tag:theconversation.com,2011:/us/topics/meteoroid-42153/articlesmeteoroid – The Conversation2022-09-19T20:14:45Ztag:theconversation.com,2011:article/1907552022-09-19T20:14:45Z2022-09-19T20:14:45ZFor the first time, robots on Mars found meteorite impact craters by sensing seismic shock waves<figure><img src="https://images.theconversation.com/files/485209/original/file-20220919-60301-kjcm6t.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2000%2C1994&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://mars.nasa.gov/insight/multimedia/raw-images/?order=sol+desc%2Cdate_taken+desc&per_page=50&page=2&mission=insight">NASA / JPL-Caltech</a></span></figcaption></figure><p>Since 2018, NASA’s <a href="https://mars.nasa.gov/insight/mission/overview/">InSight mission</a> to Mars has recorded seismic waves from more than <a href="https://www.essoar.org/doi/10.1002/essoar.10512017.1">1,300 marsquakes</a> in its quest to probe the internal structure of the red planet. The solar panels of the car-sized robotic lander have become caked with Martian dust, and NASA scientists <a href="https://mars.nasa.gov/news/9191/nasas-insight-still-hunting-marsquakes-as-power-levels-diminish/?site=insight">expect</a> it will completely power down by the end of 2022.</p>
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Read more:
<a href="https://theconversation.com/first-recorded-marsquakes-reveal-the-red-planets-rumbling-guts-132091">First recorded 'marsquakes' reveal the red planet's rumbling guts</a>
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<p>But the internal rumblings of our planetary neighbour aren’t the only things that InSight’s seismometers detect: they also pick up the thuds of space rocks crashing into the Martian soil.</p>
<p>In <a href="https://www.nature.com/articles/s41561-022-01014-0">new research</a> published in Nature Geoscience, we used data from InSight to detect and locate four high-speed meteoroid collisions, and then tracked down the resulting craters in satellite images from NASA’s Mars Reconnaissance Orbiter.</p>
<h2>Rocks from space</h2>
<p>The Solar System is full of relatively small rocks called meteoroids, and it’s common for them to collide with planets. When a meteoroid encounters a planet with an atmosphere, it heats up due to friction – and may burn up entirely before reaching the ground.</p>
<p>On Earth, we know these incoming meteoroids as shooting stars, or meteors: beautiful events to observe in the night sky. Sometimes a meteoroid explodes when it reaches the thicker atmosphere closer to the ground, creating a spectacular airburst.</p>
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Read more:
<a href="https://theconversation.com/where-do-meteorites-come-from-we-tracked-hundreds-of-fireballs-streaking-through-the-sky-to-find-out-160096">Where do meteorites come from? We tracked hundreds of fireballs streaking through the sky to find out</a>
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<p>Occasionally, a space rock survives its fiery path through the air and drops to the ground, where it is known as a meteorite. </p>
<p>A few of these meteorites hit the surface at such speed they blast a hole in the ground called an impact crater. Compared to a human lifetime, these events are very rare on Earth. </p>
<h2>Recording space rock impacts</h2>
<p>Scientists have detected the vibrations from meteoroid airbursts using seismic detectors numerous times, including <a href="https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/abs/statistical-analysis-of-fireballs-seismic-signature-survey/1683309FE1240CFCE1460AD3A11776BC">a recent survey</a> of bright meteors above Australia. </p>
<p>However, only once has a high-speed space rock crashing into the ground been observed both visually and with modern seismic equipment. This was an impact crater that <a href="https://en.wikipedia.org/wiki/2007_Carancas_impact_event">formed in 2007</a> near the village of Carancas in Peru. </p>
<p>Numerous impacts were detected on the Moon by the network of seismic sensors set up during the US Apollo missions of the 1960s and ’70s. However, there was no recording of a natural impact associated with visual detection of a new crater. </p>
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Read more:
<a href="https://theconversation.com/the-moon-is-still-geologically-active-study-suggests-116768">The moon is still geologically active, study suggests</a>
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<p>The closest things to such an observation were artificial impacts: the crash-landings of the booster rockets of the ascent modules that lifted Apollo astronauts off the Moon. </p>
<p>These human-made impacts on the Moon were recorded both in seismic data and visual imagery from orbit. These data were <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021EA001887">recently used</a> to test simulations of how impacts produce seismic waves.</p>
