tag:theconversation.com,2011:/africa/topics/chicxulub-asteroid-33367/articlesChicxulub asteroid – The Conversation2024-02-26T17:19:30Ztag:theconversation.com,2011:article/2243182024-02-26T17:19:30Z2024-02-26T17:19:30ZA Nasa mission that collided with an asteroid didn’t just leave a dent – it reshaped the space rock<figure><img src="https://images.theconversation.com/files/577638/original/file-20240223-18-v91s4p.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C1917%2C1080&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details/PIA25329">NASA/Johns Hopkins APL/Steve Gribben</a></span></figcaption></figure><p>A frequent idea in sci-fi and apocalyptic films is that of an asteroid
striking Earth and causing global devastation. While the probabilities of this kind of mass extinction occurring on our planet are incredibly small, they are not zero. </p>
<p>The results of Nasa’s Dart mission to the asteroid Dimorphos <a href="https://www.nature.com/articles/s41550-024-02200-3">have now been published</a>. They contain fascinating details about the composition of this asteroid and whether we can defend Earth against incoming space rocks.</p>
<p><a href="https://science.nasa.gov/mission/dart/">The Double Asteroid Redirection Test (Dart)</a> was a spacecraft mission that launched in November 2021. It was sent to an asteroid called Dimorphos and commanded to collide with it, head on, in September 2022. </p>
<p>Dimorphos posed and poses no threat to Earth in the near future. But the mission was designed to see if deflecting an asteroid away from a collision course with Earth was possible through “kinetic” means – in other words, a direct impact of a human-made object on its surface. </p>
<p>Asteroid missions are never easy. The relatively small size of these objects (compared to planets and moons) means there is no appreciable gravity to enable spacecraft to land and collect a sample. </p>
<p>Space agencies have launched a number of spacecraft to asteroids in recent times. For example, the Japanese space agency’s (Jaxa) <a href="https://www.isas.jaxa.jp/en/missions/spacecraft/current/hayabusa2.html">Hayabusa-2</a> mission reached the asteroid Ryugu in 2018, the same year Nasa’s <a href="https://theconversation.com/five-space-exploration-missions-to-look-%20out-for-in-2023-195839">Osiris-Rex</a> mission rendezvoused with the asteroid Bennu.</p>
<p>The Japanese Hayabusa missions (1 and 2) fired a small projectile at the surface as they approached it. They would then collect the debris as it flew by. </p>
<h2>High-speed collision</h2>
<p>However, the Dart mission was special in that it was not sent to deliver samples of asteroid material to labs on Earth. Instead, it was to fly at high speed into the space rock and be destroyed in the process.</p>
<p>A high-speed collision with an asteroid needs incredible precision. Dart’s target of Dimorphos was actually part of a <a href="https://science.nasa.gov/solar-system/asteroids/didymos/">double asteroid</a> system, known as a binary because the smaller object orbits the larger one. This binary contained both Didymus – the larger of the two objects – and Dimorphos, which behaves effectively as a moon.</p>
<p>The simulations of <a href="https://www.nature.com/articles/s41550-024-02200-3">what has happened to Dimorphos</a> show that while we might expect to see a very large crater on the asteroid from Dart’s impact, it is more likely that it has, in fact, changed the shape of the asteroid instead. </p>
<figure class="align-center ">
<img alt="Dimorphos." src="https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/577962/original/file-20240226-24-ninx49.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">Dimorphos, as pictured by the Dart spacecraft.</span>
<span class="attribution"><a class="source" href="https://science.nasa.gov/mission/dart/">NASA</a></span>
</figcaption>
</figure>
<h2>Ant hitting two buses</h2>
<p>The collision was of a mass of 580kg hitting an asteroid of roughly 5 billion kg. For comparison, this is equivalent to an ant hitting two buses. But the spacecraft is also travelling around 6 kilometres per second. </p>
<p>The simulation results based on observations of the asteroid Dimorphos have shown that the asteroid now orbits around its larger companion, Didymus, 33 minutes slower than before. Its orbit has gone from 11 hours, 55 minutes to 11 hours, 22 minutes. </p>
<p>The momentum change to the core of Dimorphos is also higher than one would predict from the direct impact, which may seem impossible at first. However, the asteroid is quite weakly constructed, consisting of loose rubble held together by gravity. The impact caused a lot of material to be blown off of Dimorphos. </p>
<p>This material is now travelling in the opposite direction to the impact. This acts <a href="http://www.dynamicscience.com.au/tester/solutions1/war/newton/recoilless.htm">like a recoil</a>, slowing down the asteroid.</p>
<p>Observations of all the <a href="https://www.newscientist.com/article/2340837-photo-shows-10000-km-debris-tail-caused-by-%20dart-asteroid-smash/">highly reflective material that has been shed from Dimorphos</a> allows scientists to estimate how much of it has been lost from the asteroid. Their result is roughly 20 million kilograms – equivalent to about six of the Apollo-era Saturn V rockets fully loaded with fuel. </p>
<p>Combining all the parameters together (mass, speed, angle and amount of material lost) and simulating the impact has allowed the researchers to be fairly confident about the answer. Confident not only regarding the grain size of the material coming from Dimorphos, but also that the asteroid has limited cohesion and the surface must be constantly altered, or reshaped, by minor impacts.</p>
<figure class="align-center ">
<img alt="Artist's impression of Chicxulub asteroid." src="https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/577961/original/file-20240226-24-p85pi2.jpg?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">The dinosaurs were wiped out by a 10km-wide asteroid that hit Earth 66 million years ago.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/planet-earth-big-asteroid-space-potentially-2107872635">Buradaki / Shutterstock</a></span>
</figcaption>
</figure>
<p>But what does this tell us about protecting ourselves from an asteroid impact? Significant recent impacts on Earth have included the <a href="https://blogs.nasa.gov/planetarydefense/2023/02/15/remembering-the-chelyabinsk-impact-10-years-ago-and-looking-to-the-future/">meteor</a> which broke up in the sky over the city of Chelyabinsk, Russia, in 2013, and the infamous <a href="https://earthsky.org/space/what-is-the-tunguska-explosion/">Tunguska
impact</a> over a remote part of Siberia in 1908. </p>
<p>While these were not the kinds of events that are able to cause mass extinctions – like the 10km object that wiped out the dinosaurs when it struck our planet 66 million years ago – the potential for damage and loss of life with smaller objects such as those at Chelyabinsk and Tunguska is very high.</p>
<p>The Dart mission cost US$324 million (£255 million), which is low for a space mission, and with its development phase completed, a similar mission to go and deflect an asteroid heading our way could be launched more cheaply. </p>
<p>The big variable here is how much warning we will have, because a change in orbit of 30 minutes – as was observed when Dart struck Dimorphos – will make little difference if the asteroid is already very close to Earth. However, if we can predict the object path from further out – preferably outside the Solar System – and make small changes, this could be enough to divert the path of an asteroid away from our planet.</p>
<p>We can expect to see more of these missions in the future, not only because of interest in the science surrounding asteroids, but because the ease of removing material from them means that private companies might want to step up their ideas of <a href="https://www.wired.com/story/things-are-looking-up-for-asteroid-mining/">mining these space rocks</a> for precious metals.</p><img src="https://counter.theconversation.com/content/224318/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Whittaker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The mission provided details about how to deflect an asteroid should one threaten Earth in future.Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1971852023-02-06T13:29:10Z2023-02-06T13:29:10ZHow did birds survive while dinosaurs went extinct?<figure><img src="https://images.theconversation.com/files/505982/original/file-20230123-25-t7bakx.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It wasn't flying that gave birds the advantage.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/miragaia-dinosaur-bellows-in-protest-as-royalty-free-illustration/495835013">Corey Ford/Stocktrek Images 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">
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<span class="caption"></span>
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<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>If dinosaurs died, how come there are birds? Caiden S., age 9, Wylie, Texas</strong></p>
</blockquote>
<hr>
<p>Everyone knows what a bird is – and pretty much everyone knows what a dinosaur is. But not everyone is aware that <a href="https://doi.org/10.1371/journal.pone.0039056">birds evolved from dinosaurs</a> approximately 160 million years ago. </p>
<p>In fact, birds and dinosaurs lived together for about 100 million years. Birds descended from a particular group of dinosaurs called the dromaeosaurs, or “running lizards,” which were a family of feathered theropod or “beast foot” dinosaurs that included velociraptor. </p>
<p>But when an <a href="https://doi.org/10.1126/science.1177265">asteroid struck Earth 66 million years ago</a> off the coast of what is now Mexico, <a href="https://theconversation.com/scientists-have-found-dust-from-the-asteroid-that-wiped-out-the-dinosaurs-inside-the-crater-it-left-156232">dinosaurs went extinct</a> – but some birds remained. You might wonder why. </p>
<p>By acting like detectives, scientists who specialize in bird evolution are trying to figure out why birds weren’t wiped out too. They piece together clues like fossils and other evidence about life on Earth long ago. For now, scientists have ideas about why birds survived, but no firm answers.</p>
<h2>Perks of being toothless</h2>
<p>Today’s <a href="https://www.allaboutbirds.org/news/do-birds-have-teeth/">birds have no teeth</a>. Instead they have beaks or bills, which come in many shapes and sizes for eating and drinking. But some of the <a href="http://dx.doi.org/10.1016/j.cub.2016.03.039">birds that lived in dinosaur times actually had teeth</a>. Others did not. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="In the foreground is an artist's rendering of a bird head. In the background is a fossil photo showing that bird's skull. Teeth are clearly seen in the jaws." src="https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=515&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=515&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=515&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=647&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=647&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503346/original/file-20230105-24-d58wgt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=647&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Ichthyornis dispar</em> was a primitive seabird with teeth that lived during the late Cretaceous Period – from 100 million to 66 million years ago – in North America.</span>
<span class="attribution"><span class="source">Courtesy of Michael Hanson and Bhart-Anjan S. Bhullar.</span></span>
</figcaption>
</figure>
<p>After the asteroid struck Earth long ago, all birds with teeth went extinct. But many of the toothless ones kept living. Some scientists think <a href="http://dx.doi.org/10.1016/j.cub.2016.03.039">not having teeth is what allowed these birds to survive</a>. </p>
