tag:theconversation.com,2011:/uk/topics/life-24867/articles
Life – The Conversation
2024-01-11T17:23:58Z
tag:theconversation.com,2011:article/215765
2024-01-11T17:23:58Z
2024-01-11T17:23:58Z
How much life has ever existed on Earth?
<figure><img src="https://images.theconversation.com/files/567152/original/file-20231221-25-fybvl8.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C3619%2C2197&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In primary production, inorganic carbon is used to build the organic molecules life needs. </span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/how-much-life-has-ever-existed-on-earth" width="100%" height="400"></iframe>
<p>All organisms are made of living cells. While it is difficult to pinpoint exactly when the first cells came to exist, geologists’ best estimates suggest at least as early as <a href="https://doi.org/10.1016/S0301-9268(00)00128-5">3.8 billion years ago</a>. But how much life has inhabited this planet since the first cell on Earth? And how much life will ever exist on Earth? </p>
<p>In our new study, published in <a href="https://doi.org/10.1016/j.cub.2023.09.040"><em>Current Biology</em></a>, my colleagues from the <a href="https://www.weizmann.ac.il/">Weizmann Institute of Science</a> and <a href="https://www.smith.edu/academics/geosciences">Smith College</a> and I took aim at these big questions.</p>
<h2>Carbon on Earth</h2>
<p>Every year, about 200 billion tons of carbon is taken up through what is known as primary production. During primary production, inorganic carbon — such as carbon dioxide in the atmosphere and bicarbonate in the ocean — is used for energy and to build the organic molecules life needs. </p>
<p>Today, the most notable contributor to this effort is <a href="https://doi.org/10.1038/nrm1525">oxygenic photosynthesis</a>, where sunlight and water are key ingredients. However, deciphering past rates of primary production has been a challenging task. In lieu of a time machine, scientists like myself rely on clues left in ancient sedimentary rocks to reconstruct past environments. </p>
<p>In the case of primary production, the isotopic composition of <a href="https://doi.org/10.1038/s41586-018-0349-y">oxygen</a> in the form of sulfate in ancient salt deposits allows for such estimates to be made. </p>
<p>In <a href="https://doi.org/10.1016/j.cub.2023.09.040">our study</a>, we compiled all previous estimates of ancient primary production derived through the method above, as well as many others. The outcome of this productivity census was that we were able to estimate that 100 quintillion (or 100 billion billion) tons of carbon has been through primary production since the origin of life. </p>
<p>Big numbers like this are difficult to picture; 100 quintillion tons of carbon is about 100 times the amount of carbon contained within the Earth, a pretty impressive feat for Earth’s primary producers. </p>
<h2>Primary production</h2>
<p>Today, primary production is mainly achieved by plants on land and marine micro-organisms such as algae and cyanobacteria. In the past, the proportion of these major contributors was very different; in the case of Earth’s earliest history, primary production was mainly conducted by an entirely different group of organisms that don’t rely on oxygenic photosynthesis to stay alive.</p>
<p>A combination of different techniques has been able to give a sense of when different primary producers were most active in Earth’s past. Examples of such techniques include identifying the <a href="https://doi.org/10.1016/j.cub.2021.07.038">oldest forests</a> or using molecular fossils called <a href="https://doi.org/10.1038/nature23457">biomarkers</a>. </p>
<p>In <a href="https://doi.org/10.1016/j.cub.2023.09.040">our study</a>, we used this information to explore what organisms have contributed the most to Earth’s historical primary production. We found that despite being late on the scene, land plants have likely contributed the most. However, it is also very plausible that cyanobacteria contributed the most.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="green hair-like strands of bacteria" src="https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567163/original/file-20231221-21-1tcat1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Filamentous cyanobacteria from a tidal pond at Little Sippewissett salt marsh, Falmouth, Mass.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/argonne/26719316190">(Argonne National Laboratory)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<h2>Total life</h2>
<p>By determining how much primary production has ever occurred, and by identifying what organisms have been responsible for it, we were also able to estimate how much life has ever been on Earth. </p>
<p>Today, one may be able to approximate how many humans exist based on how much food is consumed. Similarly, we were able to calibrate a ratio of primary production to how many cells exist in the modern environment. </p>
<p>Despite the large variability in the number of cells per organism and the sizes of different cells, such complications become secondary since single-celled microbes dominate global cell populations. In the end, we were able to estimate that about 10<sup>30</sup> (10 noninillion) cells exist today, and that between 10<sup>39</sup> (a duodecillion) and 10<sup>40</sup> cells have ever existed on Earth. </p>
<h2>How much life will Earth ever have?</h2>
<p>Save for the ability to move Earth into the orbit of a younger star, the lifetime of Earth’s biosphere is limited. This morbid fact is a consequence of <a href="https://doi.org/10.1007/978-94-010-9633-1_4">our stars life cycle</a>. Since its birth, the sun has slowly been getting brighter over the past four and half billion years as hydrogen has been converted to helium in its core. </p>
<p>Far in the future, about two billion years from now, all of the biogeochemical fail-safes that keep Earth habitable will be pushed past their <a href="https://doi.org/10.1038/s41561-021-00693-5">limits</a>. First, land plants will die off, and then eventually the oceans will boil, and the Earth will return to a largely lifeless rocky planet as it was in its infancy. </p>
<p>But until then, how much life will Earth house over its entire habitable lifetime? Projecting our current levels of primary productivity forward, we estimated that about 10<sup>40</sup> cells will ever occupy the Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a blue planet in space" src="https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567209/original/file-20231222-15-cdexst.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A planetary system 100 light-years away in the constellation Dorado is home to the first Earth-size habitable-zone planet, discovered by NASA’s Transiting Exoplanet Survey Satellite.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details/PIA23408">(NASA Goddard Space Flight Center)</a></span>
</figcaption>
</figure>
<h2>Earth as an exoplanet</h2>
<p>Only a few decades ago, exoplanets (planets orbiting other stars) were just a hypothesis. Now we are able to not only <a href="https://exoplanets.nasa.gov/">detect them</a>, but describe many aspects of thousands of far off worlds around distant stars. </p>
<p>But how does Earth compare to these bodies? In our new study, we have taken a birds eye view of life on Earth and have put forward Earth as a benchmark to compare other planets. </p>
<p>What I find truly interesting, however, is what could have happened in Earth’s past to produce a radically different trajectory and therefore a radically different amount of life that has been able to call Earth home. For example, what if oxygenic photosynthesis never took hold, or what if endosymbiosis never happened?</p>
<p>Answers to such questions are what will drive my laboratory at <a href="https://earthsci.carleton.ca/">Carleton University</a> over the coming years.</p><img src="https://counter.theconversation.com/content/215765/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Crockford receives funding from the Canadian Natural Sciences and Engineering Research Council and Carleton University</span></em></p>
Over two billion years from now, Earth will no longer be able to sustain life. A new study looks at how much life has ever existed and what this means for the discovery of new life-supporting planets.
Peter Crockford, Assistant Professor, Earth Sciences, Carleton University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/215636
2023-10-24T15:15:13Z
2023-10-24T15:15:13Z
Physics has long failed to explain life – but we’re testing a groundbreaking new theory in the lab
<figure><img src="https://images.theconversation.com/files/555341/original/file-20231023-23-dbncio.jpg?ixlib=rb-1.1.0&rect=1670%2C53%2C4113%2C3934&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/mother-panda-her-baby-snuggling-eating-1839520114">Daniel X D/Shutterstock</a></span></figcaption></figure><p>Modern physics can explain everything from the spin of the tiniest particle to the behaviour of entire galaxy clusters. But it <a href="https://theconversation.com/great-mysteries-of-physics-5-will-we-ever-have-a-fundamental-theory-of-life-and-consciousness-203127">can’t explain life</a>. There’s simply no formula to explain the difference between a living lump of matter and a dead one. Life seems to just mysteriously “emerge” from non-living parts, such as elementary particles. </p>
<p>Assembly theory is a bold new approach to explaining life on a fundamental scale, with its framework <a href="https://www.nature.com/articles/s41586-023-06600-9">recently published in Nature</a>. It assumes that complexity and information (such as DNA) are at the heart of it. The theory provides a a way to understand how these concepts emerge in chemical systems. </p>
<p>Emergence is a word physicists use to explain something that is bigger than the sum of its parts – such as how water can feel wet when individual water molecules don’t. Wetness is an emergent property.</p>
<p>While the mathematics is elegant, the theory can ultimately only be reliable if it is tested in the lab. Carefully designed experiments, such as the one my colleagues and I are carrying out right now, will be essential to ground the abstractions of assembly theory in chemical reality.</p>
<p>At the core of assembly theory is the idea that objects can be defined not as immutable entities, but by the history of how they formed. This shifts focus to the processes by which complex configurations are constructed from simpler building blocks. </p>
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<a href="https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=803&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=803&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=803&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1010&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1010&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554281/original/file-20231017-21-fti245.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1010&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Building blocks can be assembled much like lego to create molecules of life.</span>
<span class="attribution"><span class="source">Image credit Dr Anna Tanczos, Sci - Comm Studios.</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The theory proposes an “assembly index” which <a href="https://theconversation.com/life-modern-physics-cant-explain-it-but-our-new-theory-which-says-time-is-fundamental-might-203129">quantifies the minimal steps</a>, or shortest path, required to build an object. This measure tracks the degree of “selection” necessary to yield an ensemble of objects – referring to the memory, such as DNA, required to create living things.</p>
<p>Living things, after all, don’t just occur spontaneously, such as helium in stars. They require DNA as a blueprint for creating new versions.</p>
<h2>Predictions of novelty</h2>
<p>But how might these theoretical constructs actually be probed experimentally?
One key aspect of assembly theory has <a href="https://www.nature.com/articles/s41467-021-23258-x">already been tested in our lab</a>. That is the determination of the assembly index using mass spectrometry (an analytical tool which can measure the mass-to-charge ratio in molecules). </p>
<p>By fragmenting molecules and analysing their mass spectra, we can estimate their assembly index. We can literally see how many steps it takes for various fragments to piece together to form a given molecule. Assembly index can also be measured using other techniques called infrared spectroscopy and NMR spectroscopy for various types of molecules.</p>
<p>We’ve determined the assembly index on a range of molecules, both in the lab and computationally. Our work shows that molecules associated with life, such as hormones and metabolites (products of metabolic reactions), are indeed more complex and require more information to assemble than molecules that are not uniquely associated with life, such as carbon dioxide. In fact, we’ve shown that an assembly index above 15 steps <a href="https://www.nature.com/articles/s41467-021-23258-x">is only found</a> in molecules associated with life – just as the theory suggests.</p>
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<p>The theory also offers testable insights into the origin of life. That’s because it says there’s a point at which molecules become so complex that they start using information to make copies of themselves – suddenly requiring memory and information – a sort of threshold at which life arises from non-life. </p>
<p>Ultimately, it is possible to have selection and minimal memory in non-biological systems (such as how our Sun formed the planets by pulling together a ton of mass). But you can’t get living organisms or the technology they create – be that lego or rocket science – without high levels of memory and selection.</p>
<h2>Chemical soup</h2>
<p>We are planning to investigate this origin of life more closely by creating a type of chemical soup in our lab. In this soup, brand new molecules could be created over time, either by adding various reactants or by chance, while we monitor their assembly index and growth of the system. By tuning reaction rates and conditions, we could study that fascinating transition point from non-life to life – and learn whether it follows the predictions made by assembly theory.</p>
<p>We are also designing “chemical soup generators”, which mix together simple chemicals to find complex ones. These may boost our understanding of how complexity can be built using assembly theory and how selection outside of biology can be initiated. </p>
<p>This could uncover something about how life first evolved, starting with minimal selection and then requiring more and more. Under identical conditions, are objects constructed in predictable ways? Or does randomness enter the fray at some point? This would help us understand whether the emergence of life is deterministic and predictable, or more chaotic. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&rect=212%2C53%2C7726%2C4095&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=282&fit=crop&dpr=1 600w, https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=282&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=282&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=355&fit=crop&dpr=1 754w, https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=355&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/555340/original/file-20231023-27-sfk4bl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=355&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Life is special.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/elephant-herd-giraffes-walking-towards-trees-2198008341">jinnawat tawong/Shutterstock</a></span>
</figcaption>
</figure>
<p>This means assembly theory could apply much more broadly. Beyond molecules, the framework could inspire studies on other systems that rely on combinations, such as material aggregates, polymers or artificial chemistry. This may lead to new scientific insights or technological inventions. It may reveal subtle patterns whereby molecules above a threshold assembly index disproportionately possess certain properties. </p>
<p>We could also use the theory for detailed studies of evolution itself. Research could explore how fragments of cells exist in the process of forming an overall cell, arising from smaller molecules combining to form amino acids and nucleotides. Tracking the emergence of metabolic and genetic networks in this way may offer clues into transitions in evolutionary history. </p>
<p>Experimental tests pose challenges, however. Tracking how objects are assembled demands precise experimental monitoring. </p>
<p>But it might be well worth it. Assembly theory promises a radically new understanding of matter – potentially uncovering universal principles of hierarchical construction that transcend biology.</p>
<p>Complex configurations of matter may not be immutable objects, but waypoints in an open-ended process of construction propagating through time. The universe may obey certain physical laws, but it is ultimately creative.</p><img src="https://counter.theconversation.com/content/215636/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lee Cronin receives funding from the EPSRC, Templeton Foundation, DARPA, ERC, industry.</span></em></p>
Life seems to just mysteriously ‘emerge’ from non-living parts, such as elementary particles.
Lee Cronin, Regius Chair of Chemistry, University of Glasgow
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/205678
2023-05-18T16:36:00Z
2023-05-18T16:36:00Z
Did life evolve more than once? Researchers are closing in on an answer
<figure><img src="https://images.theconversation.com/files/526995/original/file-20230518-15-6vx4uf.jpg?ixlib=rb-1.1.0&rect=51%2C98%2C3407%2C2204&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/origin-life-on-earth-abstract-variation-1335681176">Maximillian cabinet/Shutterstock</a></span></figcaption></figure><p>From its humble origin(s), life has infected the entire planet with endless beautiful forms. The genesis of life is the oldest biological event, so old that no clear evidence was left behind other than the existence of life itself. This leaves many questions open, and one of the most tantalising is how many times life magically emerged from non-living elements.</p>
<p>Has all of life on Earth evolved only once, or are different living beings cut from different cloths? The question of how difficult it is for life to emerge is interesting – not least because it can shed some light on the likelihood of finding life on other planets. </p>
<p>The origin of life is a central question in modern biology, and probably the hardest to study. This event took place <a href="https://theconversation.com/ancestor-of-all-life-on-earth-evolved-earlier-than-we-thought-according-to-our-new-timescale-101752">four billion years ago</a>, and it happened at a molecular level – meaning little fossil evidence remains. </p>
<p>Many lively beginnings have been suggested, from unsavoury primordial soups to outer space. But the current scientific consensus is that life emerged from non-living molecules in a natural process called abiogenesis, most likely in the darkness of <a href="https://www.nhm.ac.uk/discover/survival-at-hydrothermal-vents.html">deep-sea hydrothermal vents</a>. But if life emerged once, why not more times?</p>
<h2>What is abiogenesis?</h2>
<p>Scientists have proposed various consecutive steps for abiogenesis. We know that Earth was rich in several chemicals, such as amino acids, a type of molecules called nucleotides or sugars, which are the building blocks of life. Laboratory experiments, such as the iconic <a href="https://nature.berkeley.edu/garbelottoat/?p=582">Miller-Urey experiment</a>, have shown how these compounds can be naturally formed under conditions similar to early Earth. Some of these compounds could also have come to Earth riding meteorites. </p>
<figure class="align-center ">
<img alt="Smoking hydrothermal vent." src="https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527004/original/file-20230518-25-61j30q.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">Smoking hydrothermal vent.</span>
<span class="attribution"><span class="source">NOAA/wikipedia.</span></span>
</figcaption>
</figure>
<p>Next, these simple molecules combined to form more complex ones, such as fats, proteins or nucleic acids. Importantly, nucleic acids — such as double-stranded DNA or its single-stranded cousin <a href="https://theconversation.com/explainer-what-is-rna-15169">RNA</a> — can store the information needed to build other molecules. DNA is more stable than RNA, but in contrast, RNA can be part of chemical reactions in which a compound makes copies of itself – self-replication. </p>
<p>The <a href="https://www.ncbi.nlm.nih.gov/books/NBK26876/">“RNA world” hypothesis</a> suggests that early life may have used RNA as material for both genes and replication before the emergence of DNA and proteins.</p>
<p>Once an information system can make copies of itself, natural selection kicks in. Some of the new copies of these molecules (which some would call “genes”) will have errors, or mutations, and some of these new mutations will improve the replication ability of the molecules. Therefore, over time, there will be more copies of these mutants than other molecules, some of which will accumulate further new mutations making them even faster and more abundant, and so on. </p>
<p>Eventually, these molecules probably evolved a lipid (fatty) boundary separating the internal environment of the organism from the exterior, forming protocells. Protocells could concentrate and organise better the molecules needed in biochemical reactions, providing a contained and efficient metabolism. </p>
<h2>Life on repeat?</h2>
<p>Abiogenesis could have happened more than once. Earth could have birthed self-replicating molecules several times, and maybe early life for thousands or millions of years just consisted of a bunch of different self-replicating RNA molecules, with independent origins, competing for the same building blocks. Alas, due to the ancient and microscopic nature of this process, we may never know. </p>
<p>Many lab experiments have successfully reproduced different <a href="https://www.newscientist.com/article/mg23130870-200-life-evolves-so-easily-that-it-started-not-once-but-many-times/">stages of abiogenesis</a>, proving they could happen more than once, but we have no certainty of these occurring in the past.</p>
<p>A related question could be whether new life is emerging by abiogenesis as you are reading this. This is very unlikely though. Early Earth was sterile of life and the physical and chemical conditions were very different. Nowadays, if somewhere on the planet there were ideal conditions for new self-replicating molecules to appear, they would be promptly chomped by existing life. </p>
<p>What we do know is that all extant life beings descend from a single shared last universal common ancestor of life (also known as <a href="https://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html">LUCA</a>). If there were other ancestors, they left no descendants behind. Key pieces of evidence support the existence of LUCA. All life on Earth uses the same genetic code, namely the correspondence between nucleotides in DNA known as A, T, C, and G – and the amino acid they encode in proteins. For example, the sequence of the three nucleotides ATG always corresponds to the amino acid methionine.</p>
<p>Theoretically, however, there could have been more genetic code variants between species. But all life on Earth uses the same code with a few minor changes in some lineages. Biochemical pathways, such as the ones used to metabolise food, also support the existence of LUCA; many independent pathways could have evolved in different ancestors, yet some (such as the ones used to metabolise sugars) are shared across all living organisms. Similarly, hundreds of identical genes are present in disparate live beings which can only be explained by being inherited from LUCA.</p>
<figure class="align-center ">
<img alt="Image of a chimp holding its ears." src="https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527005/original/file-20230518-23-my1ohk.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">Just like us…</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/chimpanzee-hear-no-evil-232172890">Sharon Morris/Shutterstock</a></span>
</figcaption>
</figure>
<p>My favourite support for LUCA comes from the Tree of Life. Independent analyses, some using anatomy, metabolism or genetic sequences, have revealed a hierarchical pattern of relatedness that can be represented as a tree. This shows we are more related to chimps than to any other living organisms on Earth. Chimps and we are more related to gorillas, and together to orangutans, and so on.</p>
<p>You can pick any random organism, from the lettuce in your salad to the bacteria in your bioactive yogurt and, if you travel back in time far enough, you will share an actual <a href="https://www.science.org/content/article/first-comprehensive-tree-life-shows-how-related-you-are-millions-species">common ancestor</a>. This is not a metaphor, but a scientific fact. </p>
<p>This is one of the most mind boggling concepts in science, Darwin’s unity of life. If you are reading this text, you are here thanks to an uninterrupted chain of reproductive events going back billions of years. As exciting as it is to think about life repeatedly emerging on our planet, or elsewhere, it is even more exciting to know that we are related to all the life beings in the planet.</p><img src="https://counter.theconversation.com/content/205678/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jordi Paps 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 question of how difficult it is for life to emerge is interesting – not least because it can shed some light on the likelihood of finding life on other planets.
Jordi Paps, Senior lecturer, School of Biological Sciences, University of Bristol, University of Bristol
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/200791
2023-04-10T12:04:23Z
2023-04-10T12:04:23Z
How do trees die?
