risinger</a></span>
</figcaption>
</figure>
<p>Did your optimism just fade too? That is okay, because here is the wonderful thing… we don’t have to find life to know it is out there, somewhere.</p>
<p>When we consider the <a href="https://theconversation.com/how-many-stars-are-there-in-space-165370">trillions of galaxies</a>, septillion of stars, and likely many more planets just in the observable Universe, it feels near impossible that we are alone.</p>
<p>We can’t fully constrain the parameters we need to estimate how many other lifeforms might be out there, as famously proposed by Frank Drake, but using our best estimates and <a href="https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/numerical-testbed-for-hypotheses-of-extraterrestrial-life-and-intelligence/0C97E7803EEB69323C3728F02BA31AFA">simulations</a> the current best answer to this is tens of thousands of possible civilisations out there. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/frank-drake-has-passed-away-but-his-equation-for-alien-intelligence-is-more-important-than-ever-189935">Frank Drake has passed away but his equation for alien intelligence is more important than ever</a>
</strong>
</em>
</p>
<hr>
<p>The Universe <a href="https://theconversation.com/is-space-infinite-we-asked-5-experts-165742">might even be infinite</a>, but that is too much for my brain to comprehend on a weekday.</p>
<h2>Don’t forget the tiny aliens</h2>
<p>So, despite keenly listening for signals, we might not find intelligent life in our lifetimes. But there is hope for aliens yet.</p>
<p>The ones hiding in plain sight, on the planetary bodies of our Solar System. In the coming decades we’ll explore the moons of Jupiter and Saturn like never before, with missions hunting to find traces of basic life.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/505682/original/file-20230121-23485-sxmcy9.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">Jupiter and the icy moon Europa. Concept art of the Europa Clipper mission currently under development.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>Mars will continue to be explored – eventually by humans – which could allow us to uncover and retrieve samples from new and unexplored regions.</p>
<p>Even if our future aliens are only tiny microbes, it would still be nice to know we have company in this Universe.</p>
<hr>
<p><em>Correction: this article has been amended to clarify that Julia and Yuri Milner are no longer Russian citizens.</em></p><img src="https://counter.theconversation.com/content/197621/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Webb 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>To date, we have not heard from any aliens. Nor have we seen any – but here are the fascinating projects working to change that.Sara Webb, Postdoctoral Research Fellow, Centre for Astrophysics and Supercomputing, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1952242022-11-24T20:14:01Z2022-11-24T20:14:01ZJames Webb space telescope uncovers chemical secrets of distant world – paving the way for studying Earth-like planets<figure><img src="https://images.theconversation.com/files/497034/original/file-20221123-22-xg8b05.jpg?ixlib=rb-1.1.0&rect=5%2C5%2C3822%2C2144&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist impression of WASP b and its star</span> <span class="attribution"><a class="source" href="https://www.esa.int/ESA_Multimedia/Images/2022/08/Artist_impression_of_WASP-39_b_and_its_star">NASA, ESA, CSA, and J. Olmsted (STScI)</a></span></figcaption></figure><p>Since the first planet orbiting a star other than the Sun was discovered in 1995, we have realised that planets and planetary systems are more diverse than we ever imagined. Such distant worlds – exoplanets – give us the opportunity to study how planets behave in different situations. And learning about their atmospheres is a crucial piece of the puzzle.</p>
<p>Nasa’s <a href="https://webb.nasa.gov/">James Webb space telescope</a> (JWST) is the largest telescope in space. Launched on Christmas Day 2021, it is the perfect tool for investigating these worlds. Now my colleagues and I have used the telescope for the first time to unveil the chemical make-up of an exoplanet. And <a href="https://www.mpg.de/19521589/Alderson_ERS_WASP39b_JWST_NIRSpec.pdf">the data</a>, <a href="https://arxiv.org/abs/2211.10488">released</a> <a href="https://arxiv.org/abs/2211.10489">in preprint</a> <a href="https://arxiv.org/abs/2211.10493">form</a> (meaning it has yet to be published in a peer-reviewed journal), <a href="https://exoplanets.nasa.gov/news/1715/nasas-webb-reveals-an-exoplanet-atmosphere-as-never-seen-before/">suggests some surprising results</a>.</p>
<p>Many exoplanets are too close to their parent stars for even this powerful telescope to distinguish them. But we can use the trick of watching as the planet passes in front of (transits) its star. During transit, the planet blocks a small fraction of the starlight, and an even tinier fraction of the starlight is filtered through the outer layers of the planet’s atmosphere. </p>
<p>Gases within the atmosphere absorb some of the light – leaving fingerprints on the starlight in the form of a reduction in brightness at certain colours, or wavelengths. JWST is particularly suited to exoplanet atmosphere studies because it is an infrared telescope. Most of the gases that are in an atmosphere – such as water vapour and carbon dioxide – absorb infrared rather than visible light.</p>
<figure class="align-center ">
<img alt="The image shows a graph with wavelength on the horizontal axis, increasing left to right, and the amount of light blocked on the vertical axis, increasing towards the top. The data resemble a bumpy line." src="https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=368&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=368&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=368&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497079/original/file-20221123-12-ba99xt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">One of four separate measurements. Each bump corresponds to a different absorbing gas in the atmosphere.</span>
<span class="attribution"><span class="source">NASA, ESA, CSA, Joseph Olmsted (STScI)</span></span>
</figcaption>
</figure>
<p>I am part of an international team of exoplanet scientists that has been using JWST to study a roughly Jupiter-sized planet called <a href="https://exoplanets.nasa.gov/exoplanet-catalog/5673/wasp-39-b/">WASP-39b</a>. Unlike Jupiter, however, this world takes only a few days to orbit its star, so it is being cooked – reaching temperatures exceeding 827°C. This gives us the perfect opportunity to explore how a planetary atmosphere behaves in extreme temperature conditions. </p>
<p>We used JWST to recover the most complete spectrum yet of this fascinating planet. In fact, our work represents the first chemical inventory of the planet’s atmosphere.</p>
<p>We already knew that most of this large planet’s atmosphere had to be a mixture of hydrogen and helium – the lightest and most abundant gases in the universe. And the Hubble telescope has previously detected water vapour, sodium and potassium there.</p>
<p>Now, we’ve been able to confirm our detection and produce a measurement of the amount of water vapour. The data also suggests there are other gases including <a href="https://scied.ucar.edu/learning-zone/how-climate-works/carbon-dioxide">carbon dioxide</a>, <a href="https://www.gov.uk/government/publications/carbon-monoxide-properties-incident-management-and-toxicology/carbon-monoxide-general-information">carbon monoxide</a>, and unexpectedly, <a href="https://www.epa.gov/so2-pollution/sulfur-dioxide-basics">sulphur dioxide</a>.</p>
<p>Having measurements of how much of each of these gases is present in the atmosphere means we can estimate the relative amounts of the elements that make up the gases – hydrogen, oxygen, carbon and sulphur. Planets are formed in a disc of dust and gas around a young star, and we expect different amounts of these elements to be available to a baby planet at different distances from the star. </p>
<p>WASP-39b appears to have a relatively low amount of carbon relative to oxygen, indicating it probably formed at a greater distance from the star where it could have easily absorbed water ice from the disc (boosting its oxygen), compared with its current very close orbit. If this planet has migrated, it could help us develop our theories about planet formation, and would support the idea that the giant planets in our Solar System also did a fair bit of moving and shaking early on.</p>
<h2>A sulphurous key</h2>
<p>The amount of sulphur we detected relative to oxygen is quite high for WASP-39b. We’d expect sulphur in a young planetary system to be more concentrated in bits of rock and rubble than as an atmospheric gas. So this indicates that WASP-39b might have undergone an unusual amount of collisions with sulphur-containing chunks of rock. Some of that sulphur would be released as gas.</p>
<p>In a planet’s atmosphere, different chemicals react with each other at different rates depending on how hot it is. Usually, these settle into an equilibrium state, with the total amounts of each gas remaining stable as the reactions balance each other. We managed to predict what gases we would see in WASP-39b’s atmosphere for a range of starting points. But none of them came up with sulphur dioxide, instead expecting any sulphur to be locked up in a different gas, hydrogen sulphide.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the chemical process that converts hydrogen sulphide to sulphur dioxide." src="https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497115/original/file-20221123-18-j3raez.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">Photochemistry on WASP-39b.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/Robert Hurt; Center for Astrophysics-Harvard & Smithsonian/Melissa Weiss</span></span>
</figcaption>
</figure>
<p>The missing piece of the chemical jigsaw puzzle was a process called <a href="https://arxiv.org/abs/2211.10490">photochemistry</a>. This is when the rates of certain chemical reactions are driven by energy from photons – packets of light – coming from the star, rather than by the temperature of the atmosphere. Because WASP-39b is so hot, and reactions generally speed up at higher temperatures, we didn’t expect photochemistry to be quite as important as it has turned out to be. </p>
<p>The data suggests that water vapour in the atmosphere is split apart by light into oxygen and hydrogen. These products would then react with the gas hydrogen sulphide, eventually stripping away the hydrogen and replacing it with oxygen to form sulphur dioxide.</p>
<h2>What’s next for JWST?</h2>
<p>Photochemistry is even more important on cooler planets that may be habitable – the ozone layer on our own planet is formed via a photochemical process. JWST will be observing the rocky worlds in the <a href="https://theconversation.com/solar-system-with-seven-earth-like-planets-found-around-nearby-star-heres-what-they-could-be-like-73394">Trappist-1 system</a> during its first year of operation. Some of these measurements have already been made – and all of these planets have temperatures more similar to Earth’s. </p>
<p>Some may even have the right temperature to have liquid water on the surface, and potentially life. Having a good understanding of how photochemistry influences atmospheric composition is going to be critical for interpreting the Webb telescope observations of the Trappist-1 system. This is especially important since an apparent chemical imbalance in an atmosphere might hint at the presence of life, so we need to be aware of other possible explanations for this. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/four-ways-to-spot-hints-of-alien-life-using-the-james-webb-space-telescope-192445">Four ways to spot hints of alien life using the James Webb Space Telescope</a>