<p>Fossils of early toothless birds show <a href="https://doi.org/10.1073/pnas.1011924108">they were able to eat more plant-based food</a> – specifically nuts, fruits and seeds. This meant they relied less on eating other animals than birds with teeth did. Some scientists think this difference in diet became a big advantage after the asteroid impact.</p>
<p>When the asteroid struck Earth, it immediately <a href="https://theconversation.com/curious-kids-what-effect-did-the-asteroid-that-wiped-out-the-dinosaurs-have-on-plants-and-trees-132386">caused massive tsunamis and earthquakes</a>. A giant pulse of heat from the impact caused enormous wildfires near where the asteroid hit. In the months that followed, huge amounts of dust filled the layer of air that surrounds Earth. It blocked the sun, making <a href="https://teachingkidsnews.com/2014/09/21/4-scientists-explain-asteroid-impact-led-dinosaur-extinction/">less light available for plants to grow</a>. </p>
<p>For animals that ate plants, there was much less food. Many went extinct, which spelled trouble for the animals that ate them. </p>
<p>Since so many animal species died – and plants were struggling to get enough sunlight – food would have been hard to find if you were a bird. But if you could peck the ground and find buried seeds or nuts to eat, that might have made all the difference in your <a href="https://doi.org/10.1073/pnas.1011924108">ability to survive as a species</a>.</p>
<h2>How science works</h2>
<p>Of course, it’s possible other factors caused toothless birds to survive while their toothy cousins perished – including luck. </p>
<p>For now, it’s a mystery with no definite answer. This is how science works. Scientists formulate ideas or hypotheses using existing knowledge and information. Then they test their ideas – either by conducting experiments or by gathering more evidence. This information either supports or disproves their ideas.</p>
<p>So the scientists who study bird evolution are ready to revise the story of how birds made it and dinosaurs didn’t as they collect more information from rocks, fossils and <a href="https://theconversation.com/is-it-possible-to-recreate-dinosaurs-from-their-dna-164060">ancient DNA</a>.</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><img src="https://counter.theconversation.com/content/197185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Lituma 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>Birds and dinosaurs lived together for millions of years, but only toothless birds survived the asteroid impact that upended life on Earth.Chris Lituma, Assistant Professor of Wildlife and Fisheries Resources, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1771182022-03-28T12:37:55Z2022-03-28T12:37:55ZHow did cockroaches survive the asteroid that led to the extinction of dinosaurs?<figure><img src="https://images.theconversation.com/files/453979/original/file-20220323-19-1ijv5iq.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5000%2C3495&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist's rendering of the Chicxulub asteroid entering Earth's atmosphere 66 million years ago, triggering events that caused a mass extermination.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/end-of-cretaceous-kt-event-illustration-royalty-free-illustration/724237133">Roger Harris/Science Photo library 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">
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<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 did cockroaches survive the asteroid that led to the extinction of dinosaurs? – Kinjal, age 11, Delhi, India</strong></p>
</blockquote>
<p>When the rock now known as the <a href="https://www.nytimes.com/2021/09/13/science/chicxulub-dinosaur-extinction.html">Chicxulub impactor</a> plummeted from outer space and slammed into the Earth 66 million years ago, cockroaches were there. The impact caused a massive earthquake, and scientists think it also <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">triggered volcanic eruptions</a> thousands of miles from the impact site. Three-quarters of plants and animals on Earth died, including all dinosaurs, <a href="https://www.birdlife.org/news/2021/12/21/its-official-birds-are-literally-dinosaurs-heres-how-we-know/">except for some species</a> that were ancestors of today’s birds.</p>
<p>How could roaches a couple of inches long survive when so many powerful animals went extinct? It turns out that they were nicely equipped to live through a meteoric catastrophe.</p>
<p>If you’ve ever seen a cockroach, you’ve probably noticed that their bodies are very flat. This is not an accident. Flatter insects can squeeze themselves into tighter places. This enables them to hide practically anywhere – and it may have helped them survive the Chicxulub impact.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/1ro6PNqkHEM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Cockroaches have flat bodies that help them squeeze through tiny spaces. They’re also strong and fast.</span></figcaption>
</figure>
<p>When the meteor struck, <a href="https://www.smithsonianmag.com/science-nature/dinosaur-killing-asteroid-impact-chicxulub-crater-timeline-destruction-180973075/">temperatures on Earth’s surface skyrocketed</a>. Many animals had nowhere to flee, but roaches could take shelter in tiny soil crevices, which provide excellent protection from heat.</p>
<p>The meteor’s impact <a href="https://www.livescience.com/dinosaur-killing-asteroid-struck-earth">triggered a cascade of effects</a>. It kicked up so much dust that the sky darkened. As the sun dimmed, temperatures plunged and conditions became wintry around the globe. With little sunlight, surviving plants struggled to grow, and many other organisms that relied on those plants went hungry. </p>
<p>Not cockroaches, though. Unlike some insects that <a href="https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/yucca_moths.shtml">prefer to eat one specific plant</a>, cockroaches are <a href="https://cockroachfacts.com/what-do-cockroaches-eat/">omnivorous scavengers</a>. This means they will eat most foods that come from animals or plants as well as cardboard, some kinds of clothing and even poop. Having appetites that aren’t picky has allowed cockroaches to survive lean times since the Chicxulub extinction and other natural disasters.</p>
<p>Another helpful trait is that cockroaches <a href="https://extension.umn.edu/insects-infest-homes/cockroaches">lay their eggs in little protective cases</a>. These egg cartons look like dried beans and are called oothecae, which means “egg cases.” Like phone cases, oothecae are hard and protect their contents from physical damage and other threats, such as flooding and drought. Some cockroaches may have waited out part of the Chicxulub catastrophe from the comfort of their oothecae. </p>
<figure class="align-right ">
<img alt="Small brown rectangular egg case on white background" src="https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453995/original/file-20220323-17-10395k5.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">Cockroach egg cases are about 0.5 inches long (10 millimeters) and contain up to 50 eggs, depending on the species.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/ootheca-of-cockroach-isolated-on-white-royalty-free-image/488873689">VitalisG/iStock via Getty Images</a></span>
</figcaption>
</figure>
<p>Modern cockroaches are little survivors that can live just about anywhere on land, from the heat of the tropics to some of the coldest parts of the globe. Scientists estimate that <a href="https://bugguide.net/node/view/342386">there over 4,000 cockroach species</a>. </p>
<p>A handful of these species like to live with humans and quickly become pests. Once cockroaches become established in a building, it’s hard to rid every little crack of these insects and their oothecae. When large numbers of roaches are present in unsanitary places, they can spread diseases. The biggest threat they pose to human health is from allergens they produce that can <a href="https://www.nytimes.com/2018/08/03/science/cockroach-diseases.html">trigger asthma attacks and allergic reactions</a> in some people.</p>
<p>Cockroach pests are hard to manage because they can <a href="https://www.nationalgeographic.com/animals/article/pesticides-are-making-german-cockroaches-stronger">resist many chemical insecticides</a> and because they have the same abilities that helped their ancestors outlive many dinosaurs. Still, cockroaches are much more than a pest to control. Researchers study cockroaches to understand <a href="https://news.umich.edu/lessons-from-cockroaches-could-inform-robotics/">how they move</a> and <a href="https://www.nytimes.com/2016/02/09/science/cockroaches-indestructible-and-instructive-to-robot-makers.html">how their bodies are designed</a> to get ideas for building better robots.</p>
<p><a href="https://www.researchgate.net/profile/Brian-Lovett">As a scientist</a>, I see all insects as beautiful, six-legged inspirations. Cockroaches have already overcome odds that were too great for dinosaurs. If another meteorite hit the Earth, I’d be more worried for humans than for cockroaches.</p>
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<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>
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<p class="fine-print"><em><span>Brian Lovett 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>Cockroaches have been on Earth far longer than humans and may outlast us. Here are a few reasons why.Brian Lovett, Postdoctoral Researcher in Mycology, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1562322021-03-02T14:27:24Z2021-03-02T14:27:24ZScientists have found dust from the asteroid that wiped out the dinosaurs inside the crater it left<figure><img src="https://images.theconversation.com/files/387199/original/file-20210302-15-1mk088s.jpg?ixlib=rb-1.1.0&rect=366%2C146%2C6109%2C4589&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A large impact.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/meteor-glowing-enters-earths-atmosphere-elements-297359225">Shutterstock/Vadim Sadovski</a></span></figcaption></figure><p>More than 99% of all organisms that have ever lived on Earth are now extinct. Most of these just died out quietly. However, in Earth’s history there have been five major <a href="https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971">mass extinction</a> events – known as <a href="http://science.sciencemag.org/content/215/4539/1501.abstract">the big five</a> – during which many species became extinct at the same time.</p>
<p>Each of the big five events caused at least a 40% loss of all species on Earth. Yet humans hold a particular grudge against the most recent one, which brought a sudden end to the 160-million-year history of the dinosaurs. This was the Cretaceous-Paleogene extinction and it happened 66 million years ago, wiping out about 75% of all species on Earth at the time. Except sea turtles and crocodiles, no four-legged animals bigger than 25kg survived.</p>
<p>After decades of heated debate, scientists have settled on two leading theories about what caused this extinction. The first possibility is the <a href="https://theconversation.com/dinosaur-killing-asteroid-struck-at-worst-angle-to-cause-maximum-damage-new-research-139394">impact of an asteroid</a> which created the 180km wide Chicxulub impact crater in the modern day Yucatán Peninsula in Mexico. Second, a series of eruptions in a volcanic area known as <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">Deccan Traps</a> in India.</p>
<p>Last week, an international team of scientists with data from four independent laboratories <a href="https://advances.sciencemag.org/content/7/9/eabe3647">published a study</a> claiming to have ended the debate. They say the 12km-wide asteroid was the one to blame.</p>
<h2>A case closed?</h2>
<p>The study looked at rock samples collected in the crater, which is now under water. They found a layer of terrestrial mud mixed with “space dust” containing the element iridium, which can be found in high concentrations in meteorites but is rare in the Earth’s crust. This layer was four times thicker in the impact crater than in the surrounding area. </p>