<figure><img src="https://images.theconversation.com/files/517217/original/file-20230323-26-hsn4ob.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6001%2C4232&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Eventually weather, pests and disease will take their toll, but the story doesn't end there. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/dried-dead-tree-with-moss-trees-in-forest-royalty-free-image/1392619431">Emanuel David / 500px via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How and why do trees die? – Anish K., age 11, Boston, Massachusetts</strong></p>
</blockquote>
<hr>
<p>Trees can die suddenly or quite slowly. </p>
<p>Fire, flood or wind can cause a quick death by severely damaging a tree’s ability to <a href="https://www.treehugger.com/process-of-using-water-by-trees-1343505">transport water and nutrients</a> up and down its trunk. </p>
<p>Sometimes a <a href="https://www.youtube.com/watch?v=vR30qlK0-Cw">serious insect attack</a> or disease can kill a tree. This kind of death usually takes from a few months to a couple of years. Again, a tree loses its ability to move water and nutrients, but does so in stages, more slowly. </p>
<p>A tree can also die of what you might call old age.</p>
<p>I am a <a href="https://scholar.google.com/citations?hl=en&user=g2KEhV4AAAAJ">scientist who studies trees</a> and the web of living things that surround them. The death of a tree is not exactly what it seems, because it directly leads to new life.</p>
<h2>Different trees, different life spans</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of an enormous old living tree." src="https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=896&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=896&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=896&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1126&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1126&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517059/original/file-20230322-3114-n72ec5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1126&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An ancient bristlecone pine (<em>Pinus longaeva</em>) in Patriarch Grove in California’s White Mountains.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nturland/5817568646/in/photostream/">Nicholas Turland/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Trees can live an <a href="https://www.scientificamerican.com/article/trees-have-the-potential-to-live-indefinitely">incredibly long time</a>, <a href="https://onetreeplanted.org/blogs/stories/oldest-tallest-biggest-trees">depending on what kind they are</a>. Some <a href="https://www.nps.gov/grba/planyourvisit/identifying-bristlecone-pines.htm">bristlecone pines</a>, for instance, are among the oldest known trees and are more than 4,000 years old. Others, like lodgepoles or poplars, will have much shorter life spans, from 20 to 200 years. The biggest trees in your neighborhood or town are probably somewhere in that range. </p>
<p>You’ve probably noticed that different living things have different life spans – a hamster is generally not going to live as long as a cat, which isn’t going to live as long as a person. Trees are no different. Their life spans are determined by their DNA, which you can think of as the <a href="https://kids.britannica.com/kids/article/DNA/390730">operating system embedded in their genes</a>. Trees that are programmed to grow very quickly will be less strong – and shorter lived – <a href="https://extension.psu.edu/why-do-some-trees-live-longer-than-others">than ones that grow very slowly</a>. </p>
<p>But even a tough old tree will eventually die. The years and years of damage done by insects and microscopic critters, combined with abuse from the weather, will slowly end its life. The death process may start with a single branch but will eventually spread to the entire tree. It may take a while for an observer to realize a tree has finally died. </p>
<p>You might think of death as a passive process. But, in the case of trees, it’s surprisingly active. </p>
<h2>The underground network</h2>
<p>Roots do more than anchor a tree to the ground. They are the place where microscopic fungi attach and <a href="https://www.nytimes.com/interactive/2020/12/02/magazine/tree-communication-mycorrhiza.html">act like a second root system for a tree</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of thin spiderweb-looking filaments attached to roots." src="https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=512&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=512&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517062/original/file-20230322-1527-aqtnic.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=512&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Some fungi look like fragile spiderwebs, but these tiny tubes act like superhighways underground.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mycorhizes-01.jpg">André-Ph. D. Picard</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Fungi form long, superfine threads called hyphae. Fungal hyphae can <a href="https://www.scientificamerican.com/article/do-trees-support-each-other-through-a-network-of-fungi">reach much farther than a tree’s roots can</a>. They gather nutrients from the soil that a tree needs. In exchange, the tree repays fungi with <a href="https://www.youtube.com/watch?v=D1Ymc311XS8">sugars it makes out of sunlight</a> in a process known as <a href="https://www.britannica.com/science/photosynthesis">photosynthesis</a>. </p>
<p>You might have heard that fungi can also pass nutrients from one tree to another. This is a topic that scientists are still working out. Some trees are likely connected to other trees by a complex underground network of fungi, sometimes called the “<a href="https://www.newyorker.com/tech/annals-of-technology/the-secrets-of-the-wood-wide-web">wood wide web</a>.”</p>
<p>How the wood wide web functions in a forest is still not well understood, but scientists do know that the fungi forming these networks are important for keeping trees healthy.</p>
<h2>Afterlife of a tree</h2>
<p>Before it topples over, a dead tree can stand for many years, providing a safe home for bees, squirrels, owls and <a href="https://www.nwf.org/Garden-for-Wildlife/Cover/Trees-and-Snags">many more animals</a>. Once it falls and becomes a log, it can host other living things, like badgers, moles and reptiles. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A mossy trunk from a dead tree lies in the forest." src="https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517065/original/file-20230322-3058-nf6b9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One day the remains of this tree will be completely gone.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/october-2021-lower-saxony-uslar-a-mossy-trunk-from-a-dead-news-photo/1236121962">Swen Pförtner/picture alliance via Getty Images</a></span>
</figcaption>
</figure>
<p>Logs also host a different kind of fungi and bacteria, called decomposers. These <a href="https://vinsweb.org/the-fallen-log/">tiny organisms help break down big dead trees</a> to the point where you would never know they had existed. Depending on the conditions, this process can take from a <a href="https://vinsweb.org/the-fallen-log/">few years to a century or more</a>. As wood breaks down, its nutrients return to the soil and become available for other living things, including nearby trees and fungal networks.</p>
<p>A tree leaves a legacy. While alive, it provides shade, home for many animals and a lifeline to fungi and other trees. When it dies, it continues to play an important role. It gives a boost to new trees ready to take its place, shelter to a different set of animals and, eventually, nourishment for the next generation of living things.</p>
<p>It’s almost as if a tree never truly dies but just passes its life on to others.</p>
<hr>
<p><em>Editor’s note: This story has been updated to emphasize that much remains unknown about the relationship between trees and fungi.</em></p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p>
<p><em>And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.</em></p><img src="https://counter.theconversation.com/content/200791/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Camille Stevens-Rumann 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>
Even in death, a tree helps others live.
Camille Stevens-Rumann, Assistant Professor of Forest & Rangeland Stewardship, Colorado State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/203129
2023-04-05T11:35:59Z
2023-04-05T11:35:59Z
Life: modern physics can’t explain it – but our new theory, which says time is fundamental, might
<figure><img src="https://images.theconversation.com/files/519329/original/file-20230404-982-boq7uk.jpg?ixlib=rb-1.1.0&rect=60%2C0%2C4378%2C2977&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/beauty-bird-paradise-cendrawasih-2021534777">Ryan Boedi/Shutterstock</a></span></figcaption></figure><iframe src="https://embed.acast.com/638f4b009a65b10011b94c5e/642d59ed65d917001197b0cf" frameborder="0" width="100%" height="190px"></iframe>
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<p>Over the short span of just 300 years, since the invention of modern physics, we have gained a deeper understanding of how our universe works on both small and large scales. Yet, physics is still very young and when it comes to using it to explain life, physicists struggle. </p>
<p>Even today, <a href="https://theconversation.com/great-mysteries-of-physics-will-we-ever-have-a-fundamental-theory-of-life-and-consciousness-203127">we can’t really explain</a> what the difference is between a living lump of matter and a dead one. But my colleagues and I are creating a new physics of life that might soon provide answers.</p>
<p>More than 150 years ago, Darwin poignantly noted the dichotomy between what we understand in physics and what we observe in life – noting at the end of <a href="https://royalsocietypublishing.org/doi/10.1098/rsnr.2018.0015">The Origin of Species</a> “…whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been and are being evolved”. </p>
<h2>The importance of time</h2>
<p>Isaac Newton described a universe where the laws never change, and time is an immutable and absolute backdrop against which everything moves. Darwin, however, observed a universe where endless forms are generated, each changing features of what came before, suggesting that time should not only have a direction, but that it in some ways folds back on itself. New evolutionary forms can only arise via selection on the past. </p>
<p>Presumably these two areas of science are describing the same universe, but how can two such diametrically opposite views be unified? The key to understanding why life is not explainable in current physics may be to reconsider our notions of time as the key difference between the universe as described by Newton and that of Darwin. Time has, in fact, been reinvented many times through the history of physics. </p>
<p>Although Newton’s time was fixed and absolute, Einstein’s time became a dimension – just like space. And just as all points in space exist all at once, so do all points in time. This <a href="https://theconversation.com/great-mysteries-of-physics-1-is-time-an-illusion-201026">philosophy of time</a> is sometimes referred to as the “block universe” where the past, present and future are equally real and exist in a static structure – with no special “now”. In <a href="https://theconversation.com/uk/topics/quantum-mechanics-157">quantum mechanics</a>, the passage of time emerges from how quantum states change from one to the next.</p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513939/original/file-20230307-20-pgea9d.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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<p><em>This is article is accompanied by a podcast series called <a href="https://podfollow.com/great-mysteries-of-physics">Great Mysteries of Physics</a> which uncovers the greatest mysteries facing physicists today – and discusses the radical proposals for solving them.</em></p>
<hr>
<p>The invention of <a href="https://www.grc.nasa.gov/www/k-12/airplane/thermo.html">thermodynamics</a> gave time its arrow, explaining why it’s moving forward rather than backwards. That’s because there are clear examples of systems in our universe, such as a working engine, that are irreversible – only working in one direction. Each new area of fundamental physics, whether describing space and time (Newton/Einstein), matter and light (quantum mechanics), or heat and work (thermodynamics) has introduced a new concept of time. </p>
<p>But what about evolution and life? To build novel things, evolution requires time. Endless novelty can only come to be in a universe where time exists and has a clear direction. Evolution is the only physical process in our universe that can generate the succession of novel objects we associate to life – things like microbes, mammals, trees and even cellphones.</p>
<h2>Information and memory</h2>
<p>Such objects cannot fluctuate into existence spontaneously. They require a memory, based on what existed in the past, to construct things in the present. It is such “selection” that determines the dividing line between the universe described by current physics, and what Darwin saw: it is the mechanism that turns a universe where memory does not matter in determining what exists, to one where it does. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="DNA helix" src="https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/519346/original/file-20230404-892-3myc8u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Life is information.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/blue-helix-human-dna-structure-1669326868">Shutterstock</a></span>
</figcaption>
</figure>
<p>Think about it, everything in the living world requires some kind of memory and information flow. The DNA in our cells is our blueprint. And to invent new things, such as rockets or medication, living beings also need information – knowledge of the laws of physics and chemistry.</p>
<p>To explain life, we therefore need to understand how the complex objects life creates exist in time. With my collaborators, we have been doing just that in a <a href="https://arxiv.org/abs/2206.02279">newly proposed theory</a> of physics called assembly theory.</p>
<p>A key conjecture of assembly theory is that, as objects become more complex, the number of unique parts that make it up increases, and so does the need for local memory to store how to assemble the object from its unique parts. We quantify this in assembly theory as the shortest number of physical steps to build an object from its elementary building blocks, called the assembly index. </p>
<p>Importantly, assembly theory treats this shortest path as an intrinsic property of the object, and indeed we have shown how assembly index can be measured for molecules using several different measuring techniques including mass spectrometry (an analytical method to measure the mass-to-charge ratio of molecules).</p>
<p>With this approach, we have shown in the lab, with measurements on both biological and non-biological samples, how molecules with an assembly index above 15 steps <a href="https://www.nature.com/articles/s41467-021-23258-x">are only found</a> in living samples.</p>
<p>This suggests that assembly theory is indeed capable of testing our hypothesis that life is the only physics that generates complex objects. And we can do so by identifying those objects that are so complex the only physical mechanism to form them is evolution. </p>
<p>We are aiming to use our theory to estimate when the origin if life happens by measuring the point at which molecules in a chemical soup become so complex that they start using information to make copies of themselves – <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsif.2012.0869">the threshold at which life arises from non-life</a>. We may then apply the theory to experiments aiming to generate a new origin of life event in the lab. </p>
<p>And when we know this, we can use the theory to look for life on worlds that are radically different to Earth, and may therefore look so alien that we wouldn’t recognise life there.</p>
<p>If the theory holds, it will force a radical rethink on time in physics. According to our theory, assembly can be measured as an intrinsic property for molecules, which corresponds to their size in time – meaning time is a physical attribute. </p>
<p>Ultimately, time is intrinsic to our experiences of the world, and it is necessary for evolution to happen. If we want physics to be capable of explaining life – and us - it may be that we need to treat time as a material property for the first time in physics. </p>
<p>This is perhaps the most radical departure for physics of life from standard physics, but it may be the critical insight needed to explain what life is.</p><img src="https://counter.theconversation.com/content/203129/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sara Imari Walker receives funding from the National Aeronautics and Space Administration and the John Templeton Foundation relevant to the work in this article. She is also a member of the External Faculty at the Santa Fe Institute and a Fellow of the Berggruen Institute. </span></em></p>
The key to understanding why life is not explainable in current physics may be to reconsider our notions of time and information.
Sara Imari Walker, Professor of Physics, School of Earth and Space Exploration, Arizona State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/203127
2023-04-05T11:32:05Z
2023-04-05T11:32:05Z
Great Mysteries of Physics 5: will we ever have a fundamental theory of life and consciousness?
<figure><img src="https://images.theconversation.com/files/518887/original/file-20230402-24-xtaeq6.jpg?ixlib=rb-1.1.0&rect=152%2C0%2C8321%2C3982&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/people-rejoicing-launch-space-rocket-2200754685">metamorworks/Shutterstock</a></span></figcaption></figure><iframe src="https://embed.acast.com/638f4b009a65b10011b94c5e/642d59ed65d917001197b0cf" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-807" class="tc-infographic" height="100px" src="https://cdn.theconversation.com/infographics/807/1668471fb1e76a459995c87bd439c36b04b754ac/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>What’s the difference between a living collection of matter, such as a tortoise, and an inanimate lump of it, such as a rock? They are, after all, both just made up of non-living atoms. The truth is, we don’t really know yet. Life seems to just somehow emerge from non-living parts.</p>
<p>This is an enigma we’re tackling in the fifth episode of our Great Mysteries of Physics podcast – hosted by me, Miriam Frankel, science editor at The Conversation, and supported by FQxI, the Foundational Questions Institute. </p>
<p>The physics of the living world ultimately seems to contradict the second law of thermodynamics: that a closed system gets more disordered over time, increasing in what physicists call entropy. Living systems have low entropy. A messy lump of tissue in the womb, for example, can grow into a highly ordered state of a foot with five toes. </p>
<p>“We maintain this high sense of order for many, many decades,” explains Jim Al-Khalili, a broadcaster and distinguished professor of physics at the University of Surrey in the UK. “It’s only when we die that entropy and the second law of thermodynamics really kicks in.”</p>
<p>Quantum biology is one approach to understanding how living matter is different from inanimate matter. It is based on the strange world of quantum mechanics, which governs the microworld of particles and atoms. The idea is that living systems may use quantum mechanics to their advantage – promoting or halting quantum processes. </p>
<p>“Evolution has had long enough to fine-tune things or to stop quantum mechanics from doing something that life doesn’t want it to do,” explains Al-Khalili, who carries out research in the area. “It’s a newish area of science.”</p>
<p>One example, albeit still controversial, is photosynthesis, the process in which plants or bacteria absorb particles of sunlight, photons, and convert it to chemical energy. Some physicists believe a quantum property known as superposition – allowing a particle to be in many possible states, such as taking different paths, simultaneously – enables this process. </p>
<p>“A lump of energy [such as a photon] just randomly bouncing around should just be lost as waste heat,” explains Al-Khalili. “There’s a quantum mechanical explanation for how that photon follows multiple paths simultaneously.”</p>
<p>Al-Khalili and his colleagues are now using quantum biology to try to understand DNA mutations – a core part of life – and they’ve made some intriguing discoveries already. And while he isn’t convinced the approach will ever be able to explain consciousness, he argues we cannot rule it out.</p>
<p>Sara Walker, an astrobiologist and theoretical physicist working as a professor at Arizona State University in the US, favours another approach, however. She is trying to create a new physical theory of life based on information theory – which takes information to be real and physical.</p>
<p>Information seems to be crucial to life. Living organisms have an inbuilt set of instructions, DNA, which non-living things simply don’t have. Similarly, when living beings invent things, such as rockets, they rely on information, such as knowledge of the laws of physics, stored in their memory. </p>
<p>We can use the current laws of physics to predict how a planet evolves over time, for example whether and when nearby objects are likely to crash into it. But we can’t use the laws to explain how and when intelligent beings arise and decide to build rockets and satellites which they launch into orbit around the planet. </p>
<p>“I do think that there are laws of physics that are yet undiscovered that explain the phenomena of life, and I think those have to do with how information structures reality in some sense,” explains Walker.</p>
<p>Walker believes that living organisms are more complex and difficult to assemble from fundamental building blocks than inanimate, naturally produced objects, such as simple molecules. And when simple living beings exist, they seem to generate even more complexity – either by evolution or through construction. </p>
<p>So Walker believes life generates a sudden boost in complexity which may have a threshold that could be a fundamental feature in the physics of life. Another central part of her theory is time. “The deeper in time an object is, the more evolution is required to produce it.”</p>
<p>Walker has designed an experiment to look at how molecules are built up by joining smaller pieces together in various ways. She says the team hasn’t found any evidence that molecules with high complexity can be produced by non-living things. The ultimate goal is to pinpoint an origin of life in which a chemical system can generate its own complexity.</p>
<p>Not only could that help us understand how life arises from non-living building blocks, we could also use it to search for life on other worlds in the cosmos.</p>
<p><em>You can listen to Great Mysteries of Physics via any of the apps listed above, our <a href="https://feeds.acast.com/public/shows/638f4b009a65b10011b94c5e">RSS feed</a>, or find out how else to listen here. You can also read a <a href="https://cdn.theconversation.com/static_files/files/2629/MoP__Ep5_-_Life_TRANSCRIPT.docx.pdf?1681213653">transcript of the episode here</a>.</em></p><img src="https://counter.theconversation.com/content/203127/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Al-Khalili receives funding for his research from various bodies: UK funding agencies (EPSRC, STFC), trusts and charities (Leverhulme Trust, John Templeton Foundation). These funds are used to pay for part of his salary, along with those of colleagues and collaborators, postdoc salaries, travel and subsistence for research and to conferences etc. Sara Walker receives funding from John Templeton Foundation and NASA. She is a fellow at Berggruen Institute and External Faculty at Santa Fe Institute.</span></em></p>
Life may be using quantum mechanics to its advantage.
Miriam Frankel, Podcast host, The Conversation
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/201622
2023-03-16T12:36:48Z
2023-03-16T12:36:48Z
Water in space – a ‘Goldilocks’ star reveals previously hidden step in how water gets to planets like Earth
<figure><img src="https://images.theconversation.com/files/515568/original/file-20230315-1821-gn9l6v.jpg?ixlib=rb-1.1.0&rect=28%2C45%2C1249%2C1038&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The star system V883 Orionis contains a rare star surrounded by a disk of gas, ice and dust.</span> <span class="attribution"><a class="source" href="http://www.eso.org/public/images/eso1626a/">A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Without water, life on Earth could not exist as it does today. Understanding the history of water in the universe is critical to understanding how planets like Earth come to be.</p>
<p>Astronomers typically refer to the journey water takes from its formation as individual molecules in space to its resting place on the surfaces of planets as “the water trail.” The trail starts in the interstellar medium with hydrogen and oxygen gas and ends with oceans and ice caps on planets, with icy moons orbiting gas giants and icy comets and asteroids that orbit stars. The beginnings and ends of this trail are easy to see, but the middle has remained a mystery.</p>
<p><a href="https://www.cv.nrao.edu/%7Ejtobin/">I am an astronomer</a> who studies the formation of stars and planets using observations from radio and infrared telescopes. In a new paper, my colleagues and I describe the <a href="https://www.nature.com/articles/s41586-022-05676-z">first measurements ever made</a> of this previously hidden middle part of the water trail and what these findings mean for the water found on planets like Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The progression of a star system from a cloud of dust and gas into a mature star with orbiting planets." src="https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515526/original/file-20230315-18-7eqg1b.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">Star and planet formation is an intertwined process that starts with a cloud of molecules in space.</span>
<span class="attribution"><a class="source" href="https://www.nrao.edu/pr/2012/clumpcores/">Bill Saxton, NRAO/AUI/NSF</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>How planets are formed</h2>
<p>The formation of stars and planets is intertwined. The so-called “emptiness of space” – or the interstellar medium – in fact contains <a href="https://doi.org/10.1146/annurev.aa.32.090194.001203">large amounts of gaseous hydrogen</a>, smaller amounts of other gasses and <a href="https://doi.org/10.1086/162480">grains of dust</a>. Due to gravity, some pockets of the interstellar medium will become <a href="https://doi.org/10.1086/311687">more dense as particles attract each other</a> and form clouds. As the density of these clouds increases, atoms begin to collide more frequently and <a href="https://doi.org/10.1086/381775">form larger molecules</a>, including water that forms <a href="https://doi.org/10.1080/0144235X.2015.1046679">on dust grains and coats the dust in ice</a>.</p>
<p>Stars begin to form when parts of the collapsing cloud reach a certain density and heat up enough to start fusing hydrogen atoms together. Since only a small fraction of the gas initially collapses into the newborn protostar, the rest of the gas and dust <a href="https://doi.org/10.48550/arXiv.1001.1404">forms a flattened disk of material</a> circling around the spinning, newborn star. Astronomers call this a proto-planetary disk.</p>
<p>As icy dust particles collide with each other inside a proto-planetary disk, <a href="https://doi.org/10.1051/0004-6361/200811158">they begin to clump together</a>. The process continues and eventually forms the familiar objects of space like asteroids, comets, rocky planets like Earth and gas giants like Jupiter or Saturn.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cloudy filament against a backdrop of stars." src="https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=679&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=679&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=679&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=854&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=854&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515633/original/file-20230315-3008-q4peeq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=854&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Gas and dust can condense into clouds, like the Taurus Molecular Cloud, where collisions between hydrogen and oxygen can form water.</span>
<span class="attribution"><a class="source" href="http://www.eso.org/public/images/eso1209a/">ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Two theories for the source of water</h2>
<p>There are two potential pathways that water in our solar system could have taken. The first, called <a href="https://doi.org/10.1051/0004-6361/200810846">chemical inheritance</a>, is when the water molecules originally formed in the interstellar medium are delivered to proto-planetary disks and all the bodies they create without going through any changes. </p>
<p>The second theory is called <a href="https://doi.org/10.1051/0004-6361/201628509">chemical reset</a>. In this process, the heat from the formation of the proto-planetary disk and newborn star breaks apart water molecules, which then reform once the proto-planetary disk cools.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Models of protium and deuterium." src="https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515531/original/file-20230315-26-gk368.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Normal hydrogen, or protium, does not contain a neutron in its nucleus, while deuterium contains one neutron, making it heavier.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Hydrogen_Deuterium_Tritium_Nuclei_Schmatic-en.svg">Dirk Hünniger/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>To test these theories, astronomers like me look at the ratio between normal water and a special kind of water called semi-heavy water. Water is normally made of two hydrogen atoms and one oxygen atom. Semi-heavy water is made of one oxygen atom, one hydrogen atom and one atom of deuterium – a heavier isotope of hydrogen with an extra neutron in its nucleus. </p>
<p>The ratio of semi-heavy to normal water is a guiding light on the water trail – measuring the ratio can tell astronomers a lot about the source of water. <a href="https://doi.org/10.1051/0004-6361/202039084">Chemical models</a> and <a href="https://doi.org/10.1086/591506">experiments</a> have shown that about 1,000 times more semi-heavy water will be produced in the cold interstellar medium <a href="https://doi.org/10.1126/science.1258055">than in the conditions of a protoplanetary disk</a>. </p>
<p>This difference means that by measuring the ratio of semi-heavy to normal water in a place, astronomers can tell whether that water went through the chemical inheritance or chemical reset pathway.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A star surrounded by a ring of gas and dust." src="https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515533/original/file-20230315-1689-gn9l6v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">V883 Orionis is a young star system with a rare star at its center that makes measuring water in the proto-planetary cloud, shown in the cutaway, possible.</span>
<span class="attribution"><a class="source" href="https://public.nrao.edu/news/water-v883-orionis/">ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Measuring water during the formation of a planet</h2>
<p>Comets have a ratio of semi-heavy to normal water almost perfectly in line with <a href="https://doi.org/10.2458/azu_uapress_9780816531240-ch037">chemical inheritance</a>, meaning the water hasn’t undergone a major chemical change since it was first created in space. Earth’s ratio sits somewhere in between the inheritance and reset ratio, making it unclear where the water came from.</p>
<p>To truly determine where the water on planets comes from, astronomers needed to find a goldilocks proto-planetary disk – one that is just the right temperature and size to allow observations of water. Doing so has <a href="https://doi.org/10.1051/0004-6361/201935994">proved to be incredibly difficult</a>. It is possible to detect semi-heavy and normal water when water is a gas; unfortunately for astronomers, the vast majority of proto-plantary disks are very cold and <a href="https://doi.org/10.1126/science.1239560">contain mostly ice</a>, and it is nearly <a href="https://doi.org/10.1051/0004-6361:20031277">impossible to measure water ratios</a> from ice at interstellar distances. </p>
<p>A breakthrough came in 2016, when my colleagues and I were studying proto-planetary disks around a rare type of young star called FU Orionis stars. Most young stars consume matter from the proto-planetary disks around them. FU Orionis stars are unique because they consume matter about 100 times faster than typical young stars and, as a result, <a href="https://doi.org/10.1146/annurev-astro-081915-023347">emit hundreds of times more energy</a>. Due to this higher energy output, the proto-planetary disks around FU Orionis stars are heated to much higher temperatures, turning ice into water vapor out to large distances from the star.</p>
<p>Using the <a href="https://public.nrao.edu/telescopes/alma/">Atacama Large Millimeter/submillimeter Array</a>, a powerful radio telescope in northern Chile, <a href="https://ui.adsabs.harvard.edu/abs/2016Natur.535..258C/abstract">we discovered</a> a large, warm proto-planetary disk around the Sunlike young star V883 Ori, about 1,300 light years from Earth in the constellation Orion.</p>
<p>V883 Ori emits 200 times more energy than the Sun, and my colleagues and I recognized that it was an ideal candidate to observe the semi-heavy to normal water ratio. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A radio image of the disk around V883 Ori." src="https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=672&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=672&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=672&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=844&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=844&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515565/original/file-20230315-14-dfl7h6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=844&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 proto-planetary disk around V883 Ori contains gaseous water, shown in the orange layer, allowing astronomers to measure the ratio of semi-heavy to normal water.</span>
<span class="attribution"><a class="source" href="https://public.nrao.edu/news/water-v883-orionis/#PRimage2">ALMA (ESO/NAOJ/NRAO), J. Tobin, B. Saxton (NRAO/AUI/NSF)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Completing the water trail</h2>
<p>In 2021, the Atacama Large Millimeter/submillimeter Array took measurements of V883 Ori for six hours. The data revealed a <a href="https://doi.org/10.1038/s41586-022-05676-z">strong signature of semi-heavy and normal water</a> coming from V883 Ori’s proto-planetary disk. We measured the ratio of semi-heavy to normal water and found that the ratio was very <a href="https://doi.org/10.1051/0004-6361/202039084">similar to ratios found in comets</a> as well as the ratios found <a href="https://doi.org/10.1051/0004-6361/201322845">in younger protostar systems</a>.</p>
<p>These results fill in the gap of the water trail forging a direct link between water in the interstellar medium, protostars, proto-planetary disks and planets like Earth through the process of inheritance, not chemical reset.</p>
<p>The new results show definitively that a substantial portion of the water on Earth most likely formed billions of years ago, before the Sun had even ignited. Confirming this missing piece of water’s path through the universe offers clues to origins of water on Earth. Scientists have previously suggested that most water on Earth <a href="https://doi.org/10.1051/0004-6361/201935554">came from comets impacting the planet</a>. The fact that Earth has less semi-heavy water than comets and V883 Ori, but more than chemical reset theory would produce, means that water on Earth likely came from more than one source.</p><img src="https://counter.theconversation.com/content/201622/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Tobin receives funding from NASA, </span></em></p>
Astronomers have long known where water is first formed in the universe and how it ends up on planets, asteroids and comets. A recent discovery has finally answered what happens in between.
