tag:theconversation.com,2011:/nz/topics/asteroids-933/articlesAsteroids – 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/2194402023-12-29T11:39:42Z2023-12-29T11:39:42ZSix space missions to look forward to in 2024<figure><img src="https://images.theconversation.com/files/565441/original/file-20231213-29-hd06pq.png?ixlib=rb-1.1.0&rect=27%2C21%2C1367%2C1253&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>It’s going to be a bumper time for space missions in 2024 – especially to the Moon, our nearest neighbour. And that’s following on from an already epic 2023. </p>
<p>I’m a laboratory scientist, so I always like to have a “proper” sample to analyse. Rather than peering through telescopes to look at the stars, I prefer to see them in a vial in my lab. My technique of choice is to burn the material to ashes while measuring the organic compounds and other species that are liberated in the process. </p>
<p>So it was a great delight to see the safe return of <a href="https://theconversation.com/osiris-rex-nasa-reveals-evidence-of-water-and-carbon-in-sample-delivered-to-earth-from-an-asteroid-215484">Nasa’s Osiris-Rex</a> mission from asteroid (101955) Bennu in September 2023. It was an even greater pleasure to receive a few precious crumbs of Bennu to study. </p>
<h2>CLPS missions</h2>
<p>Nasa’s series of <a href="https://www.nasa.gov/commercial-lunar-payload-services/">Commercial Lunar Payload Service (CLPS) missions</a>, many of which will launch in 2024, are set to bring a variety of instruments to the Moon. These missions are built and launched by different private companies under contract from Nasa. </p>
<p>The CLPS programme is part of Nasa’s <a href="https://theconversation.com/artemis-why-it-may-be-the-last-mission-for-nasa-astronauts-195065">Artemis initiative</a> to continue human exploration of the Moon. One of the main aims of the programme is to investigate the possibilities of using lunar resources as fuel – hence, some of the instruments on CLPS-1, aka <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=PEREGRN-1">Peregrine</a>, are designed to assess the amount of hydrogen on the lunar surface. In fact, my colleagues at the Open University have <a href="https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/PITMS_a_mini_mass_spectrometer_for_the_Moon">built an instrument</a> for doing so.</p>
<p>CLPS-2 is timetabled to launch in early January 2024, and there are four other CLPS missions planned for launch throughout the year. That is the good thing about the Moon – it’s so close that there aren’t many worries about launch windows (no complicated orbits to compute) or distance to travel.</p>
<p>Indeed, it is hoped that human exploration of the Moon will take a small step forward, possibly as early as November 2024, when <a href="https://www.nasa.gov/mission/artemis-ii/">Artemis II</a> orbits the Moon for several days. One of the astronauts on-board will be female – definitely a giant leap in what has, until now, been a solely masculine exploration of our nearest neighbour.</p>
<h2>Trailblazer</h2>
<p>Continuing the lunar theme, Nasa’s <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=L-TRLBLZR">Trailblazer mission</a> travels to the Moon to understand where any water is situated. Is it locked inside rock as part of the mineral structure, or is it deposited as ice on the rocky surface? </p>
<p>Trailblazer is currently scheduled for launch in the first quarter of 2024. However, no precise date has been confirmed. It’s a small mission, part of the <a href="https://www.nasa.gov/specials/artemis/">Artemis</a> human lunar exploration programme.</p>
<h2>Chang'e 6</h2>
<p>The launch of <a href="https://en.wikipedia.org/wiki/Chang%27e_6">Chang’e 6</a>, the latest Chinese mission to the Moon, is planned for May 2024 and is intended to bring material back to Earth. This is particularly significant because the spacecraft will collect material from the lunar farside – the South Pole Aitkin Basin. </p>
<p>This is a region where it is believed there is abundant frozen water. We do not have any samples of material from this part of the Moon – and although any ice will be long gone by the time the samples are back on Earth, it is anticipated we will learn a lot about this unexplored region and its potential as a source of water for human visitors. </p>
<h2>Hera</h2>
<p>In September 2022, Nasa’s <a href="https://science.nasa.gov/mission/dart/">Dart mission</a> encountered a system consisting of two asteroids called Didymos and Dimorphos, and crashed into Dimorphos (the junior partner). The impact had a purpose: to see if such a collision could divert the asteroid in its path – a necessary goal if ever Earth were to be the target of a direct hit by an incoming asteroid. </p>
<figure class="align-center ">
<img alt="Artist's impression of Hera mission." src="https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/564917/original/file-20231211-27-3yuer.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of Hera mission.</span>
<span class="attribution"><span class="source">Esa/wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Two years later, the European Space Agency’s <a href="https://www.esa.int/Space_Safety/Hera">Hera</a> mission will launch to visit the same pair of asteroids. It is not designed to hit either body, but to measure the effect of Dart’s earlier impact. At the time of the collision, the orbit of Dimorphos around Didymos got faster by 33 minutes – a significant movement that showed the path of an asteroid could be deflected. </p>
<p>But what we don’t know (and won’t until Hera arrives in 2026) is how effective the impact was. Has Dimorphos remained in its new orbit, bounced back into its old orbit, or continued to speed up? Hera will investigate in detail – and its results will help to define Earth’s planetary defence protocol. Assuming, that is, <a href="https://theconversation.com/dont-look-up-several-asteroids-are-heading-towards-earth-heres-how-we-deal-with-threats-in-real-life-174512">we take notice</a>.</p>
<h2>Europa Clipper</h2>
<p>Launching almost at the same time as Hera is a Nasa flagship mission: the <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=EUROPA-CL">Europa Clipper</a> to Jupiter’s icy moon, Europa.</p>
<p>This mission has been long-awaited, ever since the Galileo mission first showed us views of Europa’s icy surface in the late 1990s. Since then, we have learnt about the ocean that lurks beneath the icy shell. Excitingly, Europa <a href="https://theconversation.com/europa-there-may-be-life-on-jupiters-moon-and-two-new-missions-will-pave-the-way-for-finding-it-122551">may host life</a> in the form of a substantial fauna analogous to the animals that live on the deep ocean floor around hydrothermal vents. </p>
<figure class="align-center ">
<img alt="Artist's impression of Europa Clipper." src="https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&rect=9%2C9%2C1573%2C1360&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=528&fit=crop&dpr=1 600w, https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=528&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=528&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=664&fit=crop&dpr=1 754w, https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=664&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/564913/original/file-20231211-27-kjjpd2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=664&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Artist’s impression of Europa Clipper.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech</span></span>
</figcaption>
</figure>
<p>Europa Clipper will fly past Europa between 40 and 50 times, taking detailed images of the surface, monitoring the satellite for icy plumes – and, most importantly, looking to see whether this moon has the conditions suitable to support life. The mission will also investigate whether Europa’s ocean is salty, and whether the essential building blocks of life (carbon, nitrogen and sulphur) are present.</p>
<p>Sadly though, it is not until 2030 that any of these observations will be transmitted back to us, so we will have to wait patiently until then. The investigation will be complemented by observations from Esa’s Juice mission, which is currently on its way to Jupiter.</p>
<h2>MMX</h2>
<p>I began this article with mention of my delight at the return of material from Bennu. I will finish it with my anticipation of further delights to come. I know I have mentioned return of material from the Moon – but in fact, I am much more excited by the prospect of material returning from another moon. The moon in question is Phobos, one of the satellites of Mars. </p>
<p>The launch of the Japanese Space Agency’s <a href="https://theconversation.com/the-longstanding-mystery-of-mars-moons-and-the-mission-that-could-solve-it-219161">Martian Moon Exploration (MMX)</a> mission to Phobos is currently scheduled for September 2024, and designed to return material to Earth in 2029.</p>
<p>I’ll be 70 by the time the material comes back – but, I hope, not too decrepit to take pleasure in analysis of a unique sample from an enigmatic body.</p><img src="https://counter.theconversation.com/content/219440/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady works for The Open University. She receives funding from The UKRI-Science and Technology Facilities Council. She is a Senior Research Fellow at the Natural History Museum, London and Chancellor of Liverpool Hope University. She tweets (X's?) as @MonicaGrady</span></em></p>Moons and asteroids will be visited by spacecraft from Earth next year.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2201002023-12-22T15:47:25Z2023-12-22T15:47:25ZTatahouine: ‘Star Wars meteorite’ sheds light on the early Solar System<figure><img src="https://images.theconversation.com/files/567036/original/file-20231221-15-8f27sw.png?ixlib=rb-1.1.0&rect=26%2C15%2C1730%2C861&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The asteroid 4 vesta, left, and Tatooine, as seen in Star Wars, on the right. </span> <span class="attribution"><span class="source">Nasa and wikipedia</span></span></figcaption></figure><p>Locals watched in awe as a fireball exploded and hundreds of meteorite fragments rained down on the city of Tatahouine, Tunisia, on June 27, 1931. Fittingly, the city later became a major filming location of the Star Wars movie series. The desert climate and traditional villages became a huge inspiration to the director, George Lucas, who proceeded to name the fictional home planet of Luke Skywalker and Darth Vader “Tatooine”.</p>