<p>The team found a 5cm layer of sediment immediately below the limestone from the earliest Paleogene, the geologic period that began immediately after the extinction. This thin layer of sediment had iridium concentrations of one part per billion, compared to the 0.04 parts per billion in the Earth’s crust. </p>
<figure class="align-center ">
<img alt="A map showing where the Chicxulub crater is, in the Yucatán Peninsula." src="https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=560&fit=crop&dpr=1 600w, https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=560&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=560&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=703&fit=crop&dpr=1 754w, https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=703&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/387187/original/file-20210302-13-1em1hdm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=703&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The impact crater.</span>
<span class="attribution"><a class="source" href="https://www.eurekalert.org/multimedia/pub/257216.php?from=493921">The University of Texas at Austin/Jackson School of Geosciences/ Google Maps</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The asteroid is thought to have hit the planet at about 20km per second, more than 50 times faster than the speed of sound in air. Not only did it destroy the immediate surroundings, but it also sent a cloud of vaporised rock and microscopic dust with high levels of iridium that travelled across the Earth. The global blanket of cloud blocked out sunlight, cooled Earth’s surface for decades by up to 10°C, and triggered a global “impact winter”. The cold and dark regime was followed by large-scale photosynthesis shutdown, disrupted food webs worldwide and the collapse of ecosystems.</p>
<p>Spikes of iridium in dust from this time have been found in <a href="http://science.sciencemag.org/content/327/5970/1214.abstract">over 100 places</a> around the world from America, Asia, Europe, Oceania, all the way to Antarctica. These were first identified in <a href="http://science.sciencemag.org/content/208/4448/1095.abstract">findings from the 1980s</a>. </p>
<p>The early studies did not win a global consensus because the evidence couldn’t link the high iridium concentrations to the Chicxulub crater. But this new study provides this crucial link, and places an important time constraint too. The dust must have deposited within just a few decades – less than 20 years – after the impact. </p>
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<strong>
Read more:
<a href="https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971">Five mass extinctions – and what we can learn from them about the planet today</a>
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<h2>The Armageddon of dinosaurs</h2>
<p>Although the sudden nature of this extinction is backed up by changes in the fossil record, the record of microscopic organisms points towards a long-term shift instead. This is the argument in favour of a volcanic extinction, with a series of eruptions happening over tens of thousands of years.</p>
<p>Massive and prolonged volcanic eruptions have been linked to other volcanism-extinction events – like the Siberian Traps eruptions, which marked the extinction at the <a href="https://doi.org/10.1038/s41467-017-00083-9">end of the Permian</a> period. In the case of the dinosaur extinction event, however, it could not have been caused by volcanism alone. </p>
<figure class="align-center ">
<img alt="A drawing of a T-rex looking at a small flying dinosaur in a forest." src="https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&rect=40%2C54%2C1816%2C1195&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/387186/original/file-20210302-17-69grd3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">All non-avian dinosaurs were wiped out 66 million years ago.</span>
<span class="attribution"><a class="source" href="https://media.eurekalert.org/multimedia_prod/pub/media/257217.jpg">Willgard Krause/ Pixabay</a>, <span class="license">Author provided</span></span>
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<p>The Deccan Traps released more than ten million cubic kilometres of material and gases, which caused a long term global warming of between 2 and 4°C, <a href="https://pubs.geoscienceworld.org/gsa/geology/article/46/2/147/525172/A-new-high-resolution-chronology-for-the-late">150 to 300 thousand years before the extinction</a>, just before the asteroid blow. </p>
<p>The Deccan Traps eruption lasted several million years, starting long before the asteroid impact. In fact, the main phase of Deccan Traps volcanism, at around 66 million years ago, might have been <a href="http://science.sciencemag.org/content/350/6256/76.abstract">triggered by the Chicxulub</a> impact. </p>
<p>The increase of nutrients into the oceans led to <a href="https://doi.org/10.1016/j.lithos.2004.09.016">planktonic blooms and low oxygen level in the oceans</a>, yet the oceans were not completely oxygen free. Deccan volcanism might have induced biotic stress but not the organisms’ total demise. </p>
<p>Dinosaurs might have their doomsday set in an unfortunate double trouble of an asteroid volcano combo, or a single giant impact. Either way, the large asteroid has played a key role. This new study has found the missing piece of evidence that links the dinosaurs’ extinction to the Chicxulub impact, and that it happened in a geological blink of an eye.</p><img src="https://counter.theconversation.com/content/156232/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Queenie Hoi Shan Chan 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>A new study found iridium, an element found in asteroids, in the rocks of the Chicxulub impact crater.Queenie Hoi Shan Chan, Lecturer in Earth Sciences, Royal Holloway University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1393942020-05-27T09:12:03Z2020-05-27T09:12:03ZDinosaur-killing asteroid struck at worst angle to cause maximum damage – new research<figure><img src="https://images.theconversation.com/files/337874/original/file-20200527-141303-2dqgdv.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/meteor-shower-elements-this-image-furnished-324036791">Vadim Sadovski/Shutterstock</a></span></figcaption></figure><p>Few geological events fascinate as much as the one that happened 66 million years ago. Evidence suggests a huge asteroid <a href="https://theconversation.com/dinosaurs-could-have-avoided-mass-extinction-if-the-killer-asteroid-had-landed-almost-anywhere-else-87109">hit our planet</a>, triggering a chain of events that led to a <a href="https://theconversation.com/catastrophic-failure-of-earths-global-systems-led-to-the-extinction-of-the-dinosaurs-we-may-yet-go-the-same-way-114348">mass extinction</a> in which more than 70% of species on Earth – including the dinosaurs – disappeared. </p>
<p>A <a href="https://www.nature.com/articles/s41467-020-15269-x">new study</a> narrows down the trajectory of this asteroid, which could help us better understand how the impact affected the planet beneath it and how material was dispersed in its aftermath. The research suggests that the angle of impact of this asteroid may have led to the worst possible consequences for Earth’s inhabitants.</p>
<p>The asteroid is long gone – pulverised when it hit Earth – but it left a 200km-wide crater. By looking at the geometry and structure of this crater, it is possible to test asteroid trajectories with computer simulations and see which one is more likely to leave a scar as observed in real life.</p>
<p>The crater is no longer visible, it is buried beneath hundreds of metres of sediment deposited since the impact. But various pieces of evidence pointed geoscientists to the Yucatán Peninsula in Mexico as the site of the crater’s location, and it was named after a local village, Chicxulub. Various datasets have since been collected to allow researchers to appreciate the features of this crater. </p>
<p>In 2016, I joined a joint <a href="https://www.ecord.org/expedition364/">scientific expedition</a> organised by the International Ocean Discovery Program and the International Continental Scientific Drilling Program. We spent two months at sea, drilling samples from the crater in a specific location, its peak ring.</p>
<p>Peak rings are formed during large impact events. The one in the Chicxulub crater consists of a roughly 80km-diameter inner ring of hills, effectively forming a second circle within the crater. Peak rings are more easily observed on other rocky bodies in our solar system, such as the <a href="https://www.lpi.usra.edu/features/102016/schrodinger/">Schrödinger Crater on the Moon</a>. </p>
<p>Our 2016 expedition aimed at understanding how these features form, and what happens to the target rocks during an impact. It is difficult to produce experiments that replicate the high pressures, temperatures and aftermath of asteroid impacts events. That is why researchers use computer simulations.</p>
<p>The samples recovered during the 2016 expedition helped to <a href="https://science.sciencemag.org/content/354/6314/878.abstract">refine models</a> of how the peak ring, and ultimately the Chicxulub crater, was formed. For an asteroid that arrived vertically on the surface, the model suggests the object would have been pulverised within the first minute while making a cavity roughly 30km deep. </p>
<p>During the next two minutes, the bottom of this cavity was thrust up by the resulting forces to to a height of more than 10km. Then during the following two minutes, this uplifted central part of the cavity collapsed outward, forming the peak ring. In fact, the impact was so powerful it even brought up part of the Earth’s mantle, the layer below the surface crust found more than 30km deep underground.</p>
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<p>The new study from researchers at Imperial College London, published in Nature Communications, pushes the modelling even further. By testing different asteroid sizes, speeds and angles of impact – 90° (vertical), 60°, 45° and 30° relative to Earth’s surface – it is possible to simulate which scenario would have left a crater that looks like the real one.</p>
<p>The shape and continuity of Chicxulub’s peak ring suggests that the actual asteroid had an angle of between 60° and 45°. If the peak ring was truncated somewhere (like a horse-shoe), that would suggest a shallower angle, but it does not seem to be the case. The direction of the asteroid is more challenging to estimate. </p>
<p>But by looking at the relative positions of the centres of the crater, the peak ring and the uplift of the mantle mentioned above, it is possible to estimate where the asteroid was coming from. With a vertical impact, the three centres would be expected to match, but they do not. Their offset could indicate that the asteroid was coming from the north-east.</p>
<h2>After the impact</h2>
<p>Regardless of the direction, the actual angle is pretty important to picture what happened after the impact. The estimated range of angles, and especially 60° relative to Earth’s surface, would have led to the most efficient vaporising of the rocks and projection of <a href="https://theconversation.com/did-a-burning-oil-spill-wipe-out-the-dinosaurs-62456">toxic gases and particles</a> evenly in the region and globally. </p>
<p><a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL074879">Other simulations</a> suggest that a 60° to 30° range would have released much more gas and many more projectiles than with a vertical (90°) or a shallow (15°) angle. This suggests that not only did the asteroid fall in a spot more likely to release toxic material, but it also did so very efficiently, leading to the worst-case scenario for our planet – and the dinosaurs.</p>