</strong>
</em>
</p>
<hr>
<p>The WASP-39b chemical inventory has shown us just how powerful a tool JWST is. We’re at the start of a very exciting era in exoplanet science, so stay tuned.</p><img src="https://counter.theconversation.com/content/195224/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joanna Barstow receives funding from the Science and Technology Facilities Council. She is a Councillor and Trustee for the Royal Astronomical Society. </span></em></p>The James Webb space telescope is making the headlines again – this time completing its first chemical inventory of a distant, exotic world.Joanna Barstow, Ernest Rutherford Fellow, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1924452022-10-21T17:04:48Z2022-10-21T17:04:48ZFour ways to spot hints of alien life using the James Webb Space Telescope<figure><img src="https://images.theconversation.com/files/490217/original/file-20221017-19-fs1i2r.jpg?ixlib=rb-1.1.0&rect=4%2C0%2C2982%2C1994&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of planet Gliese 667 Cc at sunset. </span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Gliese_667_Cc#/media/File:Gliese_667_Cc_sunset.jpg">ESO/L. Calçada</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The study of exoplanets, worlds which orbit stars other than our sun, is currently being transformed <a href="https://theconversation.com/james-webb-space-telescope-how-our-launch-of-worlds-most-complex-observatory-will-rest-on-a-nail-biting-knife-edge-173619">by the new James Webb Space Telescope</a> (JWST). We will shortly gain our first insight into conditions on rocky, potentially Earth-like worlds beyond our solar system. One of these distant worlds might host life. But could we detect it?</p>
<p>We may be able to spot signs of life in the composition of the planet’s atmosphere. We can use a technique called <a href="https://theconversation.com/its-all-in-the-atmosphere-exploring-planets-orbiting-distant-stars-62034">transmission spectroscopy</a> – which divides up light by its wavelength – to search for traces of different gases in starlight as it passes through a planet’s atmosphere. </p>
<p>Some starlight-absorbing gases might indicate the presence of life on the planet. We call these biosignatures. </p>
<h2>1. Oxygen and ozone</h2>
<p>Oxygen is probably the most obvious biosignature. Plants make it, we breathe it and the rock record shows that levels in Earth’s atmosphere <a href="https://theconversation.com/earths-oxygen-has-varied-dramatically-over-time-heres-how-our-data-could-help-us-spot-alien-life-192349">changed dramatically as life evolved</a>. The oxygen that we breathe is O<sub>2</sub>, two oxygen atoms stuck together. But another configuration of oxygen, O<sub>3</sub> or ozone, could also be observed with JWST. </p>
<p>So, if we detected one or both of these gases, would it be job done? Unfortunately not. Another scenario that could produce large amounts of atmospheric oxygen is a planet undergoing a “<a href="https://theconversation.com/venus-the-trouble-with-sending-people-there-191534">runaway greenhouse effect</a>”. Once a planet is hot enough for its water ocean to evaporate, the resulting water vapour in the atmosphere contributes to a greenhouse effect – super-heating the planet to levels that aren’t compatible with life – in a feedback loop. </p>
<p>Eventually, the planet becomes hot enough for water molecules to break apart into hydrogen and oxygen. Hydrogen molecules are light and can move fast enough to easily escape the planet’s gravity, whereas the more sluggish oxygen tends to stick around, ready to be detected and trick unsuspecting astronomers. </p>
<h2>2. Phosphine and ammonia</h2>
<p>The current focus of the search for life might be mostly on exoplanets, but there have also been recent developments closer to home. Phosphine – a gas that occurs naturally in hydrogen-dominated atmospheres like those of gas giants Jupiter and Saturn – was recently <a href="https://www.liebertpub.com/doi/10.1089/ast.2018.1954">detected in the atmosphere of Venus</a>. Interestingly, phosphine is considered to <a href="https://www.liebertpub.com/doi/10.1089/ast.2018.1954">be a potential biosignature</a>.</p>
<p>On Earth, phosphine is produced by microorganisms, for example in the intestinal tracts of animals. If no life is present, we wouldn’t expect phosphine to occur in large quantities in Venus-like atmospheres, which are dominated by carbon dioxide. That said, we can’t yet rule out other sources of phosphine on Venus.</p>
<p>Foul-smelling ammonia is another potential biosignature gas, also produced by animals on Earth. Like phosphine, it is prevalent on gas giant planets, but not expected to occur on rocky worlds in the absence of life. </p>
<p>However, detecting phosphine or ammonia in the atmosphere of a distant exoplanet is likely to be challenging. Both reach tiny concentrations of only a few parts per billion on Earth. So unless our potential extraterrestrials are much stinkier than Earth’s animals, we probably won’t be spotting them any time soon.</p>
<h2>3. Methane plus carbon dioxide</h2>
<p>Individual gases that are unambiguous biosignatures are few and far between, so we might be better off looking for a winning combination if we want to detect life. Large amounts of <a href="https://www.pnas.org/doi/10.1073/pnas.2117933119">methane</a>, produced by farting animals on Earth, plus carbon dioxide would be a good hint that there is something going on. </p>
<p>If there’s enough oxygen available, then carbon much prefers to hang around with oxygen as carbon dioxide (CO<sub>2</sub>, one carbon atom and two oxygen atoms), rather than form methane (CH<sub>4</sub>, one carbon atom and four hydrogen atoms). In an oxygen-rich environment, any carbon finding itself in a methane molecule quickly ditches its hydrogen buddies in favour of a couple of spare oxygens. </p>
<figure class="align-center ">
<img alt="Cartoon showing a carbon atom leaving four hydrogen atoms and heading towards a pair of oxygen atoms, saying 'Bye!' as it leaves." src="https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=339&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=339&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=339&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=426&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=426&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490485/original/file-20221018-8364-beidg3.png?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">When it’s available, carbon prefers the company of oxygen.</span>
<span class="attribution"><span class="source">Author's own work.</span></span>
</figcaption>
</figure>
<p>So seeing lots of both methane and carbon dioxide coexisting would suggest that something – maybe bacteria – is constantly producing methane.</p>
<h2>4. Chemical imbalances</h2>
<p>We can apply the above argument to any combination of gases that shouldn’t happily coexist. Life disrupts the chemical equilibrium (balance) of its environment because it uses chemical reactions to generate energy. </p>
<p>On Earth, oxygen is transformed into carbon dioxide, but in a different type of atmosphere, with different chemicals available, life would use other processes to achieve the same goal. Methane-producing bacteria that live around hydrothermal vents deep in Earth’s oceans, for example, harvest chemical energy from minerals and chemical compounds. Looking for imbalances allows us to be open minded about what life elsewhere might look like.</p>
<h2>What happens if we spots signals of alien life?</h2>
<p>JWST is already <a href="https://www.nature.com/articles/s41586-022-05269-w">exceeding our expectations</a> for exoplanet atmosphere observations. As powerful as it is, though, rocky planets with mild temperatures and atmospheres dominated by nitrogen or carbon dioxide are still going to be challenging to study using transmission spectroscopy. The signals we expect from these planets are much weaker than those we have successfully observed in hot gas giant atmospheres. </p>
<p>If we are lucky enough to observe starlight-absorbing gases in the atmosphere of a rocky exoplanet – <a href="https://solarsystem.nasa.gov/resources/2686/exploring-alien-worlds-with-nasas-james-webb-space-telescope-trappist-1-system/">TRAPPIST-1e</a>, for example – we still have to measure how much of these gases are present to draw meaningful conclusions. This isn’t straightforward as the signals can overlap and need to be carefully disentangled.</p>
<p>Even if we do detect and accurately measure one of our possible biosignature gases, I don’t think we could claim to have detected alien life. JWST is only just opening up a new, rich laboratory of planetary atmospheres, and as we explore no doubt we will find many of our previous assumptions are proven wrong. </p>
<p>Jumping to conclusions about aliens every time we find something unusual would be premature. A JWST biosignature detection would be an interesting hint, with the promise of a great deal more work to do. As an astronomer, that’s exciting enough for me.</p><img src="https://counter.theconversation.com/content/192445/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joanna Barstow receives funding from the Science and Technology Faciliites Council. She is a Councillor and Trustee of the Royal Astronomical Society.</span></em></p>New telescope allows us to study the atmospheres of planets orbiting stars other than our Sun in unprecedented detail.Joanna Barstow, Ernest Rutherford Fellow, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1923492022-10-14T18:35:57Z2022-10-14T18:35:57ZEarth’s oxygen has varied dramatically over time – here’s how our data could help us spot alien life<figure><img src="https://images.theconversation.com/files/489539/original/file-20221013-19-882mfm.jpg?ixlib=rb-1.1.0&rect=0%2C44%2C4905%2C3150&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>Are we alone in the universe? This is a question that has intrigued humans for centuries and inspired countless studies and works of fiction. But are we getting closer to finding this out? Now that the <a href="https://webb.nasa.gov/">James Webb Space Telescope</a> (JWST) <a href="https://theconversation.com/james-webb-telescope-a-scientist-explains-what-its-first-amazing-images-show-and-how-it-will-change-astronomy-186668">is in operation</a>, we might have taken one giant leap in being able to answer this one day.</p>
<p>One of the four main objectives of the JWST is to study exoplanets – planets which reside outside of our solar system – and determine what gases their atmospheres are composed of. Now our new <a href="http://www.science.org/doi/10.1126/sciadv.abm8191">research</a> into the variation of oxygen on Earth over geological time has offered clues about what to actually look for.</p>
<p>To try and comprehend how, when and why life might evolve on other planets, it makes sense to look to the only planet we currently know of which hosts life: Earth. Understanding our own planet’s complicated evolutionary history might provide the key to finding other planets capable of supporting life.</p>
<h2>Life and oxygen</h2>
<p>We know that animals require oxygen in order to survive, although some, such as sponges, require less than others. Yet, while oxygen is readily available today, making up 21% of the atmosphere, we also know that this was <a href="https://www.nature.com/articles/nature06587">not true for the majority of Earth’s history</a>.</p>