John Tobin, Scientist, National Radio Astronomy Observatory
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/201720
2023-03-15T11:32:35Z
2023-03-15T11:32:35Z
Great Mysteries of Physics 2: is the universe fine-tuned for life?
<figure><img src="https://images.theconversation.com/files/515114/original/file-20230314-24-aob30p.jpg?ixlib=rb-1.1.0&rect=0%2C150%2C2044%2C1732&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our universe is just right for structure such as galaxies, planets and life to form.</span> <span class="attribution"><span class="source">NASA/James Webb Telescope</span></span></figcaption></figure><iframe src="https://embed.acast.com/638f4b009a65b10011b94c5e/640f4ac9780d480011157b20" frameborder="0" width="100%" height="190px"></iframe>
<p><iframe id="tc-infographic-807" class="tc-infographic" height="100px" src="https://cdn.theconversation.com/infographics/807/1668471fb1e76a459995c87bd439c36b04b754ac/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Imagine a universe with extremely strong gravity. Stars would be able to form from very little material. They would be smaller than in our universe and live for a much shorter amount of time. But could life evolve there? It took human life billions of years to evolve on Earth under the pleasantly warm rays from the Sun after all. </p>
<p>Now imagine a universe with extremely weak gravity. Its matter would struggle to clump together to form stars, planets and – ultimately – living beings. It seems we are pretty lucky to have gravity that is just right for life in our universe.</p>
<p>This isn’t just the case for gravity. The values of many forces and particles in the universe, represented by some 30 so-called fundamental constants, all seem to <a href="https://www.goodreads.com/book/show/817511.The_Goldilocks_Enigma">line up perfectly</a> to enable the evolution of intelligent life. But there’s no theory explaining what values the constants should have – we just have to measure them and plug their numbers into our equations to accurately describe the cosmos.</p>
<p>So why do the fundamental constants take the values they do? This is a question that physicists have been battling over for decades. It is also the topic of the second episode of our new podcast series, Great Mysteries of Physics – hosted by me, Miriam Frankel, science editor at The Conversation, and supported by FQxI, the Foundational Questions Institute.</p>
<p>“We don’t know whether some of those constants are linked deep down. If we had a deeper theory, we’d find that they’re not actually independent of each other,” explains Paul Davies, a theoretical physicists at Arizona State University. “But we don’t have that theory at the moment, we’ve just got all these numbers.”</p>
<p>Some physicists aren’t too bothered by the seemingly fine-tuned cosmos.
Others have <a href="https://theconversation.com/the-multiverse-our-universe-is-suspiciously-unlikely-to-exist-unless-it-is-one-of-many-200585">found comfort in the multiverse theory</a>. If our universe is just one of many, some would, statistically speaking, end up looking just like ours. In such a universe, says Davies, “beings will pop up and marvel at the fact that they live in a universe that looks like it’s rigged in favour of their existence, but actually we’re just winners in a cosmic lottery.”</p>
<p>But many physicists, including Davies, are holding out for a more fundamental theory of nature which can explain exactly what values the constants should have in the first place. “I usually say two cheers for the multiverse, cause I think it’s better than just saying God did it,” he argues, adding that to get to three cheers you need a more complete theory.</p>
<p>That said, in the absence of a deeper theory, it is hard to estimate exactly how fine-tuned our universe is. Fred Adams, a physicist at the University of Michigan, has done <a href="https://www.sciencedirect.com/science/article/pii/S0370157319300511">a lot of research</a> to try to find out, and he has discovered that the mass of a quark called the down quark (quarks are elementary particle which make up the atomic nucleus, for example) can only change by a factor of seven before rendering the universe, as we know it, lifeless. </p>
<p>But how fine tuned is that? “If you want to tune a radio, you have to know the frequency of the signal to 1% – and 1% is much more tuned than a factor of seven,” explains Adams. “So it’s much harder to tune a radio than to tune a universe”. Intriguingly, his work has also shown it is possible to get universes that are more life-friendly than ours. “You can make a more logical universe that produces more structure, potentially produces more habitable environments, and I guess by implication supports life better,” he explains.</p>
<p>There are experiments which could help settle the fine-tuning debate. For example, some projects are trying to find out whether the constants we see around us really are constant – perhaps they vary ever so slightly over time or space. And if that were the case, it would be a blow to those who believe the cosmos is fine-tuned.</p>
<p><em>You can also listen to Great Mysteries of Physics via any of the apps listed above, our <a href="https://feeds.acast.com/public/shows/638f4b009a65b10011b94c5e">RSS feed</a>, or find out how else to listen here. You can also read <a href="https://cdn.theconversation.com/static_files/files/2553/MoP__Ep2_-_Fundamental_Constants_TRANSCRIPT.docx.pdf?1678794242">a transcript of the episode here</a>.</em></p><img src="https://counter.theconversation.com/content/201720/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Davies has received funding from the National Cancer Institute, John Templeton Foundation, the Foundational Questions Institute, NASA: Ames Research Center, Arizona Cancer and Evolution Center, Moogsoft and the Melanie Brose Archelon Fellowship. He is on the Board of Advisors, Leverhulme Quantum Biology Centre, University of Surrey; on the Board of Trustees, Templeton World Charity Foundation; on the Grants and Programs Committee, Templeton World Charity Foundation; on the Board of Advisors, Templeton World Charity Foundation; on the Board of Advisors, John Templeton Foundation; on the Advisory Committee, Breakthrough Listen, on the Advisory Board, Copernicus; on the Advisory Board, Galileo Project; on the Advisory Board, Center for Quantum Studies, Chapman University; a member, FQXi; on the Advisory Board, Big Questions Institute (Australia) and on the International Advisory Board, Big Questions Institute, UNSW. Davies has won prizes including The Templeton Prize, the Michael Faraday Award of The Royal Society, the Kelvin Medal and Prize of the Institute of Physics and the Robinson Cosmology Prize.
Fred Adams received a grant from the Templeton Foundation in 2015.
Miriam Frankel once received funding from the Templeton Foundation in a freelance capacity to write an FQXi literature review about fine tuning, which was published last year. </span></em></p>
It seems we are pretty lucky to have gravity that is just right for life.
Miriam Frankel, Podcast host, The Conversation
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/200304
2023-03-10T18:01:48Z
2023-03-10T18:01:48Z
A brief history of the UK’s Winchcombe meteorite
<figure><img src="https://images.theconversation.com/files/512936/original/file-20230301-22-2u3bf5.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C2432%2C1964&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There was little time for water from the Earth's atmosphere to contaminate the meteorite after it fell.</span> <span class="attribution"><span class="source">Trustees of the Natural History Museum</span>, <span class="license">Author provided</span></span></figcaption></figure><p>On 28 February 2021, for the first time in 30 years, a meteorite <a href="https://www.theguardian.com/uk-news/2021/mar/01/meteorites-from-fireball-that-lit-up-sky-could-have-fallen-to-earth">fell in the UK</a> and was <a href="https://theconversation.com/meteorite-hunters-how-we-found-the-first-bit-of-uk-space-rock-in-over-30-years-157157">later recovered</a> by scientists. Today, there’s an international effort to study this space rock and learn more about its place in the early solar system.</p>
<p>This meteorite is named after <a href="https://en.wikipedia.org/wiki/Winchcombe">Winchcombe</a>, the town in Gloucestershire where several fragments were recovered – including a piece that landed on <a href="https://www.gloucestershirelive.co.uk/news/cheltenham-news/winchcombe-meteorite-how-tracked-down-5103696">the driveway of a family home.</a> </p>
<p><a href="https://www.amnh.org/exhibitions/permanent/meteorites/meteorites/what-is-a-meteorite">The meteorite</a> formed 4.5 billion years ago in the distant outer solar system, beyond the orbit of Jupiter. We refer to such objects as primitive because they contain some of the earliest solid material to form in our cosmic neighbourhood, <a href="https://theconversation.com/a-pristine-chunk-of-space-rock-found-within-hours-of-hitting-earth-can-tell-us-about-the-birth-of-the-solar-system-194725">offering insights into a time</a> when our solar system was in its infancy.</p>
<p>Over time, much of this solid material merged to form larger objects, which eventually led to the emergence of planets. Some of the early building blocks that avoided being consumed in this process of planetary assembly are present today as <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/in-depth/#many_shapes_and_sizes_otp">asteroids</a> or even smaller objects. <a href="https://theconversation.com/a-pristine-chunk-of-space-rock-found-within-hours-of-hitting-earth-can-tell-us-about-the-birth-of-the-solar-system-194725">The Winchcombe meteorite</a> is just such a celestial body.</p>
<p>Some of these free-roaming planetary building blocks may have been responsible for delivering water to the early Earth. Therefore, Winchcombe can provide a glimpse <a href="https://www.science.org/doi/10.1126/sciadv.abq3925">into the activity of water</a> on solid bodies in the ancient solar system.</p>
<h2>Path through space</h2>
<p>Winchcombe is a rare type of meteorite <a href="https://onlinelibrary.wiley.com/doi/10.1111/maps.13918">known as a CM chondrite</a>. <a href="https://en.wikipedia.org/wiki/CM_chondrite">These meteorites are characterised</a> by high concentrations of water and organic matter (molecules with chains of carbon atoms), both of which are essential ingredients for the emergence of life. </p>
<p><a href="https://www.science.org/doi/10.1126/sciadv.abq3925">We know the path through space</a> that the Winchcombe object took – its orbit – before it fell to Earth. It is one of only five primitive, water-bearing chondrites for which scientists have this information. Knowing its orbit means we can pinpoint where in the solar system it came from. </p>
<figure class="align-center ">
<img alt="Fireball generated by the Winchcombe meteorite entering the atmosphere." src="https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=494&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=494&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=494&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=621&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=621&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514468/original/file-20230309-16-suqhy6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=621&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The meteorite appeared as a yellow-green fireball over Gloucestershire.</span>
<span class="attribution"><span class="source">UKFN / Dr Martin Suttle</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The pieces of this meteorite <a href="https://academic.oup.com/astrogeo/article/63/1/1.21/6507492">were recovered very rapidly</a> – within 12 hours of arriving on Earth. This means there was little time for water from Earth’s atmosphere to react with and contaminate the meteorite. Taken together with the meteorite’s rarity, primitive characteristics and distant origin, its swift recovery makes the object an ideal candidate for studying the role of asteroids in the early solar system.</p>
<p>The meteorite was probably once part of a larger asteroid. But looking at pieces of the Winchcombe object under the microscope, it quickly became clear that <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/maps.13938">it is not one rock but many</a> –- a complex mix of fragments loosely held together. This structure is the result of collisions between larger asteroids in space. </p>
<p>The debris field created by the collision subsequently merged to form a new population of smaller second-generation asteroids referred to as rubble-pile objects because of their loose, blocky configuration. Winchcombe came from one of these rubble-pile bodies – fragmented remains of the diverse rocky objects that existed in the age before planets.</p>
<h2>Space mud</h2>
<p>Each rock fragment that makes up the Winchcombe meteorite records a distinct history, revealing, for example, differences in the amount of water it interacted with, and implying that the parent asteroid had a complex structure. </p>
<p>These observations point to either variable amounts of water on that parent body, which condensed as ice as the asteroid grew, or the uneven flow of water through the asteroid. When space rocks come into <a href="http://advances.sciencemag.org/content/3/7/e1602514">contact with liquid water</a> they begin to change, forming an unusual form of dark black, fine-grained “space mud”. </p>
<p>Researchers from across the world jump at the chance to study these minerals because they hold, inside their crystal structure, molecules of
the original water that flowed on these asteroids. </p>
<figure class="align-center ">
<img alt="Winchombe meteorite" src="https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=332&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=332&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=332&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=417&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=417&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514467/original/file-20230309-672-u0roc3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=417&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The space rock contains some of the very earliest material to form in the solar system.</span>
<span class="attribution"><span class="source">Mira Ihasz SpireGlobal</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>A group of scientists accurately measured the different isotopes (or chemical forms) of the hydrogen present in Winchcombe. Along with oxygen, hydrogen is one of the two chemical elements in water. The scientists’ findings demonstrated that water contained within the meteorite is very similar to the water on Earth. </p>
<p>This strengthens a theory that asteroids played a critical role in delivering water to the early Earth and thereby generating the oceans we see today.</p>
<h2>Catastrophic collision</h2>
<p>At some point, chemical reactions between water and rock were halted by the <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/maps.13938">catastrophic collision with another asteroid</a>. This event shattered the meteorite’s parent body. Most of the rock fragments in the Winchcombe meteorite are very small, less than 1mm in size. This pattern of small pieces is evidence of the high-energy collision but also the signature of a weak asteroid. </p>
<p>As our understanding of planetary building blocks grows, we are increasingly recognising that the types of planetary bodies represented by the Winchcombe meteorite no longer exist in their original form. </p>
<figure class="align-center ">
<img alt="Winchcombe meteorite under Scanning Electron Microscope." src="https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=297&fit=crop&dpr=1 600w, https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=297&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=297&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=373&fit=crop&dpr=1 754w, https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=373&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/514512/original/file-20230309-16-5wv0zt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=373&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The fragmented nature of the Winchcombe meteorite was visible with a powerful microscope.</span>
<span class="attribution"><span class="source">Martin Suttle</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Most, if not all, small asteroids (those measuring less than 10km in diameter) are likely to be <a href="https://en.wikipedia.org/wiki/Rubble_pile">rubble-pile bodies</a>. Winchcombe is a relic from that time and a testament to the fate of most asteroids. We can summarise their history in a few simple words: hot and wet, then smashed to rubble. </p>
<p>Studying Winchcombe has also helped us to understand how these types of meteorites break-up in the atmosphere and, therefore, why they are rarely found as large rocks.</p>
<p>Research on Winchcombe continues and there are many more science questions that we hope to answer. One particularly interesting study relates to the type and amount of organic matter within Winchcombe and whether organic matter delivered by meteorites played a role in the supply of nutrients – food, essentially – for the emerging life on Earth.</p><img src="https://counter.theconversation.com/content/200304/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Martin D. Suttle has received funding from UKRI Science and Technology Facilities Council (STFC). </span></em></p>
In 2021, searchers recovered a meteorite that fell over the UK just hours earlier. Scientists have now reconstructed its story.
Martin D. Suttle, Lecturer in Planetary Science, The Open University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/187508
2022-08-04T12:19:36Z
2022-08-04T12:19:36Z
Handwritten diaries may feel old fashioned, but they offer insights that digital diaries just can’t match
<figure><img src="https://images.theconversation.com/files/477020/original/file-20220801-70473-agy1og.jpg?ixlib=rb-1.1.0&rect=0%2C23%2C7951%2C5273&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Handwritten diaries and digital diaries both help preserve experiences and memories, but in different ways.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-writing-in-bed-royalty-free-image/1341823785">luza studios/E+ via Getty Images</a></span></figcaption></figure><p>The first time I taught a college course called “The London Diary” for young Americans studying abroad back in 2002, each student ended up with a tangible book of memories, a handwritten record of their semester in London. But when <a href="https://www.grinnell.edu/user/smithp">I</a> taught the course 15 years later, the first question my students asked was whether they could keep their journals online. The question brought home to me how the image of a diary has shifted from words scribbled in a blank book to images and digital text on a screen. </p>
<h2>Why not go digital?</h2>
<p>Even while journaling apps like <a href="https://penzu.com/">Penzu</a> and <a href="https://diaroapp.com/">Diaro</a> become more widely available, <a href="https://www.statista.com/statistics/430306/notebooks-notepads-manufacturers-sales-in-the-united-kingdom-uk/">estimates</a> and <a href="https://www.statista.com/statistics/484891/children-writing-diary-by-demographic-uk/">surveys</a> suggest that a <a href="https://notedinstyle.co.uk/blog/2019/06/why-are-paper-diaries-still-so-popular/">sizable number</a> of the world’s diary keepers still keep handwritten diaries.</p>
<p>Fans of digital diaries grant them an edge in convenience, portability, searchability and password protection. Jonathan, one of my 2018 students, described in an essay for class how digital diarists can upload entries to multiple platforms, keeping some portions offline or restricted to a select audience while other parts go completely public. It’s harder to control distribution, encrypt entries or build an index with a journal kept on paper.</p>
<p>I already expected my students to use electronic devices to read course materials, to communicate with me and with their families back home, to write essays for class, and to navigate London. Why not let them keep digital diaries, too?</p>
<figure class="align-center ">
<img alt="Man writing in journal" src="https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477023/original/file-20220801-13716-26oi57.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">Handwritten journals offer clues into the author’s life that digital diaries may not.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/your-work-ethic-speaks-volumes-about-you-in-royalty-free-image/1278396474">ljubaphoto/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>Diary as artifact</h2>
<p>Poet and literary scholar Anna Jackson was researching the private papers of novelist Katherine Mansfield for her book “<a href="https://www.worldcat.org/title/diary-poetics-form-and-style-in-writers-diaries-1915-1962/oclc/636898151">Diary Poetics</a>” when she made an unexpected discovery. Jackson came across a “piece of the world” that was also an element of Mansfield’s journal – a kowhai flower between two pages in a notebook:</p>
<blockquote>
<p>“After all this time, there it still was, still yellow, still between the same two pages Mansfield had placed it between all those years ago. A piece of the world she wrote about was right there as a piece of the world still, not a piece of writing.”</p>
</blockquote>
<p>Jackson’s experience shows the power of holding in your hand the diary as a physical object. What scholars call the manuscript’s “materiality” links writer to reader in an unexpectedly intimate way.</p>
<p>For historians and diary scholars, manuscripts are artifacts. A book’s binding, paper quality and ink can signal an anonymous diarist’s socioeconomic status. Changes in penmanship may show how the writer felt – drowsy, extra careful or agitated – while writing certain passages.</p>
<p>Some clues, like the bit of evidence provided by inserting a memento, relay intentional messages. Others, like crossed-out words, may reveal information the writer did not plan to share.</p>
<p>Physical evidence can also hint at what happened after a text was written. Damaged or missing pages may indicate a strong reaction to the contents. A few years ago, conservators at the National Maritime Museum in Greenwich, England, discovered a <a href="https://www.theguardian.com/artanddesign/2018/sep/18/secret-unearthed-sailor-17th-century-journal-edward-barlow-national-maritime-museum">concealed entry</a> in the diary of a 17th-century British sailor. In his diary, he originally confessed to committing a rape, but later wrote a different account of the event, pasting the new page so carefully over the original that it went unnoticed for more than 300 years.</p>
<h2>Digital yet material</h2>
<p>Every original mark in a diary reflects an impulse of the moment. As diary instructor Tristine Rainer says in “<a href="https://www.worldcat.org/title/new-diary-how-to-use-a-journal-for-self-guidance-and-expanded-creativity/oclc/1036808266">The New Diary</a>,” “At any time you can change your point of view, your style, your book, the pen you write with, the direction you write on the pages, the language in which you write, the subjects you include. … It’s your book, yours alone.”</p>
<p>With so many convenient features, digital diaries remain a popular choice. This option, we might be surprised to learn, even has its own form of materiality. </p>
<p>In “<a href="https://www.routledge.com/How-to-Read-a-Diary-Critical-Contexts-and-Interpretive-Strategies-for-21st-Century/Henderson/p/book/9780415789189">How to Read a Diary</a>,” literature scholar Desirée Henderson notes that digital diaries, too, are objects, shaped by tools the diarist selects – in this case, software and hardware – to create the diary. The writer’s design choices, such as site structure, networking parameters, embedding of graphics, image and audio files and hyperlinks, offer grist for interpretation not unlike reading the nonverbal signs of a traditional diary.</p>
<figure class="align-center ">
<img alt="Young man writing in journal outdoors" src="https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/477026/original/file-20220801-38718-19pzpw.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">Every diary can be read as an artifact layered with meaning.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/young-male-writing-notes-in-a-notebook-sitting-on-a-royalty-free-image/1340138630?adppopup=true">Cavan Images/Cavan via Getty Images</a></span>
</figcaption>
</figure>
<h2>Writing into the future</h2>
<p>As I thought about offering my students the online option, I began to imagine them many years from now, coming upon that London diary from their college days. I remembered my first group of students drawing sketches on their pages, attaching a Travelcard, café napkin, or theater ticket. I remembered Anna Jackson with the kowhai flower. I couldn’t shake my conviction that future diary readers will be less enthralled by a digital product – even enhanced with multimedia – than by the quirky, untidy books hand-lettered by their predecessors.</p>
<p>In the end, I assigned my students – at least those who were physically able – to create their London diaries by hand. They could still use their phones to capture images or take preliminary notes, but in the end they would produce a material keepsake. </p>
<p>Several students decided to write in their notebooks while also keeping a digital diary. The dual process felt natural to them. To his blog Jonathan posted, “Like many children of the 21st century, I love the idea of keeping everything journaled online. This way I can make notes on my phone as I walk, have them automatically update on my computer, where I can expand with more time. If I wake up in the middle of the night with an idea, I don’t need to wake up a roommate with a lamp. However, the course also requires an analog diary.”</p>
<p>Every diary, “analog” or digital, can be read as an artifact layered with meaning – one that conveys clues to its writer’s life and times in both nonverbal signals and words.</p><img src="https://counter.theconversation.com/content/187508/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paula Vene Smith 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>
As material objects, diaries give scholars an intimate look into their subjects’ lives, including handwriting and mementos. What if diaries in the future are nothing but insubstantial digital ghosts?