<p>The mysterious 1931 meteorite, a rare type of <a href="https://www.britannica.com/science/achondrite">achondrite</a> (a meteorite that has experienced melting) known as a diogenite, is obviously not a fragment of Skywalker’s home planet. But it was similarly named after the city of Tatahouine. Now, a <a href="https://www.sciencedirect.com/science/article/pii/S0016703723006002">recent study</a> has gleaned important insights into the the origin of the meteorite – and the early Solar System.</p>
<p>Lucas filmed various scenes for Star Wars in Tatahouine. These include Episode IV – A New Hope (1977), Star Wars: Episode I – The Phantom Menace (1999) and Star Wars: Episode 2 – Attack of the Clones (2002). Various famous scenes <a href="https://www.smithsonianmag.com/sponsored/star-wars-tunisia-film-locations-180960144/">were filmed there</a>, including scenes of “<a href="https://www.youtube.com/watch?v=xISvvgAmNCI">Mos Espa</a>” and “Mos Eisley Cantina”. </p>
<p>Mark Hamill, the actor who played Luke Skywalker, reminisced about filming in Tunisia and discussed it with <a href="https://www.empireonline.com/movies/features/star-wars-force-awakens-complete-history-part-4/">Empire Magazine</a>: “If you could get into your own mind, shut out the crew and look at the horizon, you really felt like you were transported to another world”.</p>
<figure class="align-center ">
<img alt="Tatahouine, Tunisia." src="https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567073/original/file-20231221-25-k58kdp.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">Tatahouine, Tunisia.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Composition and origin</h2>
<p>Diogenites, named after the <a href="https://www.britannica.com/biography/Diogenes-Greek-philosopher">Greek philosopher Diogenes</a>, are igneous meteorites (rocks that have solidified from lava or magma). They formed at depth within an asteroid and cooled slowly, resulting in the formation of relatively large crystals. </p>
<p>Tatahouine is no exception, containing crystals as big as 5mm with black veins cutting cross the <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.1999.tb01734.x">sample</a> throughout. The black veins are called shock-induced impact melt veins, and are a result of high temperatures and pressures caused by a projectile smashing into the surface of the meteorite’s parent body. </p>
<p>The presence of these veins and the structure of the grains of pyroxene (minerals containing calcium, magnesium, iron, and aluminum) suggest the sample has experienced pressures of up to 25 gigapascals (GPa) of <a href="https://pubs.geoscienceworld.org/msa/ammin/article-abstract/87/8-9/1250/134170/Cristobalite-inclusions-in-the-Tatahouine">pressure</a>. To put that into perspective, the pressure at the bottom of the Mariana Trench, the <a href="https://www.scientificamerican.com/article/the-mariana-trench-is-7-miles-deep-whats-down-there/">deepest part of our ocean</a>, is only 0.1 GPa. So it is safe to say this sample has experienced a pretty hefty impact. </p>
<p>By evaluating the spectrum (light reflecting off their surface, broken down by wavelength) of <a href="https://iopscience.iop.org/article/10.3847/PSJ/acb268/meta">meteorites</a> and comparing it to asteroids and planets in our Solar System, it has been suggested that diogenites, including Tatahouine, originate from the second largest asteroid in our asteroid belt, known as <a href="https://science.nasa.gov/solar-system/asteroids/4-vesta/">4 Vesta</a>. </p>
<p>This asteroid possesses interesting and exciting information about the early Solar System. Many of the meteorites from 4 Vesta are ancient, around ~4 billion <a href="https://www.sciencedirect.com/science/article/pii/S0016703720300594">years</a>. Therefore, they offer a window to the past events of the early Solar System that we are unable to evaluate here on Earth.</p>
<h2>Violent past</h2>
<p>The recent study investigated 18 diogenites, including Tatahouine, all from 4 Vesta. The authors undertook “<a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/argon-argon-dating#:%7E:text=Like%20the%20conventional%20method%2C%20argon,40K%20in%20the%20sample.">radiometric argon-argon age dating</a>” techniques to determine the ages of the meteorites. This is based on looking at two different isotopes (versions of elements whose nuclei have more or fewer particles called neutrons). We know that a certain argon isotope in samples increases with age at a known rate, helping scientists estimate an age of a sample by comparing the ratio between two different isotopes.</p>
<p>The team also evaluated deformation caused by collisions, called impact events, using a type of electron microscope technique called <a href="https://en.wikipedia.org/wiki/Electron_backscatter_diffraction">electron backscatter diffraction</a>. </p>
<figure class="align-center ">
<img alt="Seven of the diogenites analysed." src="https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/567075/original/file-20231221-21-k58kdp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Seven of the diogenites analysed.</span>
<span class="attribution"><span class="source">F. Jourdan et al</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>By combining the age dating techniques and the microscope technique, the authors managed to map the timing of impact events on 4 Vesta and the early Solar System. The study suggests that 4 Vesta experienced ongoing impact events until 3.4 billion years ago when a catastrophic one occurred. </p>
<p>This catastrophic event, possibly another colliding asteroid, resulted in multiple smaller rubble pile asteroids being produced known as “<a href="https://science.nasa.gov/mission/dawn/science/vesta/">vestoids</a>”. Unravelling large scale impact events such as this, reveals the hostile nature of the early Solar System. </p>
<p>These smaller bodies experienced further collisions that caused material to hurtle to Earth over the last 50 to 60 million years – including the fireball in Tunisia. </p>
<p>Ultimately, this work demonstrates the importance of investigating meteorites – impacts have played a major role in the evolution of asteroids in our Solar System.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/star-wars-planet-with-two-suns-a-step-towards-luke-skywalkers-tatooine-3379">'Star Wars' planet with two suns: a step towards Luke Skywalker's Tatooine</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/220100/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ben Rider-Stokes receives funding from STFC. </span></em></p>George Lucas named Luke Skywalker’s home planet after a Tunisian town and meteorite.Ben Rider-Stokes, Post Doctoral Researcher in Achondrite Meteorites, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2175652023-11-20T14:37:39Z2023-11-20T14:37:39ZLibyan desert’s yellow glass: how we discovered the origin of these rare and mysterious shards<figure><img src="https://images.theconversation.com/files/559038/original/file-20231113-25-wg8y9j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The pieces of Libyan desert glass that formed the basis of the study.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>The <a href="https://www.lonelyplanet.com/egypt/western-desert/attractions/great-sand-sea/a/poi-sig/1500963/355269">Great Sand Sea Desert</a> stretches over an area of 72,000km² linking Egypt and Libya. If you find yourself in a particular part of the desert in south-east Libya and south-western parts of Egypt, you’ll spot pieces of yellow glass scattered across the sandy landscape. </p>
<p>It was first described in <a href="http://www.qattara.it/DESERTO%20EGIZIANO_FILES/silica.pdf">a scientific paper in 1933</a> and is known as <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/libyan-desert">Libyan desert glass</a>. Mineral collectors value it for its beauty, its relative rarity – and its mystery. A pendant found in Egyptian pharaoh Tutankhamun’s tomb <a href="https://egypt-museum.com/winged-scarab-pendant-of-tutankhamun/">contains a piece of the glass</a>. Natural glasses are found elsewhere in the world; examples include moldavites from the Ries crater in Europe and <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tektite">tektites from the Ivory Coast</a>. But none are as rich in silica as Libyan desert glass, nor are they found in such large lumps and quantities.</p>
<iframe title="" aria-label="Locator maps" id="datawrapper-chart-sLWYp" src="https://datawrapper.dwcdn.net/sLWYp/2/" scrolling="no" frameborder="0" style="width: 0; min-width: 100% !important; border: none;" height="600" data-external="1" width="100%"></iframe>
<p>The origin of the glass has been <a href="https://adsabs.harvard.edu/full/1998M%26PS...33..951G">the subject of debate</a> among scientists for almost a century. Some suggested it might be from <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/volcanic-glass">volcanoes on the moon</a>. Others propose it’s the product of lightning strikes (“<a href="https://museumsvictoria.com.au/media/5617/jmmv19592301.pdf#page=207">fulgurites</a>” – glass that forms from fusion of sand and soil where they are hit by lightning). Other theories suggest it’s the result of sedimentary or <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/hydrothermal-deposit#:%7E:text=From%20Hydrothermal%20Veins-,Hydrothermal%20deposits%20refer%20to%20the%20accumulation%20of%20minerals%20in%20fractures,can%20also%20heat%20circulating%20groundwater">hydrothermal processes</a>; caused by a massive explosion of a meteor in the air; or <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.2001.tb01960.x">that it came from a nearby meteorite crater</a>.</p>