<h2>Martian meteorites</h2>
<p>Incoming meteoroids make waves in the atmosphere and also the ground. The atmosphere of Mars is equivalent to 1% of the Earth’s, and has a different chemical composition. This means meteor events on Mars take a different form.</p>
<p>For meteor events large enough to drop a meteorite, the fate of the meteorite and any resulting crater is <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021JE007149">different</a> from what we have come to expect on our home planet. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485232/original/file-20220919-49069-ivyabg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&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">Many craters on Mars come in clusters, because meteoroids often explode into fragments not long before they hit the surface.</span>
<span class="attribution"><a class="source" href="https://www.uahirise.org/ESP_028444_2040">MRO / HiRISE / NASA / JPL-Caltech / UArizona</a></span>
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<p>Here on Earth, or on the Moon, single craters are the norm. On Mars, however, about half the time a high-speed space rock will burst in the atmosphere shortly before impact, resulting in a tightly grouped cluster of craters.</p>
<p>The separation of these individual fragments remains close at ground level, forming a <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021JE007145">cluster of small impacts</a>.</p>
<h2>From vibrations to craters</h2>
<p>Recently, the InSight mission has observed acoustic and seismic waves from four meteoroid impact events. These waves travel at different speeds, and comparing their different arrival times and other properties allowed us to estimate the location of the impacts.</p>
<p>These impact locations were then confirmed with satellite imaging from the Mars Reconnaissance Orbiter.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=538&fit=crop&dpr=1 600w, https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=538&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=538&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=676&fit=crop&dpr=1 754w, https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=676&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/485216/original/file-20220919-65079-nfw0w4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=676&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">A sketch of how an incoming space rock makes waves that InSight can detect and interpret.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41561-022-01014-0">Garcia et al. / Nature Geoscience</a></span>
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<p>Knowing the size and exact location of these impact craters helps us calculate the size and speed of the incoming space rock and how much energy the impact released.</p>
<p>Once we are confident we know something about the impact that created the seismic waves we detected, we can use the waves to learn about the interior of Mars. What’s more, when we compare seismic observations on Mars with observations from Earth and the Moon, we can learn more about how the planets formed and how the Solar System evolved.</p><img src="https://counter.theconversation.com/content/190755/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Katarina Miljkovic works for Curtin University and is fully funded by the Australian Research Council. She is a science collaborator for the NASA InSight mission.</span></em></p>In an extraterrestrial first, scientists have linked seismic waves on Mars to meteorite impact craters spotted via satellite.Katarina Miljkovic, ARC Future Fellow, School of Earth and Planetary Sciences, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1726032021-11-26T05:23:39Z2021-11-26T05:23:39ZCould we really deflect an asteroid heading for Earth? An expert explains NASA’s latest DART mission<figure><img src="https://images.theconversation.com/files/434110/original/file-20211126-19-h79etv.jpeg?ixlib=rb-1.1.0&rect=0%2C72%2C5376%2C2945&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>A NASA spacecraft the size of a golf cart has been directed to smash into an asteroid, with the intention of knocking it slightly off course. The test aims to demonstrate our technological readiness in case an actual asteroid threat is detected in the future.</p>
<p>The Double Asteroid Redirection Test (DART) lifted off aboard a SpaceX rocket from California on November 23, and will arrive at the target asteroid system in September, next year. </p>
<p>The mission will travel to the asteroid Didymos, a member of the <a href="https://cneos.jpl.nasa.gov/about/neo_groups.html">Amor group of asteroids</a>. Every 12 hours Didymos is orbited by a mini-moon, or “moonlet”, Dimorphos. This smaller half of the pair will be DART’s target.</p>
<h2>Are we facing an extinction threat from asteroids?</h2>