Paula Vene Smith, Professor of English, Grinnell College
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/183874
2022-06-01T15:17:36Z
2022-06-01T15:17:36Z
Decisive people don’t make better decisions – new research
<figure><img src="https://images.theconversation.com/files/466264/original/file-20220531-22-kxnmq8.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7040%2C4679&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/doubtful-young-woman-wearing-trendy-round-640006879">Shutterstock</a></span></figcaption></figure><p>I’ve always been an indecisive person. What to wear, which menu item to pick, when to do house chores; always thinking through scenarios before committing to even the most trivial of choices. </p>
<p>If this sounds like you, you’re certainly not unusual: <a href="https://www.sciencedirect.com/science/article/abs/pii/S1057740814000916">many people struggle</a> with these issues. Our new research may not be able to help you choose which restaurant to go to, but it might reassure you. Decisive people may be more confident in the choices they make but they are no better at making decisions than the rest of us. </p>
<p>The starting point for <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0268501">my recent study</a> into the differences between decisive and indecisive people was finding a reliable way of distinguishing between participants. My team used the <a href="https://studylib.net/doc/8586964/action-control-scale--acs-90-.">Action Control Scale</a>, a yes or no questionnaire about everyday choices and behaviour. For example, whether you get bored quickly after learning a new game. </p>
<p>This scale <a href="https://pubmed.ncbi.nlm.nih.gov/10783541/">can reveal</a> whether a person is action or state-oriented. <a href="https://www.experisjobs.ca/ej-ca-en/Career-Resources/Career-Center/Strengthen-Action-orientation-Ability.htm#:%7E:text=If%20you%20are%20highly%20action,you%20follow%20through%20on%20it.">Action-oriented</a> people focus on action. They are more decisive, flexible and likely to implement their intentions in the face of adversity. </p>
<p><a href="https://www.cambridge.org/core/services/aop-cambridge-core/content/view/AB5F6366258C5C3348FF4DE46984141F/S1834490918000089a.pdf/div-class-title-individual-difference-in-goal-motives-and-goal-content-the-role-of-action-and-state-orientation-div.pdf">State-oriented</a> people focus on their emotional state. They are indecisive, often struggle to commit to their choices and abandon their commitments more frequently.</p>
<figure class="align-center ">
<img alt="Bird's eye view of red shows and lower legs standing between two arrows, left for no and right for yes" src="https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/466270/original/file-20220531-22-t0h7ly.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">Small decisions can feel overwhelming.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/yes-no-right-wrong-answer-business-2033158799">Shutterstock</a></span>
</figcaption>
</figure>
<p>We surveyed 723 people, from whom we chose the 60 most action-oriented and the 60 most state-oriented to take part in the main experiments. The participants went through a set of cognitive tasks, with low-risk choices. For example, we tested their simple perception (whether a cloud of dots is moving to the left or right) and preference (which of the two snacks would you rather eat). </p>
<p>We <a href="https://psycnet.apa.org/record/2015-22372-000">compared the following</a> cognitive processes between the two groups: </p>
<ul>
<li>evidence-processing speed (how fast you can acquire new information)</li>
<li>decision caution (how much you need to know to commit to a choice)</li>
<li>initial bias (how much the choice is influenced by some prior knowledge)</li>
<li>metacognitive sensitivity (how accurately you can judge the correctness of your choice)</li>
<li>metacognitive bias (how confident you are about your decision).</li>
</ul>
<h2>What we found</h2>
<p>The only difference in the two groups, across all the experiments, was that action-oriented people were more confident in their choices. There were no differences in accuracy, speed, cautiousness, bias or sensitivity. The action-oriented group was more confident, despite not being in any way better, faster or more accurate. </p>
<p>Certainly it can seem excessive, and sometimes debilitating, when you can’t even decide what to have for lunch. Indecisiveness can hinder our ability to pursue our goals. For example, exercise becomes difficult if each morning we second-guess ourselves and deliberate staying in bed. </p>
<p>But our research suggests that indecisive people are in no way worse at making choices. We can process evidence as fast and harness prior knowledge just as effectively as decisive people (and careful consideration can pay dividends when making life-changing choices, like choosing a university or buying a house – even if, as a millennial, this is only an issue in theory). </p>
<p>Being less or more confident of the choice that has been made cannot affect the outcome. It can however influence future ones. State-oriented people are less confident of whether the choice is right, which makes pursuing our goals a much greater challenge. </p>
<p>It is easy to see how this can relate to things such as preparing for an exam, exercising or learning a new skill. If you have low confidence that you are making meaningful progress, it can discourage regular practice. The reasons for this confidence gap are yet to be properly explained. But some research suggests a link with how people <a href="https://psycnet.apa.org/record/2008-00543-019">regulate their emotions</a>. This confidence gap might be the reason why some people succeed where others do not.</p><img src="https://counter.theconversation.com/content/183874/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wojciech Zajkowski received funding from the 'Diamentowy Grant' programme of the Polish Ministry of Education and Science.</span></em></p>
A new study shows indecisive people should go easier on themselves.
Wojciech Zajkowski, Research scientist in Psychology, Cardiff University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/165514
2021-09-01T23:18:07Z
2021-09-01T23:18:07Z
Defining when human life begins is not a question science can answer – it’s a question of politics and ethical values
<figure><img src="https://images.theconversation.com/files/418958/original/file-20210901-21-5hg6d6.jpg?ixlib=rb-1.1.0&rect=25%2C33%2C5572%2C4154&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Science can observe these various phases of fetal development but cannot determine when human life begins.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/pregnancy-ultrasound-royalty-free-image/168415756">UrsaHoogle/E+ via Getty Images</a></span></figcaption></figure><p>Now that the U.S. Supreme Court has <a href="https://theconversation.com/a-revolutionary-ruling-and-not-just-for-abortion-a-supreme-court-scholar-explains-the-impact-of-dobbs-185823">given states final say</a> over if and when abortions are legal, the <a href="https://www.cnn.com/2022/06/27/media/supreme-court-abortion-reliable-sources/index.html">political debates over abortion rights</a> will intensify in legislatures and <a href="https://theconversation.com/state-courts-from-oregon-to-georgia-will-now-decide-who-if-anyone-can-get-an-abortion-under-50-different-state-constitutions-184298">courthouses</a> around the nation. Many of those discussions will hinge on the question of when, exactly, is the beginning of a human life that could – or should – be protected by law.</p>
<p>A <a href="https://www.supremecourt.gov/DocketPDF/19/19-1392/185346/20210729162737297_19-1392%20BRIEF%20OF%20BIOLOGISTS%20AS%20AMICI%20CURIAE%20IN%20SUPPORT%20OF%20NEITHER%20PARTY.pdf">friend of the court filing</a> in the Supreme Court case implicitly claimed that biology – and therefore biologists – can tell when human life begins. The filing then went on to claim explicitly that a vast majority of biologists agree on which particular point in fetal development actually marks the beginning of a human life.</p>
<p>Neither of those claims is true.</p>
<h2>The role of science</h2>
<p>As a <a href="https://scholar.google.com/citations?user=wQsQxFoAAAAJ&hl=en&oi=ao">biologist and philosopher</a>, I have been watching players in the national abortion debate make claims about biology for many years. </p>
<p>Abortion rights opponents know that Americans have widely differing values and religious beliefs about abortion and the protection of human life. So they <a href="https://www.nytimes.com/2019/01/22/opinion/abortion-roe-science.html">seek to use science as an absolute standard</a> in any discussion of abortion’s constitutionality, setting a definition of human life that they hope will be immune to any counterargument.</p>
<p>While possibly well-intentioned, this appeal to scientific authority and evidence over discussions of people’s values is based on faulty reasoning. Philosophers such as the late <a href="https://plato.stanford.edu/entries/williams-bernard/">Bernard Williams</a> have long pointed out that understanding what it is to be human <a href="https://philpapers.org/rec/WILMSO">requires a lot more than biology</a>. And <a href="https://cup.columbia.edu/book/fear-wonder-and-science-in-the-new-age-of-reproductive-biotechnology/9780231170949">scientists can’t establish</a> when a fertilized cell or embryo or fetus becomes a human being.</p>
<iframe width="100%" height="480" frameborder="0" allowfullscreen="" src="https://archive.org/embed/COM_20121113_070000_The_Daily_Show_With_Jon_Stewart?start=1370&end=1412.2" webkitallowfullscreen="true" mozallowfullscreen="true"></iframe>
<h2>Political claims about science</h2>
<p>Public figures have, in recent years, prominently claimed that scientific knowledge on the topic of human life is definitive.</p>
<p>In 2012, for instance, former Arkansas Gov. Mike Huckabee, who was running for president, claimed on “The Daily Show with Jon Stewart: ”<a href="https://lincmad.blogspot.com/2012/11/transcript-huckabee-on-daily-show.html">Biologically, life begins at conception</a>. That’s irrefutable from a biological standpoint.“</p>
<p>Similarly, in his 2015 presidential bid, Florida Sen. Marco Rubio declared, ”<a href="https://www.cnn.com/2015/08/07/politics/marco-rubio-abortion-republican-debate-gop/index.html">I believe that science is clear</a> … when there is conception that that is a human life in the early stages of its development.“</p>
<p>The most recent high-profile example of this claim is in that <a href="https://www.supremecourt.gov/DocketPDF/19/19-1392/185346/20210729162737297_19-1392%20BRIEF%20OF%20BIOLOGISTS%20AS%20AMICI%20CURIAE%20IN%20SUPPORT%20OF%20NEITHER%20PARTY.pdf">amicus brief filed with the Supreme Court</a> in the Mississippi case.</p>
<p>The brief, coordinated by a University of Chicago graduate student in comparative human development, Steven Andrew Jacobs, is based on a problematic piece of research Jacobs conducted. He now seeks to enter it into the public record to influence U.S. law.</p>
<p>First, Jacobs carried out a survey, supposedly representative of all Americans, by seeking potential participants on the <a href="https://doi.org/10.1177%2F1948550619875149">Amazon Mechanical Turk crowdsourcing marketplace</a> and accepting all 2,979 respondents who agreed to participate. He found that <a href="https://papers.ssrn.com/sol3/papers.Cfm?Abstract_id=3211703">most of these respondents trust biologists over others</a> – including religious leaders, voters, philosophers and Supreme Court justices – to determine when human life begins.</p>
<p>Then, he sent 62,469 biologists who could be identified from institutional faculty and researcher lists a separate survey, offering several options for when, biologically, human life might begin. He got 5,502 responses; 95% of those self-selected respondents said that life began at fertilization, when a sperm and egg merge to form a single-celled zygote. </p>
<p>That result is not a proper survey method and does not carry any statistical or scientific weight. It is like asking 100 people about their favorite sport, finding out that only the <a href="https://news.gallup.com/poll/4735/sports.aspx">37 football fans</a> bothered to answer, and declaring that 100% of Americans love football.</p>
<p>In the end, just 70 of those 60,000-plus biologists supported Jacobs’ legal argument enough to sign the amicus brief, which makes a companion argument to the main case. That may well be because there is neither scientific consensus on the matter of when human life actually begins nor agreement that it is a question that biologists can answer using their science.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a fetus" src="https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/418960/original/file-20210901-15-10pj2s7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&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 human fetus at six to seven weeks of gestation.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/lunarcaustic/3233482244">lunarcaustic via Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Several possible options</h2>
<p><a href="https://www.swarthmore.edu/profile/scott-gilbert">Scott Gilbert</a>, the Howard A. Schneiderman Professor of Biology emeritus at Swarthmore College, is the author of the <a href="https://global.oup.com/ushe/product/developmental-biology-9781605358246?cc=us&lang=en&">standard textbook</a> of developmental biology. He has identified <a href="https://www.swarthmore.edu/news-events/when-does-personhood-begin">as many as five developmental stages</a> that, from a biological perspective, are all plausible beginning points for human life. Biology, as science knows it now, can tell these stages apart, but cannot determine at which one of these stages life begins.</p>
<p>The first of these stages is fertilization in the egg duct, when a zygote is
formed with the full human genetic material. But <a href="https://www.nytimes.com/2018/05/21/science/mosaicism-dna-genome-cancer.html">almost every cell in everyone’s body contains that person’s complete DNA sequence</a>. If genetic material alone makes a potential human being, then when we shed skin cells – as we do all the time – we are severing potential human beings.</p>
<p>The second plausible stage is called gastrulation, which happens about two weeks after fertilization. At that point, <a href="https://dx.doi.org/10.1187%2Flse.7.1.cbe12">the embryo loses the ability to form identical twins</a> – or triplets or more. The embryo therefore becomes a biological individual but not necessarily a human individual. </p>
<p>The third possible stage is at 24 to 27 weeks of pregnancy, when the characteristic <a href="https://doi.org/10.7312/gilb17094">human-specific brain-wave pattern emerges in the fetus’s brain</a>. Disappearance of this pattern is part of <a href="https://dx.doi.org/10.1007%2Fs11571-008-9047-z">the legal standard for human death</a>; by symmetry, perhaps its appearance could be taken to mark the beginning of human life.</p>
<p>The fourth possible stage, which is <a href="https://www.worldcat.org/title/abortion-medicine-and-the-law/oclc/563961118">the one endorsed in the Roe v. Wade decision</a> legalizing abortion in the United States, is viability, when a fetus typically becomes viable outside the uterus with the help of available medical technology. With the technology that we have today, <a href="https://www.rcog.org.uk/en/guidelines-research-services/guidelines/sip41/">that stage is reached at about 24 weeks</a>.</p>
<p>The final possibility is birth itself.</p>
<p>[<em>Over 100,000 readers rely on The Conversation’s newsletter to understand the world.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=100Ksignup">Sign up today</a>.]</p>
<p>The overall point is that biology does not determine when human life begins. It is a question that can only be answered by appealing to our values, examining what we take to be human. </p>
<p>Perhaps biologists of the future will learn more. Until then, when human life begins during fetal developments is a question for philosophers and theologians. And policies based on an answer to that question will remain up to politicians – and judges.</p>
<p><em>This is an updated version of an article originally published Sept. 1, 2021.</em></p><img src="https://counter.theconversation.com/content/165514/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sahotra Sarkar 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>
Some people seeking to influence public opinion about abortion rights claim the science is clear. It’s not, and that means abortion remains a political question – not a biological one.
Sahotra Sarkar, Professor of Philosophy and Integrative Biology, The University of Texas at Austin
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/157343
2021-03-17T15:27:34Z
2021-03-17T15:27:34Z
Origin of life: lightning strikes may have provided missing ingredient for Earth’s first organisms
<figure><img src="https://images.theconversation.com/files/390104/original/file-20210317-15-aa21co.jpg?ixlib=rb-1.1.0&rect=28%2C22%2C1868%2C997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lightning on early Earth.</span> <span class="attribution"><span class="source"> Lucy Entwisle</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The origin of life on Earth is one of the most complex puzzles facing scientists. It involves not only identifying the numerous chemical reactions that must take place to create a replicating organism, but also finding realistic sources for the ingredients needed for each of the reactions.</p>
<p>One particular problem that has long faced scientists who study the origin of life is the source of the elusive element, phosphorus. Phosphorus is an important element for basic cell structures and functions. For example, it forms the backbone of the double helix structure of DNA and the related molecule RNA.</p>
<p>Though the element was widespread, almost all phosphorus on the early Earth – around 4 billion years ago – was trapped in minerals that were essentially insoluble and unreactive. This means the phosphorus, while present in principle, was not available to make the compounds needed for life. </p>
<p><a href="https://www.nature.com/articles/s41467-021-21849-2">In a new paper</a>, we show lightning strikes would have provided a widespread source of phosphorus. This means lightning strikes may have helped spark life on Earth, and may be continuing to help life start on other Earth-like planets.</p>
<p>One potential source of phosphorus on the early Earth is the unusual mineral schreibersite, which is found in <a href="https://www.liebertpub.com/doi/10.1089/ast.2005.5.515">small amounts in meteorites</a>. Experiments have shown that <a href="https://doi.org/10.1016/j.gca.2006.12.018">schreibersite can dissolve in water</a>, creating aqueous phosphorus which can react and form a variety of organic molecules important for life. Examples include <a href="https://www.nature.com/articles/srep17198">nucleotides</a>, the building blocks of DNA and RNA, and <a href="https://doi.org/10.1039/C6CP00836D">phosphocholine</a>, a precursor to the lipid molecules that make up the cell membrane.</p>
<p>But there’s another potential source for schreibersite. While studying a glass structure created by a lightning strike called a fulgurite, we found a substantial amount of the unusual phosphorus mineral inside the glass.</p>
<p>If lightning strikes created a large amount of schreibersite, and other reactive phosphorus minerals, then lightning could be an alternate source of the reactive phosphorus needed for life. </p>
<p>To determine if this was the case, we estimated the amount of phosphorus made available by lightning strikes from 4.5 billion years ago, when the Earth formed, to 3.5 billion years ago when we have the earliest fossil evidence of life.</p>
<figure class="align-center ">
<img alt="A fulgurite sample of glass on the ground." src="https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390106/original/file-20210317-13-w7kjwx.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">The fulgurite sample.</span>
<span class="attribution"><span class="source">Benjamin Hess</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Our study</h2>
<p>To do this, we needed to estimate three things: the number of fulgurites formed each year; how much phosphorus was in the rocks on early Earth; and how much of that phosphorus is turned into usable phosphorus, by the lightning strikes. </p>
<p>Fulgurites form when lightning strikes the ground, so first we needed to know how much lightning there was. To determine the amount of lightning, we looked at estimates of the amount of CO₂ in the atmosphere on early Earth and estimates of how much lightning there would be on Earth for different amounts of CO₂. The CO₂ in the atmosphere can be used to estimate global temperature, which is a key factor in controlling the frequency of thunderstorms.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/phosphorus-is-vital-for-life-on-earth-and-were-running-low-74316">Phosphorus is vital for life on Earth – and we're running low</a>
</strong>
</em>
</p>
<hr>
<p>We found that, on early Earth, there would have ranged from 100 million to 1 billion lightning strikes a year, with each strike forming one fulgurite. In total, up to 1 quintillion (one followed by 18 zeroes) fulgurites would have formed in the first billion years of Earth’s history.</p>
<p>For the second factor, we know early Earth would have likely been dominated by rocks that are similar to the basalts that make up volcanic islands like Hawaii. We used the phosphorus content in some of these <a href="https://doi.org/10.1016/S0009-2541(01)00363-1">preserved rocks</a> that are over 3.5 billion years old to determine an average phosphorus content.</p>
<p>Finally, we used our fulgurite and other published fulgurite studies to estimate of how much schreibersite, or similar forms of phosphorus, would have been made available by lightning strikes. </p>
<p>Combining all these factors we calculated lightning strikes made upwards of 10,000kg of phosphorus available for organic reactions every year.</p>
<p>Based on the best of our knowledge of early Earth, lightning probably provided as much reactive phosphorus as meteorites did around the time of the origin of life, approximately 3.5 billion years ago. Therefore, lightning strikes, along with meteorite impacts, very likely provided the phosphorus needed for the emergence of life on Earth. </p>
<h2>Life on exoplanets</h2>
<p>Our research also highlights a new source of the phosphorus needed for life to emerge on other Earth-like planets. </p>
<p>Lightning strikes are a more sustainable source of phosphorus than meteorite impacts. The abundance of large meteorites in a solar system decreases exponentially over time as the leftover material in the system collides with planets. </p>
<p>So, while meteorites provide substantial usable phosphorus for life early in a planet’s history, they decrease fairly rapidly in abundance. Lightning strikes, however, are relatively constant through time.</p>
<p>Our work helps expand the conditions in which life can form on other planets in our solar system and beyond. If any planet has an active, lightning-rich atmosphere, then the phosphorus needed for life will be available any time.</p><img src="https://counter.theconversation.com/content/157343/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>
Lightning strikes may have helped spark life on Earth, and may be continuing to help life start on other Earth-like planets.