<p>A <a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/24/11/963/187987/Cretaceous-Tertiary-Chicxulub-impact-angle-and-its?redirectedFrom=PDF">previous study</a> suggested that a shallower angle and a different direction would have meant the effect of the impact was more severe in the northern hemisphere. Under the new model with a steeper angle, the ejected material would have been spread more evenly. This might allow researchers in the future to revise the wider record of the impact to better reconstruct the events that happened in its aftermath.</p><img src="https://counter.theconversation.com/content/139394/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Erwan Le Ber affiliated with the International Ocean Discovery Program.</span></em></p>The trajectory of the Chicxulub asteroid led to the most efficient release of gas and projectile rocks – which was disastrous for life on Earth.Erwan Le Ber, Research Associate, International Ocean Discovery Program, University of LeicesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308692020-04-02T21:35:38Z2020-04-02T21:35:38ZWhile we fixate on coronavirus, Earth is hurtling towards a catastrophe worse than the dinosaur extinction<figure><img src="https://images.theconversation.com/files/324623/original/file-20200401-23086-1fgcm8t.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1914%2C1195&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Pixabay </span></span></figcaption></figure><p>At several points in the history of our planet, increasing amounts of carbon dioxide in the atmosphere have caused extreme global warming, prompting <a href="https://www.sciencedaily.com/releases/2019/07/190708154057.htm">the majority of species</a> on Earth to die out.</p>
<p>In the past, these events were triggered by a huge <a href="https://www.scientificamerican.com/article/volcanoes-may-have-triggered-the-last-unexplained-mass-extinction/">volcanic eruption</a> or asteroid impact. Now, Earth is heading for another mass extinction – and human activity is to blame.</p>
<p>I am an Earth and Paleo-climate scientist and <a href="https://link.springer.com/search?dc.creator=%22Andrew%20Y.+Glikson%22">have researched</a> the relationships between asteroid impacts, volcanism, climate changes and mass extinctions of species.</p>
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Read more:
<a href="https://theconversation.com/heres-what-the-coronavirus-pandemic-can-teach-us-about-tackling-climate-change-134399">Here's what the coronavirus pandemic can teach us about tackling climate change</a>
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<p>My research suggests the current growth rate of carbon dioxide emissions is faster than those which triggered two previous mass extinctions, including the event that wiped out the dinosaurs. </p>
<p>The world’s gaze may be focused on COVID-19 right now. But the risks to nature from human-made global warming – and the imperative to act – remain clear.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The current rate of CO2 emissions is a major event in the recorded history of Earth.</span>
<span class="attribution"><span class="source">EPA</span></span>
</figcaption>
</figure>
<h2>Past mass extinctions</h2>
<p>Many species can adapt to slow, or even moderate, environmental changes. But Earth’s history shows that extreme shifts in the climate can cause many species to <a href="https://www.abc.net.au/news/2019-11-13/what-is-a-mass-extinction-are-we-in-one-now/11699372">become extinct</a>. </p>
<p>For example, about 66 million years ago an asteroid hit Earth. The subsequent smashed rocks and widespread fires released massive amounts of carbon dioxide over <a href="https://www.pnas.org/content/99/12/7836">about 10,000 years</a>. Global temperatures soared, sea levels rose and oceans became acidic. About <a href="https://www.britannica.com/science/K-T-extinction">80% of species</a>, including the dinosaurs, were wiped out.</p>
<p>And about 55 million years ago, global temperatures spiked again, over <a href="https://www.nature.com/articles/ngeo578;%20https://www.nature.com/articles/ngeo1179;https://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709">100,000 years or so</a>. The cause of this event, known as the <a href="https://www.britannica.com/science/Paleocene-Eocene-Thermal-Maximum">Paleocene-Eocene Thermal Maximum</a>, is not entirely clear. One theory, known as the <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010RG000326">“methane burp” hypothesis</a>, posits that a massive volcanic eruption triggered the sudden release of methane from ocean sediments, making oceans more acidic and killing off many species. </p>
<p>So is life on Earth now headed for the same fate?</p>
<h2>Comparing greenhouse gas levels</h2>
<p>Before industrial times began at the end of the 18th century, carbon dioxide in the atmosphere sat at around <a href="https://data.giss.nasa.gov/modelforce/ghgases/">300 parts per million</a>. This means that for every one million molecules of gas in the atmosphere, 300 were carbon dioxide.</p>
<p>In February this year, atmospheric carbon dioxide reached <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">414.1 parts per million</a>. Total greenhouse gas level – carbon dioxide, methane and nitrous oxide combined – reached almost <a href="https://www.esrl.noaa.gov/gmd/aggi/">500 parts per million of carbon dioxide-equivalent</a></p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Author provided/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Carbon dioxide is now pouring into the atmosphere at a rate of <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">two to three parts per million each year</a>. </p>
<p>Using carbon records stored in fossils and organic matter, I have determined that current carbon emissions constitute an extreme event in the recorded history of Earth.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13342">My research</a> has demonstrated that annual carbon dioxide emissions are now faster than after both the asteroid impact that eradicated the dinosaurs (about 0.18 parts per million CO2 per year), and the thermal maximum 55 million years ago (about 0.11 parts per million CO2 per year).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An asteroid wiped out the dinosaurs 66 million years ago.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The next mass extinction has begun</h2>
<p>Current atmospheric concentrations of carbon dioxide are not yet at the levels seen 55 million and 65 million years ago. But the massive influx of carbon dioxide means the climate is changing faster than many plant and animal species <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13342">can adapt</a>.</p>
<p><a href="https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/">A major United Nations report</a> released last year warned around one million animal and plant species were threatened with extinction. Climate change was listed as one of five key drivers. </p>
<p>The report said the distributions of 47% of land-based flightless mammals, and almost 25% of threatened birds, may already have been negatively affected by climate change.</p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-effect-did-the-asteroid-that-wiped-out-the-dinosaurs-have-on-plants-and-trees-132386">Curious Kids: What effect did the asteroid that wiped out the dinosaurs have on plants and trees?</a>
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<p>Many researchers fear the climate system is approaching a <a href="https://www.pnas.org/content/115/33/8252">tipping point</a> - a threshold beyond which rapid and irreversible changes will occur. This will create a cascade of <a href="https://sites.hks.harvard.edu/sed/docs/hjs_esa_environment_0510.pdf">devastating effects</a>.</p>
<p>There are already signs tipping points have been reached. For example, <a href="https://www.theguardian.com/environment/2018/feb/27/arctic-warming-scientists-alarmed-by-crazy-temperature-rises">rising Arctic temperatures</a> have led to <a href="https://www.jpl.nasa.gov/news/news.php?feature=7616">major ice melt</a>, and weakened the <a href="https://www.globalresearch.ca/melting-ice-sheets-and-weakened-polar-fronts-onset-of-climate-tipping-points/5668981">Arctic jet stream</a> – a powerful band of westerly winds.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A diagram showing the weakening Arctic jet stream, and subsequent movements of warm and cold air.</span>
<span class="attribution"><span class="source">NASA</span></span>
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<p>This allows north-moving warm air to cross the polar boundary, and cold fronts emanating from the poles to <a href="https://link.springer.com/article/10.1007%2Fs10584-019-02458-x">intrude south into Siberia, Europe and Canada</a>. </p>
<p>A shift in climate zones is also causing the tropics to expand and migrate toward the poles, at a rate of about <a href="https://theconversation.com/the-worlds-tropical-zone-is-expanding-and-australia-should-be-worried-77701">56 to 111 kilometres per decade</a>. The tracks of tropical and extra-tropical cyclones are likewise shifting toward the poles. Australia is highly vulnerable to this shift.</p>
<h2>Uncharted future climate territory</h2>
<p><a href="https://www.nature.com/articles/nature16494">Research</a> released in 2016 showed just what a massive impact humans are having on the planet. It said while the Earth might naturally have entered the next ice age in about 20,000 years’ time, the heating produced by carbon dioxide would result in a period of super-tropical conditions, delaying the next ice age to about 50,000 years from now.</p>
<p>During this period, chaotic <a href="https://www.bloomsbury.com/us/storms-of-my-grandchildren-9781608195022/">high-energy stormy conditions</a> would prevail over much of the Earth. <a href="https://www.springer.com/gp/book/9783319572369">My research suggests</a> humans are likely to survive best in sub-polar regions and sheltered mountain valleys, where cooler conditions would allow flora and fauna to persist. </p>
<p>Earth’s next mass extinction is avoidable – if carbon dioxide emissions are dramatically curbed and we develop and deploy technologies to <a href="http://www.ecosmagazine.com/?act=view_file&file_id=EC147p14.pdf">remove carbon dioxide from the atmosphere</a>. But on the current trajectory, human activity threatens to make large parts of the Earth <a href="https://www.goodreads.com/book/show/41552709-the-uninhabitable-earth">uninhabitable</a> - a planetary tragedy of our own making. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month</a>
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<img src="https://counter.theconversation.com/content/130869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Glikson 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 risks to nature from man-made global warming – and the imperative to act – are clear.Andrew Glikson, Earth and paleo-climate scientist, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1147532019-04-04T00:23:19Z2019-04-04T00:23:19ZA ‘seiche’ wave can outpace a tsunami, and both can be triggered by meteorites and earthquakes<figure><img src="https://images.theconversation.com/files/267244/original/file-20190403-177184-r6mkdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Waves can be generated in lakes and other bodies of water when seismic energy travels through land. </span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/_asfY_cHGNk">Leo Roomets / Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>A catastrophic event occurred on Earth 66 million years ago. A huge meteorite struck our planet in what is now Mexico, triggering mass extinctions of the dinosaurs and most other living creatures. </p>
<p>A new paper shows the <a href="https://www.pnas.org/content/early/2019/03/27/1817407116">first recorded victims</a> of this impact were fish and other marine animals, stranded by a wave that left them high and dry in an ancient river in North Dakota, at a site called Tanis. </p>
<p>For scientists unpacking the evidence around the event, a full picture of the cataclysm has involved looking into the details of planetary surface physics during giant impacts. </p>
<p>But beyond the first layer of fascinating results – <a href="https://www.abc.net.au/news/2019-04-02/research-into-the-day-the-dinosaurs-died/10960446">little glass impact beads stuck in the gills of fish</a>, for example – one really interesting aspect of this work is around how water behaves when it’s exposed to extreme forces.</p>