<p>If we travelled deep into our past, beyond around 450 million years ago, we would need to carry a handy supply of oxygen tanks with us. But what we are less certain of is the absolute amount of oxygen in the atmosphere and oceans through time and whether rises in oxygen levels fuelled the evolution of animal life, or vice versa. These questions have in fact sparked numerous debates and <a href="https://www.nature.com/articles/nature13068">decades of research</a>. </p>
<p>The current thinking is that oxygen levels have risen in three broad steps. The first, called the “<a href="https://www.sciencedirect.com/science/article/pii/S0960982209011890">great oxidation event</a>”, occurred around 2.4 billion years ago, transforming the Earth from a planet essentially devoid of oxygen in the atmosphere and oceans to one with oxygen as a permanent feature of it. The third occurred around 420 million years ago and is called the “<a href="https://www.nature.com/articles/s41467-018-06383-y">Paleozoic oxygenation event</a>”, which saw a rise in atmospheric oxygen to present day levels. </p>
<p>But in between, some 800 million years ago, lies the second step: the “<a href="https://www.frontiersin.org/articles/10.3389/feart.2015.00044/full">Neoproterozoic oxygenation event</a>” or NOE. Initially, information extracted from sedimentary rocks formed on the ocean floor suggested that it was <a href="https://www.geosociety.org/gsatoday/archive/21/3/article/i1052-5173-21-3-4.htm">during this time</a> that oxygen rose to something like modern levels. </p>
<p>However, more data gathered since has suggested a more <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gbi.12182">intriguing</a> oxygen history. Importantly, the NOE occurred just <a href="https://www.pnas.org/doi/10.1073/pnas.1403669112">before evidence of the very first animals</a>, appearing around 600 million years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="James Webb image of a cluster of galaxies about 4 billion light years from Earth." src="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=612&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=612&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=612&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=769&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=769&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473574/original/file-20220712-16-pndrc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=769&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">James Webb image of a cluster of galaxies about 4 billion light years from Earth.</span>
<span class="attribution"><span class="source">NASA, ESA, CSA, and STScI</span></span>
</figcaption>
</figure>
<h2>Modelling oxygen levels</h2>
<p>We set out to explore and reconstruct atmospheric oxygen levels during the NOE to see what conditions the first animals appeared under. To do this, we built a computer model of the Earth, incorporating knowledge about the various processes which can deliver oxygen to the atmosphere or remove it.</p>
<p>We investigated carbon-bearing rocks, deposited worldwide, to calculate ancient photosynthesis rates. Photosynthesis is the process by which plants and microbes use sunlight, water and carbon dioxide to create oxygen and energy in the form of sugars – the main source of oxygen on Earth. </p>
<p>Carbon naturally exists in many <a href="https://www.energy.gov/science/doe-explainsisotopes#:%7E:text=Isotopes%20are%20members%20of%20a,and%20is%20atomic%20number%206.">isotopes</a> – atoms with a different number of neutrons in their nucleus (the nucleus is made up of protons and neutrons). Different isotopes therefore have slightly different sizes and masses from one another. </p>
<p>We looked at isotopes of carbon known as carbon-12 and carbon-13, which do not undergo radioactive decay. Plants prefer to use carbon-12 - the lightest isotope - during photosynthesis, leaving the seawater and subsequently the rocks which form on the ocean floor enriched in carbon-13 instead. </p>
<p>When we analyse these rocks, millions or even billions of years later, if we find more carbon-13 than carbon-12 we can predict that more photosynthesis, and thus more oxygen production, occurred. We then modelled volcanic activity, which can release gases that react with oxygen, removing it from the atmosphere. </p>
<p>This approach might sound a little strange, and you might ask why there was nothing more direct for us to measure. This is because most geological evidence from this time is not preserved, and these carbon isotope ratios are one of the few well-defined data sets we have through this time period.</p>
<p>What we found is that, rather than a simple jump in oxygen levels during the Neoproterozoic era, the amount of oxygen in the atmosphere changed significantly and, on geological timescales, very rapidly. While 750 million years ago, oxygen made up 12% of the atmosphere, in just a few tens of millions of years, it had dropped to about 0.3% – a tiny fraction – before rising again a few million years later. </p>
<p>Our research shows that atmospheric oxygen probably continued this dance between high and low levels until plants gained a foothold on the land some 450 million years ago.</p>
<h2>Searching for alien life</h2>
<p>These results are intriguing for a number of reasons. We have often thought that the relative stability that Earth has experienced for much of the last 4.5 billion years is necessary for life to flourish. After all, when big events, such as asteroid impacts, have occurred it has not gone well for some of Earth’s inhabitants (sorry, dinosaurs). </p>
<p>But if the first animals did evolve against a backdrop of highly variable oxygen levels, it suggests that some dynamic changes might instead be required in order to foster ecological innovation. </p>
<p>Our results suggest that periods of low atmospheric oxygen levels could have been important for developing more complex life by driving the extinction of some simple organisms and allowing the survivors to <a href="https://www.pnas.org/doi/pdf/10.1073/pnas.91.15.6758">expand and diversify</a> when oxygen levels rose again. So, we should not rule out taking a closer look at exoplanets that have a poorly oxygenated atmosphere. </p>
<p>Of course, this is a very Earth and even animal-centric view. Alien life may be completely different to life on Earth. For example, it could well exist on planetary bodies such as Titan – one of Saturn’s moons – which has seas of liquid methane and ethane. But as a starting point in our search for extra-terrestrial life, understanding the history of atmospheric oxygen on Earth is a useful guide.</p><img src="https://counter.theconversation.com/content/192349/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Krause received funding from the NERC SPHERES Doctoral Training Partnership NE/L002574/1.</span></em></p><p class="fine-print"><em><span>Benjamin J. W. Mills receives funding from UK Research and Innovation / NERC grant NE/S009663/1</span></em></p>We should not rule out taking a closer look at exoplanets that have a poorly oxygenated atmosphere.Alex Krause, Research Fellow in Earth System Modelling, UCLBenjamin J. W. Mills, Associate Professor of Biogeochemical Modelling, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1839272022-05-26T12:58:03Z2022-05-26T12:58:03ZOur Mars rover mission was suspended because of the Ukraine war – here’s what we’re hoping for next<figure><img src="https://images.theconversation.com/files/465514/original/file-20220526-23-yco451.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C2880%2C1784&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Oxia Planum on Mars – where the rover was set to land.</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>Just a few months ago, we were confidently expecting to launch our rover, Rosalind Franklin, to Mars in September as part of the ExoMars mission, a collaboration between Europe and Russia. The <a href="https://theconversation.com/decades-of-attempts-show-how-hard-it-is-to-land-on-mars-heres-how-we-plan-to-succeed-in-2021-69734">landing was planned</a> for June 2023. Everything was ready: the rover, the operations team and the eager scientists. </p>
<p>The final preparations started in February 21, with part of our team heading to Turin, Italy, to carry out the final alignment and calibration tests. All was going well, though some of the team were slightly delayed by Storm Eunice in the UK. Three days later, they had nevertheless finished the work – leaving some wonderful data, which would help us decide where Rosalind would drill on Mars. The industry team started packing the rover, which was ready to be shipped to the launch site. </p>
<p>Then, a storm far more powerful and tragic than Eunice descended on Ukraine: Russia’s invasion. The situation developed in the next days and weeks, leading to a series of emergency meetings. On March 17, the European Space Agency (Esa)‘s council and member states decided to <a href="https://www.bbc.co.uk/news/science-environment-60782932">suspend our mission</a>. We won’t know for sure what happens next until a study by Esa and industry partners reports back in July – but there are causes for optimism.</p>
<p>The Rosalind Franklin rover is unique among all the rovers planned for Mars. It can drill deeper than any before it – up to 2 metres below the harsh surface. This is important as the subsurface is protected from harmful radiation, and could therefore contain signs of past or present life.</p>
<p>Rosalind’s instruments include our PanCam, which is a camera that will do geology and atmospheric science on Mars – complemented by the other cameras and a sub-surface sounding radar. Rosalind will also collect pristine samples from below the surface which will be deposited in the “analytical drawer”, where three instruments will do mineralogy and search for signs of life. </p>
<figure class="align-center ">
<img alt="Image of the ExoMars rover on top of landing platform." src="https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465513/original/file-20220526-13-6o194p.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">ExoMars rover on top of landing platform.</span>
<span class="attribution"><span class="source">Thales Alenia Space/ESA</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Some 3.8 billion years ago, at the same time as life was emerging on Earth, Mars was habitable too. There is evidence from orbiters and landers of water on the surface then – there would have been clouds, rain and a thick atmosphere. There was also a global protective magnetic field, and volcanos. This means Mars essentially had all the right ingredients for life – carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur. If life emerged there like it did on Earth, we were on a track to find it. </p>
<p>The climate <a href="https://theconversation.com/how-did-mars-lose-its-habitable-climate-the-answer-is-blowing-in-the-solar-wind-50258">has changed significantly</a> since Mars lost its magnetic field 3.8 billion years ago, though. The planet is now is dry, cold, has a thin atmosphere and a surface hostile for life. But below the surface, some living species may have survived, or remains of them could be conserved.</p>
<p>Other missions to Mars are looking for life too. The amazing Nasa Perseverance rover <a href="https://theconversation.com/mars-perseverance-rover-set-for-nail-biting-landing-heres-the-rocket-science-154886">landed in February 2021</a>. Its scientists are partly guided by images from a Nasa helicopter on the planet, called Ingenuity, and it recently reached an ancient river delta. </p>
<p>Perseverance is collecting samples from Jezero crater, ready to be brought back to powerful labs on Earth by the <a href="https://theconversation.com/plan-to-bring-back-rocks-from-mars-is-our-best-bet-for-finding-clues-of-past-life-95797">Mars sample return missions</a>. The results will hopefully complement those from Rosalind Franklin – which will examine deeper samples from a different and slightly older site, Oxia Planum, where there is also abundant evidence of a watery past.</p>