<p>Now, thanks to advanced microscopy technology, we believe we have the answer. Along with colleagues from universities and science centres in Germany, Egypt and Morocco, I <a href="https://www.degruyter.com/document/doi/10.2138/am-2022-8759/html">have identified</a> Libyan desert glass as originating from the impact of a meteorite on the Earth’s surface.</p>
<p>Space collisions are a primary process in the solar system, as planets and their natural satellites accreted via the asteroids and planet embryos (also called planetesimals) colliding with each other. These impacts helped our planet to assemble, too.</p>
<h2>Under the microscope</h2>
<p>In 1996 scientists determined that the glass was close to <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1945-5100.1996.tb02017.x">29 million years old</a>. A <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/maps.12223">later study</a> suggested the source material was composed of quartz grains, coated with mixed clay minerals and iron and titanium oxides. </p>
<p>This latter finding raised more questions, since the proposed age is older than the matching source material in the relevant area of the Great Sand Sea desert. To put it simply: those source materials didn’t exist in that location 29 million years ago.</p>
<p>For our recent study, a co-author obtained two pieces of the glass from a local who had collected them in the Al Jaouf region in south-eastern Libya. </p>
<p>We studied the samples with a state-of-the-art transmission electron microscopy (TEM) technique, which allows us to see tiny particles of material – 20,000 times smaller than the thickness of a paper sheet. Using this super-high magnification technique, we found small minerals in this glass: different types of zirconium oxide (ZrO₂). </p>
<p>Minerals are composed of chemical elements, atoms of which form regular three-dimensional packaging. Imagine putting eggs or soda bottles on the shelf of a supermarket: layers on top of layers to ensure the most efficient storage. Similarly, atoms assemble into a crystal lattice that is unique for each mineral. Minerals that have the same chemical composition but different atomic structure (different ways of atom packaging into the crystal lattice) are called polymorphs. </p>
<p>One polymorph of ZrO₂ that we observed in Libyan desert glass is called cubic zirconia – the kind seen in some jewellery as a synthetic replacement for diamonds. This mineral can only form at a high temperature between 2,250°C and 2,700°C. </p>
<p>Another polymorph of ZrO₂ that we observed was a very rare one called ortho-II or OII. It forms at very high pressure – about 130,000 atmospheres, a unit of pressure. </p>
<p>Such pressure and temperature conditions provided us with the proof for the meteorite impact origin of the glass. That’s because such conditions can only be obtained in the Earth’s crust by a meteorite impact or the explosion of an atomic bomb.</p>
<h2>More mysteries to solve</h2>
<p>If our finding is correct (and we believe it is), the parental crater – where the meteorite hit the Earth’s surface – should be somewhere nearby. The nearest known meteorite craters, named GP and Oasis, are 2km and 18km in diameter respectively, and quite far away from where the glass we tested was found. They are too far and too small to be considered the parental craters for such massive amounts of impact glass, all concentrated in one spot.</p>
<figure class="align-center ">
<img alt="A landscape photograph of sand dunes that appear almost golden in colour, stretching far into the distance." src="https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559039/original/file-20231113-25-mccnnq.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">The Great Sand Sea desert.</span>
<span class="attribution"><span class="source">Sylvester Adams</span></span>
</figcaption>
</figure>
<p>So, while we’ve solved part of the mystery, more questions remain. Where is the parental crater? How big is it – and where is it? Could it have been eroded, deformed or covered by sand? More investigations will be required, likely in the form of remote sensing studies coupled with geophysics.</p><img src="https://counter.theconversation.com/content/217565/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizaveta Kovaleva receives funding from the Alexander von Humboldt Foundation. </span></em></p>Libyan desert glass originated from the impact of a meteorite on the Earth’s surface.Elizaveta Kovaleva, Lecturer, University of the Western CapeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2163252023-11-14T20:40:34Z2023-11-14T20:40:34ZNASA’s first successful recovery of asteroid samples may reveal information about the origins of the universe<figure><img src="https://images.theconversation.com/files/557189/original/file-20231101-21-frh04h.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2047%2C1363&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The OSIRIS-REx capsule carrying samples from the asteroid Bennu lands in Utah on Sept. 24, 2023. </span> <span class="attribution"><a class="source" href="https://www.nasa.gov/news-release/nasas-first-asteroid-sample-has-landed-now-secure-in-clean-room/">(NASA/Keegan Barber)</a></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/nasas-first-successful-recovery-of-asteroid-samples-may-reveal-information-about-the-origins-of-the-universe" width="100%" height="400"></iframe>
<p>The <a href="https://science.nasa.gov/mission/osiris-rex/">OSIRIS-REx mission</a> is NASA’s first mission to collect samples from an asteroid — in this case <a href="https://science.nasa.gov/solar-system/asteroids/101955-bennu/">101955 Bennu</a> — and return to Earth.</p>
<p>OSIRIS-REx is an acronym for Origins, Spectral Interpretation, Resource Identification, and Security - Regolith Explorer. The sealed capsule landed on Sept. 24 near Salt Lake City, Utah, a feat that was broadcast live by NASA.</p>
<p>My research investigates geologic samples in craters formed by meteorite collisions on Earth. These samples include materials that can be found on other planetary bodies like the moon, Mars and asteroids. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Kdwyqctp908?wmode=transparent&start=5" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">NASA’s live feed of OSIRIS-REx landing on Sept. 24.</span></figcaption>
</figure>
<h2>Asteroid samples</h2>
<p>Planning for the OSIRIS-REx mission <a href="https://doi.org/10.1007/s11214-017-0405-1">dates back to the 2010s</a>, but the vision of a mission to bring back samples of an asteroid goes back even further. </p>
<p>The importance of planetary sample return missions was already being recognized in the 1960s, during the <a href="https://www.nasa.gov/specials/apollo50th/missions.html">Apollo era</a>, with the collection of <a href="https://curator.jsc.nasa.gov/lunar/">several suites of lunar rock samples by astronauts</a>. </p>
<p>In 1986, comet Halley’s <a href="https://science.nasa.gov/solar-system/comets/1p-halley/">close approach to Earth</a> sparked an interest in the global scientific community to explore planetary objects like comets and asteroids. The European Space Agency’s <a href="https://rosetta.esa.int/">Rosetta mission to comet 67P/Churyumov–Gerasimenko</a>, which also performed fly-bys of two asteroids on the journey, and the Japan Aerospace Exploration Agency’s (JAXA) <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2003-019A">Hayabusa 1</a> and <a href="https://www.hayabusa2.jaxa.jp/en/">Hayabusa 2</a> missions to near-Earth asteroids (NEAs) are some of the important milestones that laid the foundation for exploratory missions to comets and asteroids. </p>
<p>Asteroid Bennu was chosen by NASA for the OSIRIS-REx mission after rigorous discussions that considered the scientific and engineering capabilities of the mission. Bennu is a <a href="https://www.jpl.nasa.gov/asteroid-watch">near-Earth asteroid (NEA)</a> that has been studied extensively by Earth-based telescopic observations in the last two decades, making it a strategic target for an exploratory mission.</p>
<p>Bennu is a carbonaceous asteroid — a class of asteroids that contain <a href="https://www.nasa.gov/news-release/nasas-bennu-asteroid-sample-contains-carbon-water/">a high amount of carbon</a>. It is also pristine, meaning that its material was created in the early stages of solar system formation and is preserved in an unaltered condition.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1714381659418591654"}"></div></p>
<h2>Mission significance</h2>
<p>The question of how life came to be on Earth has fascinated people for <a href="https://www.esa.int/Science_Exploration/Space_Science/Searching_for_the_origins_of_life_Charles_Darwin">a long time</a>. Understanding the origin and history of the Earth can shed light on how life on Earth began.</p>
<p>Earth has a very dynamic environment, from a thick atmosphere to a very active biosphere and a vast expanse of water oceans. Most material on Earth that was present when the Earth first formed has been significantly modified by dynamic processes like weathering and erosion by elements like water or wind, active plate tectonics, active volcanism, as well as human activities such as mining or excavation. </p>
<p>Asteroids, on the other hand, have very little to no modification since their formation, going back to the time of the formation of our solar system. </p>
<p>Pieces of asteroids, and other planetary bodies such as the moon or Mars, land on the Earth’s surface, in the form of meteorites, <a href="https://ares.jsc.nasa.gov/meteorite-falls/events/">almost every year</a>. These meteorites are invaluable to our knowledge of the solar system, but most of these samples originate from unknown sources. </p>
<h2>Known sources</h2>
<p>A planned robotic mission to bring a sample from an asteroid ensures that the source of the material is known and can help correlate the information gained from <a href="https://doi.org/10.2343/geochemj.2.0350">previous studies of unknown samples</a>, as well as remote observations of the asteroid to direct observations from collected samples. </p>