<p>If you’ve never heard of a form of wave called a seiche, this is your chance to catch up. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Z7kNr354PJs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This is a seiche – a standing wave – in a swimming pool, during a large earthquake in Nepal.</span></figcaption>
</figure>
<h2>Waves of damage</h2>
<p>The Chicxulub meteorite crater in coastal Mexico is strongly associated with the mass extinction of the dinosaurs (<a href="https://www.pnas.org/content/115/23/5820">and 75% of all species</a>), 66 million years ago. </p>
<p>The first victims were right at the site. Any marine creatures close to the point of impact would have been instantly <a href="https://www.nature.com/articles/ngeo2095">vaporised</a> (sadly leaving no fossil record), along with much of the surrounding rock. </p>
<p>Around the periphery, the energy of the impact melted and ejected tonnes of molten rock, which together with condensing rock vapour, formed little glass beads (“<a href="https://www.lpi.usra.edu/science/kring/Chicxulub/discovery/">impact spherules</a>”) that can be found in a layer around the world at this time. </p>
<p>The shock wave itself pulverised the adjacent rock enough to metamorphise it, forming features like “shocked quartz” – fractured quartz indicative of enormous pressures. It carried the energy equivalent of a magnitude 11 earthquake – 1,000 times more energy than the <a href="https://www.abc.net.au/news/2014-12-24/boxing-day-tsunami-how-the-disaster-unfolded/5977568">2004 Boxing Day quake</a> which killed almost 230,000 people. </p>
<h2>Vast inland sea now gone</h2>
<p>North Dakota is more than 3,000km away from the Chicxulub crater, and was a similar distance at the time of the meteorite impact event. </p>
<p>Separating them back then, however, was a vast inland sea that covered much of midwest USA, from Texas up to the Dakotas. Feeding into that inland sea was a river system upon which the Tanis site in North Dakota was formed. This site has preserved the earliest recorded deaths of the Chicxulub impact. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=555&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=555&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=555&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=697&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=697&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=697&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Different views of the Tanis site. A: Tanis (starred) within a regional context (large map) and on a national map (inset). B: Photo and interpretive overlay of an oblique cross-section through Tanis. C: Simplified schematic depicting the general deposits at the site (not to scale). Most fish carcasses were found at point 3.</span>
<span class="attribution"><a class="source" href="https://www.pnas.org/content/early/2019/03/27/1817407116">Robert A DePalma and colleagues</a></span>
</figcaption>
</figure>
<p>The site itself is unusual. The deposition of sediments can tell us about the flow of water in the river. </p>
<p>Most ripples (or <a href="https://blogs.egu.eu/divisions/ts/2016/10/17/soft-sediment-structures-slumps-and-flames/">flame structures</a>) indicate a southerly flow of the river before and after the Tanis deposit. However, these flow indicators point the wrong way during the time the Tanis unit formed. Water was flowing upstream, fast. </p>
<p>At the site are also found the fossilised remains of species, like sharks and rays, that occupied brackish water, rather than the freshwater of the stream. These had to be brought inland from the sea by something, and left to die, smothered in sediment, on a riverbank. </p>
<h2>Stranded in Dakota</h2>
<p>The obvious candidate is an impact tsunami. Perhaps the impact of the meteorite hitting the ocean generated a huge wave that carried fish from the inland sea, and against the flow of fresh water, to leave the creatures stranded in Dakota? </p>
<p>But there are problems with this hypothesis. The tiny impact spherules that formed in Chicxulub can be found throughout the deposit (many clogging the gills of fish), and pockmarks in the sedimentary layers means rocks were still raining down. This means the surge of water occurred within around 15 minutes to two hours of the impact itself.</p>
<p>For a tsunami to travel the 3,000km from the point of impact, to the Tanis site across the inland sea, would have taken almost 18 hours. Something else killed these creatures.</p>
<p>The seismic waves from the impact would have travelled through the Earth much faster than a tsunami travelled across water – and arrived near Tanis between 6-13 minutes later. The <a href="https://www.pnas.org/content/early/2019/03/27/1817407116">authors of the Tanis study</a> suggest these seismic waves may have triggered an unusual type of wave in the inland sea, called a seiche. </p>
<h2>Standing waves</h2>
<p>Seiches are <a href="https://commons.wikimedia.org/wiki/File:Standing_wave_2.gif">standing waves</a> in bodies of water, and are often found in large lake systems <a href="https://www.youtube.com/watch?v=SwLGX21Jflo">during strong winds</a>. The winds themselves cause waves and water displacement, which can have a harmonic effect, causing the water to slosh side to side like an <a href="https://www.youtube.com/watch?v=bYI1zIjJr4g">overfull bathtub</a>. </p>
<p>However, earthquakes are also known to cause seiches. Particularly dramatic seiches are often seen in <a href="https://www.youtube.com/watch?v=Z7kNr354PJs">swimming pools during large quakes</a>. The interaction of the seismic wave’s period (the time between two waves) with the timescale of waves sloshing in a pool can amplify their effect. </p>
<p>But seiches can affect larger bodies of water too. </p>
<p>During the 2011 Tohuku earthquake in Japan, seiches <a href="https://www.youtube.com/watch?v=uYJjMqYdmmo">over 1m high</a> were observed in Norwegian fjords more than 8,000km away. With an energy more than 1,000 times greater, the Chicxulub event could quite conceivably have generated bigger than 10 metre swells in the North American inland sea – the scale implied by the deposition of the Tanis site. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/uYJjMqYdmmo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">These waves in Norwegian fjords were created by seismic waves from the 2011 Tohoku earthquake in Japan.</span></figcaption>
</figure>
<p>Given a seiche can be driven by seismic waves, it’s conceivable that one drove the surge that stranded marine creatures at Tanis, resulting in the short time between the impact debris and the surge deposit. </p>
<h2>Still lots of questions</h2>
<p>But a lot remains unclear regarding exactly what did happen 66 million years ago. </p>
<p>Could the fish stranding have been driven by the first seismic activity to appear at Tanis (the <a href="https://www.sciencedirect.com/science/article/pii/S0264370716301089">P and S waves</a> in science parlance, which travel through the interior of the Earth, arriving at Tanis 6 and 10 minutes after impact, respectively), or the more destructive but slower surface waves at the top of the Earth’s crust, which arrived 13 minutes after impact? </p>
<p>How might seiche waves have interacted with <a href="https://www.lpi.usra.edu/meetings/lpsc2005/pdf/1544.pdf">global hurricane-strength wind storms</a> caused by the impact? </p>
<p>Would the period of sloshing of a seiche be consistent with the scale of the inland sea? (The inland sea was much larger than most lakes seiches are traditionally observed in – and may or may not have been open to the ocean). Given so little is really known about the dimensions of the inland sea, this is hard to constrain. </p>
<p>The Tanis site has given us an incredible window into the first few hours of a mass-extinction. But it has also highlighted how little we have probed into the fatal surface physics of these extreme events.</p><img src="https://counter.theconversation.com/content/114753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig O'Neill has received past funding from the ARC. </span></em></p>If you’ve never heard of a form of wave called a ‘seiche’ – which can occur in swimming pools during earthquakes – this is your chance to catch up.Craig O'Neill, Director of the Macquarie Planetary Research Centre/Associate Professor in Geodynamics, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1121342019-02-21T19:06:05Z2019-02-21T19:06:05ZHow the dinosaurs went extinct: asteroid collision triggered potentially deadly volcanic eruptions<figure><img src="https://images.theconversation.com/files/260092/original/file-20190221-148542-149z4bm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of an asteroid about to hit Earth: it's what happens next that could have helped wipe out the dinosaurs 66 million years ago.</span> <span class="attribution"><span class="source">Shutterstock/Mopic</span></span></figcaption></figure><p>It’s almost 40 years since scientists discovered what wiped out the dinosaurs: an asteroid hitting Earth near modern-day Mexico. That was it, or so we thought.</p>
<p>A paper published today in <a href="http://science.sciencemag.org/content/363/6429/866" title="The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary">Science</a> further supports an alternative hypothesis: that catastrophic events following the impact could have helped cause the end of the dinosaurs and many other forms of life.</p>
<p>This builds on earlier work – including some published <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">last year</a> – suggesting a connection between the asteroid impact, increased volcanic eruptions, and the mass extinction event.</p>
<h2>Sudden impact</h2>
<p>Back in 1980, the American experimental physicist <a href="https://www.britannica.com/biography/Luis-Alvarez">Luis Alvarez</a>, his geologist son <a href="http://eps.berkeley.edu/people/walter-alvarez">Walter</a> and their colleagues published an <a href="http://science.sciencemag.org/content/208/4448/1095" title="Extraterrestrial Cause for the Cretaceous-Tertiary Extinction">influential paper in the journal Science</a>.</p>
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Read more:
<a href="https://theconversation.com/life-quickly-finds-a-way-the-surprisingly-swift-end-to-evolutions-big-bang-110984">Life quickly finds a way: the surprisingly swift end to evolution's big bang</a>
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<p>In it, they outlined evidence of a global catastrophe, buried in a layer spread all over the planet, about 66 million years ago.</p>
<p>They found high levels of iridium – a rare element in Earth’s crust, but common in meteorites. They found shocked quartz – grains of quartz with telltale fractures from the blast wave of the impact, as well as evidence of molten rock thrown out from the impact blast.</p>
<p>With the later <a href="https://doi.org/10.1130/0091-7613(1991)019%3C0867:CCAPCT%3E2.3.CO;2" title="Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico">discovery of the Chicxulub impact crater</a> on the Yucatan Peninsula, Mexico, the case seemed sealed.</p>
<p>The reign of the dinosaurs ended with a meteorite impact, marking the end of the Cretaceous, and start of the Paleogene period, called the K-Pg boundary.</p>
<h2>Was there something else?</h2>
<p>Yet within the Earth science community, discontent continued to simmer.</p>
<p>Two of the largest mass extinctions in the geological record both coincide with the largest exposed continental flood basalt events in the past 542 million years. They are the <a href="https://dx.doi.org/10.1126/sciadv.1500470" title="High-precision geochronology confirms voluminous magmatism before, during, and after Earth’s most severe extinction">end of the Permian 251 million years ago</a>, and – as today’s Science paper highlights – the dinosaur extinction at the end of the Cretaceous 66 million years ago. </p>
<p>The coincidence seems too great. </p>
<p>In understanding the link between flood volcanism, meteorite impacts and extinctions, timing is everything.</p>