<h2>Options for Rosalind</h2>
<p>Russia was meant to help launch Rosalind Franklin on one of its rockets. While a European-built spacecraft would then take it to Mars, a Russian-built platform would again be needed to land it. Russia was also meant to provide radioactive heaters to keep the batteries of the rover warm in the cold Martian nights.</p>
<p>Now, Esa is looking at options. Given that continuing with Russia in 2024 is most unlikely, the main possibilities are either Esa going it alone, or teaming up with a partner such as Nasa. Esa’s new <a href="https://www.esa.int/Enabling_Support/Space_Transportation/Launch_vehicles/Ariane_6">Ariane-6 rocket</a>, which is nearly ready, could help launch the rover, as could a SpaceX rocket. For the lander and heaters, Esa would need to develop these alone or in collaboration with Nasa, by adapting existing technology.</p>
<p>It could therefore take time. What’s more, because of the way the planets orbit the Sun, there are opportunities for launches to Mars only every two years: in 2024, 2026 and so on. My expectation is that 2028 is most likely for our mission, but it will require hard work. The positive thing is that Esa and the member states are still keen to go ahead, and we are eagerly looking forward to the launch whenever that will be.</p>
<p>Ultimately, life changed for the Rosalind Franklin team on February 24. I’ve been working on the mission since 2003, when we first proposed a camera system for what became ExoMars. We had already provided the “stereo camera system” for Esa’s ill-fated Beagle 2, which very nearly worked when it landed on Christmas Day 2003. But orbiter images later showed that the last solar panel didn’t quite unfurl, so communications with Earth <a href="https://theconversation.com/how-we-found-our-lost-mars-lander-after-a-decade-of-searching-and-whats-next-85374">were impossible</a>. The wait for data from the Martian surface for our team goes on.</p>
<p>There is no getting away from the huge disappointment we felt when the ExoMars Rosalind Franklin rover that we had worked on for almost 20 years was suspended. But it was ultimately a necessary and understandable step, and we now look forward to a future launch. </p>
<p>This still is cutting-edge science, and it will be for the rest of this decade. Due to the uniquely deep drilling, Rosalind Franklin still may be the first mission to find <a href="https://theconversation.com/our-rover-could-discover-life-on-mars-heres-what-it-would-take-to-prove-it-89625">signs of life</a> in space.</p><img src="https://counter.theconversation.com/content/183927/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Coates receives funding at UCL-MSSL from UK Space Agency and from STFC-UKRI, UK. He is PI of the PanCam instrument on the ExoMars Rosalind Franklin rover, leading an international team from UK, Germany, Switzerland, Austria and others. He is currently on the board of the Centre for Planetary Sciences at UCL-Birkbeck, a member of STFC Science Board, and is President of the Society for Popular Astronomy (popastro), UK.</span></em></p>The European space agency will need both a launch vehicle and a lander platform to launch its ExoMars rover without help from Russia.Andrew Coates, Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1727012021-12-01T11:37:18Z2021-12-01T11:37:18ZAI can reliably spot molecules on exoplanets – and might one day even discover new laws of physics<figure><img src="https://images.theconversation.com/files/434280/original/file-20211128-27-aweizs.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4931%2C3490&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's impression of exoplanet KELT-11 b.</span> <span class="attribution"><span class="source">Impression by Léa Changeat.</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Do you know what the Earth’s atmosphere is made of? You’d probably remember it’s oxygen, and maybe nitrogen. And with a little help from Google you can easily reach a more precise answer: 78% nitrogen, 21% oxygen and 1% argon gas. However, when it comes to the composition of exo-atmospheres – the atmospheres of planets outside our solar system – the answer is not known. This is a shame, as atmospheres can indicate the nature of planets, and whether they can host life.</p>
<p>As exoplanets are so far away, it has proven extremely difficult to probe their atmospheres. Research suggests that artificial intelligence (AI) may be our best bet to explore them – but only if we can show that these algorithms think in reliable, scientific ways, rather than cheating the system. Now our new paper, published in the <a href="https://iopscience.iop.org/article/10.3847/1538-3881/ac1744/meta">Astrophysical Journal</a>, has provided reassuring insight into their mysterious logic.</p>
<p>Astronomers typically exploit the <a href="https://exoplanets.nasa.gov/faq/31/whats-a-transit/#:%7E:text=Most%20known%20exoplanets%20have%20been,between%20us%20and%20the%20Sun.">transit method</a> to investigate exoplanets, which involves measuring dips in light from a star as a planet passes in front of it. If an atmosphere is present on the planet, it can absorb a very tiny bit of light, too. By observing this event at different wavelengths – colours of light – the fingerprints of molecules can be seen in the absorbed starlight, forming recognisable patterns in what we call a spectrum. </p>
<p>A typical signal produced by the atmosphere of a Jupiter-sized planet only reduces the stellar light by ~0.01% if the star is Sun-like. Earth-sized planets produce 10-100 times lower signals. It’s a bit like spotting the eye colour of a cat from an aircraft.</p>
<p>In the future, the James Webb Space Telescope (<a href="https://jwst.nasa.gov/content/webbLaunch/index.html">JWST</a>) and the <a href="https://arielmission.space/">Ariel</a> Space Mission, both probes that will investigate exoplanets from their orbit in space, will help by providing high-quality spectra for thousands of exo-atmospheres. But while scientists are excited about this, the <a href="https://iopscience.iop.org/article/10.3847/1538-4357/abf2bb">latest research</a> suggests it may be tricky. Due to the complex nature of atmospheres, the analysis of a single transiting planet may take days or even weeks to complete. </p>
<p>Naturally, researchers have started to look for alternative tools. AI are renowned for their ability to assimilate and learn from a large amount of data and their superb performance on different tasks once trained. Scientists have therefore attempted to train AI to predict the abundance of various chemical species in atmospheres. </p>
<p>Current research has established that <a href="https://www.nature.com/articles/s41550-018-0504-2">AIs are well-suited for this task</a>. However, scientists are meticulous and sceptical, and to prove this is really the case, they want to understand how AIs think. </p>
<h2>Peeking inside the black box</h2>
<p>In science, a theory or a tool cannot be adopted if it is not understood. After all, you don’t want to go through the excitement of discovering life on an exoplanet, just to realise it is simply a “glitch” in the AI. The bad news is that AIs are terrible at explaining their own findings. Even AI experts have a hard time identifying what causes the network to provide a given explanation. This disadvantage has often prevented the adoption of AI techniques in astronomy and other scientific fields. </p>
<p>We developed a method that allows us a glimpse into the decision-making process of AI. The approach is quite intuitive. Suppose an AI has to confirm whether an image contains a cat. It would presumably do this by spotting certain characteristics, such as fur or face shape. To understand which characteristics it is referencing, and in what order, we could blur parts of the cat’s image and see if it still spots that it is a cat.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of a blurred cat." src="https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434286/original/file-20211128-27-1tkes37.jpeg?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">How an AI’s predictions works for blurred cat image (please click on the image to enlarge it).</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This is exactly what we did for an exoplanet-probing AI by “perturbing”, or changing, regions of the spectrum. By observing how the AI’s predictions on the abundances of exoplanet molecules changed (say water in the atmosphere) when each region was doctored, we started to build a “picture” of how the AI thought, such as which regions of the spectrum it used for deciding the level of water in the atmosphere. </p>
<figure class="align-center ">
<img alt="Map showing the AI's sensitivity to the characteristics of a cat." src="https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=168&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=168&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=168&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=211&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=211&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434290/original/file-20211128-23-1moc5rn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=211&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We can combine features highlighted by the AI together with the original image to produce what we called a sensitivity map which outlines the areas it is looking closely at.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Reassuringly for us astronomers, we found that a well-trained AI relies heavily on physical phenomena, such as unique spectroscopic fingerprints – just like an astronomer would. This may come as no surprise, after all, where else can the AI learn it from? </p>
<p>In fact, when it comes to learning, AI is not so different from a cheeky high-school student – it will try its best to avoid the hard way (such as understanding difficult mathematical concepts) and find any shortcuts (such as memorising the mathematical formulae without understanding why) in order to get the correct answer. </p>
<p>If the AI made predictions based on memorising every single spectrum it had come across, that would deeply undesirable. We want the AI to derive its answer from the data, and perform well on unknown data, not just the training data for which there is a correct answer.</p>
<p>This finding provided the first method to have a sneaky peek into so-called “AI black-boxes”, allowing us to evaluate what the AIs have learnt. With these tools, researchers now can not only use AIs to speed up their analysis of exo-atmospheres, but they can also verify that their AI uses well-understood laws of nature.</p>
<p>That said, it’s too early to claim that we fully understand AIs. The next step is to work out precisely how important each concept is, and how it gets processed into decisions.</p>