<p>We’ve all seen disaster movies in which an asteroid hits Earth, creating an extinction event similar to the one that killed off the dinosaurs millions of years ago. Could that happen now? </p>
<p>Well, Earth is actually bombarded frequently by small asteroids, ranging from 1-20 metres in diameter. Almost all asteroids of this size disintegrate in the atmosphere and are usually harmless. </p>
<p>There is an <a href="https://en.wikipedia.org/wiki/Impact_event">inverse relationship</a> between the size of these objects and the frequency of impact events. This means we get hit much more frequently by small objects than larger ones – simply because there are many more smaller objects in space.</p>
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<a href="https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=420&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=420&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=420&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=528&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=528&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434047/original/file-20211125-21-1lg3gh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=528&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">Small asteroid impacts showing day-time impacts (in yellow) and night-time impacts (in blue). The size of each dot is proportional to the optical radiated energy of the impact.</span>
<span class="attribution"><span class="source">NASA JPL</span></span>
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<p>Asteroids with a 1km diameter strike Earth every 500,000 years, on average. The most “recent” impact of this size is thought to have formed the <a href="https://en.wikipedia.org/wiki/Tenoumer_crater">Tenoumer impact crater in Mauritania</a>, 20,000 years ago. Asteroids with an approximate 5km diameter impact Earth about once every 20 million years. </p>
<p>The <a href="https://earthsky.org/space/meteor-asteroid-chelyabinsk-russia-feb-15-2013/">2013 Chelyabinsk meteoroid</a>, which damaged buildings in six Russian cities and injured around 1,500 people, was estimated to be about 20m in diameter.</p>
<h2>Assessing the risk</h2>
<p>NASA’s DART mission has been sparked by the threat and fear of a major asteroid hitting Earth in the future. </p>
<p>The <a href="https://en.wikipedia.org/wiki/Torino_scale">Torino scale</a> is a method for categorising the impact hazard associated with a near-Earth object (NEO). It uses a scale from 0 to 10, wherein 0 means there is negligibly small chance of collision, and 10 means imminent collision, with the impacting object being large enough to precipitate a global disaster.</p>
<p>The <a href="https://www.planetary.org/notable-asteroid-impacts-in-earths-history">Chicxulub impact</a> (which is attributed to the extinction of non-avian dinosaurs) was a Torino scale 10. The impacts that created the Barringer Crater, and the 1908 Tunguska event, both correspond to Torino Scale 8. </p>
<p>With the increase of online news and individuals’ ability to film events, asteroid “near-misses” tend to generate fear in the public. Currently, NASA is keeping a close eye on asteroid Bennu, which is the object with the largest “cumulative hazard rating” right now. (You can keep <a href="https://cneos.jpl.nasa.gov/sentry/">up to date too</a>).</p>
<p>With a 500m diameter, Bennu is capable of creating a 5km crater on Earth. However, NASA has also said there is a 99.943% chance the asteroid will miss us.</p>
<h2>Brace for impact</h2>
<p>At one point in their orbit around the Sun, Didymos and Dimorphos come within about 5.9 million km of Earth. This is still further away than our Moon, but it’s very close in astronomical terms, so this is when DART will hit Dimorphos.</p>
<p><a href="https://dart.jhuapl.edu/Mission/Impactor-Spacecraft.php">DART</a> will spend about ten months travelling towards Didymos and, when it’s close by, will change direction slightly to crash into Dimorphos at a speed of about 6.6km per second.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434097/original/file-20211126-15-1ve7m9j.gif?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">This animation shows DART’s trajectory around the Sun. Pink = DART | Green = Didymos | Blue = Earth | Turquoise = 2001 CB21 | Gold = 3361 Orpheus.</span>
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<p>The larger Didymos is 780m in diameter and thus makes a better target for DART to aim for. Once DART has detected the much smaller Dimorphos, just 160m in diameter, it can make a last-minute course correction to collide with the moonlet. </p>
<p>The mass of Dimorphos is 4.8 million tonnes and the mass of DART at impact will be about 550kg. Travelling at 6.6km/s, DART will be able to transfer a huge amount of momentum to Dimorphos, to the point where it’s expected to actually change the moonlet’s orbit around Didymos.</p>