<p>Specifically, as asteroid Bennu is a carbonaceous asteroid, analyses of its samples can lead to a higher knowledge of pristine carbon in our solar system and improve our understanding of the role that asteroids may have played in the origin of life on Earth. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/oFvIuSpACQA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Watch NASA scientists reveal the asteroid sample for the first time.</span></figcaption>
</figure>
<p>OSIRIS-REx was not the first global asteroid sample return mission. In 2010, the Japan Aerospace Exploration Agency completed the <a href="https://doi.org/10.1016/S0094-5765(96)00118-X">first asteroid sample return mission</a>, Hayabusa 1, that brought back <a href="https://curator.jsc.nasa.gov/hayabusa/">a sample weighing less than one gram from the asteroid Itokawa</a>. More recently, in 2020, <a href="https://www.hayabusa2.jaxa.jp/en/">Hayabusa 2 returned from asteroid 162173 Ryugu with a 5.4g soil sample</a>.</p>
<p>The Hayabusa 2 mission has already resulted in research revealing the nature of <a href="https://doi.org/10.1038/s41467-023-36268-8">some of the oldest known materials in our solar system</a>.</p>
<h2>A continued search</h2>
<p>The OSIRIS-REx mission continues to explore space. The spacecraft has been rebranded as OSIRIS-APEX, and is <a href="https://www.hou.usra.edu/meetings/acm2023/pdf/2353.pdf">currently on its way to the asteroid Apophis</a> on a nearly six-year long journey to conduct a fly-by of the asteroid.</p>
<p>Innovations required for the exploration of space and planetary bodies have historically been shown to <a href="https://www.asc-csa.gc.ca/eng/about/everyday-benefits-of-space-exploration/">benefit life on Earth</a>. </p>
<p>For example, satellite technology, a concept that we depend so heavily upon in our daily lives — from navigation systems as well as national security or monitoring of natural landforms and ecosystems — is a product of space exploration. </p>
<p>As we attempt to venture deeper into the outer space, we can expect to see more creative technological advancements that will eventually help solve problems on Earth.</p><img src="https://counter.theconversation.com/content/216325/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neeraja Chinchalkar 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>In September 2023, a NASA mission successfully brought samples of an asteroid down to Earth in a sealed capsule. Analysis of these samples may reveal information about the origins of the universe.Neeraja Chinchalkar, PhD in Earth and Planetary Science and Exploration, Western UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2149172023-11-02T12:33:11Z2023-11-02T12:33:11ZNASA’s robotic prospectors are helping scientists understand what asteroids are made of – setting the stage for miners to follow someday<figure><img src="https://images.theconversation.com/files/557153/original/file-20231101-25-cep1ng.jpg?ixlib=rb-1.1.0&rect=11%2C5%2C3982%2C2233&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mining an asteroid probably won't look exactly like mining does on Earth, but some principles will stay the same. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/mining-and-extraction-of-raw-materials-on-the-royalty-free-image/1433072451?phrase=asteroid+mining&adppopup=true">posteriori/iStock via Getty Images</a></span></figcaption></figure><p>The cars, cellphones, computers and televisions that people in the U.S. use every day require metals like copper, cobalt and platinum to build. Demand from the electronics industry for these metals is only rising, and companies are constantly searching for new places on Earth to mine them.</p>
<p>Scientists estimate that lots of these metals exist thousands of miles beneath Earth’s surface, in its molten core, but that’s far <a href="https://www.youtube.com/watch?v=NXFBJr8XRlQ">too deep and hot to mine</a>. Instead, some companies hope to one day search for deposits that are literally out of this world — on asteroids.</p>
<p>The commercialization of asteroid mining is still a ways off, but in October 2023, NASA launched a scientific mission to explore the <a href="https://science.nasa.gov/mission/psyche">metal-rich asteroid Psyche</a>. The <a href="https://theconversation.com/nasas-psyche-mission-to-a-metal-world-may-reveal-the-mysteries-of-earths-interior-206913">main goal of the mission</a> is studying the composition and structure of this asteroid, which could tell scientists more about Earth’s core since the two objects might have a similar makeup. </p>
<p>Both likely contain platinum, nickel, iron and possibly even gold – materials of commercial interest.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/TgVorJfM8BM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Experts need to know what’s out there on asteroids before considering whether they’re worth mining. NASA’s Psyche mission could answer some of these questions.</span></figcaption>
</figure>
<p><a href="https://valeriepayre.weebly.com/">I am a planetary geologist</a> whose work explores other planets and astronomical objects like Mars, Venus and the Moon. I will be following the Psyche mission closely, as this is the first time that scientists will be able to learn about the composition and structure of <a href="https://www.jpl.nasa.gov/missions/psyche">a possible piece of a planetary core similar to the Earth’s</a>, without indirect seismic or magnetic measurements, or replicating the pressure and temperature conditions of the Earth’s core in our labs. </p>
<p>With the spacecraft estimated to arrive at the asteroid’s orbit in 2029, the findings from the Psyche mission will provide unique insights into the type of metals present on the asteroid’s surface, as well as their amount, and the minerals containing these metals. This data is essential both for scientists like me exploring the formation and evolution planetary bodies, as well as for companies investigating the possibility of asteroid mining.</p>
<h2>Asteroid formation</h2>
<p>Asteroids come in a <a href="https://science.nasa.gov/solar-system/asteroids/facts/">variety of sizes</a>. Some are the size of a town, while others are the size of a state. Most asteroids are made of rocks and represent the leftovers from the early <a href="https://science.nasa.gov/solar-system/facts/">formation of our solar system</a> around 4.6 billion years ago.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's illustration of a gray asteroid with some yellow-ish surfaces, and two large circular craters." src="https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=533&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=533&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=533&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=670&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=670&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554412/original/file-20231017-29-nm2shd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=670&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 Psyche asteroid.</span>
<span class="attribution"><a class="source" href="https://science.nasa.gov/solar-system/asteroids/16-psyche/">NASA/JPL-Caltech/ASU</a></span>
</figcaption>
</figure>
<p>Not every asteroid is the same – some, like Bennu, the target of <a href="https://science.nasa.gov/mission/osiris-rex/">NASA’s OSIRIS-REx mission</a>, are rich in carbon. These are very old, and they will teach scientists more about how planets formed and how life may have begun on Earth. </p>
<p><a href="https://theconversation.com/nasas-psyche-mission-to-a-metal-world-may-reveal-the-mysteries-of-earths-interior-206913">Others, like Psyche</a>, are made of metals and potentially result from one or more collisions between astronomical objects when the solar system was forming. These collisions left debris flying through space — including potential pieces of a planet’s metal-rich core. A NASA spacecraft will orbit and analyze the surface of Psyche.</p>
<h2>Mining in space</h2>
<p>Not every mineral deposit on Earth is mineable. Companies first look for deposits with a <a href="https://www.americangeosciences.org/critical-issues/faq/what-happens-during-and-after-mining">high level of metal purity</a>. They also investigate how affordable and feasible extracting the metal would be before choosing where to mine. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A bird's eye view of a gray rock, with a red crane on it." src="https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557155/original/file-20231101-25-m9vm22.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"></a>
<figcaption>
<span class="caption">Before mining, companies think about whether a deposit will yield enough metal. The same principle applies to asteroid mining.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aerial-image-directly-above-an-industrial-machine-royalty-free-image/1443957870?phrase=mine&adppopup=true">Abstract Aerial Art/DigitalVision via Getty Images</a></span>
</figcaption>
</figure>
<p>Similarly, before mining an asteroid, companies will have to think about all those factors, and they’ll have to come up with the infrastructure needed to mine at a distance and transport the metals they mine hundreds of millions of miles back to Earth. The technology to do that is still years away, and transporting metals would require major funding.</p>
<p>A <a href="https://builtin.com/aerospace/top-space-mining-companies">few companies</a> around the world have already started to think about what the best and lowest cost approach would be, drawing from processes similar to those used on Earth. </p>
<p>The first step would be <a href="https://doi.org/10.1007/978-3-319-90303-3_6">finding a mineable metal deposit</a>. Next, they’d drill and <a href="https://www.hou.usra.edu/meetings/acm2023/pdf/2492.pdf?ref=karmanplus.com">extract the metals on the asteroid</a>. One of the most important differences with Earth mines is that each step would be undertaken remotely with spacecrafts orbiting around the asteroid and robots landing on its surface. Then, a spacecraft would send the resulting materials back to Earth. </p>