<p>The prospect is exciting for AI experts, but even more so for us scientists. AI’s incredible learning power originates from its ability to learn a “representation”, or pattern, from the data – a technique similar to how physicists have discovered laws of nature in order to better understand our world. Having access to the minds of AI may therefore grant us the opportunity to learn new, undiscovered laws of physics.</p><img src="https://counter.theconversation.com/content/172701/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kai Hou (Gordon) Yip receives funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme ExoAI and from the Science and Technology Funding Council (STFC).</span></em></p><p class="fine-print"><em><span>Quentin Changeat receives funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme ExoAI, from the Science and Technology Funding Council (STFC) and from the UK Space Agency (UKSA).</span></em></p>AI loves to cheat, but new research shows it doesn’t do so when analysing the atmospheres of exoplanets.Kai Hou (Gordon) Yip, Postdoctoral Research Fellow at ExoAI, UCLQuentin Changeat, Postdoctoral Research Fellow in Astronomy, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1618112021-06-13T20:07:22Z2021-06-13T20:07:22ZDo aliens exist? We asked five experts<figure><img src="https://images.theconversation.com/files/405853/original/file-20210611-17-1fcr2df.jpg?ixlib=rb-1.1.0&rect=170%2C89%2C5793%2C3880&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>Speculation has been rife about the contents of an unclassified report set to be released later this month from the Pentagon’s Unidentified Aerial Phenomena (UAP) task force. </p>
<p>The document, <a href="https://www.scientificamerican.com/article/experts-weigh-in-on-pentagon-ufo-report/">expected to drop</a> on June 25, will supposedly provide a comprehensive summary of what the US government knows about UAPs — or, to use the more popular term, UFOs.</p>
<p>While the report is not yet public, the New York Times recently <a href="https://www.nytimes.com/2021/06/03/us/politics/ufos-sighting-alien-spacecraft-pentagon.html">published</a> what it claimed was a preview of the findings, provided by unnamed senior officials who were privy to the report’s contents. </p>
<p>According to the Times’s sources, the report does not provide any clear link or association between more than 120 incidents of UFO sightings from the past two decades, and a possibility of Earth having been visited by aliens.</p>
<p>If the Times’s sources are to be believed, there’s clearly still no good reason to interpret an unexplained object in the sky as evidence of aliens. But does that mean aliens aren’t out there, somewhere else in the universe? And if they are, could we ever find them? Or might they be so different to us that “finding” them is impossible in any meaningful sense?</p>
<p>We asked five experts. </p>
<h2>Four out of five experts said aliens do exist</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=99&fit=crop&dpr=1 600w, https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=99&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=99&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=125&fit=crop&dpr=1 754w, https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=125&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/315871/original/file-20200218-11005-1x9b2hg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=125&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"></span>
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</figure>
<p><strong>Here are their detailed responses:</strong></p>
<p><iframe id="tc-infographic-587" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/587/04f8cf2f024c65ae2010dc729c28c7600cecda2d/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
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Read more:
<a href="https://theconversation.com/the-us-military-has-officially-published-three-ufo-videos-why-doesnt-anybody-seem-to-care-137498">The US military has officially published three UFO videos. Why doesn't anybody seem to care?</a>
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<img src="https://counter.theconversation.com/content/161811/count.gif" alt="The Conversation" width="1" height="1" />
Even if aliens exist, are intelligent like humans and interested in making contact with us, what are the chances they’ll be close enough for us to hear them screaming their presence into the cosmos?Noor Gillani, Digital Culture EditorChynthia Wijaya-Kovac, Social Media Producer, The Conversation AustraliaLicensed 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/1550112021-02-18T13:43:55Z2021-02-18T13:43:55ZWhat belief in extraterrestrial visitors to Earth reveals about trust in elections<figure><img src="https://images.theconversation.com/files/384561/original/file-20210216-21-74x41x.jpg?ixlib=rb-1.1.0&rect=6%2C13%2C4420%2C3922&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">People who believe aliens have visited Earth are less likely to trust the 2020 election results.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/beam-from-ufo-over-tractor-at-farm-royalty-free-image/672154467"> Colin Anderson Productions pty ltd/DigitalVision via Getty Images</a></span></figcaption></figure><p><a href="https://doi.org/10.1111/ajps.12234">Partisanship is not enough</a> to explain why so many Americans – <a href="https://www.muhlenberg.edu/media/contentassets/pdf/about/polling/surveys/pennsylvania/PPEPP%20KEY%20FINDINGS%20REPORT%20(2).pdf">mostly Republicans</a> – <a href="http://maristpoll.marist.edu/npr-pbs-newshour-marist-poll-results-the-trump-legacy-biden-administration/">distrust the outcome</a> of the 2020 presidential election. </p>
<p>As <a href="https://scholar.google.com/citations?user=3sQSen4AAAAJ&hl=en&oi=ao">scholars in political</a> <a href="https://www.uno.edu/profile/faculty/anthony_">behavior and methods</a>, we are aware of another <a href="https://theconversation.com/conspiracy-theories-why-are-they-thriving-in-the-pandemic-153657">factor in voters’ thinking that has increased</a> right alongside electoral distrust: Americans’ beliefs in conspiracy theories, especially those that express mistrust of government officials. </p>
<p>Our research, which has not yet been published, finds that <a href="https://www.bigeasymagazine.com/2021/02/11/la-statewide-survey-on-voter-religiosity-belief-in-extraterrestrials-and-voter-fraud-in-the-2020-u-s-presidential-election/">these two beliefs are linked</a> – to the extent that Americans who believe aliens have visited Earth are more likely than disbelievers to say that Joe Biden is not the legitimate winner of the 2020 presidential election. As conspiracy theory beliefs grow in the U.S., we expect a corresponding drop in public trust in elections.</p>
<h2>Polling voters</h2>
<p>Drawing on <a href="https://doi.org/10.1177%2F1065912917721061">academic literature</a> focused on <a href="https://doi.org/10.1080/17457289.2019.1593181">trust in electoral processes</a>, we decided to look specifically at voters’ conspiratorial beliefs. On Jan. 19, 2021, the eve of President Joe Biden’s inauguration, we conducted a survey of 633 Louisiana registered voters, selected at random. We asked a series of questions about their religious beliefs, their beliefs in extraterrestrial life and whether Joe Biden had been the rightful winner of the 2020 U.S. presidential election.</p>
<p>The key questions we asked were:</p>
<ul>
<li>Do you believe that there is life in the universe other than on Earth?</li>
<li>Do you believe that extraterrestrials have visited the Earth?</li>
<li>Do you believe that Joe Biden is the rightful winner of the 2020 U.S. presidential election?</li>
</ul>
<p>We weighted the answers to reflect the statewide population balance of gender, age and race.</p>
<p><iframe id="qTVgM" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/qTVgM/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Aliens and electoral trust</h2>
<p>We found that Democrats and third-party and independent voters were somewhat more inclined to believe conspiracy theories than Republicans. That fits with other recent surveys indicating that both parties do indeed have <a href="https://www.americansurveycenter.org/research/conspiracy-theories-misinformation-covid-19-and-the-2020-election/">conspiratorial leanings</a>, though the partisan divide may influence which particular conspiracies a person believes. </p>
<p>Belief in conspiracy theories – the idea that <a href="https://doi.org/10.1093/acprof:oso/9780199351800.001.0001">secret causes</a> are behind real-world events – have circulated broadly in the <a href="https://www.vox.com/21558524/conspiracy-theories-2020-qanon-covid-conspiracies-why">pandemic crisis and election cycle</a> in part because of the evolution of social media networks and their ability to create <a href="https://theconversation.com/dont-blame-fox-news-for-the-attack-on-the-capitol-154047">echo chambers</a>, communities where people encounter only those who agree with them.</p>
<p>The QAnon movement, which holds the <a href="https://www.nature.com/articles/d41586-021-00257-y">election was fraudulent</a> in particular, has developed from periphery to <a href="https://medium.com/curiouserinstitute/a-game-designers-analysis-of-qanon-580972548be5">a growing mainstream group</a> with <a href="https://theconversation.com/trumps-time-is-up-but-his-twitter-legacy-lives-on-in-the-global-spread-of-qanon-conspiracy-theories-153298">widespread influence</a>. </p>
<p>Conspiracist thinking fits well with Donald Trump’s false claims that the election was fraudulent. QAnon believers consider the fact that he has <a href="https://theconversation.com/why-trumps-election-fraud-claims-arent-showing-up-in-his-lawsuits-challenging-the-results-150505">lost all the legal challenges</a> attempting to prove his claim to be <a href="https://www.nature.com/articles/d41586-021-00257-y">more evidence that powerful and secretive forces are at work</a> to steal the election and hide the truth from the public.</p>
<p>Most of our survey’s respondents – 59.7% – believe the <a href="https://theconversation.com/why-the-idea-of-alien-life-now-seems-inevitable-and-possibly-imminent-115643">defensible possibility that life exists elsewhere in the universe</a> than just on Earth. And 32.3% – nearly one-third – of the respondents believe that <a href="https://theconversation.com/internet-jokesters-call-for-people-to-storm-area-51-to-find-aliens-heres-some-science-to-consider-120715">aliens have actually visited Earth</a>, though <a href="https://www.popularmechanics.com/military/research/a29771548/navy-ufo-witnesses-tell-truth/">governments continue to deny</a> any such thing. Third-party and independent voters are more likely to believe this than Democrats or Republicans.</p>
<p><iframe id="475Ez" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/475Ez/1/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>We also found that just over half of the respondents did not believe Biden was rightfully elected president. There was a clear partisan split there, with 74% of Democrats trusting the results but only 12% of Republicans believing them. Third-party and independent voters were more evenly divided, with 36% trusting the results, 45% not believing them and 19% unsure.</p>
<p>Both of these beliefs express doubt about government officials’ truth-telling: In one, leaders are covering up an alien visit, and in the other, they are misleading the public about election results. When we look at people who share both of these beliefs, we find that out of the respondents who believe aliens have visited Earth, 57.6% also believe Biden was not rightfully elected president.</p>
<p><iframe id="D9vdO" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/D9vdO/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The connection between belief in ET visitation and electoral mistrust is statistically significant, even when controlling for various other determinants such as partisanship, age, race and sex. </p>
<p>These findings are limited because we surveyed only Louisiana voters. But we believe voters’ beliefs could be similar in several other states where Trump also won by double-digit margins, including Alabama, Idaho, Kansas and West Virginia.</p>
