tag:theconversation.com,2011:/au/topics/calcite-54856/articlesCalcite – The Conversation2021-01-27T03:35:53Ztag:theconversation.com,2011:article/1533812021-01-27T03:35:53Z2021-01-27T03:35:53ZAncient marvels: the first shell-crushing predators ground up their prey between their legs<p>Shell-crushing predation was already in full swing half a billion years ago, as our <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2020.2075">new research</a> published in the Proceedings of the Royal Society B reveals.</p>
<p>A hyena devouring an antelope carcass, a bonnethead shark feasting on hard-shelled crabs, a dog chewing on a bone: these are all examples of “durophagy”, which basically means “to eat hard parts”. </p>
<p>Durophagy typically involves crushing or chewing and is one of the most effective ways to consume a prey’s hard internal or external skeleton, including shells. While today this feeding style is most common among apex predators such as crocodiles, it can be seen right across the animal kingdom.</p>
<h2>An age-old appetite for destruction</h2>
<p>Durophagy extends far back in time. More than 500 million years ago, during the Cambrian period, an array of creepy and curious organisms were swimming, crawling and floating through Earth’s oceans. </p>
<p>Evidence of durophagy in the Cambrian usually comes in the form of shell injuries, and sometimes as fossilised poo containing shell fragments. But rarely in the fossil record can we identify the suspects responsible for this carnage.</p>
<p>Enter the arthropods — animals with exoskeletons and jointed legs. Modern examples include insects, spiders and crustaceans. During Cambrian times, there was one particular group of arthropod that dominated the oceans: the trilobites.</p>
<p>These now-extinct creatures had exoskeletons made entirely of “<a href="https://geology.com/minerals/calcite.shtml#">calcite</a>”, which is effectively nature’s version of having a suit of armour made out of rock. </p>
<p>Looking like enlarged woodlice, some trilobite species after the Cambrian grew to be more than 90 centimetres in length. Most would have walked along the seafloor in search of their next meal.</p>
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Read more:
<a href="https://theconversation.com/a-giant-species-of-trilobite-inhabited-australian-waters-half-a-billion-years-ago-118452">A giant species of trilobite inhabited Australian waters half a billion years ago</a>
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<h2>A cannibal with an axe to grind</h2>
<p>Lucky for us, some Cambrian trilobites are so well preserved we can study their non-calcite anatomy, including their appendages. What’s particularly interesting about these arthropods is they didn’t have jaws or other structures in the mouth to chew. </p>
<p>Instead, they used spines on their many pairs of legs to grind up or shred prey in a similar fashion to modern-day horseshoe crabs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1045&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1045&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1045&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1314&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1314&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379097/original/file-20210116-15-hzl3t8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1314&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">One of the largest known Cambrian trilobites, <em>Redlichia rex</em>, was found in South Australia. This species could reach up to 25cm in length and had large, spiny legs.</span>
<span class="attribution"><span class="source">Russell Bicknell</span></span>
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<p>But despite being aware of this spectacular anatomical detail, nobody had ever tested whether trilobite species could potentially crush, or “chew”, shells with their spiny legs. We set out to find the answer.</p>
<p>Using advanced modelling techniques, we compared the legs of two Cambrian trilobite species, <em>Olenoides serratus</em> and <em>Redlichia rex</em>, to the legs of the modern horseshoe crab (<em>Limulus polyphemus</em>), which is a known clam eater.</p>
<p>We also compared them to another Cambrian arthropod, <em><a href="https://royalsocietypublishing.org/doi/10.1098/rstb.1981.0164">Sidneyia inexpectans</a></em>, which is known to have been durophagous due to shell fragments found in its gut. </p>
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<a href="https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1203&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1203&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1203&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1512&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1512&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379096/original/file-20210116-19-4r339h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1512&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">3D leg reconstructions of the modern horseshoe crab (top), <em>Redlichia rex</em> (middle) and <em>Olenoides serratus</em> (bottom). The spines used for shredding or crushing are visible on the inner part of the appendage, in green.</span>
<span class="attribution"><span class="source">Russell Bicknell, Katrina Kenny</span></span>
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<p>Our modelling confirmed <em>Sidneyia inexpectans</em> was indeed capable of crushing shells, as indicated by its fossilised gut contents. However, it could not do this very effectively.</p>
<p>On the other hand <em>Redlichia rex</em> — Australia’s most menacing Cambrian trilobite, spanning 25cm and armed with bulky legs — was effectively built like a tank. As such, it was probably highly capable of shell-crushing destruction. </p>
<p>Separate to our modelling, <a href="https://www.tandfonline.com/doi/abs/10.1080/03115518508618965">past research</a> has suggested <em>Redlichia rex</em> also ate other trilobites, including its own kind. Thus, this species represents one of the oldest known cannibals.</p>