<p>This change, to the tune of about 1%, will be detected by ground telescopes within weeks or months. While this may not seem like a lot, 1% is actually a promising shift. If DART were to slam into a lone asteroid, its orbital period around the Sun would change by only about 0.000006%, which would take many years to measure. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433919/original/file-20211125-1794-vtv1ni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&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 DART mission dates and timeline events.</span>
<span class="attribution"><span class="source">Johns Hopkins University</span></span>
</figcaption>
</figure>
<p>So we’ll be able to detect the 1% change from Earth, and meanwhile the pair will continue along its orbit around the Sun. DART will also deploy a small satellite ten days before impact to capture everything.</p>
<p>This is NASA’s first mission dedicated to demonstrating a <a href="https://www.nasa.gov/feature/nasa-s-first-planetary-defense-technology-demonstration-to-collide-with-asteroid-in-2022">planetary defence technique</a>. At a cost of US$330 million, it’s relatively cheap in space mission terms. The <a href="https://www.nasa.gov/mission_pages/webb/about/index.html">James Webb Telescope</a> set to launch next month, costs close to <a href="https://www.planetary.org/articles/cost-of-the-jwst">US$10 billion</a>.</p>
<p>There will be little to no debris from DART’s impact. We can think of it in terms of a comparable event on Earth; imagine a train parked on the tracks but with no brakes on. Another train comes along and collides with it. </p>
<p>The trains won’t break apart, or destroy one another, but will move off together. The stationary one will gain some speed, and the one impacting it will lose some speed. The trains combine to become a new system with different speeds than before. </p>
<p>So we won’t experience any impact, ripples or debris from the DART mission.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=426&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=426&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=426&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=535&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=535&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434099/original/file-20211126-21-1jrvgbd.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=535&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Typical asteroid orbits remain between Mars and Jupiter, but some with elliptical orbits can pass close to Earth.</span>
<span class="attribution"><span class="source">Pearson</span></span>
</figcaption>
</figure>
<h2>Is the effort really worth it?</h2>
<p>Results from the mission will tell us just how much mass and speed is needed to hit an asteroid that may pose a threat in the future. We already track the vast majority of asteroids that come close to Earth, so we would have early warning of any such object.</p>
<p>That said, we have <a href="https://www.livescience.com/surprise-asteroid-flyby">missed objects in the past</a>. In October 2021, <a href="https://en.wikipedia.org/wiki/2021_UA1">Asteroid UA_1</a> passed about 3,047km from Earth’s surface, over Antarctica. We missed it because it approached from the direction of the Sun. At just 1m in size it wouldn’t have caused much damage, but we should have seen it coming. </p>
<p>Building a deflection system for a potential major asteroid threat would be difficult. We would have to act quickly and hit the target with very good aim. </p>
<p>One candidate for such a system could be the new technology developed by the US spaceflight company <a href="https://www.spinlaunch.com/">SpinLaunch</a>, which has designed technology to launch satellites into orbit at rapid speeds. This device could also be used to fire masses at close-passing asteroids. </p>
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Read more:
<a href="https://theconversation.com/where-do-meteorites-come-from-we-tracked-hundreds-of-fireballs-streaking-through-the-sky-to-find-out-160096">Where do meteorites come from? We tracked hundreds of fireballs streaking through the sky to find out</a>
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<img src="https://counter.theconversation.com/content/172603/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gail Iles 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>An asteroid that landed in Russia in 2013 injured 1,500 people – and was just 20 metres in diameter. What could we do if a major threat was detected?Gail Iles, Senior Lecturer in Physics, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1080272018-12-03T17:14:06Z2018-12-03T17:14:06ZNASA spacecraft gets up close with an asteroid that could one day collide with Earth<figure><img src="https://images.theconversation.com/files/248731/original/file-20181204-34134-hj5let.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Image of Bennu from a distance of around 50 miles (80 km).