<p>Asteroid mining plans are still at their earliest stages. A few companies like <a href="https://spacenews.com/asteroid-mining-company-planetary-resources-acquired-by-blockchain-firm/">Planetary Resources</a> and <a href="https://spacenews.com/deep-space-industries-acquired-by-bradford-space/">Deep Space Industries</a>, with goals to extract metals from space, were acquired by other companies. </p>
<p>Experts can’t quite tell yet how acquiring valuable metals from asteroids would affect the global economy, but these metals could potentially flood the market and <a href="https://hir.harvard.edu/economics-of-the-stars/">lower their values</a>.</p>
<p>The Psyche mission is a huge step in figuring out what sort of metals are out there, and it may also answer questions about the composition and properties of Earth’s core.</p><img src="https://counter.theconversation.com/content/214917/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Valerie Payré 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>Upcoming NASA missions will help scientists understand the composition of asteroids – which could inform companies one day hoping to commercially mine asteroids.Valerie Payré, Assistant Professor of Earth and Environmental Sciences, University of IowaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2161372023-10-27T12:17:17Z2023-10-27T12:17:17ZAsteroids in the solar system could contain undiscovered, superheavy elements<figure><img src="https://images.theconversation.com/files/555902/original/file-20231025-23-pgf5be.jpg?ixlib=rb-1.1.0&rect=52%2C30%2C4981%2C3426&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An illustration of an asteroid orbiting through space. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/illustration-of-an-asteroid-royalty-free-illustration/973895632?phrase=asteroid&adppopup=true">Mark Garlick/Science Photo Library via Getty Images</a></span></figcaption></figure><p>For centuries, the <a href="https://sciencenotes.org/when-were-the-elements-discovered-timeline-and-periodic-table/">quest for new elements</a> was a driving force in many scientific disciplines. Understanding an atom’s structure and the development of nuclear science allowed scientists to accomplish the old goal of <a href="https://www.merriam-webster.com/dictionary/alchemy">alchemists</a> – <a href="https://www.britannica.com/science/transmutation">turning one element into another</a>. </p>
<p>Over the past few decades, scientists in the <a href="https://www.lbl.gov/">United States</a>, <a href="https://www.helmholtz.de/en/about-us/helmholtz-centers/centers-a-z/centre/gsi-helmholtz-centre-for-heavy-ion-research/">Germany</a> and <a href="https://www.iaea.org/contact/joint-institute-for-nuclear-research-jinr">Russia</a> have figured out how to use special tools <a href="https://physicalsciences.lbl.gov/2023/10/16/berkeley-lab-to-test-new-approach-to-making-superheavy-elements/">to combine two atomic nuclei</a> and create new, <a href="https://doi.org/10.1146/annurev-nucl-102912-144535">superheavy elements</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A periodic table, with each group a different color." src="https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=411&fit=crop&dpr=1 754w, https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=411&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/555904/original/file-20231025-30-pcmast.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=411&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 heaviest element on the periodic table has 118 protons.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Periodic_table_%28JPEG_version%29.jpg">Licks-rocks/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>These heavy elements usually aren’t stable. Heavier elements <a href="https://www.energy.gov/science/doe-explainsprotons">have more protons</a>, or positively charged particles in the nucleus; some that scientists have created <a href="https://www.smithsonianmag.com/science-nature/when-will-we-reach-end-periodic-table-180957851/">have up to 118</a>. With that many protons, the electromagnetic repulsive forces between protons in the atomic nuclei overwhelm the attractive nuclear force that keeps the nucleus together. </p>
<p>Scientists have <a href="https://doi.org/10.1007/BF01172015">predicted for a long time</a> that elements with around 164 protons could have a relatively long <a href="https://www.britannica.com/science/half-life-radioactivity">half-life</a>, or even be stable. They call this the “<a href="https://www.eurekalert.org/news-releases/627973">island of stability</a>” – here, the attractive nuclear force is strong enough to balance out any electromagnetic repulsion. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A purple piece of machinery in a concrete room with metal boxes and cables coming off it." src="https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556194/original/file-20231026-23-l75f9c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scientists at Lawrence Berkeley National Laboratory have constructed experiments that can weigh superheavy elements.</span>
<span class="attribution"><a class="source" href="https://science.osti.gov/np/Highlights/2019/NP-2019-08-c">Marilyn Chung, Lawrence Berkeley National Laboratory</a></span>
</figcaption>
</figure>
<p>Since heavy elements are difficult to make in the lab, <a href="https://scholar.google.com/citations?user=7GzPpUgAAAAJ&hl=en">physicists like me</a> have been looking for these elements everywhere, <a href="https://www.scientificamerican.com/article/the-quest-for-superheavy-elements-and-the-island-of-stability/">even beyond the Earth</a>. To narrow down the search, we need to know what sort of natural processes could produce these elements. We also need to know what properties they have, like their mass densities. </p>
<h2>Calculating density</h2>
<p>From the outset, my team wanted to figure out the mass density of these superheavy elements. This property could tell us more about how the atomic nuclei of these elements behave. And once we had an idea about their density, we could get a better sense of where these elements might be hiding. </p>
<p>To figure out the mass density and other <a href="https://doi.org/10.1007/BFb0116498">chemical properties</a> of these elements, my research team used a model that represents an atom of each of these heavy elements as a single, charged cloud. This model works well for large atoms, particularly metals that are laid out in a lattice structure.</p>
<p>We first <a href="https://doi.org/10.1140/epjp/s13360-023-04454-8">applied this model</a> to atoms with known densities and calculated their chemical properties. Once we knew it worked, we used the model to calculate the density of elements with 164 protons, and other elements in this island of stability. </p>
<p>Based on our calculations, we expect stable metals with atomic numbers around 164 to have densities between 36 to 68 g/cm<sup>3</sup> (21 to 39 oz/in<sup>3</sup>). However, in our calculations, we used a conservative assumption about the mass of atomic nuclei. It’s possible that the actual range is up to 40% higher. </p>
<h2>Asteroids and heavy elements</h2>
<p>Many scientists <a href="https://www.nationalgeographic.com/science/article/101209-asteroid-collisions-earth-gold-science-space">believe that gold</a> and other heavy metals were deposited on Earth’s surface after <a href="https://earthsky.org/earth/did-meteorites-bombard-earth-with-gold/">asteroids collided with the planet</a>. </p>
<p>The same thing could have happened with these superheavy elements, but super mass dense heavy elements sink into ground and are eliminated from near the Earth’s surface by the <a href="https://www.usgs.gov/news/science-snippet/earthword-subduction">subduction of tectonic plates</a>. However, while researchers might not find superheavy elements on Earth’s surface, they could still be in asteroids like the ones that might have brought them to this planet.</p>
<p>Scientists have estimated that some asteroids have mass densities greater than that of <a href="https://www.rsc.org/periodic-table/element/76/osmium">osmium</a> (22.59 g/cm<sup>3</sup>, 13.06 oz/in<sup>3</sup>), the densest element found on Earth. </p>
<p>The largest of these objects is asteroid 33, which is <a href="https://en.wikipedia.org/wiki/33_Polyhymnia">nicknamed Polyhymnia</a> and has a calculated density of 75.3 g/cm<sup>3</sup> (43.5 oz/in<sup>3</sup>). But this density might not be quite right, since it’s quite difficult to measure the mass and volume of far-away asteroids.</p>
<p>Polyhymnia isn’t the only dense asteroid out there. In fact, there’s a whole class of superheavy objects, including asteroids, which could contain these superheavy elements. Some time ago, I introduced the name <a href="https://doi.org/10.1103/PhysRevLett.110.111102">Compact Ultradense Objects, or CUDOs</a>, for this class. </p>
<p>In a study published in October 2023 in the <a href="https://doi.org/10.1140/epjp/s13360-023-04454-8">European Physical Journal Plus</a>, my team suggested some of the CUDOs orbiting in the solar system might still contain some of these <a href="https://www.youtube.com/watch?v=wj7BM6Jt-4I">dense, heavy elements</a> in their cores. Their surfaces would have accumulated normal matter over time and would appear normal to a distant observer.</p>
<p>So how are these <a href="https://doi.org/10.1103/RevModPhys.93.015002">heavy elements produced</a>? Some extreme astronomical events, like <a href="https://www.scientificamerican.com/article/how-star-collisions-forge-the-universes-heaviest-elements/">double star mergers</a> could be hot and dense enough to produce stable superheavy elements. </p>
<p>Some of the superheavy material could then remain on board asteroids created in these events. They could stay packed in these asteroids, which orbit the solar system for billions of years.</p>
<h2>Looking to the future</h2>