<p>While a specific belief in extraterrestrial visits to Earth may not be directly causing a belief in election fraud, these two ideas are conspiracy-oriented: People who believe the government is lying about one are more likely to believe officials are hiding the truth about the other.</p><img src="https://counter.theconversation.com/content/155011/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 organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Americans who believe aliens have visited Earth are more likely than disbelievers to say that Joe Biden is not the legitimate winner of the 2020 presidential election.Joshua Lambert, Postdoctoral Research Fellow, School of Politics, Security, and International Affairs, University of Central FloridaAnthony Licciardi Jr., Research Associate in Political Science, University of New OrleansLicensed 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>
<hr>
<p>
<em>
<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>
</strong>
</em>
</p>
<hr>
<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>
<hr>
<p>
<em>
<strong>
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>
</strong>
</em>
</p>
<hr>
<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/1544082021-02-05T15:57:15Z2021-02-05T15:57:15ZMars missions from China and UAE are set to go into orbit – here’s what they could discover<p>How times have changed since the Apollo era. Within the space of a few days, two space missions from China and the United Arab Emirates (UAE), respectively, are set to reach Mars. The <a href="https://www.emiratesmarsmission.ae">UAE’s Hope mission</a> will go into orbit around Mars on February 9. The next day, the <a href="https://www.nature.com/articles/s41550-020-1148-6">Chinese Tianwen-1 mission</a> – an orbiter and lander - will swing into orbit, with a predicted landing date sometime in May. </p>
<p>It is a very big moment for both countries. Hope is the first interplanetary mission by an Arab nation ever. And if China succeeds, it will be the first country ever to visit and land on Mars on its first try. The odds are stacked against them with <a href="https://www.space.com/32199-mars-missions-history-successes-failures.html">nearly 50% of all Mars missions failing</a>. China already <a href="https://www.bbc.co.uk/news/science-environment-16491457">lost a Mars orbiter mission (Yinghuo-1)</a> back in 2011.</p>
<hr>
<p><em>For more on the upcoming Mars missions, listen to 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>
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<p>But before the missions can start doing science, tense moments await. As they arrive at the planet, they need to trigger a burn of their engines just at the right time to slow the probes down so they can be captured by Mars’ gravitational field. Given the large distance from Earth, this needs to be carried out automatically by the probe. </p>
<h2>Tianwen-1</h2>
<p>If all goes well, the orbiter Tianwen, which means <a href="https://www.nature.com/articles/s41550-020-1148-6">“Questions to Heaven”</a> and the yet unnamed rover will attempt to measure Mars’s climate and “<a href="https://solarsystem.nasa.gov/news/1127/10-things-to-know-about-the-ionosphere/">ionosphere</a>”, a layer of electrically charged particles surrounding the planet. This work might help to understand <a href="https://www.nasa.gov/press-release/nasas-maven-reveals-most-of-mars-atmosphere-was-lost-to-space">how Mars is losing its atmosphere</a>. But it will also support future crewed missions to Mars by exploring its surface <a href="http://www.cjss.ac.cn/CN/article/downloadArticleFile.do?attachType=PDF&id=2602">and mapping</a> its shape, geology and internal structure. </p>
<p>The orbiter is packed with cameras, a magnetometer (used to measure magnetic fields) and various particle analysers. It will also act as a relay station to stay in communication with the rover. The rover, the size of a small car, is just a little bit smaller than the <a href="https://mars.nasa.gov/mars2020/">NASA Perseverance rover</a>, which is also approaching Mars. It flouts a similar look, with a six-wheel drive, large solar panels and a pole with cameras attached. The latter will be able to identify surface compositions at a distance of between two metres and five metres.</p>
<p>What makes this mission even more fascinating is that the rover contains a ground-penetrating radar. During the rover’s estimated lifespan of 90 Martian days - a Martian day being nearly 38 minutes longer than ours - it can explore the sub-surface structure and search for water deposits below the ground. Evidence of underground saltwater lakes <a href="https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_detects_liquid_water_hidden_under_planet_s_south_pole">was found</a> using radar in 2018 by the <a href="https://sci.esa.int/web/mars-express">European Mars Express Orbiter</a>, but never followed up with measurements from the surface. </p>
<p>The rover will not visit these specific sites but could find similar conditions at the proposed landing site, which we know used to be covered by mudflats. There’s huge interest in such deposits as they represent a resource for future astronauts on the planet. We also can’t rule out the possibility that the lakes <a href="https://theconversation.com/mars-mounting-evidence-for-subglacial-lakes-but-could-they-really-host-life-146732">could host some form of life</a>.</p>
<p>China has already used the radar technology with great success on its recent Yutu-2 rover to identify <a href="https://skyandtelescope.org/astronomy-news/what-lies-beneath-moon-farside/">separate unique layers of water ice</a> up to 40m below the surface on the Moon. </p>
<p>The Chinese National Space Administration stated that <a href="https://www.space.com/china-mars-rover-tianwen-1-landing-site">the rover will land</a> in the region known as Utopia Planitia, the largest known impact basin in the solar system. In the first three months, the orbiter will survey and identify the precise location.</p>
<p>Curiously, a press release from after the successful launch of the mission initially indicated the <a href="http://www.spaceflightfans.cn/77341.html">intended coordinates within Utopia Planitia</a> (110.318 degrees east longitude and 24.748 degrees north latitude), but these were swiftly removed, possibly to ensure this does not contradict a later slight alteration – or with political motivatation. <a href="https://www.space.com/china-mars-rover-tianwen-1-landing-site">Speaking to Space.com</a>, <a href="https://www.lpl.arizona.edu/faculty/mcewen">Alfred McEwen</a>, director of the Planetary Image Research Laboratory at the University of Arizona, said the intended landing area is safe and scientifically very interesting. </p>
<p>China’s first Mars rover will need to go through the so-called <a href="https://www.jpl.nasa.gov/videos/curiositys-seven-minutes-of-terror/">seven minutes of terror</a>: the automated decent of any lander through the Martian atmosphere to successfully decelerate and land in one piece, all without any active communication with an orbiter or ground control. To achieve this, it will do an initial deceleration using a “conical aeroshell”, which is a protective shield that causes aerodynamic drag (resistance) but will heat up immensely, followed by a parachute and then the firing of retrorockets to the allow a soft touch down. </p>
<h2>Hopeful UAE</h2>
<p>The Hope mission is the UAE’s first ever interplanetary mission arriving at Mars at the same time as the UAE is <a href="https://www.bbc.co.uk/news/science-environment-53394737">celebrating its 50th anniversary of formation</a>. This mission blasted off from Japan in July 2020 using the same “launch window” (the best time for a probe to set off and easily reach Mars from Earth) to reach Mars as the Chinese and Nasa missions. </p>
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<p>Hope is set to orbit Mars for one Martian year – nearly two Earth years. From distances between 22,000km up to 44,000km, it will explore in more detail the martian atmosphere. The <a href="https://www.emiratesmarsmission.ae/">mission will investigate</a> the global weather, its links to the upper atmosphere and how this can explain the changing abundance of hydrogen and oxygen there. This will help us understand how Mars is gradually losing its atmosphere and the role that dust plays in the Martian weather – also important information for those who want to settle on Mars one day.</p>
<p>These busy times for all interested in Mars exploration have been kicked off by two relative newcomers in the treacherous business of Martian exploration, bringing a welcome, fresh perspective. It’s brilliant to see the group of nations exploring Mars expanding. And if you haven’t had enough seeing these missions arriving, then sit back for a few days until February 18, when NASA’s Perseverance rover will join them.</p><img src="https://counter.theconversation.com/content/154408/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Brown 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>If China succeeds, it will be the first country ever to visit and land on Mars on its first try.Daniel Brown, Lecturer in Astronomy, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1543242021-02-03T14:01:33Z2021-02-03T14:01:33ZCurious Kids: We have been trying to contact aliens – but do they want to contact us?<figure><img src="https://images.theconversation.com/files/382008/original/file-20210202-17-szujfl.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3214%2C2590&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/alien-spacecraft-hovering-over-trees-714589369">Yuriy Mazur/Shutterstock</a></span></figcaption></figure><p><strong>Humans have been trying to contact aliens for many years, but do the aliens want to contact us? – Sai, aged eight, London, UK</strong></p>
<p>This is a great question – and the truth is that we don’t know the answer.</p>
<p>For starters, we haven’t found any aliens yet, so we haven’t been able to ask them and receive a reply. When we try to answer the question “do they want to contact us”, we have to put ourselves in their shoes – that is, if they have feet. </p>
<p>The question presumes that aliens do exist. And again, because we haven’t found any yet, we don’t know if they do. It is possible they may exist, for one simple reason: we exist. Whatever made the likes of bacteria evolve into complex bodies with intelligent brains on Earth may have also occurred on another planet.</p>
<p>On Earth this transformation seems to have taken place quite suddenly some <a href="https://www.newscientist.com/term/complex-life-evolve/">700 million years ago</a>. At that time the Earth was already almost 4 billion years old, and had been inhabited by simple lifeforms such as bacteria for much of that time. Why did it not happen sooner? And what made it happen? Until we find the answers to those questions we cannot tell how likely it is that it also occurred elsewhere.</p>
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<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.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">
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<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>. We won’t be able to answer every question, but we’ll do our very best.</em></p>
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<p>If there are aliens out there, they might want to contact us for the same reasons we want to contact them. </p>
<p>One reason why scientists on Earth are looking for aliens is that we are curious. We want to know if they exist, what they are like, and what our relationship with them might be. Curiosity is a powerful force, leading us to look beyond the horizon and to try new things. It is how we have developed science and technology, why we can have video calls with friends on the other side of the world and why we can now venture out into space. Aliens may be curious about us, too. </p>