</span> <span class="attribution"><span class="source"> NASA/Goddard/University of Arizona</span></span></figcaption></figure><p>NASA’s spacecraft <a href="https://www.asteroidmission.org/">OSIRIS-REx</a> has finally reached the asteroid <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/maps.12353">101955 Bennu</a> – which may be on collision course with the Earth – after travelling for just over two years since its <a href="https://theconversation.com/lift-off-for-nasa-mission-to-collect-grains-from-an-asteroid-that-may-be-on-collision-course-with-earth-65112">launch in September 2016</a>. This mission, which will bring grains back for us to study on Earth, is latest to return asteroid samples to Earth after the Japanese Space Agency’s missions <a href="http://www.hayabusa2.jaxa.jp/en/">Hayabusa 1 and 2</a> and <a href="https://stardust.jpl.nasa.gov/home/index.html">StarDust</a>. The data will help unveil more about the origins of the solar system and how to protect the Earth from possible asteroid impact. </p>
<p>The spacecraft will spend the next year completing a detailed survey of the surface of Bennu (492 metres in diameter) – including locating the most suitable landing sites. Once a site is selected, the spacecraft will land for about five seconds to collect a sample of the surface material using a burst of nitrogen gas to liberate material from the surface into the sampler head. </p>
<p>The spacecraft has enough gas to attempt three sample collections from the surface. This will hopefully provide a sample of between 60g and 2,000g of surface regolith material (the layer of material covering solid rock). It will start heading back to Earth in 2021 – getting here in 2023. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/248437/original/file-20181203-194925-1tvj2w3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This artist’s concept shows the OSIRIS-REx spacecraft approaching the asteroid Bennu.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Asteroids are material left over from the early solar system, which means they offer a unique look into its early composition. Bennu orbits the sun <a href="https://www.space.com/42602-where-is-asteroid-bennu-osiris-rex-target.html">between the Earth and Mars</a>. Its composition is of particular interest as we already know it is rich in carbon. This means it may contain organic materials that have remained unaltered since the formation of the solar system. It is not impossible that asteroids like it delivered the building blocks of life to the early Earth – the mission could help us investigate this theory. </p>
<p>Though sample return is a major and complex part of this mission, OSIRIS-REx will study other aspects of the asteroid too. During the survey of the surface the spacecraft will also be looking out for plumes and natural satellites orbiting the body. Instruments on board will allow enable us to identify different chemicals on it. This will help finding the most interesting and richest sample sites to a resolution of about two metres. </p>
<h2>Secret threat</h2>
<p>The asteroid Bennu is of interest to Earth for another reason. Bennu may be on collision course with Earth in the future. It is theorised from the <a href="https://cneos.jpl.nasa.gov/sentry/details.html#?des=101955">study of the orbit of Bennu</a> that gravity interaction between the two bodies during a close approach to Earth in 2060 (750,000km) will slightly alter its course. This means that there is a <a href="https://cneos.jpl.nasa.gov/sentry/details.html#?des=101955">cumulative one in 2,700 chance</a> of an Earth impact between 2175 and 2199.</p>
<p>OSIRIS-REx may be able to aid in preventing such events. One of the thing it will measure is the body’s <a href="http://earthsky.org/astronomy-essentials/the-yarkovsky-effect-pushing-asteroids-around-with-sunlight">“Yarkovsky acceleration”</a>. This effect is a force that acts on a rotating body in space, caused by the uneven release of heat from the surface of the asteroid. Once this is known, it will be possible to investigate whether we could use this force to change the orbit of Bennu and other threatening asteroids. For example, it may be possible to use solar radiation to heat up one side of the rock more than the other – changing its rotation and the orbit trajectory. </p>
<p>The next two years is going to be an exciting one for small body research. This mission will provide the most detailed analysis of carbon rich asteroids and will provide answers about the evolution of the solar system and our own planet. Analysis of the regolith will also tell us more about the effects of space weathering on the surface of small bodies from harsh solar radiation. </p>