<h2>Long spines mean soft food only</h2>
<p>Meanwhile, trilobite species <em>Olenoides serratus</em> had a very different leg shape to <em>Redlichia rex</em>, with more elaborate spines. This presented an unexpected outcome. </p>
<p>We found <em>Olenoides serratus</em> would have been unable to crush very much at all due to its very long, and therefore less powerful, leg spines. We concluded this particular trilobite was strictly on a soft seafood diet. </p>
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<a href="https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=572&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=572&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379099/original/file-20210116-17-isejt9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=572&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Biomechanical models of examined arthropod legs. On the left is the modern horseshoe crab and on the right is <em>Sidneyia inexpectans</em> (top), <em>Redlichia rex</em> (middle) and <em>Olenoides serratus</em> (bottom). Warmer colours represent areas of higher strain.</span>
<span class="attribution"><span class="source">Russell Bicknell</span></span>
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<p>By showing which ancient arthropods were equipped for shell-crushing, our research paints a more vibrant picture of life underwater more than half a billion years ago. </p>
<p>During the dawn of animals, the emergence of this feeding style would have placed immense pressure on prey species with shells and skeletons — forcing them into an evolutionary ultimatum: become the tougher “nut to crack” or face extinction.</p>
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Read more:
<a href="https://theconversation.com/freaky-frankenprawns-ancient-deep-sea-monsters-called-radiodonts-had-incredible-vision-that-likely-drove-an-evolutionary-arms-race-146104">Freaky ‘frankenprawns’: ancient deep sea monsters called radiodonts had incredible vision that likely drove an evolutionary arms race</a>
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<img src="https://counter.theconversation.com/content/153381/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Russell Dean Christopher Bicknell receives funding from the University of New England. </span></em></p><p class="fine-print"><em><span>John Paterson receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>James D. Holmes 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>Looking a bit like enlarged woodlice, ancient trilobites crawled along the seabed and had an exoskeleton made of calcite — nature’s version of a suit of armour.Russell Dean Christopher Bicknell, Post-doctoral researcher in Palaeobiology , University of New EnglandJames D. Holmes, University of AdelaideJohn Paterson, Professor of Earth Sciences, University of New EnglandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/979982018-06-11T10:09:57Z2018-06-11T10:09:57ZThe hunt for life on Mars: new findings on rock ‘chimneys’ could hold key to success<p>The search for life on Mars has taken a step forward with the NASA Curiosity rover’s <a href="http://science.sciencemag.org/content/360/6393/1096">discovery</a> of organic matter on the bottom of what was once a lake. <a href="https://theconversation.com/rover-detects-ancient-organic-material-on-mars-and-it-could-be-trace-of-past-life-97755">It may once</a> have been part of an alien life form or it might have a non-biological origin – either way this carbon would have provided a food source for any organic living thing in the vicinity. </p>
<p>The discovery adds extra intrigue to NASA’s search for extra-terrestrial life forms themselves. When hunting remotely with one car-sized machine, the question is where best to focus your efforts. It makes sense to look for the same types of places we expect to find fossilised microorganisms on Earth. This is complicated by the fact that these fossils are measured in microns – mere millionths of a metre. </p>
<p>The Curiosity rover looks for certain sedimentary rocks deposited near water, as it did for the latest discovery. This is based on the latest geological advice about the best prospects. Yet which rocks to prioritise is still a matter of some debate – and it’s a question that is just as relevant to geologists trying to unlock the secrets of our own ancient world. The Earth’s rocks and fossils are the nearest thing we have to time machines. </p>
<p>For a century or so, geologists focused on a type of rock called a stromatolite – devoting long hours to crawling around in awkward spaces trying to find them. Stromatolites occur mainly in shallow water and are layered on a millimetre scale. Many of them are undoubtedly built by slimy microbial “biofilms”, but to cut a long story short we now appreciate there is more than one way to make a stripy rock – and they don’t all involve microbes. </p>
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<a href="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=527&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=527&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221981/original/file-20180606-137306-1vsbzhq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=527&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Stromatolite city.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/31856336@N03/6188521133">Mike Beauregard</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>More recently geologists have become more interested in other types of rocks, including the “<a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/black-smoker">black smoker</a>” tube-type deposits formed by hot hydrothermal water being squeezed out of the Earth’s crust in the deep sea. Slightly easier to examine are similar chimney-like formations found in certain alkaline lakes around the world. </p>
<h2>Mono Lake</h2>
<p>One place on Earth where these chimneys occur is Mono Lake in California, a vast and beautiful stretch of water several hundred miles north of Los Angeles on the eastern slope of the Sierra Nevada mountains. In October 2014, our team obtained permission from the California State Parks to examine and sample some of the calcium carbonate chimneys that have formed there.</p>