<p>But there are other reasons why we want to contact others. We have sometimes needed help from others, or companionship. Perhaps aliens, too, would look to us for help or friendship. </p>
<p>They may also be interested in our planet. Earth has <a href="https://www.nationalgeographic.com/magazine/2018/03/one-strange-rock-interactive-earth-solar-system-milky-way-galaxy/">perfect conditions for life</a>. Aliens might need another home, if for some reason – such as climate change, nuclear war or an enormous asteroid impact – they had to leave their own planet.</p>
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<img alt="Planet Earth in space" src="https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382009/original/file-20210202-17-ey5pt0.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">
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<span class="caption">Earth is a perfect place for life.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/planet-earth-starry-sky-solar-system-1666159696">24K-Production/Shutterstock. This image has elements furnished by NASA.</a></span>
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<p>It’s also possible that they would not be looking for friendship. There are plenty of examples from our history of times when humans have travelled somewhere on Earth and acted cruelly, killing or enslaving the people that lived there. Aliens settling on Earth might want us out of their way. There’s another reason – humans are predators who eat other lifeforms. Aliens might find us nutritious or tasty too.</p>
<p>These are all possible reasons why aliens might want to contact us. But what if they didn’t? Some aliens might find us boring, hard to understand, too primitive to deserve their attention, or potentially bearing disease. Conversations across the vastness of space take many years, and travel <a href="https://www.bbc.com/future/article/20161003-the-myths-and-reality-about-interstellar-travel">much longer still</a>. Some aliens might simply not be interested in life beyond their own world.</p>
<p>On the other hand, it may be that life such as ours is actually very common. With so many worlds and civilisations to choose from, we may simply not yet have caught their eye. If that is the case, we might soon detect alien life around nearby stars for ourselves.</p>
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<p><em>When sending in questions to Curious Kids, make sure you include the asker’s first name, age and town or city. You can:</em></p>
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<hr><img src="https://counter.theconversation.com/content/154324/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacco van Loon 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>Aliens might want to contact us for the same reasons we are looking for them.Jacco van Loon, Astrophysicist and Director of Keele Observatory, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1524982021-01-04T16:46:21Z2021-01-04T16:46:21ZSETI: new signal excites alien hunters – here’s how we could find out if it’s real<figure><img src="https://images.theconversation.com/files/376923/original/file-20210103-13-1cqpdit.jpg?ixlib=rb-1.1.0&rect=23%2C0%2C2657%2C1750&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Parkes radio telescope.</span> <span class="attribution"><span class="source">CSIRO/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The US$100m (£70m) <a href="https://breakthroughinitiatives.org/initiative/1">Breakthrough Listen Initiative</a>, founded by the billionaire, technology and science investor Yuri Milner and his wife Julia, has identified a mysterious radio signal that seems to come from the nearest star to the Sun – Proxima Centauri. This has generated a flood of excitement in the press and among scientists themselves. The discovery, which was <a href="https://www.theguardian.com/science/2020/dec/18/scientists-looking-for-aliens-investigate-radio-beam-from-nearby-star">reported by the Guardian</a> but has yet to be published in a scientific journal, may be the search for extraterrestrial intelligence’s (SETI) first bona fide candidate signal. It has been dubbed Breakthrough Listen Candidate 1 or simply BLC-1.</p>
<p>Although the Breakthrough Listen team are still working on the data, we know that the radio signal was detected by <a href="https://www.csiro.au/en/Research/Facilities/ATNF/Parkes-radio-telescope/About-Parkes">the Parkes telescope</a> in Australia while it was pointing at Proxima Centauri, which is <a href="https://theconversation.com/how-we-spotted-a-potential-new-planet-around-the-suns-neighbouring-star-129975">thought to be orbited</a> by at least one habitable planet. The signal was present for the full observation, lasting several hours. It also was absent when the telescope pointed in a different direction. </p>
<figure class="align-center ">
<img alt="Sun rises over rocky alien landscape." src="https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/376968/original/file-20210104-13-12ojsib.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Artist’s impression of a planet orbiting Proxima Centauri.</span>
<span class="attribution"><span class="source">ESO/M. Kornmesser/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>The signal was “narrow-band”, meaning it only occupied a slim range of radio frequencies. And it drifted in frequency in a way that you would expect if it came from a moving planet. These characteristics are exactly the kind of attributes the SETI scientists have been looking for since the astronomer <a href="https://www.nationalgeographic.com/science/2020/06/father-launched-quest-find-alien-intelligence-changed-astronomy/">Frank Drake</a> first began the pioneering initiative some 60 years ago. </p>
<p>While this represents remarkable progress in our pursuit of the ultimate question of whether we are alone in the universe, the BLC-1 signal also presents some food for thought on how we conduct these searches. In particular, BLC-1 highlights a problem that has dogged SETI research right from the beginning: disappearing signals. BLC-1 hasn’t been seen since it was first detected in the spring of 2019. </p>
<p>If BLC-1 finally emerges as a true SETI signal candidate, it will be the first since the <a href="https://www.theguardian.com/science/across-the-universe/2016/apr/14/alien-wow-signal-could-be-explained-after-almost-40-years">“Wow! signal”</a> recorded back in 1977. This is perhaps the most famous example of an inconclusive SETI candidate – it was never observed again. That doesn’t mean it cannot be extraterrestrial in nature. The perfect celestial alignment of moving and potentially rotating transmitters and receivers, separated by interstellar distances, is always likely to be a fortuitous and sometimes temporary circumstance. </p>
<p>Nevertheless, this represents a challenge for the Breakthrough Listen team. If BLC-1 is never seen to repeat, it will be very difficult to conduct the kind of detailed follow-up that will fully convince scientists that it was a message from aliens. Sceptics will rightly argue that this is more likely to be either a new form of human-generated radio interference or a rare feature of the complex observing instrumentation itself. </p>
<p>Indeed, it may never be possible to provide really compelling evidence of the extraterrestrial nature of a SETI event based on a telescope with a single dish, such as Parkes. This is especially the case for one-off events. </p>
<h2>Ways forward</h2>
<p>One way forward would be to abandon the traditional approach of using large single dishes for SETI. While a parabolic dish has the useful property of being sensitive to a fairly large area of sky, if a candidate signal is detected, there is no way of knowing exactly where it came from. So, while the Parkes telescope was nominally pointing at Proxima Centauri, literally hundreds of thousands of other galactic stars were also present in the field of view. Ultimately, any one of them could potentially be the source of the BLC-1. </p>
<p>We can overcome this problem by observing with several large dishes simultaneously, preferably separated by hundreds and even thousands of kilometres. By combining their signals using a powerful technique known as <a href="https://www.esa.int/Science_Exploration/Space_Science/Observations_Very_Long_Baseline_Interferometry_VLBI">Very Long Baseline Interferometry</a>, we can pin-point the position of a signal with exquisite accuracy, such as to a single star. </p>
<p>For nearby systems such as Proxima Centauri, we can achieve a precision of approximately one thousandth of an astronomical unit (the distance between the Sun and Earth). This should allow us to identify not just the stellar system but the associated planet that transmitted the signal.</p>
<p>With such an approach, the motion on the sky of most signals could be measured in a year or even less. There are <a href="https://arxiv.org/abs/1810.07235">other advantages</a> to observing with an interferometric array of telescopes, such as having many completely independent telescopes detecting the same signal. </p>
<p>In addition, radio interference from Earth wouldn’t be registered by telescope sites separated by hundreds of kilometres. So the human made interference that has contributed to so many false positives for SETI, and has included orbiting satellites and even <a href="https://theconversation.com/were-no-strangers-to-alien-false-alarms-one-was-caused-by-a-microwave-oven-64716">microwave ovens</a>, would completely disappear. </p>
<p>This kind of interferometry is a well established technique that has been around since the late 1960s. So why are we not doing SETI with it systematically? One reason is that combining data together from an array of telescopes requires more effort in almost all regards, including greater computing resources. An observation of a few minutes would generate many terabytes of data (1 terabyte is 1,024 gigabytes). </p>
<figure class="align-center ">
<img alt="Hundreds of large satellite dishes in a desert." src="https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/376970/original/file-20210104-13-1esoa4l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Artist’s impression of the Square Kilometre Array.</span>
<span class="attribution"><span class="source">SPDO/TDP/DRAO/Swinburne Astronomy Productions - SKA Project Development Office and Swinburne Astronomy Productions</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>But none of these issues are show stoppers, especially as technology continues to advance at unprecedented rates. Perhaps a more important factor is human inertia. Until recently, the SETI community has been quite conservative in its approach, with staff traditionally drawn from <a href="https://www.seti.org/goodbye-arecibo">single-dish telescopes</a>. These scientists aren’t necessarily familiar with the quirks and foibles of interferometric arrays.</p>
<p>Luckily, that’s finally changing. Breakthrough Listen now looks towards incorporating arrays such as <a href="https://breakthroughinitiatives.org/news/23">MeerKAT</a>, the <a href="https://www.sciencemag.org/news/2020/09/how-big-money-powering-massive-hunt-alien-intelligence">Jansky Very Large Telescope</a> (JVLA) and eventually the <a href="https://theconversation.com/the-square-kilometre-array-finally-has-a-home-or-two-7274">Square Kilometre Array (SKA)</a> in their future survey programmes. In the meantime, prepare for a rising tide of ambiguous radio events – and hopefully the reappearance of BLC-1. Determining the precise location and motion of these signals may be the only way of reaching unequivocal conclusions.</p><img src="https://counter.theconversation.com/content/152498/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Garrett is a member of the Breakthrough Listen Advisory Board.