<p>The collection method for the mission is called “<a href="http://spaceflight101.com/osiris-rex/osiris-rex-tagsam/">Touch and Go Sample Acquisition Mechanism</a>”. And touch and go is exactly what the spacecraft must achieve, rather than a full landing. This will be extremely difficult and we will have to wait a year to see if the new method is successful. Let’s keep our fingers crossed that it all goes according to plan.</p><img src="https://counter.theconversation.com/content/108027/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathryn Harriss receives funding from STFC. </span></em></p>Osiris-REx will spend the next year looking for a good place to land on asteroid Bennu before it collects grains and brings them home.Kathryn Harriss, Post-Doctoral Research Associate in Planetary Science, University of KentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/827982017-08-23T08:22:33Z2017-08-23T08:22:33ZHere’s the blueprint for a global fireball observatory – and why we need one<figure><img src="https://images.theconversation.com/files/182802/original/file-20170821-4987-91zqm6.png?ixlib=rb-1.1.0&rect=0%2C2%2C786%2C519&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> </figcaption></figure><p>Bright shooting stars are one of nature’s great wonders. Like the one in the main image, which was <a href="http://www.devonlive.com/watch-as-a-fireball-lights-up-the-skies-over-south-devon/story-30369572-detail/story.html">visible from</a> Devon in the south-west of England in June, these fireballs are caused by space rocks hitting Earth’s atmosphere. The friction forces them to slow down, producing a tremendous amount of heat at the same time. If the rock is big enough, a fragment will survive this fiery transition and fall to Earth as a meteorite. </p>
<p>Planetary scientists study these rocks to extract clues as to how our solar system formed. But this work is complicated by the fact that we don’t know where in the solar system most of Earth’s <a href="https://www.lpi.usra.edu/meteor/">50,000 or so meteorites</a> came from. </p>
<p>To improve this situation, you have to determine a new fireball’s orbit once it breaches Earth’s atmosphere. This means observing it from multiple angles. You then ideally want to recover the meteorite before the weather changes the chemistry of the sample – usually in the first shower of rain. A new network of cameras is being set up in the UK to help in this endeavour, phase two of a global network that started five years ago in Australia. </p>
<h2>Fireball hunting</h2>
<p>Meteorites are arriving from outer space all the time. About 50 tonnes of extraterrestrial material enters Earth’s atmosphere each year. Most are sand-sized particles known as cosmic dust, including the majority of the <a href="https://www.space.com/37829-perseid-meteor-shower-2017-skywatcher-photos.html">Perseid meteor shower</a> that took place earlier in August. </p>
<p>But even over a relatively small space like the UK, <a href="http://www.lpi.usra.edu/books/MESSII/9021.pdf">about 20 meteorites</a> of a searchable size land each year – of which the Devon fireball was a good example. Most are barely 10g, about the size of a six-sided dice. Two or three will be bigger; usually up to a kilogram in mass or the size of a tennis ball. </p>
<p>This is but a remnant of the 6,000 to 20,000 meteorites in the same size range that we see each year in the land mass of the world as a whole. Yet observing and finding these is still no mean feat. To date, only around 30 meteorites <a href="http://www.meteoriteorbits.info/">have been recovered</a> after their fireball was observed. This has mostly been through remote camera networks including in Canada, France, the Czech Republic, Finland and Australia. </p>
<p>Such networks are continuously imaging the night sky over a huge area, which is ideal for tracking orbits back to space and reaching the landing site fast. I used to work as a researcher for the <a href="https://theconversation.com/how-to-find-a-meteorite-thats-fallen-to-earth-52906">Desert Fireball Network</a> in Australia. Since it was set up five years ago, its 52 cameras have found four meteorites. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182826/original/file-20170821-4969-9p19yd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the cameras in the Nullarbor Desert in southern Australia.</span>
<span class="attribution"><span class="source">DFN</span></span>
</figcaption>
</figure>
<p>The project to extend the Desert Fireball Network has already seen three high-resolution cameras installed in different parts of England in recent months, along with sophisticated image-processing software. A further seven will be in place by next summer, in a collaboration between Imperial College London, University of Glasgow, the Open University, the Natural History Museum and Curtin University in Perth, Australia. </p>