<p>In the new Science paper, a team from the United States and India present some of the most precise dates yet for the enormous eruptions in India, in a unit known as the Deccan Traps - an enormous flood basalt province in Western India that covers more than 500,000km<sup>2</sup> and in places is more than 2km thick.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map outlining exposed areas of the Deccan Traps in modern day India.</span>
<span class="attribution"><span class="source">Courtney Sprain</span></span>
</figcaption>
</figure>
<p>They found that the best date for the Chicxulub impact – at 66.052 million years ago – was within 50,000 years of the peak eruption period of the Deccan Traps, meaning that the impact, and the ramp-up in volcanism, were essentially simultaneous.</p>
<h2>A seismic connection</h2>
<p>A connection between an impact in the Caribbean and volcanism in the Indian Ocean may seem tenuous, but in planetary science these associations are not uncommon.</p>
<p>One dramatic example is the <a href="https://www.britannica.com/place/Caloris">Caloris Basin</a> on the planet Mercury – a 1,500km-wide structure from an earlier meteorite impact. </p>
<p>Antipodal (at the opposite side of the planet) to this is a bizarre, fractured landscape called the disrupted terrain, which formed from <a href="https://www.sciencedirect.com/science/article/pii/S0032063311002340">shock waves from the impact</a> at Caloris. </p>
<p>This forms a precedent of sorts - an impact can create geological changes at vast distances. But back on Earth 66 million years ago, Chicxulub and the Deccan Traps weren’t quite antipodal.</p>
<p>The Deccan Traps formed when that part of what is now India was roughly over present-day Reunion Island, a small French Island near Madagascar. This island is still volcanically active, and powered by the same mantle upwelling that caused the Deccan volcanism.</p>
<p>The Yucatan Peninsula, like much of the Americas, was significantly closer to Europe (see below). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=457&fit=crop&dpr=1 600w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=457&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=457&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=574&fit=crop&dpr=1 754w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=574&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=574&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">Reconstruction of Earth’s plates at 66 million years ago. The stars show the position of the Deccan Traps near India, and Chicxulub impact in Mexico.</span>
<span class="attribution"><span class="source">Image created by C O'Neill using GPlates (Gplates.org)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But that may not matter. It has long been argued, <a href="http://trn.lyellcollection.org/content/S2-5/3/601" title="On the Connexion of certain Volcanic Phenomena in South America; and on the Formation of Mountain Chains and Volcanos, as the Effect of the same Power by which Continents are elevated">since at least Charles Darwin in 1840</a>, that <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125" title="SEISMIC TRIGGERING OF ERUPTIONS IN THE FAR FIELD: Volcanoes and Geysers">earthquakes may trigger eruptions</a>. </p>
<p>The mechanisms are not well understood. Suggestions range from bubble formation in magmas, to the development of fractures in the crust <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125" title="SEISMIC TRIGGERING OF ERUPTIONS IN THE FAR FIELD: Volcanoes and Geysers">allowing magma to escape faster</a>.</p>
<p>It has been recognised, though, that despite their distance from earthquakes, some volcanoes are simply more sensitive to earthquake activity than others, particularly <a href="https://link.springer.com/article/10.1007/s00445-018-1232-2" title="Revisiting short-term earthquake triggered volcanism">very active volcanoes</a>. Few volcanic events were more active than the Deccan Traps.</p>
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<a href="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.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>
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<span class="caption">Deccan Traps lava flows in Western Ghats, India.</span>
<span class="attribution"><span class="source">Courtney Sprain</span></span>
</figcaption>
</figure>
<h2>Increased volcanic activity</h2>
<p>At the same time as the Deccan volcanic ramp-up, the global mid-ocean ridge system in the Pacific and Indian Oceans seems to have <a href="https://dx.doi.org/10.1126/sciadv.aao2994" title="Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism">experienced increased activity</a>.</p>
<p>Formed when two plates move apart, ocean ridges form the most extensive volcanic system on the planet.</p>
<p><a href="https://dx.doi.org/10.1126/sciadv.aao2994" title="Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism">Analysis of global gravity</a> has indicated anomalously thick crust at the K-Pg boundary, formed due to excess volcanic activity. This effect is only seen in the fastestspreading, and thus most volcanically active, systems in the Pacific and Indian Oceans.</p>
<p>Together, these observations suggest a global pulse of volcanic input at the time of the Cretaceous mass extinction, driven by the shock wave of the Chicxulub impact.</p>
<h2>Wipeout</h2>
<p>Exactly how this perfect storm of natural disasters – an asteroid collision and increased volcanic activity – drove the mass extinction of so much life on Earth is unclear at the moment.</p>
<p>As Science paper’s first author, Courtney Sprain, a former UC Berkeley doctoral student now at the University of Liverpool, UK, puts it:</p>
<blockquote>
<p>Either the Deccan eruptions did not play a role - which we think unlikely - or a lot of climate-modifying gases were erupted during the lowest volume pulse of the eruptions.</p>
</blockquote>
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<em>
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Read more:
<a href="https://theconversation.com/curious-kids-how-many-dinosaurs-in-total-lived-on-earth-during-all-periods-100460">Curious Kids: How many dinosaurs in total lived on Earth during all periods?</a>
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<p>Volcanism can warm the Earth, due to eruption of greenhouse gases like methane and carbon-dioxide. It can, along with impacts, also cool the atmosphere by adding <a href="https://doi.org/10.1146/annurev.ea.16.050188.000445" title="Volcanic Winters">sulfur aerosols</a> or <a href="http://science.sciencemag.org/content/219/4582/287" title="Environmental Effects of an Impact-Generated Dust Cloud: Implications for the Cretaceous-Tertiary Extinctions">dust</a>, respectively. </p>
<p>Gases can also reach the atmosphere from magma stewing below the surface, even without eruptions.</p>
<p>It’s not precisely clear how all these combined to decimate terrestrial and marine ecosystems, but an accurate timeline of events is critical to unravelling these interactions.</p><img src="https://counter.theconversation.com/content/112134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig O'Neill has received funding from the Australian Research Council.</span></em></p>More evidence that the asteroid hit on Earth that marked the end of the dinosaurs could have triggered a deadly increase in volcanic activity.Craig O'Neill, Director of the Macquarie Planetary Research Centre/Associate Professor in Geodynamics, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/979752018-06-28T11:01:48Z2018-06-28T11:01:48ZNew telescope will scan the skies for asteroids on collision course with Earth<figure><img src="https://images.theconversation.com/files/224506/original/file-20180622-26558-f8q147.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Artist depiction of an asteroid on a collision course with Earth</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/large-asteroid-closing-on-earth-95167171?src=to8AFSoMLoWFaKqU7UeLig-1-41">By Mopic/shutterstock.com</a></span></figcaption></figure><p>Around sunrise on Feb. 15, 2013, an extremely bright and otherworldly object was seen streaking through the skies over Russia before it exploded about 97,000 feet above the Earth’s surface. The resulting blast damaged thousands of buildings and injured almost 1,500 people in Chelyabinsk and the surrounding areas. While this sounds like the first scene of a science fiction movie, this invader wasn’t an alien spaceship attacking humanity, but a <a href="http://doi.org/10.1126/science.1242642">20-meter-wide asteroid that had collided with the Earth</a>. </p>
<p>What is worrisome is that no one had any idea this 20-meter asteroid existed until it entered the Earth’s atmosphere that morning.</p>
<p>As an astronomer, I study objects in the sky that change in brightness over short time scales – observations that I use to detect planets around other stars. A large part of my research is understanding how we can better design and run telescopes to monitor an ever-changing sky. That’s important because the same telescopes I’m using to explore other star systems are also being designed to help my colleagues discover objects in our own solar system, like asteroids on a collision course with with Earth.</p>
<h2>Near-Earth objects</h2>
<p>A meteor is any chunk of matter that enters the Earth’s atmosphere. Before the Chelyabinsk meteor met its demise on Earth, it was orbiting our sun as an asteroid. These rocky objects are normally thought to be restricted to the asteroid belt between Mars and Jupiter. However, there are many asteroids throughout the solar system. Some, like the Chelyabinsk meteor, are known as near-Earth objects (NEOs). </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224509/original/file-20180622-26567-1nep0we.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>
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<span class="caption">Aerial view of Arizona Meteor Crater, September 2010.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Meteor_Crater#/media/File:Meteorcrater.jpg">Shane Torgerson</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The Chelyabinsk meteor likely came from a group of NEOs called Apollo asteroids, named after the asteroid 1862 Apollo. There are more than 1,600 known Apollo asteroids logged in the <a href="https://ssd.jpl.nasa.gov/sbdb.cgi">JPL Small-Body Database</a> that have orbits that may cross the Earth’s path, and are large enough (over 140 meters), that they’re considered potentially hazardous asteroids (PHAs) because a collision with Earth would devastate the region hit. </p>
<p>The scars of these past collisions are prominent on the moon, but the Earth also bears the marks of such impacts. <a href="http://www.passc.net/EarthImpactDatabase/chicxulub.html">Chicxulub crater</a> on Mexico’s Yucatan Peninsula was created by the Chicxulub asteroid that drove the dinosaurs to extinction. The <a href="http://www.passc.net/EarthImpactDatabase/barringer.html">Barringer Crater in Arizona is just 50,000 years old</a>. The question is not if a dangerously large asteroid will collide with the Earth, but when?</p>
<h2>Searching for threats</h2>
<p>The U.S. government is taking the threat of an asteroid collision seriously. In Section 321 of the <a href="https://www.congress.gov/bill/109th-congress/senate-bill/1281/text?overview=closed">NASA Authorization Act of 2005</a>, Congress required NASA develop a program to search for NEOs. NASA was assigned the task of identifying 90 percent of all NEOs greater than 140 meters in diameter. Currently, they estimate that <a href="https://www.nasa.gov/planetarydefense/faq">three-quarters of the 25,000 PHAs have yet to be found</a>. </p>
<p>To reach this goal, an international team of of hundreds of scientists, including myself, is completing construction of the Large Synoptic Survey Telescope (LSST) in Chile, which will be an essential tool for alerting us of PHAs. </p>
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<a href="https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224507/original/file-20180622-26564-uvawfp.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">Exterior view of the Large Synoptic Survey Telescope, which is still under construction.