<p>The <a href="https://www.esa.int/Science_Exploration/Space_Science/Gaia_overview">Eurpoean Space Agency’s Gaia mission</a> aims to create the largest, most precise three-dimensional map of everything in the sky. Researchers could use these extremely precise results to <a href="https://doi.org/10.3847/1538-3881/ace52b">study the motion of asteroids</a> and figure out which ones might have an unusually large density.</p>
<p>Space missions are being conducted to collect material from the surfaces of asteroids and analyze them back on Earth. Both NASA and the <a href="https://global.jaxa.jp/">Japanese state space agency JAXA</a> have targeted low density near-Earth asteroids with success. Just this month, NASA’s <a href="https://science.nasa.gov/mission/osiris-rex/">OSIRIS-REx</a> mission brought back a sample. Though the sample analysis is just getting started, there is a very small chance it could harbor dust containing superheavy elements accumulated over billions of years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A diagram showing the Psyche spacecraft's approach to the asteroid, where it starts at Earth in the center and moves in a counterclockwise spiral to the top of the screen, where it arrives at the asteroid." src="https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/556232/original/file-20231026-29-oeel6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Psyche spacecraft has left Earth. It will use the gravitational field of Mars to carry it closer to the asteroid. It will then orbit the asteroid and collect data.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia24930-psyches-mission-plan">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>One mass-dense dust and rock sample brought back to Earth would be enough. <a href="https://science.nasa.gov/mission/psyche/">NASA’s Psyche mission</a>, which launched in October 2023, will fly to and sample <a href="https://www.smithsonianmag.com/smart-news/nasa-launches-mission-to-study-distant-asteroid-180983072/">a metal-rich asteroid</a> with a greater chance of harboring superheavy elements. More asteroid missions like this will help scientists better understand the properties of asteroids orbiting in the solar system.</p>
<p>Learning more about asteroids and exploring potential sources of superheavy elements will help scientists continue the century-spanning quest to characterize the matter that makes up the universe and better understand how objects in the solar system formed. </p>
<p><em>Evan LaForge, an undergraduate student studying physics and mathematics, is the lead author on <a href="https://doi.org/10.1140/epjp/s13360-023-04454-8">this research</a> and helped with the writing of this article, along with Will Price, a physics graduate student.</em></p><img src="https://counter.theconversation.com/content/216137/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Johann Rafelski 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>Scientists have been searching Earth’s surface for superheavy elements too difficult to make in the lab, but now, many are looking to the skies instead.Johann Rafelski, Professor of Physics, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2146142023-10-24T12:22:02Z2023-10-24T12:22:02ZSpace rocks and asteroid dust are pricey, but these aren’t the most expensive materials used in science<figure><img src="https://images.theconversation.com/files/552576/original/file-20231006-23-aam2il.jpg?ixlib=rb-1.1.0&rect=0%2C34%2C5751%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Meteorites can get pricey, but they're not the most expensive material. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/FranceMeteoriteAuction/e075e1b22656489db39610bafb0682af/photo?Query=meteorites&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=341&currentItemNo=5&vs=true">AP Photo/Thibault Camus</a></span></figcaption></figure><p>After a journey of seven years and nearly 4 billion miles, <a href="https://science.nasa.gov/mission/osiris-rex">NASA’s OSIRIS-REx</a> <a href="https://www.space.com/osiris-rex-asteroid-samples-land-houston">spacecraft landed</a> gently in the Utah desert on the morning of Sept. 24, 2023, with a precious payload. <a href="https://science.nasa.gov/mission/osiris-rex">The spacecraft</a> brought back a sample from the asteroid Bennu.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artist's illustration of a gray metallic spacecraft hovering above the dark surface of an asteroid, with an arm that reaches down to the surface." src="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552573/original/file-20231006-27-cm9a07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">OSIRIS-REx collected a sample from the asteroid Bennu.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/20c047ec48f74f6995ffad6b0f54422c?ext=true">NASA/Goddard Space Flight Center via AP</a></span>
</figcaption>
</figure>
<p>Roughly half a pound of material collected from the <a href="https://science.nasa.gov/solar-system/asteroids/101955-bennu/facts/">85 million-ton asteroid</a> (77.6 billion kg) will help scientists learn about the <a href="https://solarsystem.nasa.gov/missions/osiris-rex/in-depth/">formation of the solar system</a>, including whether <a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/101955-bennu/in-depth/">asteroids like Bennu</a> include the chemical ingredients for life.</p>
<p>NASA’s mission was budgeted at <a href="https://www.asteroidmission.org/qa/">US$800 million</a> and will end up costing around <a href="https://www.planetary.org/space-policy/cost-of-osiris-rex">$1.16 billion</a> for <a href="https://www.nasa.gov/news-release/nasas-first-asteroid-sample-has-landed-now-secure-in-clean-room/">just under 9 ounces of sample</a> (255 g). But is this the most expensive material known? Not even close.</p>
<p>I’m a <a href="https://scholar.google.com/citations?user=OrRLRQ4AAAAJ&hl=en">professor of astronomy</a>. I use Moon and Mars rocks in my teaching and have a modest collection of meteorites. I marvel at the fact that I can hold in my hand something that is billions of years old from billions of miles away.</p>
<h2>The cost of sample return</h2>
<p>A handful of asteroid works out to $132 million <a href="https://www.hoodmwr.com/things-that-weigh-around-1-ounce/">per ounce</a>, or $4.7 million per gram. That’s about 70,000 times the <a href="https://goldprice.org/">price of gold</a>, which has been in the range of $1,800 to $2,000 per ounce ($60 to $70 per gram) for the past few years.</p>
<p>The first extraterrestrial material returned to Earth came from the Apollo program. Between 1969 and 1972, six Apollo missions brought back 842 pounds (382 kg) of <a href="https://curator.jsc.nasa.gov/lunar/">lunar samples</a>.</p>
<p>The <a href="https://www.planetary.org/space-policy/cost-of-apollo">total price tag</a> for the Apollo program, adjusted for inflation, was $257 billion. These Moon rocks were a relative bargain at $19 million per ounce ($674 thousand per gram), and of course Apollo had additional value in demonstrating technologies for human spaceflight. </p>
<p>NASA is planning to bring samples back from Mars in the early 2030s to see if any contain traces of ancient life. The <a href="https://mars.nasa.gov/msr/">Mars Sample Return</a> mission aims to return <a href="https://www.universetoday.com/161264/we-can-only-bring-30-samples-of-mars-back-to-earth-how-do-we-decide/">30 sample tubes</a> with a <a href="https://downloads.regulations.gov/NASA-2022-0002-0002/attachment_5.pdf">total weight of a pound</a> (450 g). The <a href="https://science.nasa.gov/mission/mars-2020-perseverance">Perseverance rover</a> has already <a href="https://www.universetoday.com/160109/perseverance-is-building-up-a-big-collection-of-mars-samples/">cached 10 of these samples</a>. </p>
<p>However, <a href="https://www.science.org/content/article/mars-sample-return-got-new-price-tag-it-s-big">costs have grown</a> because the mission is complex, involving multiple robots and spacecraft. Bringing back the samples could run $11 billion, putting their cost at $690 million per ounce ($24 million per gram), five times the unit cost of the Bennu samples.</p>
<h2>Some space rocks are free</h2>
<p>Some space rocks cost nothing. Almost 50 tons of free samples from the solar system <a href="https://science.nasa.gov/solar-system/meteors-meteorites/">rain down on the Earth</a> every day. Most burn up in the atmosphere, but if they reach the ground <a href="https://www.amnh.org/explore/news-blogs/on-exhibit-posts/meteor-meteorite-asteroid">they’re called meteorites</a>, and most of those come from asteroids. </p>
<p><a href="https://www.nhm.ac.uk/discover/types-of-meteorites.html">Meteorites can get costly</a> because it can be difficult to recognize and retrieve them. Rocks all look similar unless you’re a geology expert. </p>