I'm the co-vice-chair of the Int. Academy of Astronautics SETI Permanent Commitee (SETI PC) </span></em></p>One way forward would be to abandon the traditional approach of using single-dish telescopes for SETI.Michael Garrett, Sir Bernard Lovell chair of Astrophysics and Director of Jodrell Bank Centre for Astrophysics, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1464072020-09-20T19:42:37Z2020-09-20T19:42:37ZIf there is life on Venus, how could it have got there? Origin of life experts explain<figure><img src="https://images.theconversation.com/files/358781/original/file-20200918-18-1xkxztj.jpg?ixlib=rb-1.1.0&rect=71%2C35%2C5919%2C3458&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 <a href="https://theconversation.com/life-on-venus-traces-of-phosphine-may-be-a-sign-of-biological-activity-146093">recent discovery of phosphine</a> in the atmosphere of Venus is exciting, as it may serve as a potential sign of life (among other possible explanations). </p>
<p>The researchers, who <a href="https://www.nature.com/articles/s41550-020-1174-4">published their findings in Nature Astronomy</a>, couldn’t really explain how the phosphine got there. </p>
<p>They explored all conceivable possibilities, including lightning, volcanoes and even delivery by meteorites. But each source they modelled couldn’t produce the amount of phosphine detected.</p>
<p>Most phosphine in Earth’s atmosphere is produced by living microbes. So the possibility of life on Venus producing phosphine can’t be ignored. </p>
<p>But the researchers, led by UK astronomer Jane Greaves, say their discovery “is not robust evidence for life” on Venus. Rather, it’s evidence of “anomalous and unexplained chemistry”, of which biological processes are just one possible origin.</p>
<p>If life were to exist on Venus, how could it have come about? Exploring the origins of life on Earth might shed some light.</p>
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Read more:
<a href="https://theconversation.com/life-on-venus-traces-of-phosphine-may-be-a-sign-of-biological-activity-146093">Life on Venus? Traces of phosphine may be a sign of biological activity</a>
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<h2>The ingredients for life (as we know it)</h2>
<p>Understanding how life formed on Earth not only helps us understand our own origins, but could also provide insight into the key ingredients needed for life, as we know it, to form. </p>
<p>The details around the origins of life on Earth are still shrouded in mystery, with <a href="https://www.scientificamerican.com/article/lifes-origins-by-land-or-sea-debate-gets-hot/">multiple competing scientific theories</a>. But most theories include a common set of environmental conditions considered vital for life. These are: </p>
<p><strong>Liquid water</strong></p>
<p>Water is needed to dissolve the molecules needed for life, to facilitate their chemical reactions. Although other solvents (such as methane) have been suggested to potentially support life, water is most likely. This is because it <a href="http://sitn.hms.harvard.edu/uncategorized/2019/biological-roles-of-water-why-is-water-necessary-for-life/">can dissolve a huge range of different molecules</a> and is found throughout the universe.</p>
<p><strong>Mild temperatures</strong> </p>
<p>Temperatures higher than 122°C destroy most complex organic molecules. This would make it almost impossible for carbon-based life to form in very hot environment. </p>
<p><strong>A process to concentrate molecules</strong> </p>
<p>As the origin of life would have required a large amount of organic molecules, a process to concentrate organics from the diluted surrounding environment would be required – either through absorption onto mineral surfaces, evaporation or floating on top of water in oily slicks. </p>
<p><strong>A complex natural environment</strong></p>
<p>For life to have originated, there would have had to be a complex natural environment wherein a diverse range of conditions (temperature, pH and salt concentrations) could create chemical complexity. Life itself is incredibly complex, so even the most primitive versions would need a complex environment to originate.</p>
<p><strong>Trace metals</strong></p>
<p>A range of trace metals, amassed through water-rock interactions, would be needed to promote the formation of organic molecules.</p>
<p>So if these are the conditions required for life, what does that tell us about the likelihood of life forming on Venus? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of Venus" src="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Venus has 90 times the atmospheric pressure of Earth.</span>
<span class="attribution"><span class="source">NASA</span></span>
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<h2>It’s unlikely today …</h2>
<p>The possibility of life as we know it forming on the surface of present-day Venus is incredibly low. An average surface temperature above 400°C means the surface can’t possibly have liquid water and this heat would also destroy most organic molecules. </p>
<p>Venus’s milder upper atmosphere, however, has temperatures low enough for water droplets to form and thus could potentially be suitable for the formation of life. </p>
<p>That said, this environment has its own limitations, such as clouds of sulfuric acid which would destroy any organic molecules not protected by a cell. For example, on Earth, molecules such as DNA are rapidly destroyed by acidic conditions, although some <a href="https://sciencing.com/types-bacteria-living-acidic-ph-9296.html">bacteria can survive</a> in extremely acidic environments.</p>
<p>Also, the constant falling of water droplets from Venus’s atmosphere down to its extremely hot surface would destroy any unprotected organic molecules in the droplets. </p>
<p>Beyond this, with no surfaces or mineral grains in the Venusian atmosphere on which organic molecules could concentrate, any chemical building blocks for life would be scattered through a diluted atmosphere – making it incredibly difficult for life to form. </p>
<h2>… but possibly less unlikely in the past</h2>
<p>Bearing all this in mind, if atmospheric phosphine is indeed a sign of life on Venus, there are three main explanations for how it could have formed. </p>
<p>Life may have formed on the planet’s surface when its conditions were very different to now. </p>
<p>Modelling suggests the surface of early Venus was very similar to early Earth, with lakes (or even oceans) of water and <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">mild conditions</a>. This was before a runaway greenhouse effect turned the planet into the hellscape it is today.</p>
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<a href="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Computer generated surface view of Eistla Regio region on Venus." src="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=587&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">This is a computer-generated picture of the Eistla Regio region on Venus’s surface.</span>
<span class="attribution"><span class="source">NASA</span></span>
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<p>If life formed back then, it might have adapted to spread into the clouds. Then, when intense climate change boiled the oceans away – killing all surface-based life – microbes in the clouds would have become the last outpost for life on Venus.</p>
<p>Another possibility is that life in Venus’s atmosphere (if there is any) came from Earth. </p>
<p>The planets of our inner solar system have been documented to exchange materials in the past. When meteorites crash into a planet, they can send that planet’s rocks hurtling into space where they occasionally intersect with the orbits of other planets.</p>
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Read more:
<a href="https://theconversation.com/meteorites-from-mars-contain-clues-about-the-red-planets-geology-130104">Meteorites from Mars contain clues about the red planet's geology</a>
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<p>If this happened between Earth and Venus at some point, the rocks from Earth may have contained microbial life that could have adapted to Venus’s highly acidic clouds (similar to Earth’s acid-resistant bacteria).</p>
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<a href="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Rendered image of meteorite hitting Earth." src="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">If rocks from Earth containing microbial life entered Venus’s orbit in the past, this life may have adapted to Venus’s atmospheric conditions.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<h2>A truly alien explanation</h2>
<p>The third explanation to consider is that a truly alien form of life (life as we <em>don’t</em> know it) could have formed on Venus’s 400°C surface and survives there to this day. </p>
<p>Such a foreign life probably wouldn’t be carbon-based, as nearly all complex carbon molecules break down at extreme temperatures. </p>
<p>Although carbon-based life produces phosphine on Earth, it’s impossible to say <em>only</em> carbon-based life can produce phosphine. Therefore, even if totally alien life exists on Venus, it may produce molecules that are still recognisable as a potential sign of life. </p>
<p>It’s only through further missions and research that we can find out whether there is, or was, life on Venus. As prominent scientist Carl Sagan <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114207/#:%7E:text=non%2Dlocal%20perception-,Introduction,et%20al.%2C%201999">once said</a>: “extraordinary claims require extraordinary evidence”. </p>
<p>Luckily, two of the <a href="https://www.nasa.gov/press-release/nasa-selects-four-possible-missions-to-study-the-secrets-of-the-solar-system">four finalist proposals</a> for NASA’s next round of funding for planetary exploration are focused on Venus.</p>
<p>These include VERITAS, an orbiter proposed to map the surface of Venus, and DAVINCI+, proposed to drop through the planet’s skies and sample different atmospheric layers on the way down.</p><img src="https://counter.theconversation.com/content/146407/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Steller receives funding from a Research Training Program scholarship provided by the Australian government. </span></em></p><p class="fine-print"><em><span>Martin Van Kranendonk receives funding from the Australian Research Council and BHP. </span></em></p>Considering what we know about the key ingredients for life’s formation on Earth, here are three explanations for how this process may have occurred on our sister planet.Luke Steller, PhD Student, UNSW SydneyMartin Van Kranendonk, Professor and Head of School, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.