Benjamin Hess, PhD Candidate, Earth & Planetary Sciences, Yale University
Jason Harvey, Associate Professor of Geochemistry, University of Leeds
Sandra Piazolo, Professor in Structural Geology and Tectonics, University of Leeds
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/153851
2021-02-04T13:12:43Z
2021-02-04T13:12:43Z
Bringing Mars rocks back to Earth: On Feb. 18, Perseverance Rover landed safely on Mars – a lead scientist explains the tech and goals
<figure><img src="https://images.theconversation.com/files/385145/original/file-20210218-14-1pm2m5k.png?ixlib=rb-1.1.0&rect=191%2C13%2C672%2C440&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Perseverance Rover's first image sent back to NASA from Mars shows the surface of the Jezero crater.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/press-release/touchdown-nasas-mars-perseverance-rover-safely-lands-on-red-planet">NASA/JPL</a></span></figcaption></figure><p><em>Editor’s note: On Feb. 18, NASA’s <a href="https://mars.nasa.gov/mars2020/">Mars 2020 mission</a> arrived at the red planet and successfully landed the Perseverance Rover on the surface. <a href="https://scholar.google.com/citations?user=KR2ejsUAAAAJ&hl=en&oi=sra">Jim Bell</a> is a professor in the School of Earth and Space Exploration at Arizona State University and has worked on a number of Mars missions. He is the primary investigator leading a team in charge of one of the camera systems on Perseverance. We spoke with him in late January for The Conversation’s new podcast, <a href="https://theconversation.com/why-its-a-big-month-for-mars-the-conversation-weekly-podcast-154326">The Conversation Weekly</a>.</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>
<p><em>Below are excerpts from our conversation that have been edited for length and clarity.</em></p>
<h2>What’s the goal of this mission?</h2>
<p>What we’re looking for is evidence of past life, either direct chemical or organic signs in the composition and the chemistry of rocks, or textural evidence in the rock record. The environment of Mars is extremely harsh compared to the Earth, so we’re not really looking for evidence of current life. Unless something actually gets up and walks in front of the cameras, we’re really not going to find that.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A topographic, top down photo with colors showing the ancient river delta in the Jezero Crater" src="https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=481&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=481&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=481&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=604&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=604&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382059/original/file-20210202-21-xtkpmh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=604&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This color–enhanced photo shows the ancient river delta in the Jezero Crater where Perseverance will look for signs of life.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?search=jezero+crater+delta&title=Special:Search&go=Go&ns0=1&ns6=1&ns12=1&ns14=1&ns100=1&ns106=1&searchToken=8mo5vr95t586fpr7e67m1ighw#%2Fmedia%2FFile%3A260184-JezeroCrater-Delta-Full.jpg">NASA/JPL/JHU-APL/MSSS/Brown University</a></span>
</figcaption>
</figure>
<h2>Where is the Perseverance Rover landing to look for ancient life?</h2>
<p>There was a three- or four-year process that involved the entire global community of Mars and planetary science researchers to figure out where to send this rover. We chose a <a href="https://en.wikipedia.org/wiki/Jezero_(crater)">crater called Jezero</a>. Jezero has a beautiful river delta in it, preserved from an ancient river that flowed down into that crater and deposited sediments. This is kind of like the delta at the end of the Mississippi River in Louisiana which is depositing sediments very gently into the Gulf of Mexico.</p>
<p>On Earth, this shallow water is a very gentle environment where organic molecules and fossils can actually be gently buried and preserved in very fine-grained <a href="https://en.wikipedia.org/wiki/Mudstone">mudstones</a>. If a Martian delta operates the same way, then it’s a great environment for preserving evidence of things that were flowing in that water that came from the ancient highlands above the crater. </p>
<p>There’s lots of things we don’t know, but there was liquid water there. There were heat sources – there were active volcanoes 2, 3, 4 billion years ago on Mars – and there are impact craters from asteroids and comets dumping lots of heat into the ground as well as organic molecules. It’s a very short list of places in the solar system that meet those constraints, and Jezero is one of those places. It’s one of the best places that we think to go to do this search for life.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&rect=86%2C135%2C6745%2C5327&q=45&auto=format&w=1000&fit=clip"><img alt="The Perseverance Rover in a NASA lab on earth." src="https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&rect=86%2C135%2C6745%2C5327&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382056/original/file-20210202-15-17clle0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Perseverance Rover is 90% spare parts from the Curiosity Rover but has a few new tools on board.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Perseverance_(rover)#/media/File:PIA23499-Mars2020Rover-FirstTestDrive-20191217a.jpg">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>What scientific tools is Perseverance carrying?</h2>
<p>The <a href="https://mars.nasa.gov/mars2020/spacecraft/rover/">Perseverance Rover</a> looks a lot like <a href="https://mars.nasa.gov/msl/home/">Curiosity</a> on the outside because it’s made from something like 90% spare parts from Curiosity – that’s how NASA could afford this mission. Curiosity has a pair of cameras – one wide angle, one telephoto.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The Mastcam-Z cameras side by side. They are cylindrical, copper colored tubes with square lenses." src="https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382063/original/file-20210202-21-1uivdco.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&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 Mastcam-Z includes two cameras with zoom lenses allowing researchers to create three-dimensional images of the Martian landscape.</span>
<span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/25282/ready-for-a-close-up-or-a-wide-angle/">MSSS/ASU</a></span>
</figcaption>
</figure>
<p>In Perseverance, we’re sending similar cameras, but with zoom technology so we can zoom from wide angle to telephoto with both cameras – the “Z” in <a href="https://mars.nasa.gov/mars2020/spacecraft/instruments/mastcam-z/">Mastcam-Z</a> stands for zoom. This allows us to get great stereo images. Just like our left eye and our right eye build a three-dimensional image in our brain, the zoom cameras on Perserverance are a left eye and a right eye. With this, we can build a three-dimensional image back on Earth when we get those images.</p>
<p>3D images allow us to do a whole range of things scientifically. We want to understand the topography of Mars in much more detail than we’ve been able to in the past. We want to put the pieces of the delta geology story together not just with two-dimensional, spatial information, but with height as well as texture. And we want to make 3D maps of the landing site. </p>
<p>Our engineering and driving colleagues really need that information too. These 3D images will help them decide where to drive by helping to identify obstacles and slopes and trenches and rocks and stuff like that, allowing them to drive the rover much deeper into places than they would have been able to otherwise.</p>
<p>And finally, we’re going to make really cool 3D views of our landing site to share with the public, including movies and flyovers.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the sample collection tubes which are made from titanium and include a sealing mechanism." src="https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382064/original/file-20210202-21-1h5xf7o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The sample tubes are specially built to store the rock and soil cores for future pickup.</span>
<span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/25483/anatomy-of-a-sample-tube-interior/">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>What else is different about this mission?</h2>
<p>Perseverance is intended to be the first part of a robotic sample return mission from Mars. So instead of just drilling into the surface like the Curiosity Rover does, Perseverance will drill and core into the surface and <a href="https://mars.nasa.gov/mars2020/mission/science/objectives/">cache those little cores into tubes</a> about the size of a dry-erase marker. It will then put those tubes onto the surface for a future mission later this decade to pick up and then bring back to the Earth. </p>
<p>Perseverance won’t come back to the Earth, but the plan is to bring the samples that we collect back.</p>
<p>In the meantime, we’ll be doing all of the science that any great rover mission would do. We are going to characterize the site, explore the geology and measure the atmospheric and weather properties. </p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<h2>How will you get those samples back to Earth?</h2>
<p>This is where it gets a little less certain, because these are all ideas and missions in the works. NASA and the European Space Agency are collaborating on a concept to build and launch a lander that will send a little fetch rover that goes and gets the little tubes, picks them up and brings them back to the lander. Waiting on the lander would be a small rocket called a <a href="https://mars.nasa.gov/resources/24764/mars-ascent-vehicle-launching-with-samples-artists-concept/">Mars Ascent Vehicle</a>, or MAV. Once the samples are loaded into the MAV, it launches them into Mars orbit.</p>
<p>Then you’ve got this grapefruit- to soccer-ball-sized canister up there, and NASA and the Europeans are collaborating on an orbiter that will search for that canister, capture it and then rocket it back to the Earth, where it will land in the Utah desert. What could possibly go wrong?</p>
<p>If successful, that’ll be the first time we’ve done that from Mars. The scientific tools on the rovers are good, but nothing like the labs back on Earth. Bringing those samples back is going to be absolutely critical to getting the most out of the samples.</p>
<p><em>This is an updated version of an article originally published on Feb. 4. The editor’s note was updated to reflect the successful landing of the Perseverance Rover on Mars.</em></p><img src="https://counter.theconversation.com/content/153851/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Bell receives funding from NASA for his work on the Perseverance rover mission.. He is also an unpaid member of the Board of Directors of The Planetary Society, engaging in activities including education and advocacy of space exploration with elected officials.</span></em></p>
NASA’s Mars 2020 mission has arrived and landed the Perseverance Rover on the red planet. The rover’s goal is to collect rock and soil samples to be brought back to Earth in the future.
Jim Bell, Professor of Earth and Space Exploration, Arizona State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/146185
2020-09-18T12:07:59Z
2020-09-18T12:07:59Z
The detection of phosphine in Venus’ clouds is a big deal – here’s how we can find out if it’s a sign of life
<figure><img src="https://images.theconversation.com/files/358693/original/file-20200917-16-6y1m7g.png?ixlib=rb-1.1.0&rect=93%2C1%2C1005%2C671&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A radar mosaic image of Venus.</span> <span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/stellar_items/image_files/3_feature_1600x900_venus.jpg">NASA.gov</a></span></figcaption></figure><p>On Sept. 14, 2020, a new planet was added to the list of potentially habitable worlds in the Solar System: Venus. </p>
<p><a href="https://en.wikipedia.org/wiki/Phosphine">Phosphine</a>, a toxic gas made up of one phosphorus and three hydrogen atoms (PH₃), <a href="https://news.mit.edu/2019/phosphine-aliens-stink-1218">commonly produced by organic life forms</a> but otherwise difficult to make on rocky planets, <a href="https://doi.org/10.1038/s41550-020-1174-4">was discovered in the middle layer of the Venus atmosphere.</a> This raises the tantalizing possibility that something is alive on our planetary neighbor. With this discovery, Venus joins the exalted ranks of Mars and the icy moons Enceladus and Europa among planetary bodies where life may once have existed, or perhaps might even still do so today.</p>
<p>I’m a planetary scientist and something of a <a href="https://twitter.com/ThePlanetaryGuy/status/1306052714074443776?s=20">Venus evangelical</a>. This discovery is one of the most exciting made about Venus in a very long time — and opens up a new set of possibilities for further exploration in search of life in the Solar System. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Venus as seen in the infrared by the Japanese Akatsuki spacecraft. The warm colors are from the hot lower atmosphere glowing through the cooler cloud layers above. Image credit: JAXA/ISAS/DARTS/Damia Bouic.</span>
<span class="attribution"><a class="source" href="https://planetary.s3.amazonaws.com/web/assets/pictures/20180113_ir2_20160927_090331_226_l2b_v10_PRGB.jpg">JAXA/ISAS/DARTS/Damia Bouic</a></span>
</figcaption>
</figure>
<h2>Atmospheric mysteries</h2>
<p>First, it’s critical to point out that this detection does not mean that astronomers have found alien life in the clouds of Venus. Far from it, in fact. </p>
<p>Although the discovery team identified phosphine at Venus <a href="https://alma-telescope.jp/en/news/press/venus-202009">with two different telescopes</a>, helping to confirm the initial detection, phosphine gas can result from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity. </p>
<p>However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than those processes are capable of generating, allowing the team to <a href="http://astrobiology.com/2020/09/phosphine-on-venus-cannot-be-explained-by-conventional-processes.html">rule out</a> numerous inorganic possibilities. But our understanding of the chemistry of Venus’ atmosphere is sorely lacking: Only a handful of missions have plunged through the inhospitable, <a href="https://solarsystem.nasa.gov/planets/venus/overview/">carbon dioxide-dominated atmosphere</a> to take samples among the global layer of <a href="https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Acid_clouds_and_lightning">sulfuric acid clouds</a>.</p>
<p>So we planetary scientists are faced with two possibilities: Either there is some sort of life in the Venus clouds, generating phosphine, or there is unexplained and unexpected chemistry taking place there. How do we find out which it is?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A model of the Soviet Vega 1 spacecraft at the Udvar-Hazy Center, Dulles International Airport. Vega 1 carried a balloon to Venus on its way to visit Halley’s Comet in 1985.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/5/52/Vega_model_-_Udvar-Hazy_Center.JPG">Daderot</a></span>
</figcaption>
</figure>
<p>First and foremost, we need more information about the abundance of PH₃ in the Venus atmosphere, and we can learn something about this from Earth. Just as the discovery team did, existing telescopes capable of detecting phosphine around Venus can be used for follow-up observations, to both definitively confirm the initial finding and figure out if the amount of PH₃ in the atmosphere changes with time. In parallel, there is now a huge opportunity to carry out lab work to better understand the types of chemical reactions that might be possible on Venus — for which we have <a href="https://twitter.com/PlanetDr/status/1306308300397596672?s=20">very limited information</a> at present.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antennas of the Atacama Large Millimeter/submillimeter Array telescope, on the Chajnantor Plateau in the Chilean Andes. The telescope was used to confirm the initial detection of phosphine in Venus’ atmosphere.</span>
<span class="attribution"><a class="source" href="https://cdn.eso.org/images/screen/ann13016a.jpg">ESO/C. Malin.</a></span>
</figcaption>
</figure>
<h2>Once more unto the breach</h2>
<p>But measurements on and from Earth can take us only so far. To really get to the heart of this mystery, <a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">we need to go back to Venus</a>. Spacecraft equipped with spectrometers that can detect phosphine from orbit could be dispatched to the second planet with the express purpose of characterizing where, and how much, of this gas is there. Because spacecraft <a href="https://en.wikipedia.org/wiki/Pioneer_Venus_Orbiter">can survive for many years in Venus’ orbit</a>, we could obtain continuous observations with a dedicated orbiter over a much longer period than with telescopes on Earth.</p>
<p>But even orbital data can’t tell us the whole story. To fully get a handle on what’s happening at Venus, we have to actually get into the atmosphere. <a href="https://solarsystem.nasa.gov/resources/2197/aerial-platforms-for-the-scientific-exploration-of-venus/">And that’s where aerial platforms come in</a>. Capable of operating above much of the acidic cloud layer – where the temperature and pressure are almost Earthlike – for potentially months at a time, balloons or <a href="https://www.northropgrumman.com/vamp/">flying wings</a> could take detailed atmospheric composition measurements there. These craft could even carry the kinds of instruments <a href="https://www.lpi.usra.edu/opag/meetings/apr2019/presentations/Schulte.pdf">being developed to look for life on Europa</a>. At that point, humanity might finally be able to definitively tell if we share our Solar System with Venusian life.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1827&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1827&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1827&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=2296&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=2296&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=2296&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A concept for an aerial platform at Venus. Two connected balloons could take turns to inflate, allowing the balloon to control the altitude at which it floats. An instrument package would then hang from below the balloons.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/resources/detail_files/2197_Venus_Aerial_Platforms_Final_Report_Summary_Report_10_25_2018-1.jpg">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>A new dawn for Venus exploration?</h2>
<p>Thirty-one years have elapsed since the United States last sent a dedicated mission to Venus. That could soon change as NASA considers two of four missions in the late 2020s targeting Venus. One, called <a href="https://science.jpl.nasa.gov/projects/VERITAS/">VERITAS</a>, would carry a powerful radar to peer through the thick clouds and return unprecedented high-resolution images of the surface. The other, <a href="https://www.nasa.gov/feature/goddard/2020/nasa-goddard-team-selected-to-design-concept-for-probe-of-mysterious-venus-atmosphere">DAVINCI+</a>, would plunge through the atmosphere, sampling the air as it descended, perhaps even able to sniff any phosphine present. NASA plans to pick at least one mission in April 2021.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p><a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">I have argued before for a return to Venus</a>, and will continue to do so. Even without this latest scientific discovery, Venus is a compelling exploration target, with tantalizing evidence that the planet <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">once had oceans</a> and perhaps even suffered a hellish fate at the hands of <a href="https://eos.org/research-spotlights/how-long-was-venus-habitable">its own volcanic eruptions</a>. </p>
<p>But with the detection of a <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2018.1954?journalCode=ast">potential biomarker</a> in Venus’ atmosphere, we now have yet another major reason to return to the world ancient Greek astronomers called Phosphorus — a name for Venus that, it turns out, is wonderfully prescient.</p><img src="https://counter.theconversation.com/content/146185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul K. Byrne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>
News that Venus may harbor life has swept the globe. So how do we find out for sure? A planetary scientist explains what’s next.
Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/146358
2020-09-18T11:50:53Z
2020-09-18T11:50:53Z
The four most promising worlds for alien life in the solar system
<figure><img src="https://images.theconversation.com/files/358659/original/file-20200917-14-1qdn4n4.jpg?ixlib=rb-1.1.0&rect=36%2C36%2C1238%2C782&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">NASA's Curiosity Rover takes a selfie on Mars in June, 2018.</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA22486">NASA/JPL-Caltech/MSSS</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The Earth’s biosphere contains all the known ingredients necessary for life as we know it. Broadly speaking these are: liquid water, at least one source of energy, and an inventory of biologically useful elements and molecules.</p>
<p>But the recent discovery of possibly biogenic phosphine <a href="https://theconversation.com/venus-could-it-really-harbour-life-new-study-springs-a-surprise-145981">in the clouds of Venus</a> reminds us that at least some of these ingredients exist elsewhere in the solar system too. So where are the other most promising locations for extra-terrestrial life?</p>
<h2>Mars</h2>
<p>Mars is one of the most Earth-like worlds in the solar system. It has a 24.5-hour day, polar ice caps that expand and contract with the seasons, and a large array of surface features that were sculpted by water during the planet’s history.</p>
<figure class="align-center ">
<img alt="Red planet Mars in space with polar ice caps visible" src="https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.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">Mars has polar ice caps.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/0/02/OSIRIS_Mars_true_color.jpg">ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The detection of <a href="https://www.sciencemag.org/news/2018/07/liquid-water-spied-deep-below-polar-ice-cap-mars">a lake beneath</a> the southern polar ice cap and methane in the Martian atmosphere (which varies with the seasons and even the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083800">time of day</a>) make Mars a very interesting candidate for life. Methane is significant as it can be produced by biological processes. But the actual source for the methane on Mars is not yet known.</p>
<p>It is possible that life may have gained a foothold, given the <a href="https://advances.sciencemag.org/content/4/6/eaar3330">evidence</a> that the planet once had a much more benign environment. Today, Mars has a very thin, dry atmosphere comprised almost entirely of carbon dioxide. This offers scant protection from solar and cosmic radiation. If Mars has managed to retain some reserves of water beneath its surface, it is not impossible that life may still exist. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/life-on-mars-europe-commits-to-groundbreaking-mission-to-bring-back-rocks-to-earth-128328">Life on Mars? Europe commits to groundbreaking mission to bring back rocks to Earth</a>
</strong>
</em>
</p>
<hr>
<h2>Europa</h2>
<p>Europa was discovered by Galileo Galilei in 1610, along with Jupiter’s three other larger moons. It is slightly smaller than Earth’s moon and orbits the gas giant at a distance of some 670,000km once every 3.5 days. Europa is constantly squeezed and stretched by the competing gravitational fields of Jupiter and the other <a href="https://www.universetoday.com/44796/galilean-moons/">Galilean moons</a>, a process known as tidal flexing. </p>
<p>The moon is believed to be a geologically active world, like the Earth, because the strong tidal flexing heats its rocky, metallic interior and keeps it partially molten.</p>
<figure class="align-center ">
<img alt="Jupiter's white with brown streaks moon Europa in space," src="https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Europa’s icy surface is a good sign for alien hunters.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA19048">NASA/JPL-Caltech/SETI Institute</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The surface of Europa is a vast expanse of water ice. Many scientists think that beneath the frozen surface is a layer of liquid water – a global ocean – which is prevented from freezing by the heat from flexing and which maybe over 100km deep. </p>
<p>Evidence for this ocean includes geysers erupting through <a href="https://www.nature.com/articles/s41550-019-0933-6">cracks in the surface ice</a>, a <a href="http://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Justin_Long/Justin_Long/magnetic.html">weak magnetic field</a> and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103599961870?via%3Dihub">chaotic terrain</a> on the surface, which could have been deformed by ocean currents swirling beneath. This icy shield insulates the subsurface ocean from the extreme cold and vacuum of space, as well as Jupiter’s ferocious radiation belts.</p>
<p>At the bottom of this ocean world it is conceivable that we might find <a href="https://oceanservice.noaa.gov/facts/vents.html">hydrothermal vents</a> and ocean floor volcanoes. On Earth, such features often support very rich and diverse ecosystems.</p>
<hr>
<p>
<em>
<strong>
Read more:
<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">Europa: there may be life on Jupiter's moon and two new missions will pave the way for finding it</a>
</strong>
</em>
</p>
<hr>
<h2>Enceladus</h2>
<p>Like Europa, <a href="https://solarsystem.nasa.gov/moons/saturn-moons/enceladus/in-depth/">Enceladus</a> is an ice-covered moon with a subsurface ocean of liquid water. Enceladus orbits Saturn and first came to the attention of scientists as a potentially habitable world following the <a href="https://solarsystem.nasa.gov/resources/806/bursting-at-the-seams-the-geyser-basin-of-enceladus/">surprise discovery</a> of enormous geysers near the moon’s south pole.</p>
<p>These jets of water escape from large cracks on the surface and, given Enceladus’ weak gravitational field, spray out into space. They are clear evidence of an underground store of liquid water.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"906891543780323328"}"></div></p>
<p>Not only was water detected in these geysers but also an array of organic molecules and, crucially, tiny grains of rocky silicate particles that can only be present if the sub-surface ocean water was in physical contact with the rocky ocean floor at a <a href="https://solarsystem.nasa.gov/missions/cassini/science/enceladus/">temperature of at least 90˚C</a>. This is very strong evidence for the existence of hydrothermal vents on the ocean floor, providing the chemistry needed for life and localised sources of energy. </p>
<h2>Titan</h2>
<p>Titan is the largest moon of Saturn and the only moon in the solar system with a substantial atmosphere. It contains a thick orange haze of complex organic molecules and a methane weather system in place of water – complete with seasonal rains, dry periods and surface sand dunes created by wind.</p>
<figure class="align-center ">
<img alt="Yellow/orange moon Titan in space" src="https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.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">Titan’s atmosphere makes it look like a fuzzy orange ball.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA14602">NASA/JPL-Caltech/Space Science Institute</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The atmosphere consists mostly of nitrogen, an important chemical element used in the construction of proteins in all known forms of life. Radar observations have detected the presence of <a href="https://theconversation.com/titan-first-global-map-uncovers-secrets-of-a-potentially-habitable-moon-of-saturn-126985">rivers and lakes</a> of liquid methane and ethane and possibly the presence of cryovolcanoes – volcano-like features that erupt liquid water rather than lava. This suggests that Titan, like Europa and Enceladus, has a sub-surface reserve of liquid water.</p>
<p>At such an enormous distance from the Sun, the surface temperatures on Titan are a frigid -180˚C – way too cold for liquid water. However, the bountiful chemicals available on Titan has raised speculation that lifeforms – potentially with fundamentally different chemistry to terrestrial organisms – <a href="https://www.space.com/8547-strange-discovery-titan-leads-speculation-alien-life.html">could exist</a> there.</p><img src="https://counter.theconversation.com/content/146358/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>
The clouds of Venus may harbour alien life. But where else?
Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of Birmingham
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/139639
2020-06-08T13:18:13Z
2020-06-08T13:18:13Z
Are viruses alive? Perhaps we’re asking the wrong question
<figure><img src="https://images.theconversation.com/files/339125/original/file-20200602-133933-f57k8e.jpg?ixlib=rb-1.1.0&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-illustration/3d-illustration-showing-corona-virus-mers-1625661736">Axel_Kock/Shutterstock</a></span></figcaption></figure><p>Viruses are an inescapable part of life, especially in a global viral pandemic. Yet ask a roomful of scientists if viruses are alive and you’ll get a very mixed response.</p>
<p>The truth is, we don’t fully understand viruses, and we’re still trying to understand life. Some <a href="https://www.khanacademy.org/science/high-school-biology/hs-biology-foundations/hs-biology-and-the-scientific-method/a/what-is-life">properties of living things</a> are absent from viruses, such as cellular structure, metabolism (the chemical reactions that take place in cells) and homeostasis (keeping a stable internal environment).</p>
<p>This sets viruses apart from life as we currently define it. But there are also properties that viruses <a href="https://www.livescience.com/53272-what-is-a-virus.html">share with life</a>. They evolve, for instance, and by infecting a host cell they multiply using the same cellular machinery.</p>
<p><a href="https://www.nature.com/articles/ismej201716">Many viruses</a> can cut the DNA of infected cells and intertwine their own genetic material so that they are copied along with the DNA of their host whenever the cell divides. This process is called lysogeny and it can be contrasted with the more destructive <a href="https://www.technologynetworks.com/immunology/articles/lytic-vs-lysogenic-understanding-bacteriophage-life-cycles-308094">lytic strategy</a> of viruses where they multiply in great numbers within a cell, only to burst the cell open and spread out to infect other cells.</p>
<p>There is an undeniable genetic and physiological connection between viruses and the organisms they infect. The discovery of giant viruses <a href="https://theconversation.com/are-viruses-alive-giant-discovery-suggests-theyre-more-like-zombies-75661">further blurs the distinction</a>. These viruses can have as many genes as bacteria, some of which code for functions <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6563228">previously thought</a> to be unique to cellular organisms.</p>
<p>Does this new information lead to confusion or clarity? Can we ever answer the elusive question of whether viruses are alive, instead of just a non-living part of the living world? If we approach this puzzle correctly, we may find that we are focusing on the wrong question. Is “life” a box-like category that we can place things in as we discover them, or is it something far more mysterious?</p>
<h2>A cosmological thought experiment</h2>
<p>Let us distance ourselves from the details and indulge in a thought experiment. There are hundreds of billions of stars spread out across the universe, clustered into galaxies, many guiding the orbits of planets around them. Some planets, in turn, are acting as gravitational centres for orbiting moons. We <a href="https://medium.com/starts-with-a-bang/how-many-planets-in-the-universe-9153a05bd0d5">know this much</a>.</p>
<p>Now, imagine that lifeforms are scattered across these moons and planets, uncommon in any one galaxy perhaps, but numerous over the vast expanse of the universe. A team of intergalactic scientists has been working diligently for centuries, characterising the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005285/">different forms of life</a> and their unique properties and, more importantly, what they share. They might all use a certain type of molecule, for instance, or share a definitive process like Darwinian evolution.</p>
<p>Why would a shared characteristic of life be so important? Because it suggests that life is not a chance happening but an emergent property of the universe. The team of alien scientists might conclude that life is less of an accident and more of a universal principle.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/339127/original/file-20200602-133886-ff2fgq.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">
<figcaption>
<span class="caption">If we found life on another planet, would we even recognise it?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-illustration-distant-deserted-planet-lightened-1290974512">CROCOTHERY</a></span>
</figcaption>
</figure>
<p>This all feels reassuring but is not necessarily true. Carol Cleland, professor of philosophy and author of several books on the nature and origin of life, <a href="http://lcd-www.colorado.edu/%7Eaxbr9098/teach/ASTR_2040/material/Cleland2012_Life_without_Definitions.pdf">speculates that</a> life might not be a “natural kind”. This means that life is defined by people instead of by nature. </p>
<p>It is like grouping bats with birds due to their shared ability to fly, instead of with mammals. This categorisation gives flight a priority over evolutionary history, even though it is evolution that reflects the most natural relationships among lifeforms on our planet.</p>
<p>Cleland ultimately doubts that life is just a <a href="http://lcd-www.colorado.edu/%7Eaxbr9098/teach/ASTR_2040/material/Cleland2012_Life_without_Definitions.pdf">manmade concept</a>. She might well be right. This is what makes the alternative so intriguing. What if there is life on a distant planet so unimaginably unlike our own that we would not recognise it if we found it? Could we even call it “life”?</p>
<h2>Back down on Earth</h2>
<p>We are not so advanced as our hypothetical intergalactic explorers. We have yet to find life on another planet, despite our <a href="https://theconversation.com/explainer-why-is-everyone-vying-for-a-piece-of-mars-32078">missions to Mars</a> and <a href="https://www.space.com/alien-life-ocean-moons-europa-enceladus.html">recent speculation</a> about Saturn’s icy moon, Enceladus, and Jupiter’s Europa. </p>
<p>These moons are <a href="https://astronomynow.com/2017/04/13/new-discoveries-raise-prospects-for-life-on-moons-of-jupiter-and-saturn/">thought to have</a> active hydrothermal vents that spew out geothermally heated water, much like those at the bottom of Earth’s oceans. <a href="https://www.chemistryworld.com/features/hydrothermal-vents-and-the-origins-of-life/3007088.article">One hypothesis</a> on the origin of life on our planet is that it began close to these energetic, chemically rich fissures in the ocean floor. </p>
<p>Our scientists have a sample size of one. All life on Earth arose from a <a href="https://phys.org/news/2018-12-luca-universal-common-ancestor.html">common ancestor</a> in the deep geological past. This was <a href="https://link.springer.com/article/10.1007/s11214-019-0624-8">long before</a> we had oxygen, or even continents. We do not know what this ancestor looked like in any detail, but it is <a href="https://phys.org/news/2018-12-luca-universal-common-ancestor.html">hypothesised to be</a> a primitive cell containing the basic machinery for copying genetic material and expressing proteins.</p>
<p>Did viruses predate this common ancestor? Or did they somehow originate from early evolving lifeforms? Events so ancient are always tortured with uncertainty, but <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3575434/">speculation involves</a> numerous intriguing scenarios, all of which may be false.</p>
<p>The <a href="https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005912">tree of life</a>, a model of the evolutionary history of life on Earth, might find viruses among its branches after all. The caveat is to keep an open mind. Models themselves evolve with our increased understanding of reality. And who knows what the future of biology will reveal?</p>
<p>Are viruses alive? Perhaps this isn’t the question we should be asking. Viruses are evolving entities that are intimately related to cellular life. But we do not understand life.</p>
<p>Whenever we get too confident with our opinions and our definitions, we should wonder at that hypothetical planet holding lifelike entities in a remote galaxy, the existence of which could change everything we know.</p>
<p>Someday, we may be lucky enough to find it.</p><img src="https://counter.theconversation.com/content/139639/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hugh Harris works as a postdoctoral researcher at APC Microbiome Ireland, University College Cork where he is funded by Science Foundation Ireland under the Microbes to Molecules research theme.</span></em></p>
We don’t fully understand viruses, and we’re still trying to understand life.
Hugh Harris, Postdoctoral researcher in Microbiology and Bioinformatics, University College Cork
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/129290
2020-01-07T00:43:45Z
2020-01-07T00:43:45Z
An Earth-sized planet found in the habitable zone of a nearby star
<figure><img src="https://images.theconversation.com/files/308458/original/file-20200103-11891-16j6k7w.jpg?ixlib=rb-1.1.0&rect=26%2C17%2C5865%2C3413&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of an exoplanet in the habitable zone around a star.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2019/nasa-s-hubble-finds-water-vapor-on-habitable-zone-exoplanet-for-1st-time">ESA/Hubble, M. Kornmesser</a></span></figcaption></figure><p>A few months ago a group of NASA exoplanet astronomers, who are in the business of discovering planets around other stars, called me into a secret meeting to tell me about a planet that had captured their interest. Because <a href="https://scholar.google.com/citations?user=SVYEFJcAAAAJ&hl=en">my expertise</a> lies in modeling the climate of exoplanets, they asked me to figure out whether this new planet was habitable – a place where liquid water might exist. </p>
<p>These NASA colleagues, <a href="https://science.gsfc.nasa.gov/sed/bio/joshua.e.schlieder">Josh Schlieder</a> and his students <a href="https://astro.uchicago.edu/people/emily-gilbert.php">Emily Gilbert</a>, <a href="https://science.gsfc.nasa.gov/sed/bio/thomas.barclay">Tom Barclay</a> and <a href="https://science.gsfc.nasa.gov/sed/bio/elisa.quintana">Elisa Quintana</a>, had been studying data from TESS (<a href="https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite">Transiting Exoplanet Survey Satellite</a>) when they discovered what may be TESS’ first known Earth-sized planet in a zone where liquid water could exist on the surface of a terrestrial planet. This is very exciting news because this new planet is relatively close to Earth, and it may be possible to observe its atmosphere with either the <a href="https://www.jwst.nasa.gov/">James Webb Space Telescope</a> or ground-based large telescopes. </p>
<h2>Habitable zone planets</h2>
<p>The host star of the planet that <a href="https://arxiv.org/abs/2001.00952">Gilbert’s team discovered</a> is called TESS of Interest number 700, or TOI-700. Compared to the Sun, it is a small, dim star. It is 40% the size, only about 1/50 of the Sun’s brightness and is located about 100 light-years from Earth in the constellation Dorado, which is visible from our Southern Hemisphere. For comparison, the nearest star to us, Proxima Centauri, is 4.2 light-years away from Earth. To get a sense of these distances, if you were to travel on the fastest spacecraft (<a href="http://parkersolarprobe.jhuapl.edu">Parker Solar Probe</a>) to reach Proxima Centauri, it would take nearly 20,000 years.</p>
<p>There are three planets around TOI-700: b, c and d. Planet d is Earth-size, within the star’s habitable zone and orbits TOI-700 every 37 days. My colleagues wanted me to create a climate model for Planet d using the known properties of the star and planet. Planets b and c are Earth-size and mini-Neptune-size, respectively. However, they orbit much closer to their host star, receiving 5 times and 2.6 times the starlight that our own Earth receives from the Sun. For comparison, Venus, a dry and hellishly hot world with surface temperature of approximately 860 degrees Fahrenheit, receives twice the sunlight of Earth.</p>
<p>Until about a decade ago, only two habitable zone planets of any size were known to astronomers: Earth and Mars. Within the last decade, however, thanks to discoveries made through both ground-based telescopes and the <a href="https://www.nasa.gov/mission_pages/kepler/main/index.html">Kepler mission</a> (which also looked for exoplanets from 2009 to 2019, but is now retired), astronomers have discovered about a dozen terrestrial-sized exoplanets. These are between half and two times larger than the Earth within the habitable zones of their host stars. </p>
<p>Despite the relatively large number of small exoplanet discoveries to date, the majority of stars are between 600 to 3,000 light-years away from Earth – too far and dim for detailed follow-up observation. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/QU0qsIGS6MQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">TESS has discovered its first Earth-size planet in its star’s habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface.</span></figcaption>
</figure>
<h2>Why is liquid water important for habitability?</h2>
<p>Unlike Kepler, TESS’ mission is to search for planets around the Sun’s nearest neighbors: those bright enough for follow-up observations. </p>
<p>Between April 2018 and now, TESS discovered more than 1,500 planet candidates. Most are more than twice the size of Earth with orbits of less than 10 days. Earth, of course, takes 365 days to orbit around our Sun. As a result, the planets receive significantly more heat than Earth receives from the Sun and are too hot for liquid water to exist on the surface. </p>
<p>Liquid water is essential for habitability. It provides a medium for chemicals to interact with each other. While it is possible for exotic life to exist at higher pressures, or hotter temperatures – like the extremophiles found near hydro-thermal vents or the microbes found half a mile beneath the West Antarctic ice sheet – those discoveries were possible because humans were able to directly probe those extreme environments. They would not have been detectable from space. </p>
<p>When it comes to finding life, or even habitable conditions, beyond our solar system, humans depend entirely upon remote observations. Surface liquid water may create habitable conditions that can potentially promote life. These life forms can then interact with the atmosphere above, creating remotely detectable bio-signatures that Earth-based telescopes can detect. These bio-signatures could be current Earth-like gas compositions (oxygen, ozone, methane, carbon dioxide and water vapor), or the composition of ancient Earth 2.7 billion years ago (mostly methane and carbon dioxide, and no oxygen).</p>
<p>We know one such planet where this has already happened: Earth. Therefore, astronomers’ goal is to find those planets that are about Earth-size, orbiting at those distances from the star where water could exist in liquid form on the surface. These planets will be our primary targets to hunt for habitable worlds and signatures of life outside our solar system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308701/original/file-20200106-123381-1lx7dio.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The three planets of the TOI 700 system orbit a small, cool M dwarf star. TOI 700 d is the first Earth-size habitable-zone world discovered by TESS.</span>
<span class="attribution"><span class="source">NASA's Goddard Space Flight Center</span></span>
</figcaption>
</figure>
<h2>Possible climates for planet TOI-700 d</h2>
<p>To prove that TOI-700 d is real, Gilbert’s team needed to confirm using data from a different type of telescope. TESS detects planets when they cross in front of the star, causing a dip in the starlight. However, such dips could also be created by other sources, such as spurious instrumental noise or binary stars in the background eclipsing each other, creating false positive signals. Independent observations came from <a href="https://exoplanets.cfa.harvard.edu/people/joseph-rodriguez">Joey Rodriguez</a> at Center for Astrophysics at Harvard University. Rodriguez and his team <a href="https://arxiv.org/abs/2001.00954">confirmed the TESS detection of TOI-700 d</a> with the <a href="http://www.spitzer.caltech.edu/">Spitzer telescope</a>, and removed any remaining doubt that it is a genuine planet.</p>
<p>My student <a href="https://science.gsfc.nasa.gov/sed/bio/gabrielle.engelmann-suissa">Gabrielle Engelmann-Suissa</a> and I used our modeling software to figure out what type of <a href="https://arxiv.org/abs/2001.00955">climate might exist on planet TOI-700 d</a>. Because we do not yet know what kind of gases this planet may actually have in its atmosphere, we use our climate models to explore possible gas combinations that would support liquid oceans on its surface. Engelmann-Suissa, with the help of my longtime collaborator <a href="https://www.researchgate.net/profile/Eric_Wolf3">Eric Wolf</a>, tested various scenarios including the current Earth atmosphere (77% nitrogen, 21% oxygen, remaining methane and carbon dioxide), the composition of Earth’s atmosphere 2.7 billion years ago (mostly methane and carbon dioxide) and even a Martian atmosphere (a lot of carbon dioxide) as it possibly existed 3.5 billion years ago. </p>
<p>Based on our models, we found that if the atmosphere of planet TOI-700 d contains a combination of methane or carbon dioxide or water vapor, the planet could be habitable. Now our team needs to confirm these hypotheses with the James Webb Space Telescope. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=202&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=202&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=202&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=254&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=254&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308466/original/file-20200103-11914-1nt7jrs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=254&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bacteria living in harsh conditions like this geothermal basin in Yellowstone National Park provide clues about habitable zones on other planets.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/scenic-view-colorful-geothermal-basin-yellowstone-174313916">1tomm/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Strange new worlds and their climates</h2>
<p>The climate simulations our NASA team has completed suggest that an Earth-like atmosphere and gas pressure isn’t adequate to support liquid water on its surface. If we put the same quantity of greenhouse gases as we have on Earth on TOI-700 d, the surface temperature on this planet would still be below freezing. </p>
<p>Our own atmosphere supports a liquid ocean on Earth now because our star is quite big and brighter than TOI-700. One thing is for sure: All of our teams’ modeling indicates that the climates of planets around small and dim stars like TOI-700 are very unlike what we see on our Earth. </p>
<p>The field of exoplanets is now in a transitional era from discovering them to characterizing their atmospheres. In the history of astronomy, new techniques enable new observations of the universe including surprises like the discovery of hot-Jupiters and mini-Neptunes, which have no equivalent in our solar system. The stage is now set to observe the atmospheres of these planets to see which ones have conditions that support life. </p>
<p>[ <em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>. ]</p><img src="https://counter.theconversation.com/content/129290/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ravi kumar Kopparapu receives funding from NASA.</span></em></p>
NASA scientists have discovered a new planet orbiting around a nearby star that is in a habitable zone. But does this planet have liquid oceans that can support life?
Ravi Kumar Kopparapu, Research Scientist of Planetary Studies, NASA
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/127289
2019-11-20T21:48:36Z
2019-11-20T21:48:36Z
Curious Kids: What would aliens be like?
<figure><img src="https://images.theconversation.com/files/302759/original/file-20191120-467-p344md.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could an alien world look like this?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/otherworldly-plant-life-growing-on-alien-125289035">Shutterstock</a></span></figcaption></figure><p><strong>Why do we always think that aliens would need similar life resources as we need on Earth for humans? The term “alien” means it’s unknown to us. Shouldn’t we change our thoughts about aliens? They might not need conditions like Earth – Arushi, 11, Houston</strong></p>
<p>We don’t know whether there are any aliens or not. But there are so many planets in the universe – some say more planets than <a href="https://www.bbc.co.uk/programmes/w3cswk2g">all the grains of sand on Earth</a> – that many scientists think it’s <a href="https://www.seti.org/">worth looking</a>.</p>
<p>To help narrow our search, we often try to figure out <a href="https://theconversation.com/what-evolutionary-theory-can-teach-us-about-the-appearance-of-aliens-86719">what aliens might be like</a>, and therefore what conditions they might require. For example, if we think aliens will be made mostly of carbon, like us, then we should look for planets that have carbon. If we think they will depend on liquid water, we should look for planets with liquid water, <a href="https://www.nationalgeographic.com/science/2019/09/first-water-found-in-habitable-exoplanets-atmosphere-hubble-kepler-k2-18b/">some of which we have found</a>.</p>
<p>The problem is that figuring out what aliens will be like isn’t so easy. We have only one example of life – life on Earth – to learn from. To see why this is challenging, imagine we wanted to learn about butterflies.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=334&fit=crop&dpr=1 600w, https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=334&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=334&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/302758/original/file-20191120-479-13xy58q.png?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">What alien life might look like.</span>
<span class="attribution"><span class="source">©Helen Cooper</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Normally, we would look at as many butterflies as possible, and figure out from all those examples what things are true of all butterflies. We might learn that butterflies can come in a range of different colours and sizes, but that <em>all</em> butterflies have, for example, two antennae and six legs. If we only looked at one butterfly, <a href="https://www.nationalgeographic.com/animals/invertebrates/m/monarch-butterfly/">say a Monarch</a>, we might wrongly predict that all butterflies were orange and black.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_-nnc6dWUJg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Similarly, with only one example of life (life on Earth), it’s hard to know which features of life are universal and which are special to Earth. Here, all life is carbon-based and needs water. Is that true for all aliens, or a special feature of life on Earth?</p>
<h2>Big guesses</h2>
<p>Sometimes scientists make <a href="https://theconversation.com/what-do-aliens-look-like-the-clue-is-in-evolution-63899">guesses</a> based on a process called “<a href="https://www.sciencedaily.com/terms/convergent_evolution.htm">convergent evolution</a>” on Earth. This is when different traits, such as eyes or limbs, evolve multiple times in separate groups of organisms.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/evolution-tells-us-we-might-be-the-only-intelligent-life-in-the-universe-124706">Evolution tells us we might be the only intelligent life in the universe</a>
</strong>
</em>
</p>
<hr>
<p>For example, eyes have evolved <a href="https://pdfs.semanticscholar.org/0777/0fe786da597c6d80658fbd3055e827a8a370.pdf">independently many times</a> on Earth, so we might think it likely that aliens have eyes. The problem is that the different species on Earth are not independent examples, because they all descended from a <a href="https://www.nature.com/articles/nature09014">single common</a> <a href="https://theconversation.com/ancestor-of-all-life-on-earth-evolved-earlier-than-we-thought-according-to-our-new-timescale-101752">ancestor</a>. All life on Earth is related (literally!). Eyes may be common on a bright planet like Earth, but not a dark planet. Or they may be common in DNA-based life, but not some other kind of life.</p>
<hr>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p><em>Hello, <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>! Have you got a question you’d like an expert to answer? Send it in to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>, along with your name, age and area where you live. We won’t be able to answer every question, but we’ll do our best.</em></p>
<hr>
<p>Another option is to use chemistry and physics. Living things require lots of energy, and lots of chemical reactions. Liquid water is a particularly good place for chemical reactions. Similarly, carbon is especially good at forming the kinds of big, long, complex molecules that help support complex life forms. These are arguments in favour of looking for carbon-based life on planets where there is liquid water.</p>
<p>On the other hand, there are other liquids that are good alternatives to water, such as liquid methane. And there are other chemicals, including silicon, that can form complicated bonds. Perhaps we should be looking for silicon life on liquid methane planets. In fact, some scientists want to <a href="https://www.nasa.gov/press-release/nasas-dragonfly-will-fly-around-titan-looking-for-origins-signs-of-life/">explore</a> <a href="https://www.reuters.com/article/us-space-titan/possibility-of-life-scientists-map-saturns-exotic-moon-titan-idUSKBN1XS2H2">Titan</a>, a moon of Saturn, which seems to be covered in oceans of liquid methane.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/9L471ct7YDo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>There is one thing, <a href="https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/darwins-aliens/89B3E0F2165EB8D63A7C5EAA7D9702D3">I would argue</a>, that we do know: aliens, like us, will be the products of evolution by natural selection. Natural selection is the process by which some individuals have more offspring than others, and so the traits that led to having more offspring become more common over time. This is a major cause of evolution, and is the reason why organisms are well-adapted.</p>
<h2>Universal natural selection</h2>
<p>What sets life apart from non-life, what distinguishes a planet with aliens from just another planet with piles of rocks and sand, is life’s complexity. Living things are made of many intricate parts which work together for a common purpose – staying alive, replicating, eating. This kind of complex adaptedness can only be achieved by one process: natural selection.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/titan-first-global-map-uncovers-secrets-of-a-potentially-habitable-moon-of-saturn-126985">Titan: first global map uncovers secrets of a potentially habitable moon of Saturn</a>
</strong>
</em>
</p>
<hr>
<p>This is probably the one thing we know for sure about aliens: they will be products of evolution by natural selection. It can be fun to think about what this means for aliens. Does the fact that they evolve through natural selection, just like us, tell us anything about what they will be like? Does it tell us anything about what kinds of conditions aliens need?</p>
<p>Like all good questions, this one led to more new questions than answers. But while you ponder those questions, remember: somewhere out there, just maybe, an alien – probably stranger looking than in our wildest imagination – might be pondering them, too.</p>
<hr>
<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>, which gives children the chance to have their questions about the world answered by experts. When sending in questions, make sure you include the asker’s first name, age and town or city. You can:</em></p>
<ul>
<li><em>email <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a></em></li>
<li><em>tweet us <a href="https://twitter.com/ConversationUK">@ConversationUK</a> with #curiouskids</em></li>
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</ul><img src="https://counter.theconversation.com/content/127289/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Samuel Levin owns shares in Melonfrost, Inc. He receives funding from the Natural Environment Research Council. </span></em></p>
Somewhere out there, just maybe, an alien – probably stranger looking than in our wildest imagination – might be pondering this very question.
Samuel Levin, PhD in Evolutionary Biology, University of Oxford
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/109401
2019-09-03T11:17:44Z
2019-09-03T11:17:44Z
Evolution doesn’t proceed in a straight line – so why draw it that way?