<p>Most meteorites are stony, <a href="https://www.britannica.com/science/chondrite">called chondrites</a>, and they can be bought online for as little as $15 per ounce (50 cents per gram). Chondrites differ from normal rocks in containing <a href="https://www.amnh.org/exhibitions/permanent/meteorites/origins-of-the-solar-system/chondrules">round grains called chondrules</a> that formed as molten droplets in space at the birth of the solar system 4.5 billion years ago.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A meteorite that looks like a long gray rock with dark gray veins running across it." src="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=305&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=305&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=305&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=384&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=384&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552568/original/file-20231006-19-kgbnz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=384&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A chondrite from the Viñales meteorite, which originated from the asteroid belt between Mars and Jupiter.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Ordinary_chondrite_%28Vi%C3%B1ales_Meteorite%29_15.jpg">Ser Amantio di Nicolao/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p><a href="https://aerolite.org/shop/iron-meteorites/">Iron meteorites</a> are distinguished by a dark crust, caused by melting of the surface as they come through the atmosphere, and an internal pattern of long metallic crystals. They cost $50 per ounce ($1.77 per gram) or even higher. <a href="https://geology.com/meteorites/value-of-meteorites.shtml">Pallasites</a> are stony-iron meteorites laced with the mineral olivine. When cut and polished, they have a translucent yellow-green color and can cost over $1,000 per ounce ($35 per gram).</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A brown-gray meteorite that's roughly circular with textured ridges" src="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552571/original/file-20231006-21-vjnv0r.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">An iron meteorite.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Odessa_%28iron%29_meteorite.jpg">Llez/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>More than a few meteorites have reached us from the Moon and Mars. Close to 600 have been recognized as <a href="https://sites.wustl.edu/meteoritesite/items/lunar-meteorites/">coming from the Moon</a>, and <a href="https://www.catawiki.com/en/stories/4683-10-most-expensive-meteorites-ever-offered-up-on-earth">the largest</a>, weighing 4 pounds (1.8 kg), sold for a price that works out to be about $4,700 per ounce ($166 per gram). </p>
<p>About 175 meteorites are identified as <a href="https://www2.jpl.nasa.gov/snc/">having come from Mars</a>. <a href="https://aerolite.org/shop/mars-meteorites/">Buying one</a> would cost about $11,000 per ounce ($388 per gram). </p>
<p>Researchers can figure out <a href="https://science.nasa.gov/solar-system/meteors-meteorites/facts/">where meteorites come from</a> by using their landing trajectories to project their paths back to the asteroid belt or comparing their composition with different classes of asteroids. Experts can tell where Moon and Mars rocks come from by their geology and mineralogy.</p>
<p>The limitation of these “free” samples is that there is no way to know where on the Moon or Mars they came from, which limits their scientific usefulness. Also, they start to get contaminated as soon as they land on Earth, so it’s hard to tell if any microbes within them are extraterrestrial.</p>
<h2>Expensive elements and minerals</h2>
<p>Some elements and minerals are expensive because they’re scarce. Simple <a href="http://www.leonland.de/elements_by_price/en/list">elements in the periodic table</a> have low prices. Per ounce, carbon costs one-third of a cent, iron costs 1 cent, aluminum costs 56 cents, and even mercury is less than a dollar (per 100 grams, carbon costs $2.40, iron costs less than a cent and alumnium costs 19 cents). Silver is $14 per ounce (50 cents per gram), and gold, $1,900 per ounce ($67 per gram). </p>
<p><a href="https://alansfactoryoutlet.com/how-much-do-elements-cost-the-price-of-75-elements-per-kilogram/">Seven radioactive elements</a> are extremely rare in nature and so difficult to create in the lab that they eclipse the price of NASA’s Mars Sample Return. Polonium-209, the most expensive of these, costs $1.4 trillion per ounce ($49 billion per gram).</p>
<p>Gemstones can be expensive, too. <a href="https://www.gemsociety.org/article/emerald-jewelry-and-gemstone-information/">High-quality emeralds</a> are 10 times the <a href="https://goldprice.org/">price of gold</a>, and <a href="https://ajediam.com/diamond-prices/white-natural-diamond/">white diamonds</a> are 100 times the price of gold. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A circular white diamond sitting on a white surface." src="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=727&fit=crop&dpr=1 600w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=727&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=727&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=914&fit=crop&dpr=1 754w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=914&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/554101/original/file-20231016-15-63z3ek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=914&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">High-quality white diamonds can cost millions of dollars.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/eeaab33d812a487ebfd2e5a76a25eb03?ext=true">AP Photo/Mary Altaffer</a></span>
</figcaption>
</figure>
<p>Some diamonds have a boron impurity that gives them a <a href="https://www.diamonds.pro/education/blue/">vivid blue hue</a>. They’re found in only a handful of mines worldwide, and at <a href="https://www.usatoday.com/story/money/2022/04/28/worlds-largest-blue-diamond-sells/9567999002/">$550 million per ounce</a> ($19 million per gram) they rival the cost of the upcoming Mars samples – an ounce is 142 carats, but very few gems are that large. </p>
<p>The <a href="https://www.sciencealert.com/scientists-create-world-s-most-expensive-material-valued-at-145-million-per-gram">most expensive synthetic material</a> is a tiny spherical “cage” of carbon with a nitrogen atom trapped inside. The atom inside the cage is extremely stable, so can be used for timekeeping. <a href="https://arstechnica.com/science/2015/12/oxford-company-now-selling-endohedral-fullerenes-priced-at-110-million-per-gram/">Endohedral fullerenes</a> are made of carbon material that may be used to create extremely accurate atomic clocks. They can cost $4 billion per ounce ($141 million per gram).</p>
<h2>Most expensive of all</h2>
<p><a href="https://www.livescience.com/32387-what-is-antimatter.html">Antimatter</a> occurs in nature, but it’s exceptionally rare because any time an antiparticle is created it quickly annihilates with a particle and produces radiation. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/7MkfMGzMcf8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">At CERN’s ‘antimatter factory,’ scientists create antimatter in very small quantities.</span></figcaption>
</figure>
<p>The <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2010.0026">particle accelerator at CERN</a> can produces 10 million antiprotons per minute. That sounds like a lot, but <a href="https://archive.ph/6RUrA">at that rate</a> it would take billions of years and cost a billion billion (10<sup>18</sup>) dollars to generate an ounce (3.5 x 10<sup>16</sup> dollars per gram). </p>
<p><a href="https://www.newscientist.com/article/mg24232342-600-how-star-treks-warp-drives-touch-on-one-of-physics-biggest-mysteries/">Warp drives</a> as envisaged by “Star Trek,” which are powered by matter-antimatter annihilation, will have to wait.</p><img src="https://counter.theconversation.com/content/214614/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Impey receives funding from the National Science Foundation. </span></em></p>Some space rocks you can get for free – if you know how to identify them. Rarer materials cost more, and the asteroid sample NASA just brought back has a high price tag.Chris Impey, University Distinguished Professor of Astronomy, University of ArizonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2157072023-10-17T19:08:01Z2023-10-17T19:08:01ZNASA’s Psyche asteroid mission: a 3.6 billion kilometre ‘journey to the centre of the Earth’<figure><img src="https://images.theconversation.com/files/554157/original/file-20231017-17-gr95ww.jpg?ixlib=rb-1.1.0&rect=11%2C41%2C3982%2C3652&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA24471">NASA / JPL-Caltech / ASU</a></span></figcaption></figure><p>Psyche was the Greek goddess of the soul, born a mere mortal and later married to Eros, the God of love. Who knows why the Italian astronomer Annibale de Gasparis gave her name to a celestial object he observed one night in 1852?</p>
<p>Psyche was only the 16th “asteroid” ever discovered: inhabitants of the Solar System that were neither the familiar planets nor the occasional visitors known as comets. Today we know the asteroid belt between the orbits of Mars and Jupiter contains millions of space rocks, ranging in size from the dwarf planet Ceres down to tiny pebbles and grains of dust.</p>
<p>Among all these, Psyche is still special. With an average diameter of around 226km, the potato-shaped planetoid is the largest “M-type” asteroid, made largely of iron and nickel, much like Earth’s core. </p>
<p>Last week NASA <a href="https://www.jpl.nasa.gov/missions/psyche">launched a spacecraft to rendezvous with Psyche</a>. The mission will take a six-year, 3.6 billion kilometre journey to gather clues that Earth scientists like me will interrogate for information about the inaccessible interior of our own world. </p>
<h2>Natural laboratories</h2>
<p>M-type asteroids like Psyche are thought to be the remnants of planets destroyed in the early years of the Solar System. In these asteroids, heavier elements (like metals) sank toward the centre and lighter elements floated up to the outer layers. Then, due to collisions with other objects, the outer layers were torn away and most of the material was ejected into space, leaving behind the metal-rich core.</p>
<p>These metallic worlds are perfect “natural laboratories” for studying planetary cores.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/nasas-psyche-mission-is-set-for-launch-heres-how-it-could-unveil-the-interior-secrets-of-planets-215547">Nasa's Psyche mission is set for launch – here's how it could unveil the interior secrets of planets</a>
</strong>
</em>
</p>
<hr>
<p>Our current methods for studying Earth’s core are quite indirect. We sometimes get tiny glimpses into the Solar System’s early history – and hence our planet’s own history – from metallic meteorites, parts of asteroids that fall to Earth. However, this view is very limited.</p>
<p>Another way to study the core is using seismology: studying how the vibrations caused by earthquakes travel through the planet’s interior, in much the same way doctors can use ultrasound to see the inside of our bodies.</p>