Sublocation Cerro Pachón, Chile.</span>
<span class="attribution"><a class="source" href="https://gallery.lsst.org/bp/#/folder/3989372/71658815">LSST Project/NSF/AURA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>With significant funding from the U.S. National Science Foundation, LSST will search for PHAs during its 10-year mission by observing the same area of sky at hourly intervals searching for objects that have changed position. Anything that moves in just one hour has to be so close that it is within our solar system. Teams led by researchers at the <a href="https://arxiv.org/pdf/1711.10621.pdf">University of Washington</a> and <a href="https://arxiv.org/pdf/1706.09398.pdf">JPL</a> have both produced simulations showing that LSST on its own will be capable of finding around 65 percent of PHAs. If we combine LSST data with other astronomical surveys like <a href="http://pswww.ifa.hawaii.edu/pswww/">Pan-STARRS</a> and the <a href="https://catalina.lpl.arizona.edu/">Catalina Sky Survey</a>, we think we can help reach that goal of discovering 90 percent of potentially hazardous asteroids.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/224508/original/file-20180622-26573-hlszro.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A photograph and a baseline design rendering mix, showing a view of the completed exterior building from the road leading up to the site.</span>
<span class="attribution"><a class="source" href="https://gallery.lsst.org/bp/#/search/51636894?q=telescope&folderId=2334407&folderName=Facility&filters=%257B%2522date_created_unix%2522%253A%257B%2522from%2522%253A%252201%252F01%252F2018%2522%252C%2522to%2522%253A%252206%252F30%252F2018%2522%257D%257D">LSST Project/NSF/AURA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<h2>Preparing to avert disaster</h2>
<p>Both the Earth and these asteroids are orbiting the sun, just on different paths. The more observations taken of a given asteroid, the more precisely its orbit can be mapped and predicted. The biggest priority, then, is finding asteroids that may collide with the Earth in the future. </p>
<p>If an asteroid is on a collision course hours or days before it occurs, the Earth won’t have many options. It’s like a car suddenly pulling out in front of you. There is little that you can do. If, however, we find these asteroids years or decades before a potential collision, then we may be able to use spacecraft to nudge the asteroid enough to change its path so that it and the Earth don’t collide.</p>
<p>This is, however, easier said than done, and currently, no one really knows how well an asteroid can be redirected. There have been several proposals for <a href="https://www.nasa.gov/planetarydefense/dart">missions by NASA</a> and the <a href="https://www.esa.int/Our_Activities/Space_Engineering_Technology/Hera/Asteroid_Impact_Mission2">European Space Agency to do this</a>, but so far, they have not passed early stages of mission development. </p>
<p>The <a href="http://www.b612foundation.org/">B612 Foundation</a>, a private nonprofit group, is also trying to privately raise money for a mission to redirect an asteroid, and they may be the first to attempt this if the government space programs don’t. Pushing an asteroid sounds like an odd thing to do, but when we one day find an asteroid on a collision course with Earth, it may well be that knowledge that will save humanity.</p><img src="https://counter.theconversation.com/content/97975/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael B. Lund is affiliated with one of the science collaborations for the Large Synoptic Survey Telescope.</span></em></p>An asteroid on a collision course with Earth is inevitable. Astronomer Michael Lund explains how a new telescope under construction in Chile will become a vital tool for detecting objects that could devastate our planet.Michael B. Lund, Post-doctoral researcher, Department of Physics & Astronomy, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/910532018-02-07T19:00:46Z2018-02-07T19:00:46ZMore bad news for dinosaurs: Chicxulub meteorite impact triggered global volcanic eruptions on the ocean floor<figure><img src="https://images.theconversation.com/files/205347/original/file-20180207-74479-1ragczb.jpg?ixlib=rb-1.1.0&rect=229%2C0%2C4290%2C3149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Seismic shockwaves after a meteorite’s collision could affect systems all over the planet.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/large-meteor-burning-glowing-hits-earths-488993764">solarseven/Shutterstock.com</a></span></figcaption></figure><p>The end of the Cretaceous period 66 million years ago was a rough time to be living on Earth.</p>
<p>Three global catastrophes occurred nearly simultaneously: The <a href="https://doi.org/10.1126/science.208.4448.1095">Chicxulub meteorite slammed</a> into what is now Mexico’s Yucatan Peninsula, the massive <a href="https://doi.org/10.1038/333843a0">Deccan Traps volcanic province in modern-day India erupted</a>, and some three-quarters of Earth’s plants and animals, including all non-avian dinosaurs, went extinct. The occurrence of these three events at the same time in our planet’s history has fueled a decades-long <a href="https://doi.org/10.1016/S1631-0713(03)00006-3">debate about causal links</a>. Either a large sequence of volcanic eruptions or an extraterrestrial impact could conceivably cause a mass extinction – but were they all somehow connected?</p>
<p>As Earth scientists, we have reason to believe that there may be another event to add to the list. <a href="http://advances.sciencemag.org/content/4/2/eaao2994">Our new research</a>, published in Science Advances, shows that the Chicxulub impact may have triggered additional volcanic activity far from the Deccan Traps – along tens of thousands of miles of undersea volcanic ridges that lie at the edges of tectonic plates. The meteorite impact caused large seismic waves that traveled around the globe and were apparently capable of flushing magma out of the mantle and into the oceanic crust. This would presumably be more bad news for the dinosaurs and other flora and fauna of the time.</p>
<h2>Ripple effects of seismic activity</h2>
<p>It is well known that seismic activity can trigger a variety of hydrologic phenomena, and sometimes even volcanic eruptions. In the aftermath of nearby large earthquakes, <a href="https://doi.org/10.1038/ncomms8597">dry streams can start flowing</a>, well levels can go up or down, and <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125">geysers sometimes erupt</a>. Seismicity also sets off volcanic activity, but only when conditions are just right – it’s only about <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125">0.4 percent of explosive volcanic eruptions</a> that might be triggered by large earthquakes.</p>
<p>So could the massive earthquake generated when the Chicxulub meteorite crashed into Earth be related to the ongoing eruptions in the Deccan Traps? This volcanic province covered much of India with lava flows in less than a million years. A University of California, Berkeley-led team of researchers (including one of us, Leif Karlstrom) <a href="https://doi.org/10.1130/B31167.1">revisited the possibility of a connection</a> between these two events.</p>
<p>The most recent efforts to date these eruptions have clearly shown that the <a href="https://doi.org/10.1126/science.aaa0118">Deccan Traps began spewing lava</a> before the meteorite impact and the mass extinction occurred. But the Berkeley-led study suggested that the <a href="https://doi.org/10.1126/science.aac7549">Chicxulub impact triggered a rapid increase in their eruption rate</a>. If true, all three events could conceivably be connected: The impact would be followed by accelerated volcanic activity that could contribute to the mass extinction.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.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">Underwater lava flows ooze out between tectonic plates, as at Axial Seamount, where it lies on top of older lavas.</span>
<span class="attribution"><span class="source">Bill Chadwick, Oregon State University, and ROV Jason, Woods Hole Oceanographic Institution</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Looking to the ocean floor</h2>
<p>If the triggering-by-impact hypothesis is right, we’d expect that other volcanic systems would have been set off as well.</p>
<p>At any given time, the vast majority of the volcanic activity on Earth isn’t occurring in continent-covering floods of magma or in explosions like at Mount St. Helens. It’s on the seafloor, where the tectonic plates are spreading apart. As the Earth’s crust splits, the mostly solid mantle layer rises to fill the space created. It melts as it decompresses on the way up.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=203&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=203&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=203&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=255&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=255&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=255&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Illustration of a mid-ocean ridge, with magma rising from the mantle and erupting through the crust at the boundary between tectonic plates.</span>
<span class="attribution"><span class="source">Background, E. Paul Oberlander, WHOI Graphic Services. Inset, Bill Chadwick, Oregon State University, and ROV Jason, Woods Hole Oceanographic Institution. Modified by Joseph Byrnes</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This new magma percolates its way to the surface and fuels nearly continuous volcanic activity along what are known as <a href="https://en.wikipedia.org/wiki/Mid-ocean_ridge">mid-ocean ridges</a>. This process creates practically all of the crust on the bottom of the ocean. Since the <a href="http://www.earthbyte.org/Resources/agegrid2008.html">ages of the seafloor are relatively well-known</a>, it preserves a record of oceanic volcanic activity stretching back over 100 million years. This remarkable record of volcanic activity creates an opportunity to test the triggering hypothesis.</p>
<p><a href="http://advances.sciencemag.org/content/4/2/eaao2994">In our new study</a>, we used publicly available data sets to make a record of the structure of the seafloor stretching back 100 million years. Since better topographic maps exist for <a href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA02820">Mars</a> and <a href="https://sos.noaa.gov/datasets/venus-topography/">Venus</a> than do for the <a href="http://topex.ucsd.edu/marine_topo/">Earth’s seafloor on a global scale</a>, we were forced to use indirect methods to look for variations in seafloor structures.</p>
<p>Minute variations in the strength of gravity at different locations as measured by satellites <a href="http://topex.ucsd.edu/marine_grav/mar_grav.html">provide the requisite mapping tool</a>. Spots that have an excess amount of rock sitting on the seafloor, as you’d expect to result from accelerated volcanic activity, will have a slightly stronger measurement for Earth’s gravitational field.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=298&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=298&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=298&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=375&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=375&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=375&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 time with the most small structural anomalies on the sea floor – indicating 8 percent more mass anomalies than on average – occurs at 66 million years ago and coincides with the age of the Chicxulub meteorite impact.</span>
<span class="attribution"><span class="source">Byrnes and Karlstrom, Sci. Adv. 2018;4: eaao2994</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We then inspected the record of these “gravity anomalies” to look for any changes to the structure of the seafloor that happened quickly. We found an unusual abundance of these small structural anomalies on the seafloor happened within 1 million years of the Chicxulub impact. The gravity anomalies are consistent with roughly 650 foot high piles of excess material lying on 66-million-year-old seafloor in the Indian and Pacific Oceans.</p>
<p>The total volume of excess material is difficult to pin down, because a large amount of magma could have been injected into the lower crust where it would have a weaker gravitational signature. But we estimate that around the time of the Chicxulub impact, on the order of 23,000 to 230,000 cubic miles of magma erupted out of the mid-ocean ridges, all over the globe. This is on par with the largest eruptive events in Earth’s 4.5-billion-year history, including the Deccan Traps.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=261&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=261&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=261&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=327&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=327&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=327&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dots mark areas on the seafloor that show high rates of spreading at the time of the Chicxulub impact 66 million years ago. Colors indicate the maximum gravity anomaly within 2 degrees.</span>
<span class="attribution"><span class="source">Byrnes and Karlstrom, Sci. Adv. 2018;4: eaao2994</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Refining the picture</h2>
<p>Our observations suggest the following sequence of events at the end of the Cretaceous period. Just over 66 million years ago, the Deccan Traps start erupting – likely initiated by a plume of hot rock rising from the Earth’s core, similar in some ways to what’s happening beneath Hawaii or Yellowstone today, that impinged on the side of India’s tectonic plate. The mid-ocean ridges and dinosaurs continue their normal activity.</p>
<p>About 250,000 years later, Chicxulub hits off the coast of what will become Mexico. The impact causes a massive disruption to the Earth’s climate, injecting particles into the atmosphere that will eventually settle into <a href="https://doi.org/10.1126/science.1177265">a layer of clay found across the planet</a>. In the aftermath of impact, volcanic activity accelerates for perhaps tens to hundreds of thousands of years. The mid-ocean ridges erupt large volumes of magma, while the Deccan Traps eruptions flood lava across much of the Indian subcontinent. In the end, three-quarters of the Earth’s plant and animal species have disappeared; the only remaining dinosaurs are the feathered, flying variety, normally referred to as birds. </p>