<p>The rocks, which are frequently between two and three metres tall, are very young in geological terms, usually only tens of thousands of years old. But since first being <a href="https://books.google.co.uk/books/about/Quaternary_History_of_Mono_Valley_Califo.html?id=AE7nAAAAMAAJ&redir_esc=y">described</a> by the famous American geologist Israel Russell in 1889 they have proven an excellent natural laboratory for groups of scientists trying to understand how these structures came about. </p>
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<span class="caption">Exploration begins.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
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<p>Before our visit, geologists were essentially divided about these chimneys. A group we might call “pure geochemists” <a href="https://www.sciencedirect.com/science/article/pii/001670379390339X">proposed</a> they were nothing to do with microbes, but produced by calcium-rich spring waters coming into contact with the alkaline lake, with its abundance of carbonate ions. </p>
<p>A smaller opposing camp <a href="http://archives.datapages.com/data/sepm/journals/v33-37/data/034/034002/0309.htm">agreed</a> it should be possible for these structures to emerge in the way that pure geochemists were suggesting. But they pointed out that, in the few recorded observations of carbonate rocks forming at the lake in the 19th and 20th centuries, some kind of biofilm did appear to have an influence. They also cited other studies that had shown that waterborne microbes called cyanobacteria did produce slimy substances that can accumulate calcium. </p>
<p>We went to Mono Lake to find out who was right. Our six-strong expedition divided into two factions: one looked for chimneys on the lake bottom using a research boat, while the other explored the famous “tufa towers” that rise up from the lake shore. </p>
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<a href="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221983/original/file-20180606-137309-1mr6wj3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Tufa towers on the shoreline.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
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<p>The boat party toiled and cursed the astonishingly salty waters of the lake, while the shore party made steady progress with the invaluable assistance of local state park ranger, Dave Marquart. Their peace was interrupted only by a phone call from the stranded boaters requesting they urgently try to find someone with a four-wheel drive capable of pulling the boat back out of the water – luckily help was at hand. </p>
<p>One of the sites the shore party visited was in Marquart’s own back garden to the north-west of the lake. The rocks there were part of a set of ancient chimneys formed along a small tectonic fault. Their features suggested they had been built by microbes, but we needed to send them to a lab to be sure. </p>
<h2>Microbial ‘threads’</h2>
<p>Using an optical microscope, we were able to see dark thread-like structures entombed in slices of the rock. As we outline in our <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gbi.12292">new study</a> published in Geobiology, these “threads” are millions of fossilised photosynthesising cyanobacteria that once surrounded waters rising from a spring on the lake floor. </p>
<p>We sent the samples to Australia for further testing to establish whether the microbes played a key role in building the chimneys. This revealed surrounding patches of carbon and nitrogen, which we took to be fossilised cyanobacterial slime. This slime traps calcium and when it breaks down it creates calcium carbonate, entombing any living and dead cells in rock. </p>
<p>We found other ways in which this microbial slime had affected the fabric of the rock: grains of quartz and aluminosilicates that were clearly sand that had got stuck there, too. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221982/original/file-20180606-137315-1fu6owr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Thread-like filaments in the Mono Lake rock.</span>
<span class="attribution"><span class="source">Alexander Brasier</span></span>
</figcaption>
</figure>
<p>In short, we found evidence that cyanobacteria formed tubular mats around rising spring water in the ancient Mono Lake – probably producing the majority of the resulting chimneys there, though there may be examples of “pure geochemistry” chimneys as well. This suggests that these rock formations do indeed represent a promising and fairly large target for exploring ancient or extra-terrestrial life. </p>
<p>They have the added advantage that the calcite rocks in question are geologically quite stable. This means the fossils could potentially be preserved for a very long time – easily hundreds of millions, quite plausibly billions of years. </p>
<p>To our knowledge no chimneys have been found on Mars yet, but they are not common on Earth and there is every chance that they have a Martian equivalent. There, and on other planets and moons, we should be looking for areas with conditions as similar as possible to where these chimneys exist on Earth – volcanic rocks where spring waters might once have risen through the bedrock into an alkaline lake. Without any question, NASA’s hunt for suitable rocks on the red planet should make finding them a high priority.</p><img src="https://counter.theconversation.com/content/97998/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Following NASA’s latest discovery of organic matter on the red planet, new findings in a salt lake in California could point to where to look for alien life.Alexander Brasier, Lecturer in Geology, University of AberdeenDavid Wacey, Australian Research Council Future Fellow, The University of Western AustraliaMike Rogerson, Senior Lecturer in Earth System Science, University of HullLicensed as Creative Commons – attribution, no derivatives.