<figure><img src="https://images.theconversation.com/files/290294/original/file-20190830-166009-xkfpe9.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3041%2C1037&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Evolution has no final endpoint in mind.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/theory-evolution-manhuman-developmentcromagnon-neanderthaljava-man-529853602">Uncle Leo/Shutterstock.com</a></span></figcaption></figure><figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=748&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=748&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287932/original/file-20190813-9431-1n4k8u8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=748&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 high school marching band’s T-shirt places a horn-playing <em>Homo sapiens</em> at the end of the evolutionary process.</span>
<span class="attribution"><span class="source">Brian Kloppenburg, Jordan Summers, Main Street Logo</span></span>
</figcaption>
</figure>
<p>Evolution doesn’t follow a preordained, straight path. Yet images abound that suggest otherwise. From museum displays to editorial cartoons, evolution is depicted as a linear progression from primitive to advanced.</p>
<p>You’ve certainly seen the pictures of a chimpanzee gradually straightening up and progressing through various hominids all the way to a modern human being. Yes, they can be humorous. But these kinds of popular representations about evolution get it all wrong.</p>
<p><a href="https://scholar.google.com/citations?user=X33EfdQAAAAJ&hl=en&oi=ao">As</a> <a href="http://orcid.org/0000-0002-5665-4906">three</a> <a href="https://orcid.org/0000-0002-6399-2823">scholars</a> of biodiversity and biology, these images bother us because they misrepresent how the process of evolution really works – and run the risk of reinforcing the public’s misconceptions.</p>
<h2>Climbing a ladder to perfection</h2>
<p>This misunderstanding is a holdover from before 1859, the year Charles Darwin first published his scientific theory of evolution via natural selection.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=865&fit=crop&dpr=1 600w, https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=865&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=865&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1087&fit=crop&dpr=1 754w, https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1087&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/289291/original/file-20190823-170918-g8supk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1087&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 scala naturae presents a hierarchy of creation.</span>
<span class="attribution"><span class="source">Retorica Christiana, Didacus Valdes, 1579</span></span>
</figcaption>
</figure>
<p>Until then, the traditional view of how the world was organized was through a “progression in perfection.” This concept is explicit in the idea of the “great chain of being,” or “<a href="http://images.tanyabonakdargallery.com/www_tanyabonakdargallery_com/1993_TBG8596_Scala_Naturae_19930.jpg">scala naturae</a>” in Latin: All beings on earth, animate and inanimate, could be organized according to an increasing scale of perfection from, say, mushrooms at the bottom up through lobsters and rabbits, all the way to human beings at the top.</p>
<p>Originating with Plato and Aristotle, this view gets three main things wrong.</p>
<p>First, it holds that nature is organized hierarchically. It is not a random assortment of beings.</p>
<p>Secondly, it envisions two organizing criteria: things progress from simple to perfect and from primitive to modern.</p>
<p>And thirdly, it supposes there are no intermediary stages between levels in this hierarchy. Each level is a watertight compartment of similar complexity – a barnacle and a coral reef on the same rung are equally complex. No one is halfway between two steps.</p>
<p>In the 1960s a variation of the scala naturae conceived by Jesuit philosopher <a href="https://www.britannica.com/biography/Pierre-Teilhard-de-Chardin">Pierre Teilhard de Chardin</a> became popular. His idea was that, although life is somewhat branched, there is <a href="https://witnessforlife.com/2018/07/21/pierre-teilhard-de-chardins-legacy-of-eugenics-and-racism-cant-be-ignored/">direction in evolution</a>, a progression toward greater cognitive complexity and, ultimately, to identification with the divine, that is, God.</p>
<h2>Gradual changes, in every direction</h2>
<p>At least since Darwin, though, scientists’ idea of the world is organized through transitions – from inanimate molecules to life, from earlier organisms to different kinds of plants and animals, and so on. All life on Earth is the product of gradual transformations, which diversified and gave rise to the exuberance of organisms that we know today.</p>
<p>Two transitions are of particular interest to evolutionary biologists. There’s the jump from the inanimate to the animate: the origin of life. And there’s the appearance of the human species from a monkey ancestor.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=827&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=827&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=827&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1039&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1039&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288078/original/file-20190814-136199-180vfci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1039&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Book covers are just one place you might see a riff on this evolutionary march.</span>
<span class="attribution"><a class="source" href="https://www.amazon.com/Uncommon-Dissent-Evolution-Kiwi-Nationalist/dp/0987657348">Howling at the Moon Press/Amazon</a></span>
</figcaption>
</figure>
<p>The most popular way to represent the emergence of human beings is as linear and progressive. You’ve probably seen images, logos and political and social propaganda that draw on this representation.</p>
<p>But none of these representations capture the dynamics of Darwin’s theory. The <a href="http://darwin-online.org.uk/graphics/Origin_Illustrations.html">one image he included</a> in his book “On the Origin of Species” is a tree diagram, the branching of which is a metaphor for the way species originate, by splitting. The absence of an absolute time scale in the image is an acknowledgment that gradual change happens on timescales that vary from organism to organism based on the length of a generation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287933/original/file-20190813-9400-s2z8zj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Forget a hierarchy – each organism alive now is the most evolved of its kind.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/evolutionary-tree-life-showing-diversification-branching-230430481?src=gBQFtG1TJPsM75J9qiNTHQ-1-2">Zern Liew/Shutterstock.com</a></span>
</figcaption>
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<p>According to Darwin, all current organisms are equally evolved and are all still affected by natural selection. So, a starfish and a person, for example, are both at the forefront of the evolution of their particular building plans. And they happen to share a common ancestor that lived about 580 million years ago.</p>
<p>Darwin’s theory doesn’t presuppose any special direction in evolution. It assumes gradual change and diversification. And, as evolution is still operating today, all present organisms are the most evolved of their kind.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=663&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=663&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=663&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=833&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=833&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273637/original/file-20190509-183109-hj00z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=833&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Man Is But A Worm’ caricature of Darwin’s theory in the Punch almanac for 1882.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Man_is_But_a_Worm.jpg">Edward Linley Sambourne</a></span>
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<h2>An enduring misconception</h2>
<p>Having been around nearly 2,000 years, the idea of the scala naturae did not disappear during Darwin’s time. It might actually have been reinforced by something so unexpected as a cartoon. Illustrator <a href="http://victorian-era.org/edward-linley-sambourne.html">Edward Linley Sambourne’s</a> immensely popular caricature of evolution “Man Is But a Worm,” published in Punch’s Almanack for 1882, combined two concepts that were never linked in Darwin’s mind: gradualism and linearity.</p>
<p>Given centuries of religious belief in a “great chain of being,” the idea of linearity was an easy sell. The iconic version of this concept is, of course, the depiction of a supposed ape-to-human “progression.” Variations of all kinds have been made of this depiction, some with a humorous spirit, but most to ridicule the monkey-to-man theory.</p>
<p>A linear depiction of evolution may, consciously or not, confirm false preconceptions about evolution, such as intelligent design – the idea that life has an intelligent creator behind it. Historians can work to unravel how such a simple caricature could have helped distort Darwin’s theory. Meanwhile, science writers and educators face the challenge of explaining the gradual branching processes that explain the diversity of life.</p>
<p>While less pithy, it might be better for the public’s knowledge of science if these T-shirts and bumper stickers ditch the step by step images and use branching diagrams to make a more nuanced and correct point about evolution. Contrary to the Sambourne picture, evolution is better represented as a process producing continuous branching and divergence of populations of organisms.</p>
<p>[ <em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/109401/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>
If you go by editorial cartoons and T-shirts, you might have the impression that evolution proceeds as an orderly march toward a preordained finish line. But that’s not right at all.
Quentin Wheeler, Senior Fellow for Biodiversity Studies, State University of New York College of Environmental Science and Forestry
Antonio G. Valdecasas, Senior Researcher in Biodiversity at the Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas (CSIC)
Cristina Cánovas, Biologist at the Natural History Museum in Madrid, Consejo Superior de Investigaciones Científicas (CSIC)
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/110984
2019-02-18T21:40:24Z
2019-02-18T21:40:24Z
Life quickly finds a way: the surprisingly swift end to evolution’s big bang
<figure><img src="https://images.theconversation.com/files/257124/original/file-20190204-86198-hsz0ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A modern arthropod (the centipede _Cormocephalus_) crawls over its Cambrian 'flatmate' (the trilobite _Estaingia_). </span> <span class="attribution"><span class="source">Michael Lee / South Australian Museum and Flinders University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>The <a href="https://www.britannica.com/topic/Cambrian-explosion">Cambrian explosion</a> more than 500 million years ago is often considered biology’s “big bang”. </p>
<p>Virtually all the major kinds of animals evolved in life’s greatest ever burst of evolution, rapidly populating a weird and biologically sparse planet with everything from jellyfish to vertebrates, and turning it into the Earth we recognise today. </p>
<p>But our recent study, published this week in <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1819366116">PNAS</a>, shows this burst of rapid evolutionary innovation also ended surprisingly quickly.</p>
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Read more:
<a href="https://theconversation.com/new-study-confirms-what-scientists-already-know-basic-research-is-under-valued-110778">New study confirms what scientists already know: basic research is under-valued</a>
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<p>Animals took perhaps only 20 million years to fill most of the empty ecological niches (ways to make a living) on our entire planet. From then on, the pace of evolution slowed drastically, reverting to rates considered more normal and which have held sway for most of the subsequent 520 million years up to the present. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=358&fit=crop&dpr=1 600w, https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=358&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=358&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=449&fit=crop&dpr=1 754w, https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=449&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/256899/original/file-20190202-103164-1lled1c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=449&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cambrian seascape off South Australia, dominated by large (<em>Redlichia</em>) and small (<em>Estaingia</em>) trilobites.</span>
<span class="attribution"><a class="source" href="https://katrinakennyartist.com.au/">Katrina Kenny</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<p>Our work suggests that evolution can fill even huge ecological vacuums extremely rapidly.</p>
<p>This has implications given the widespread global changes currently being wrought by humans. Ecological niches are being destroyed and created <a href="https://www.knowablemagazine.org/article/sustainability/2018/has-humankind-driven-earth-new-epoch">more rapidly</a> than at any time since the <a href="https://www.britannica.com/science/K-T-extinction">mass extinction that killed the dinosaurs</a> 66 million years ago.</p>
<h2>The largest adaptive radiation of all time</h2>
<p><a href="https://www.britannica.com/science/adaptive-radiation">Adaptive radiation</a> is when a species finds itself surrounded by empty niches, and rapidly evolves into a range of different species with different lifestyles (such as herbivores or carnivores) to fill the entire vacuum. </p>
<p>As the environment becomes saturated, evolution gradually slows down to normal rates. Famous examples of adaptive radiation include marsupials in Australia and <a href="https://www.cell.com/current-biology/comments/S0960-9822(09)00722-2">anole lizards</a> in the Caribbean. </p>
<p>The biggest adaptive radiation of all is the <a href="https://burgess-shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php">Cambrian Explosion</a>. Life first appeared at least 3.5 billion years ago, but for the subsequent <a href="https://theconversation.com/life-on-earth-was-nothing-but-slime-for-a-boring-billion-years-23358">3 billion years</a> little more than microbes and simple blobs existed.</p>
<p>At (or shortly before) the start of the Cambrian Period (541 million years ago), modern animals evolved. They rapidly diversified into all the major groups (phyla) of animals we see today, such as jellyfish and corals, segmented worms (such as earthworms), molluscs (such as snails), arthropods (such as crabs), and even vertebrates (backboned animals, which eventually included ourselves).</p>
<p>The strange-yet-familiar evolutionary products of the Cambrian period are exquisitely preserved in spectacular fossil sites around the world, such as the <a href="https://burgess-shale.rom.on.ca/en/science/burgess-shale/00-overview.php">Burgess Shale</a> in Canada and <a href="https://whc.unesco.org/en/list/1388/gallery/">Chengjiang</a> in China. Australia has its own: the <a href="http://jgs.lyellcollection.org/content/173/1/1">Emu Bay Shale</a> on Kangaroo Island.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/256898/original/file-20190202-103164-11twpbw.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Trilobites (<em>Estaingia</em>) freshly excavated from Cambrian rocks (Emu Bay Shale) on Kangaroo Island.</span>
<span class="attribution"><span class="source">John Paterson, University of New England</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>There is widespread agreement that evolution must have been turbocharged during the Cambrian explosion. But we didn’t really know for sure how long this unprecedented burst of rapid innovation and adaptation lasted. </p>
<p>If sustained across most of the Cambrian Period (which stretches from 541 million to 485 million years ago), then this would suggest that animals took more than 50 million years to fill up our planet.</p>
<h2>Over in a (geological) eyeblink</h2>
<p>Our study is the most thorough and mathematically precise measurement of evolution across the Cambrian Period.</p>
<p>Evolutionary rates are usually hard to calculate, partly because of the patchy fossil record. The complicated chain of events required for a dead organism to turn to stone means most carcasses are lost to time.</p>
<p>There are certainly rare instances where an evolving population is preserved across successively younger deposits, providing irrefutable <a href="https://www.open.edu/openlearn/history-the-arts/history/history-science-technology-and-medicine/history-science/fossil-evidence-evolution">evidence of evolution-in-action</a>. More often, though, we find (say) a jaw bone in one place, followed by a limb bone on a different continent that is millions of years younger.</p>
<p>We circumvented the patchiness of the Cambrian fossil record in two ways. First, we focused on the dominant creatures of the Cambrian, the <a href="https://www.trilobites.info/">trilobites</a> (an extinct group of marine arthropods related to other jointed-legged creatures like crabs, spiders and insects).</p>
<p>Trilobites are diverse and abundant (giving us a large and dense sample of fossils to work with), and also have very complex, robustly mineralised exoskeletons or “shells” (giving us lots of anatomical traits to measure). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/256896/original/file-20190202-108334-1ptou4d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Trilobites, such as this <em>Olenellus</em>, were the most diverse and abundant animals in the Cambrian.</span>
<span class="attribution"><span class="source">Russell Bicknell, University of New England; Museum of Comparative Zoology, Harvard University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Second, we used powerful new <a href="https://theconversation.com/bayes-theorem-the-maths-tool-we-probably-use-every-day-but-what-is-it-76140">Bayesian methods</a> called <a href="https://towardsdatascience.com/a-zero-math-introduction-to-markov-chain-monte-carlo-methods-dcba889e0c50">Markov-Chain Monte Carlo</a>, which fully account for the uncertainty generated by missing data (such as gaps in the fossil record).</p>
<p>When faced with incomplete data, these methods don’t try to do the impossible and spit out a single precise answer. Rather, they cleverly infer the universe of probable answers given the fuzzy information at hand.</p>
<p>Our study reveals that evolution had subsided to the more normal rates within the early Cambrian – by at least 520 million years ago. Thus, the Cambrian explosion was over much earlier than many had suspected, indeed almost as soon as the first trilobites appeared.</p>
<p>If modern animals first evolved at the very beginning of the Cambrian, then their global adaptive radiation took a mere 20 million years.</p>
<p>While this is still substantial, it represents only 0.5% of the 3.5-billion-year history of life on Earth: a surprisingly brief interval to fill the Earth with body plans as disparate as starfish, snails, shrimps and fish. </p>
<h2>Life finds a way</h2>
<p>The rapid rise of animals suggested by our study emphasises the ability of evolution to quickly take advantage of every opportunity.</p>
<p>As the fictional mathematician Ian Malcolm put it in the first <a href="https://www.imdb.com/title/tt0107290/">Jurassic Park</a> (1993) movie, “<a href="https://www.imdb.com/title/tt0107290/quotes/qt0463040">life finds a way</a>”! </p>
<p>The Cambrian explosion represented the first time animals evolved to fill the planet. Since then, several <a href="https://theconversation.com/5-periods-of-mass-extinction-on-earth-are-we-entering-the-sixth-57575">mass extinctions</a> – such as the meteorite impact that contributed to the extinction the non-avian dinosaurs and much else – have partially cleared the decks. </p>
<p>Every time, life has rebounded rapidly.</p>
<p>Today, as humans transform and stress our planet, we are facing <a href="https://www.theguardian.com/environment/2017/jul/10/earths-sixth-mass-extinction-event-already-underway-scientists-warn">another mass extinction</a>. Evolutionary niches are being destroyed and created at a rate faster than at any time since the dinosaur age.</p>
<p>The rapidity of evolution in the past might lead to optimism that life might adapt to the worst that humans can throw at it. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-killing-off-earths-little-creatures-109719">Climate change is killing off Earth’s little creatures</a>
</strong>
</em>
</p>
<hr>
<p>But this artificially rapid global change might be too fast for many species. Furthermore, much of the rapid evolution triggered by humans is far from desirable.</p>
<p>Swallows that <a href="https://www.nature.com/news/swallows-may-be-evolving-to-dodge-traffic-1.12614">evolve wingshapes</a> to better manoeuvre through heavy traffic might be cute. But superbugs resistant to every known antibiotic, and <a href="http://www.bbc.com/earth/story/20160323-the-unique-mosquito-that-lives-in-the-london-underground">subterranean mosquitos</a> adapted to feast on London tube commuters, are less so!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=833&fit=crop&dpr=1 600w, https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=833&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=833&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1047&fit=crop&dpr=1 754w, https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1047&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/256900/original/file-20190202-75085-3i9xo8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1047&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 particularly vicious subspecies of mosquito has evolved on the London underground to bite humans.</span>
<span class="attribution"><a class="source" href="https://pixabay.com/en/insects-mosquito-culex-pipiens-820484/">francok35/pixabay</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/110984/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Lee received funding for this research from the Australian Research Council and Flinders University</span></em></p><p class="fine-print"><em><span>Greg Edgecombe receives funding from the Leverhulme Trust. </span></em></p><p class="fine-print"><em><span>John Paterson receives funding from the Australian Research Council. </span></em></p>
Modern animals took over our planet much more quickly than previously thought. This has both welcome and disturbing implications for the future of life on our rapidly changing planet
Mike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders University
Greg Edgecombe, Merit Researcher, Natural History Museum
John Paterson, Professor of Earth Sciences, University of New England
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/111759
2019-02-15T14:51:15Z
2019-02-15T14:51:15Z
How the oldest evidence of movement could change what we know about life on Earth
<figure><img src="https://images.theconversation.com/files/259265/original/file-20190215-56208-cljxpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fossilised burrows are changing what we know about the evolution of life.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>In a suspension of disbelief, the countless readers who have picked up J.R.R. Tolkien’s Lord of the Rings books have readily accepted that Ents, the <a href="https://www.youtube.com/watch?v=RB6EERl0P30">ancient treelike creatures</a> of the fictional Fangorn forest, walk, talk and even dispense wisdom for hobbits lost in the woodland they shepherd. But while our imaginations can readily accept that tree people walk around Middle Earth, it can be harder to fathom how the first creatures that lived on our own planet came into being and started moving around.</p>
<p>We know that the first life on Earth was in the form of microscopic single cell organisms, which have been <a href="https://www.pnas.org/content/115/1/53">dated back to at least 3,400 million years ago</a>. But these creatures didn’t just stay where they were and then all of a sudden start evolving into complex cells, the predecessors of plants and animals – they moved around.</p>
<p>Locomotion enables life to escape danger, reach new food sources and find mating partners. While complex animals walk around on legs and feet, swim with fins or fly with wings, these primitive prokaryotes (single cell organisms which don’t have a nucleus) had a very different, rather bizarre, style of locomotion. In addition to <a href="https://study.com/academy/lesson/what-is-amoeboid-movement.html">amoeboid movements</a> (in which cells move in a crawling motion), <a href="https://www.nature.com/articles/nrmicro1900">researchers have found</a> that prokaryotes tumble, swarm, and glide.</p>
<p>Until recently, scientists believed that the first credible and abundant traces of locomotion associated with macroscopic life only appeared relatively recently in the geological record, <a href="https://pubs.geoscienceworld.org/gsa/geology/article/38/2/123/130173/first-evidence-for-locomotion-in-the-ediacara">around 600 million years ago</a>. But now our team of international scientists <a href="https://www.pnas.org/content/early/2019/02/05/1815721116">has found evidence</a> that sets a new upper boundary to when complex eukaryotic-like locomotion first appeared on Earth. </p>
<p>As detailed in our newly published paper, what we found shows that previous
examples of mobility were not the first on the planet. In fact, we have found proof of locomotion on Earth 2.1 billion years ago – much further back than previous evidence of single cell organisms alone, let alone their movement.</p>
<h2>Moving the time frame</h2>
<p>The type of movement we found was more than just a single cell going it alone. In rocks from Gabon, West Africa, we found fossilised burrows which suggest a cluster of single eukaryotic cells came together to form a slug-like multicellular organism. Alongside these burrows, which are just a few millimetres in diameter, we also found fossilised microbial mats (communities of microbes), which we think the organism that produced the trails may have fed on.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=458&fit=crop&dpr=1 600w, https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=458&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=458&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=576&fit=crop&dpr=1 754w, https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=576&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/259270/original/file-20190215-56229-11ksx8m.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=576&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scans of the fossilised burrows found in the rocks from West Africa.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>After analysing these burrows and trails with sophisticated x-ray imaging techniques, together with biological and chemical characterisation of isotopes of sulphur, and mineralogical information captured in the trace fossils, we concluded that they were produced by an object that was moving through preformed seafloor sediments, and that this object was biological in origin. These primitive creatures probably went about their business in the same way <a href="https://www.youtube.com/watch?v=mOI-JlNcDVs">slime moulds</a> – unrelated eukaryotic organisms that live together as a mass – do today, coming together to push through the sediments of an oxygenated inland coastal sea. </p>
<p>So what does this mean for our understanding of life on Earth? Oxygen first appeared permanently in the atmosphere around 2,450 million years ago. It is <a href="https://www.nature.com/articles/nature13068">believed that</a> some time after 2,100 million years ago, for reasons that are still unclear, atmospheric oxygen content began to fall below the level needed to sustain the successful development of complex life forms. Then, around 635 million years ago, <a href="https://www.nature.com/articles/ncomms10157">oxygen began to take a reverse turn</a> and rose again in the atmosphere. Intriguingly, this second rise in atmospheric oxygen content coincides with the first widespread and unambiguous appearance of complex animals.</p>
<p>Around this time, <a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/38/2/123/130173/first-evidence-for-locomotion-in-the-ediacara?redirectedFrom=fulltext">similar locomotive traces</a> like those reported in our paper appeared in oxygenated seafloor sediments. These remained a permanent fixture and can be found in modern marine sediments, where they are linked to the movements of complex diverse eukaryotic organisms.</p>
<p>The question now is whether the trails and burrows we found from 2,100 million years ago are life’s first failed experimentation at locomotion at a complex level. If so, this may also be indicative of the fact that the decline in atmospheric oxygen content could have accounted for why it took hundreds of millions of years for complex animal life to emerge after the first rise in atmospheric oxygen content. </p>
<p>If this is true, then it may be pointing us to the fact that the appearance of sufficient oxygen in the atmosphere after 635 million years ago may have spurred and supported the large-scale emergence and radiation of complex life to ecological dominance.</p><img src="https://counter.theconversation.com/content/111759/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ernest Chi Fru receives funding from European Research Council.</span></em></p>
Newly found fossils point to a link between a rise in atmospheric oxygen and the first emergence of complex life on Earth.
Ernest Chi Fru, Senior Lecturer in Earth Sciences, Cardiff University
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/105128
2019-01-14T04:10:36Z
2019-01-14T04:10:36Z
Curious Kids: why has nobody found any life outside of Earth?