<p>Now, the goal is to further refine our understanding of each event and their interactions. Was there enough mid-ocean ridge activity to contribute to the mass extinction, or was the triggered submarine volcanism merely a symptom of some more significant planetary ailment? Were other volcanic systems triggered by the Chicxulub impact? Which played a larger role in driving the extinction: the volcanism or the meteor?</p>
<p>What is clear is that this new research points to global-scale connections between catastrophes, a good reminder that events happening on the other side of the planet can have effects felt everywhere.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8wy33t0U1DE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Massive eruption of magma may have contributed to mass extinction at the end of the Cretaceous.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/91053/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Leif Karlstrom receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Joseph Byrnes 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>Research suggests a new threat to life on Earth from the meteorite’s crash: Via seismic waves, the impact triggered massive undersea eruptions, as big as any ever seen in our planet’s history.Leif Karlstrom, Assistant Professor of Earth Sciences, University of OregonJoseph Byrnes, Postdoctoral Associate of Earth Sciences, University of MinnesotaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/871092017-11-09T14:17:43Z2017-11-09T14:17:43ZDinosaurs could have avoided mass extinction if the killer asteroid had landed almost anywhere else<figure><img src="https://images.theconversation.com/files/193808/original/file-20171108-14177-b9ea8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The decline of the dinosaurs, the rise of mammals and, ultimately, the origins of humans were even more unlikely than previously thought, according to new research. The huge asteroid collision that sparked this change in the Earth’s diversity was already a highly improbable roll of the celestial dice. But <a href="http://nature.com/articles/doi:10.1038/s41598-017-14199-x">a new study</a> suggests the mass extinction that followed it was only so severe because of where the asteroid struck.</p>
<p><a href="https://theconversation.com/did-a-burning-oil-spill-wipe-out-the-dinosaurs-62456">Scientists believe</a> the dinosaurs were largely wiped out 66m years ago when an asteroid collision released a huge dust and soot cloud that triggered global climate change. The researchers, from Tohoku University in Japan, claim that the soot necessary for such a global catastrophe could only have come from a direct impact on rocks especially rich in hydrocarbons.</p>
<p>Rocks like this would only have been found on about 13% of the Earth’s surface. Add to this the need for a liberal dose of toxic sulphurous compounds in the rocks, and the odds that an impact of the same size (an already astronomically rare event) would have such devastating consequences lengthen to just one in 100.</p>
<p>The impact crater created by the 10km-diameter asteroid is located close to Chicxulub on Mexico’s Yucatán peninsula, and was only identified as recently as 1991. Before then, it was hidden to scientists because it lay partly under a blanket of <a href="http://geology.geoscienceworld.org/content/19/9/867">sediment on the seabed</a>.</p>
<p>The underlying rocks were composed of gypsum (rich in sulphur) and also contained large reserves of hydrocarbons. Had the impact occurred a few hundred miles away, or indeed at most locations on the globe, then the consequences of the collision may have been vastly less severe. Terrestrial dinosaurs and many other groups may never have been driven to extinction, and their survival may have hindered or completely prevented the later spread of mammals – and, of course, humans. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Global blackout.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The immediate blast and resulting shock and tidal waves would have killed much in their path no matter where the impact had occurred. Earthquakes and volcanic activity would have been triggered worldwide, and pieces of burning debris may have started <a href="http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20018/full">extensive wildfires</a>. </p>
<p>But it’s unlikely this would have caused the global extinction of huge numbers of species. Such immediate effects were relatively short-lived, and the real damage, as the researchers show, probably came from fine particulate matter ejected high into the stratosphere. The worst culprit, they argue, would have been fine hydrocarbon soots. This new research claims that those catapulted into the upper atmosphere probably originated from rocks at the impact site rather than from forest fires. </p>
<p>Soot in the stratosphere could have simply blocked out the sun over a period of years, creating the equivalent of a <a href="http://www.pnas.org/content/114/36/E7415.full">nuclear winter</a>, shutting down photosynthesis and decimating ecosystems as a result. But the researchers argue that as well as general darkening, the effects upon climate were more varied, resulting in droughts towards the equator and more extreme cooling at mid to high latitudes. Sulphate aerosols would also have caused acid rain, altering ocean chemistry and stressing marine and terrestrial ecosystems alike.</p>
<p>The Tohoku scientists used global climate models to predict the size of these effects depending upon the geology of where the asteroid struck, as well as the volume and chemistry of the material thrown into the upper atmosphere. In most other locations, it wouldn’t have produced such devastating results. It seems that the Earth could not have been hit anywhere much worse.</p>
<h2>The next mass extinction</h2>
<p>All species inevitably go extinct and the history of life on Earth is one of constant turnover. Extinctions also occur at all scales, from the demise of individual species to what we call “mass events” that see 75% or more of species wiped out globally. There have been five such <a href="https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971">mass events</a> over the last half billion years, and we appear to be sleepwalking <a href="https://theconversation.com/which-species-will-survive-the-earths-sixth-mass-extinction-47893">into a sixth</a> of our own making thanks to pollution, habitat destruction and hunting.</p>
<p>The possibility of a future asteroid impact is also very real. NASA’s <a href="https://cneos.jpl.nasa.gov/">Near Earth Object Program</a> seeks to map out the trajectories of comets and asteroids that appear set to come close to the Earth. Plans are afoot to develop technologies capable of <a href="https://www.nasa.gov/feature/nasa-s-first-asteroid-deflection-mission-enters-next-design-phase">deflecting objects</a> on a collision course.</p>
<p>But in the meantime, this new research suggests that we should worry slightly less about the probable consequences of the next extraterrestrial disaster, focus our attention closer to home, and reflect on our outrageous good fortune for being here in the first place.</p><img src="https://counter.theconversation.com/content/87109/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Wills has received or currently receives funding from BBSRC, NERC, The Leverhulme Trust and the John Templeton Foundation.</span></em></p>The mass extinction of the dinosaurs was down to the location of the asteroid’s impact and the kind of rocks it landed on.Matthew Wills, Professor of Evolutionary Palaeobiology at the Milner Centre for Evolution, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/689252016-11-17T19:06:46Z2016-11-17T19:06:46ZExpedition reveals how the dinosaur-killing asteroid shook and shaped the Earth<figure><img src="https://images.theconversation.com/files/146403/original/image-20161117-18128-1f5dz91.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The asteroid thought to have killed the dinosaurs smashed into the Earth with <a href="http://science.sciencemag.org/content/327/5970/1214">a billion times more energy</a> than the atomic bombs dropped on Hiroshima and Nagasaki. Many believe the impact caused a mass extinction, wiping out the dinosaurs on land and numerous lifeforms in the oceans. But one of the difficulties in knowing exactly whether and how this happened is that the Chicxulub crater left by the asteroid is buried below a thick layer of sedimentary rock.</p>
<p>Earlier this year, an expedition to a site off the coast of Mexico retrieved rock samples drilled from rocky inner ridges of the crater – known as the “peak ring” – buried up to 1,300 metres below the sea bed. Now the first analysis of these samples has given us new evidence for how this ring may have been formed.</p>
<p>It also shows how the impact made the peak ring rocks more porous. This is important because nutrient-rich porous rocks create good conditions for simple lifeforms. So perhaps the Chicxulub impact can show us how other asteroids that hit the Earth earlier in its history helped create the conditions for life to develop. However, there are so many other factors that would have shaped the origins of life that we should be careful about drawing too many conclusions from this one study.</p>
<p><a href="http://dx.doi.org/10.1126/science.aah6561">The new research</a>, led by Professor Joanna Morgan of Imperial College London and published in the journal Science, tries to explain why there is a concentric ring of mountain peaks within the crater. The Chicxulub crater is the only one on Earth that has a peak ring like this. So the researchers also used observations from Venus, Mars and Earth’s moon to bolster support for their theory.</p>
<p>They argue the evidence supports what is known as the “<a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.519.5958&rep=rep1&type=pdf">dynamic collapse model</a>” of how the peak ring formed. According to this model, the initial impact pushed underground rocks down and then outwards, after which they rose back to the surface to form a central peak. This then collapsed, pushing out rock from both the deep crust and the overlying sedimentary layers to create a ring of peaks.</p>
<p>This contrasts with another model known as the <a href="http://planetary.brown.edu/pdfs/3925.pdf">nested melt-cavity model</a>, which is less consistent with the evidence from the Chicxulub crater. In this second model, the central portion of the impact became so hot that it melted, and this led to the peak ring by processes that are not fully defined.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/146405/original/image-20161117-18131-6fpjdl.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">Recovered core from the Chicxulub impact crater.</span>
<span class="attribution"><span class="source">@ECORD_IODP</span></span>
</figcaption>
</figure>
<p>The data from the drilling samples includes direct physical evidence of high levels of shock and temperature that affected the rocks. These features wouldn’t be possible in Earth’s surface rocks without extreme events such as an asteroid impact. They’re also not part of the processes of plate tectonics, which occur at lower temperatures and pressures than those required to form these shocked materials.</p>
<p>As a result, the new research is highly significant in helping us understand what happened in the space of a few minutes after the impact. It shows that the layer of sedimentary rocks covering the deeper crust (often called the “basement”) was highly disturbed. In places, there are basement rocks lying on top of sedimentary rocks within the crater, which would only be possible due to a high-energy impact. </p>
<p>These kind of impacts are instrumental in modifying the surface rocks of a planet or moon by vertically mixing its crust materials. So we can presume that asteroid impacts are very important in the early histories of planets, including the Earth. The new paper even briefly mentions that the research could possibly help us understand the processes by which life originated on our planet.</p>
<p><a href="http://phys.org/news/2016-11-asteroid-impacts-niches-life-chicxulub.html">Morgan has commented</a> that by making Earth’s rocks more porous, asteroids may have helped to create environments that were suitable for the first organisms to develop. In particular, these porous rocks could have contained nutrients from circulating water that was heated inside the Earth’s crust.</p>
<h2>Origins still a mystery</h2>
<p>Yet there are enormous problems in explaining how life could have been created by inorganic processes on planetary bodies. <a href="http://www.abenteuer-universum.de/pdf/miller_1953.pdf">The famous experiments</a> of Stanley Miller in the 1950s showed amino acids can be created in high-energy events (such as a lightning strike) in the presence of carbon dioxide, methane, hydrogen and nitrogen compounds as could be found on the Earth’s surface.</p>
<p>However, as the Earth had no ozone shield in its early history to protect it from life-destroying ultraviolet light, <a href="https://theconversation.com/weve-been-wrong-about-the-origins-of-life-for-90-years-63744">many now argue</a> that life formed in the deep oceans. Modern volcanic eruptions in the deep ocean floor produce mineral emissions that sustain communities of organisms, providing a potential alternative location for the first life.</p>
<p>So as an interpretation of the processes involved in the formation of impact craters, the new research is an impressive advance in our understanding. But the evidence it provides for how the the Earth was prepared to create life is limited to a hint of what may have happened.</p><img src="https://counter.theconversation.com/content/68925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Kershaw 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>New research suggests how asteroids may have helped create conditions for life on Earth. But we shouldn’t get too carried away with the idea – yet.Stephen Kershaw, Senior Lecturer in Environmental Geosciences, Brunel University LondonLicensed as Creative Commons – attribution, no derivatives.