<p>The new network will track any fast-moving object flying across the skies above the UK, including things like satellites. It will complement an existing network of 30 video cameras called the <a href="https://ukmeteornetwork.co.uk">UK Meteor Observation Network</a>, which is already run by citizen scientists to spot fireballs and smaller meteors. UKMON focuses on capturing images rather than meteorite recovery. The two operations will share data, enhancing one another’s abilities. There are also plans to extend the new network to the US, South America, New Zealand and Saharan Africa in the next few years. </p>
<p>The challenges facing the UK operation are quite different to those in Australia. Where the Australian network needs to be able to survive unattended in the brutal desert heat, the UK cameras will work in a distinctly colder, wetter climate. </p>
<p>They will have to contend with light pollution, unpredictable weather and significant cloud cover, reducing the number of nights they will be able to take images. But most problematic of all is the ground itself. The Australian outback is ideal for meteorite hunting: uniformly red and with very little vegetation, meaning you can spot a little black rock from several hundred metres. By contrast, the UK’s lush vegetation and woodland can easily camouflage meteorites.</p>
<p>Yet the UK network also has advantages. Most cameras will be within a day’s drive and connected to the internet to provide instant warnings when a camera needs some tender loving care – the Australian cameras tend to be on rougher terrain that takes longer to reach and many are not internet-connected. At the same time, the UK population density is such that quite a lot of people are likely to spot a large fireball and take pictures on their smartphones. </p>
<h2>Apps upside your head</h2>
<p>Unlocking the assistance of these 65m independent autonomous observatories in the UK is part of the project. The Australian fireball team has developed an app in conjunction with US software consultancy ThoughtWorks. Known as Fireballs in the Sky and free for <a href="https://itunes.apple.com/gb/app/fireballs-in-the-sky/id709019924?mt=8">Apple</a> and <a href="https://play.google.com/store/apps/details?id=com.tw.fireballs&hl=en_GB">Android</a> phones alike, it allows anyone to become a citizen scientist. Users can report any fireball, as well as getting details of the next big meteor shower and where in the sky to look for it – and here’s a grab of what it looks like.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=531&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=531&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=531&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=667&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=667&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182827/original/file-20170821-4938-lfmj1h.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=667&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 app.</span>
<span class="attribution"><span class="source">DFN/ThoughtWorks</span></span>
</figcaption>
</figure>
<p>The app is already up and running. In fact, the latest recovered meteorite in Australia, called Dingle Dell, was <a href="http://www.abc.net.au/news/2016-11-22/meteorite-recovered-with-the-help-of-dedicated-star-gazers/8046880">initially observed</a> by a citizen scientist using it. </p>
<p>This made it possible to find the pristine meteorite before delicate minerals inside it were irreparably altered or washed away by rain, revealing extraterrestrial salts formed early in the solar system that usually quickly disappear on the surface of Earth. These could potentially tell us things about the origins of life and water on our planet. </p>
<p>These kinds of exciting discoveries give a taste of why it will be a race against time to recover the first meteorite tracked by the UK network. So do we have any volunteers?</p><img src="https://counter.theconversation.com/content/82798/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Daly’s PhD was funded under The Australian Research Council Laureate fellowship awarded to Professor Phil Bland. Luke is an associate of the Royal School of Mines at Imperial College London, and a member of the Meteoritical Society.</span></em></p><p class="fine-print"><em><span>Gareth Collins has received funding from the UK Research Councils (NERC, STFC & EPSRC).</span></em></p><p class="fine-print"><em><span>Martin Suttle receives funding from the STFC. </span></em></p>Ten new remote cameras will soon be scouring the British night skies for meteorites.Luke Daly, Research Associate, School of Geographical and Earth Sciences, University of GlasgowGareth Collins, Reader in Planetary Science, Imperial College LondonMartin D. Suttle, Researcher in Meteoritics and Planetary Science, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.