<figure><img src="https://images.theconversation.com/files/252595/original/file-20190106-32130-1ern33n.jpg?ixlib=rb-1.1.0&rect=3%2C3%2C1036%2C776&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. It is the first planet that NASA's Kepler mission has confirmed to orbit in a star's habitable zone - the region around a star where liquid water, a requirement for life on Earth, could persist. </span> <span class="attribution"><a class="source" href="https://www.nasa.gov/content/kepler-22b-closer-to-finding-an-earth">NASA/Ames/JPL-Caltech</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. Send your question to curiouskids@theconversation.edu.au. You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Why has nobody found any life outside of Earth? – Anna G, age 12, Strathfield, Sydney.</strong></p>
</blockquote>
<p>Anna, thank you for your amazing question. </p>
<p>Astronomers like us are hunting for “Earth-like” planets, but they’re not easy to find. And the conditions needed for life to exist have to be just right.</p>
<p>It’s likely that if such a planet exists, it will be outside our Solar System, and it’s very hard to study planets so far away. </p>
<p>But before we go on, it helps to remember how big the Universe is. </p>
<h2>Our place in the Universe</h2>
<p>Earth is inside our Solar System, along with the other planets (like Mars, Mercury, and Jupiter) orbiting a star we call the Sun. </p>
<p>But our Solar System is just one of many inside the huge Milky Way galaxy. And the Milky Way is just one of many, many galaxies in the Universe. Plus, we have no way of knowing exactly <a href="https://theconversation.com/curious-kids-does-space-go-on-forever-74532">how big the Universe</a> is beyond what we can directly see. </p>
<p>So while there may be life on other planets, it could be in another solar system in a different part of the Milky Way galaxy. Or in another galaxy far, far away. </p>
<p>We don’t have the technology yet to study such far away planets. But we are still trying to collect what clues we can using the technology we’ve got.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-where-are-all-the-other-galaxies-hidden-101977">Curious Kids: Where are all the other galaxies hidden?</a>
</strong>
</em>
</p>
<hr>
<h2>What makes a planet liveable? Follow the water</h2>
<p>Much of the search for life has focused on trying to find liquid water, because it is essential for all life forms here on Earth. </p>
<p>Cells are mostly made up of water. Many of the chemical reactions that occur in our metabolism can only occur in the presence of water because it is an incredibly good solvent (meaning it will happily dissolve most things you put in it).</p>
<p>And water is very common. In fact, the components that make up water (hydrogen and oxygen) are the first and third most abundant elements in the Milky Way galaxy. </p>
<p>Oxygen loves grabbing onto other elements to make different chemicals. This means that we find water almost everywhere we look, from the surface of planets in our Solar System, to the depths of interstellar space.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=508&fit=crop&dpr=1 600w, https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=508&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=508&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=639&fit=crop&dpr=1 754w, https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=639&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/246077/original/file-20181118-194500-1iilit8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=639&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fountains of water expel out from Saturn’s icy moon, Enceladus.</span>
<span class="attribution"><span class="source">NASA/JPL/Space Science Institute</span></span>
</figcaption>
</figure>
<p>But for life as we know it to exist, you would need a planet where water exists in a liquid state. Otherwise your cells would freeze or boil away.</p>
<p>Earth is in a perfect position from our Sun to support water in a liquid state. Astronomers call this ideal location from a star the “habitable” or “Goldilocks zone”. </p>
<p>Scientists last year discovered that there is <a href="https://theconversation.com/discovered-a-huge-liquid-water-lake-beneath-the-southern-pole-of-mars-100523">permanent liquid water on Mars</a>, which made a lot of people very excited. Water is also inside craters on Mercury, and there are vast water oceans on some of Jupiter’s and Saturn’s moons.</p>
<p>But we still haven’t found life on Mars, or any other planet in our Solar System.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-plants-could-grow-in-the-goldilocks-zone-of-space-76918">Curious Kids: What plants could grow in the Goldilocks zone of space?</a>
</strong>
</em>
</p>
<hr>
<h2>What about outside our Solar System?</h2>
<p>Planets outside our Solar System are called exoplanets. They orbit their own stars (as you know, our Sun is really just a big star).</p>
<p>For example, there is an exoplanet called Kepler-22b, which is in the habitable zone of another star called Kepler-22. Kepler 22b is bigger than Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/252594/original/file-20190106-32154-dfi1h2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An artist’s depiction of Kepler 22b, an exoplanet in the habitable zone of a star called Kepler 22.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/kepler/multimedia/images/kepler-22b-diagram.html">NASA/Ames/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>Fainter stars have habitable zones that are closer to them and brighter stars have their habitable zones further away. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=309&fit=crop&dpr=1 600w, https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=309&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=309&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=388&fit=crop&dpr=1 754w, https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=388&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/246084/original/file-20181118-194500-jb5140.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=388&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 star’s habitable zone (shown here between the orange and red lines) ultimately depends upon how bright and hot the star is.</span>
<span class="attribution"><span class="source">Sonny Harman</span></span>
</figcaption>
</figure>
<p>Finding a world within a star’s habitable zone where liquid water can exist would be a great start to finding life. Unfortunately, we have not perfected the technology for it yet. </p>
<p>But finding a planet with the right conditions for life isn’t enough; we need to be able to detect signatures of life itself (scientists call these “biosignatures”). For example, we can look at a planet’s atmosphere and see what gases are in it. If we found a planet with lots of oxygen, we can infer there may be life there.</p>
<p>At the moment, it is not possible to detect biosignatures on Earth-like planets around others stars.</p>
<p>Maybe, Anna, you might be one of the scientists who develops the technology that makes all this possible, and will discover the first inhabited world beyond Earth. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-started-the-big-bang-79845">Curious Kids: what started the Big Bang?</a>
</strong>
</em>
</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #curiouskids, or
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* Tell us on <a href="http://www.facebook.com/conversationEDU">Facebook</a></em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/105128/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Josh Calcino is supported by an Australian Government Research Training Program (RTP) Scholarship.</span></em></p><p class="fine-print"><em><span>Jake Clark is supported by an Australian Government Research Training Program (RTP) Scholarship.</span></em></p>
Life could exist in another solar system in a different part our galaxy. Or in another galaxy far away. We don’t have the perfect technology yet to study such far away places but we’re still trying.
Josh Calcino, PhD Candidate, The University of Queensland
Jake Clark, PhD Candidate, University of Southern Queensland
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/108184
2018-12-07T00:17:11Z
2018-12-07T00:17:11Z
Why biodiversity is key to our survival
<figure><img src="https://images.theconversation.com/files/248670/original/file-20181204-126674-kzzgdn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">file fastu</span> </figcaption></figure><p>Diversity, be it genetic, morphological, behavioural or ecological, is at the heart of many controversies. It fascinates us or worries us, depending on the context. But what is biological diversity? How useful is it, how is it generated and what are the foreseeable consequences of reducing it?</p>
<h2>The incredible diversity of life</h2>
<p>The life sciences have only recently begun to imagine the true extent of the diversity of life forms and the difficulty of quantifying it. Recent estimates of total <a href="https://en.wikipedia.org/wiki/Eukaryote">eukaryotic</a> diversity range from <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001127">1 to 5 × 10<sup>7</sup> species</a>. Although only about ten thousand species of <a href="https://en.wikipedia.org/wiki/Prokaryote">prokaryotes</a> have been described, mainly because only a small number of bacteria can be grown in the laboratory, indirect molecular approaches (without culture) based on the analysis of <a href="https://en.wikipedia.org/wiki/DNA">DNA</a> extracted from the environment suggest that <a href="https://link.springer.com/article/10.1023/A:1000665216662">there may be 10<sup>9</sup> or more</a> prokaryotic species. However, even these already astronomical figures do not reflect the real diversity of life forms.</p>
<p>First, <a href="https://en.wikipedia.org/wiki/Genotype">genotypic</a> diversity within the same prokaryote species can be incredibly high. Members of one bacterial species share parts of their genome encoding essential metabolic and informational functions (called the core genomes), but often carry unique, <a href="https://link.springer.com/protocol/10.1007/978-1-60327-853-9_21">strain-specific sequences</a> for adaptation to local environmental pressures. In the case of the bacterium Escherichia coli, the core genome represents only <a href="https://link.springer.com/article/10.1007%2Fs00248-010-9717-3">6% of the genes present in 61 sequenced strains</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=548&fit=crop&dpr=1 754w, https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=548&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/245579/original/file-20181114-194516-1eheem6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=548&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>E. coli</em> bacteria.</span>
<span class="attribution"><span class="source">Eric Erbe, digital colorisation by Christopher Pooley, USDA</span></span>
</figcaption>
</figure>
<p>Secondly, the <a href="https://en.wikipedia.org/wiki/Phenotype">phenotypic</a> diversity of living forms is greater than their genotypic diversity. Biological entities may exhibit complex life cycles with multiple states of differentiation and display <a href="https://en.wikipedia.org/wiki/Phenotypic_plasticity">phenotypic plasticity</a>. This can confer the capacity to anticipate predictable seasonal changes or react to unpredictable changes by remodelling physiological processes to compensate for the potentially negative effects of changing conditions.</p>
<p>Third, genetically and morphologically identical individuals can also express considerable <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1461-0248.2012.01846.x">behavioural diversity</a>. While behavioural variation among individuals in <a href="https://en.wikipedia.org/wiki/Eusociality">eusocial insect</a> societies (queen and various workers) has been described since antiquity, the existence of individual behavioural specialization is now well documented throughout the animal kingdom.</p>
<h2>Why such diversity?</h2>
<p>Darwin proposed that species diversity might increase the productivity of ecosystems due to the division of labour among species, suggesting that each species is unique in how it exploits its environment. It thus follows that species-rich systems can exploit resources more efficiently than species-poor systems (known as the complementarity effect).</p>
<p>Diversity is also thought to make ecosystems, species and populations more resilient to environmental stresses. A large number of species may imply a certain level of functional redundancy: the loss of one species has a smaller effect in a diverse system than in a species-poor one (known as the <a href="http://www.pnas.org/content/96/4/1463.long">insurance effect</a>). Genotypic or phenotypic diversity within one population of the same species may also improve resistance to environmental change. For example, it is well documented that <a href="https://www.frontiersin.org/articles/10.3389/fimmu.2014.00208/full">the diversity of a population can increase its resistance to epidemics</a>.</p>
<p>Diversity could also favour the emergence of complex collective behaviours, including in organisms without a nervous system, as demonstrated by the <a href="https://www.nature.com/articles/nrmicro.2016.111">cooperative division of labour</a> in certain species of bacteria. This allows groups of bacteria to assume mutually incompatible tasks and acquire new functions. In this way, multicellular <a href="https://en.wikipedia.org/wiki/Cyanobacteria">cyanobacteria</a> gain the ability to simultaneously perform photosynthesis and nitrogen fixation even though these two tasks are incompatible, as the oxygen produced during photosynthesis permanently damages the enzymes involved in nitrogen fixation.</p>
<h2>How is diversity generated?</h2>
<p>The <a href="https://en.wikipedia.org/wiki/Modern_synthesis_(20th_century)">neo-Darwinian theory</a> of evolution proposes that biological diversity is the consequence of genetic accidents (mutations and recombinations of genes, for example) that occur spontaneously and randomly, without regard for their usefulness. However, the magnitude of adaptive gains from diversity suggests that partial control of its generation may be beneficial to the survival of biological systems. In support of this <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2018.00223/full">hypothesis</a>, numerous examples of mechanisms generating individual genetic and phenotypic diversity, here called “diversity generators” (DG), have been described in systems ranging from prokaryotes to complex multicellular organisms.</p>
<p>While they may differ in their origin and components, these DGs share common functional properties. They contribute to the high unpredictability of the composition and behaviour of biological systems, promote robustness and cooperation among populations, and operate mainly by manipulating the systems that control the interaction of living entities with their environment.</p>
<p>The nature of DGs seems to depend on <a href="https://en.wikipedia.org/wiki/R/K_selection_theory">r/K reproductive strategies</a>. Organisms with short generation time and large populations (r strategy) have reactive DGs, such as <a href="https://en.wikipedia.org/wiki/Horizontal_gene_transfer">horizontal gene transfer</a> and <a href="https://en.wikipedia.org/wiki/SOS_response">SOS systems</a>. They generate diversity in response to environmental stresses and participate in the well-known <a href="http://rspb.royalsocietypublishing.org/content/281/1797/20141382.long">Red Queen</a> dynamic, where competitors must constantly evolve to survive: “Now here, you see, it takes all the running you can do to keep in the same place” (<em><a href="https://en.wikipedia.org/wiki/Through_the_Looking-Glass">Through the Looking-Glass</a></em>, Lewis Carroll, 1871).</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/y6rqugj_mVk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The emergence of complex multicellular organisms, with a long reproductive life cycle and smaller populations (K strategy), has favoured the selection of a new class of DGs such as mandatory <a href="https://en.wikipedia.org/wiki/Reproduction">sexual reproduction</a> and generation of a large <a href="https://en.wikipedia.org/wiki/Adaptive_immune_system">adaptive immune repertoire</a>, which act in anticipation of stress. Sexual reproduction, through the process of <a href="https://en.wikipedia.org/wiki/Meiosis">meiosis</a>, allows for significant mixing of alleles between the parents and thus great genetic diversity for the offspring. Likewise, the adaptive immune repertoire is randomly generated by <a href="https://en.wikipedia.org/wiki/V(D)J_recombination">recombination of the genes</a> encoding the <a href="https://en.wikipedia.org/wiki/T-cell_receptor">antigen receptors</a> within <a href="https://en.wikipedia.org/wiki/T_cell">lymphocytes</a>. </p>
<p>Its potential for diversity is such that an individual randomly expresses only a fraction, which ensures the maintenance of significant individual diversity of the immune response within populations. These DGs generate the distinct so-called <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2018.00223/full#B32">White Queen</a> dynamic in reference to the famous quote of the White Queen in Through the Looking-Glass: “Sometimes I’ve believed as many as six impossible things before breakfast.” This metaphor seems particularly appropriate because the activity of these DGs is based on random phenotypic diversification, which is rarely adaptive at the individual level and favours the population (<em>impossible things</em>), and anticipates stress (<em>before breakfast</em>).</p>
<p>The existence of DGs leads us to consider evolution as a much more dynamic process and to give a new meaning to chance. If, as Einstein said, “God does not play dice,” biological entities seem to do so frequently, which would partly explain their great adaptability and survival. The ubiquity of DGs in living organisms also confirms that diversity is essential for adapting to environmental stress and that regulated self-generation of diversity must be considered as a fundamental trait of biological systems.</p>
<h2>What consequences?</h2>
<p>It is urgent to reconsider the importance of diversity, which is more than just icing on the cake. It is both a property of living organisms and a necessary condition for their survival.</p>
<p>Education and fundamental research are both subject to an increasing number of evaluation criteria. While these controls were initially developed to optimise the outcomes, they also lead to standardisation. Yet, we should perhaps ask ourselves: is it wise to homogenise the intellectual formation of individuals and research activities, while diversity is a source of robustness, synergy and complexity in all living systems?</p>
<p>Global population growth will require sustained food production during the 21st century. However, the industrialisation of agriculture over the past 50 years has led to a dramatic fall in the diversity of agricultural products. Plants and animals have been intensively selected for strength and productivity. While this strategy led to good results over the short term, it is reasonable to doubt the ability of standardised populations to resist future climate changes that will likely lead to the emergence of new pathogens. Each particular genotype/phenotype is optimised for one given set of environmental conditions and only individual diversity can guarantee the adaptation of populations to unpredictable changes in their environment.</p>
<p>Finally, the importance of diversity in ensuring the robustness of biological systems suggests that decreasing the diversity of natural ecosystems could, in the near future, lead to their sudden disruption, which would further hamper our ability to maintain stable food production.</p><img src="https://counter.theconversation.com/content/108184/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eric Muraille has received funding from the National Fund for Scientific Research (FNRS-FRS), Belgium.</span></em></p>
There is an urgent need to reconsider the importance of diversity. It is not a simple wealth. It is both a property of the living and an essential condition for its survival.
Eric Muraille, Biologiste, Immunologiste. Maître de recherches au FNRS, Université Libre de Bruxelles (ULB)
Licensed as Creative Commons – attribution, no derivatives.
tag:theconversation.com,2011:article/103117
2018-09-28T07:58:09Z
2018-09-28T07:58:09Z
Want to be happy? Then live like a Stoic for a week
<figure><img src="https://images.theconversation.com/files/236838/original/file-20180918-158234-99irw2.jpg?ixlib=rb-1.1.0&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/cute-portrayal-range-different-emotions-1023568351?src=n3Zv9ExUpvtVUhG-hoitOQ-1-1">Shutterstock</a></span></figcaption></figure><p>What have the Romans ever done for us? Well, obviously the roads – the roads go without saying. How about guidance for how to live in the 21st century? That seems less likely, but in fact the last few years have seen a flurry of interest in the work of three Roman Stoic philosophers who offered just that. They were Seneca, tutor to the Emperor Nero; Epictetus, a former slave; and Marcus Aurelius, himself emperor. </p>
<p>Modern books drawing on their ideas and repackaged as guidance for how to live well today include <a href="https://www.goodreads.com/book/show/5617966-a-guide-to-the-good-life">A Guide to the Good Life</a> by William Irvine, <a href="https://www.goodreads.com/book/show/17841317-stoicism-and-the-art-of-happiness">Stoicism and the Art of Happiness</a> by Donald Robertson, <a href="https://www.goodreads.com/book/show/29093292-the-daily-stoic">The Daily Stoic</a> by Ryan Holiday and Stephen Hanselman, and <a href="https://www.goodreads.com/book/show/31423245-how-to-be-a-stoic">How to Be a Stoic</a> by Massimo Pigliucci. What all these books share is the conviction that people can benefit by going back and looking at the ideas of these Roman Stoics. There’s even an <a href="https://learn.modernstoicism.com/p/stoic-week">annual week</a> dedicated to Stoicism. </p>
<p>Stoicism holds that the key to a good, happy life is the cultivation of an excellent mental state, which the Stoics identified with virtue and being rational. The ideal life is one that is in harmony with Nature, of which we are all part, and an attitude of calm indifference towards external events. It began in Greece, and was founded around 300BC by Zeno, who used teach at the site of the Painted Stoa in Athens, hence the name Stoicism. The works of the early Stoics are for the most part lost, so it is the Roman Stoics who have been most influential over the centuries, and continue to be today.</p>
<h2>Control how you think</h2>
<p>So, what were the ideas? Two foundational principles can both be found in <a href="https://en.wikipedia.org/wiki/Enchiridion_of_Epictetus">the Handbook</a>, a short work <a href="http://classics.mit.edu/Epictetus/epicench.html">summarising the ideas</a> of Epictetus. The first is that some things are within our control and some are not, and that much of our unhappiness is caused by thinking that we can control things that, in fact, we can’t. </p>
<p>What can we control? Epictetus argues that we actually control very little. We don’t control what happens to us, we can’t control what the people around us say or do, and we can’t even fully control our own bodies, which get damaged and sick and ultimately die without regard for our preferences. The only thing that we really control is how we think about things, the judgements we make about things. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236844/original/file-20180918-158246-14yi0si.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">You control how you react.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/business-concept-vector-illustration-human-head-789686476?src=gdzVPU8NzNQSTIlwmNIjNQ-1-3">rudall30/Shutterstock</a></span>
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</figure>
<p>This leads us to the second foundational principle from Epictetus: it’s not things that upset us, but how we think about things. Stuff happens. We then make judgements about what happens. If we judge that something really bad has happened, then we might get upset, sad, or angry, depending on what it is. If we judge that something bad is likely to happen then we might get scared or fearful. All these emotions are the product of the judgements we make. Things in themselves are value neutral, for what might seem terrible to us might be a matter of indifference to someone else, or even welcomed by others. It’s the judgements we make that introduce value into the picture, and it’s those value judgements that generate our emotional responses. </p>
<p>The good Stoic news is that these value judgements are the one thing over which we have complete control. Things happen, none of which are inherently good or bad, and it’s within our power to decide how we value them. The paradox of Stoicism, as Epictetus formulates it, is that we have almost no control over anything, yet at the same time we have potentially complete control over our happiness.</p>
<h2>Train your mind</h2>
<p>At first glance, this might seem to understate the very real challenges that people face in their daily lives. How can just thinking differently help someone who is struggling to put food on their table, for instance? The Stoics didn’t shy away from this. They fully acknowledged that life can be hard sometimes. </p>
<p>Seneca knew this all too well: he suffered exile, multiple bereavements, and was ultimately forced to commit suicide by Nero. He also knew that it was all too easy to say “I’m not going to let these external things disturb me” but quite another to follow through and not be disturbed oneself. </p>
<p>So the Stoics developed a whole series of practical exercises designed to help train people to incorporate Stoic ideas into their daily lives. Seneca recommended taking stock at the end of each day, noting when you become irritated by something trivial, or act angrily in response to someone who perhaps didn’t deserve it, and so on. By noting his mistakes, he hoped to do better the next day. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&rect=19%2C109%2C1536%2C1156&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=523&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=523&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=523&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=657&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=657&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236492/original/file-20180915-177941-1vncsac.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=657&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Marcus Aurelius writing his Meditations.</span>
<span class="attribution"><span class="license">Author provided</span></span>
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</figure>
<p>Marcus Aurelius had another strategy, reminding himself each morning that he was probably going to encounter a lot of angry, stressed, impatient, ungrateful people during the coming day. By reflecting on this in advance, the hope was that he would be less likely to respond in kind. But he also reflected on the fact that none of these people would be like this intentionally. They were the victims of their own mistaken judgements. </p>
<p>Here we get another paradox: no one chooses to be unhappy, stressed, angry, miserable, and yet these are in fact all the product of our judgements, the one thing within our control. </p>
<h2>Accept what happens</h2>
<p>Another Stoic strategy is to remind ourselves of our relative unimportance. The world does not revolve around us. Aurelius regularly reflected in his <a href="https://en.wikipedia.org/wiki/Meditations">Meditations</a> on the vastness of the universe and the infinity of time stretching into the past and future, in order to put his own short life into wider context. </p>
<p>Our lives are but moments when placed within this cosmic perspective. Given this, why should we expect the universe to deliver whatever it is that we might happen to want? On the contrary, it would be absurd to expect it to conform to our will. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236841/original/file-20180918-158243-1ffq3gw.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">Take a cosmic perspective.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/girl-watching-space-stars-digital-illustration-258738323?src=7QDB6oPy731i-hUtsfwI2w-1-31">AstroStar/Shutterstock</a></span>
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<p>As Epictetus put it, if you expect the universe to deliver what you want, you are going to be disappointed, but if you embrace whatever the universe gives, then life will be a whole lot smoother. Again, this is easier said than done, but more and more people are taking note of this Stoic advice and working hard to incorporate it into their daily lives.</p><img src="https://counter.theconversation.com/content/103117/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Sellars is a member of Modern Stoicism, a non-profit organisation that runs Stoic Week and organises Stoicon events.</span></em></p>
What a group of ancient Roman philosophers can teach you about how to live in the 21st century.
John Sellars, Lecturer in Philosophy, Royal Holloway University of London
Licensed as Creative Commons – attribution, no derivatives.