<p>However, on Earth we have fewer seismographs in the oceans and in the Southern Hemisphere, which restrict what we can see of the core.</p>
<p>What’s more, the core is buried beneath the planet’s outer layers, which obscure our view even further. It is like looking at a distant object through an imperfect lens.</p>
<p>As well as seismology, we learn about the core through lab experiments attempting to recreate the high pressures and temperatures of Earth’s interior.</p>
<p>We take the observations from seismology and lab experiments and try to explain them using computer simulations. In <a href="https://www.nature.com/articles/s41467-023-41725-5">a recent paper in Nature Communications</a>, we discussed the current challenges in studying Earth’s core – and the ways forward.</p>
<h2>What the Psyche mission hopes to discover</h2>
<p>We can think of NASA’s mission to Psyche as a journey to the centre of Earth without having to travel down through the planet’s rocky crust, the slowly moving mantle and the liquid core.</p>
<p>The mission aims to find out whether Psyche really is the core of a destroyed planet, that was initially hot and molten but slowly cooled and solidified like the core of our planet. On the other hand it’s possible Psyche is made of material that was never melted at all.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-asteroids-made-of-a-sample-returned-to-earth-reveals-the-solar-systems-building-blocks-176548">What are asteroids made of? A sample returned to Earth reveals the Solar System's building blocks</a>
</strong>
</em>
</p>
<hr>
<p>NASA also wants to discover how old Psyche’s surface is, which would reveal how long ago it lost its outer layers. The mission will also investigate the asteroid’s chemical composition: whether it contains lighter elements alongside iron and nickel, such as oxygen, hydrogen, carbon, silicon and sulphur. The presence or absence of these could give us clues about our own planet’s evolution.</p>
<p>Information about Psyche’s shape, mass, and gravity distribution will also be gathered. Also, the potential for future mineral exploration should be studied.</p>
<p>All of this will be possible with the broad-spectrum cameras, spectrometers, magnetometers, gravimeters and other instruments the spacecraft carries. Scientists like me will follow with impatience the mission’s long journey through space.</p><img src="https://counter.theconversation.com/content/215707/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hrvoje Tkalčić receives funding from the Australian Research Council. </span></em></p>A distant lump of space rock may have a surprising amount in common with the core of our own planet.Hrvoje Tkalčić, Professor, Head of Geophysics, Director of Warramunga Array, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2154842023-10-13T12:11:57Z2023-10-13T12:11:57ZOsiris-Rex: Nasa reveals evidence of water and carbon in sample delivered to Earth from an asteroid<figure><img src="https://images.theconversation.com/files/553639/original/file-20231013-21-8i85py.jpg?ixlib=rb-1.1.0&rect=8%2C0%2C2846%2C1517&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The "coal-like" material from Bennu.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details/jsc2023e058642">Nasa / Erika Blumenfeld & Joseph Aebers</a></span></figcaption></figure><p>On September 24 this year, a Nasa capsule parachuted down to Earth carrying a precious cache of material grabbed from an asteroid. The space agency has now revealed images and a preliminary analysis of the space rocks it found after lifting the lid off that capsule.</p>
<p>The mission to the asteroid was called <a href="https://science.nasa.gov/mission/osiris-rex/">Osiris-Rex</a>, and in 2020, it collected a sample of material from the asteroid Bennu. Afterwards, it travelled back to Earth and released the capsule containing the rocks into our atmosphere three weeks ago. </p>
<p>The fine black dust and small coal-like rocks shimmering in the capsule are beautiful – and somewhat unassuming. But this handful of space rock has the potential to answer questions about not only how the Earth was created, but
also how water arrived here and how life got started.</p>
<p><a href="https://www.youtube.com/watch?v=oFvIuSpACQA">At the Nasa press conference</a> on October 11 held to <a href="https://www.nasa.gov/news-release/nasas-bennu-asteroid-sample-contains-carbon-water/">reveal details about the sample</a>, Dr Francis McCubbin hinted that, with careful storage and preparation, the material could be analysed and used in experiments for years to come. </p>
<p>“Scientists that aren’t even born yet, (will be able to) answer questions about the Universe using technology that has not even been invented,” said the <a href="https://curator.jsc.nasa.gov/curation.cfm">astromaterials curator</a> at Nasa’s Johnson Space Center, Houston, where the Bennu sample is being stored.</p>
<h2>Why collect asteroid samples?</h2>
<p>Sometimes material from space comes to Earth without our help, <a href="https://science.nasa.gov/solar-system/meteors-meteorites/">arriving as meteorites</a>. Nasa has hundreds of meteorite samples in its collection, which are believed to have come from asteroids. Useful analysis can be carried out on these samples.</p>
<p>However, it’s often not possible to track down which asteroids these meteorites came from. This limits the potential of the resulting science. Meteorites <a href="https://www.gla.ac.uk/news/headline_915275_en.html">are also contaminated</a> by their journey through the atmosphere and onto the Earth. The Osiris-Rex sample, in contrast, is “pristine”. We can be sure any discoveries made from this sample tell us about Bennu. </p>
<p>Some of the finer dust in the Bennu sample would never have been able to form a meteorite and fall to Earth. Going and retrieving it is the only way we would ever have seen this type of material.</p>
<figure class="align-center ">
<img alt="The Osiris-Rex sample return capsule shortly after touching down in the Utah desert." src="https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553640/original/file-20231013-22-rk5i1m.jpeg?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 Osiris-Rex sample return capsule shortly after touching down in the Utah desert.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details/NHQ202309240003">NASA/Keegan Barber</a></span>
</figcaption>
</figure>
<p>This is not the first asteroid sample delivered to Earth. Two Japanese space agency (Jaxa) missions, <a href="https://www.isas.jaxa.jp/en/missions/spacecraft/past/hayabusa.html">Hayabusa 1</a> <a href="https://www.isas.jaxa.jp/en/missions/spacecraft/current/hayabusa2.html">and 2</a>, made deliveries of asteroid material in 2010 and 2020. However, this is the first US mission to do so. It also returned with significantly more material than the Hayabusa missions. </p>
<p>Osiris-Rex delivered an estimated 250g of space rock, compared to Hayabusa 2’s 5g. This means the sample can be distributed to scientists around the world and put on display in museums for the public to enjoy. It also means that some larger rock fragments were included, which gives a unique opportunity to examine how different minerals are arranged in bigger chunks of the asteroid. This unlocks even more scientific potential.</p>
<h2>What have they found?</h2>
<p><a href="https://science.nasa.gov/solar-system/asteroids/101955-bennu/">Bennu</a> is what is known as a “carbonaceous”, or C-Type, asteroid. These contain a large proportion of carbon and <a href="https://en.wikipedia.org/wiki/Volatile_(astrogeology)">“volatiles”</a> – compounds that can be readily vaporised, like water. These asteroids are believed to be relics from the formation of the Solar System, and so can help explain how the planets, including Earth, came to be. </p>
<p>Analysis of the main portion of the sample has taken longer than expected to get started, but it’s a nice problem to have. The sample collection technique was so successful that the sample was “spilling out” of the container within the return capsule. Because every grain is precious, all of this bonus material must be meticulously collected before the sample canister itself can be opened and preparation of the main body of the sample can begin.</p>
<figure class="align-center ">
<img alt="Tiny grain from Bennu sample." src="https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=377&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=377&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=377&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=474&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=474&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553665/original/file-20231013-15-now15p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=474&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Magnification of a tiny grain from the sample. The small bright specks in the image on the right (under UV light) reveal the presence of organic compounds.</span>
<span class="attribution"><a class="source" href="https://www.youtube.com/watch?v=oFvIuSpACQA">Nasa</a></span>
</figcaption>
</figure>
<p>Still, there have already been some exciting results from the initial analysis. Water has been found locked inside clay minerals from Bennu, which is an incredibly important discovery. One proposed mechanism for how water came to be on Earth and the other inner planets is that water was <a href="https://link.springer.com/article/10.1007/s11214-018-0474-9">trapped inside clay minerals</a> like these, which then formed rocks. These were eventually incorporated into planets during the birth of the solar system. </p>
<p>There’s abundant carbon in the sample – nearly 5% by weight – and sulphur. Both elements are essential for life. Carbon is the key ingredient in the organic compounds that make biology possible. Sulphur is an important component of amino acids, which form proteins.</p>
<p>Asteroids like Bennu are thought to have <a href="https://news.uchicago.edu/explainer/origin-life-earth-explained">“seeded” Earth with prebiotic compounds</a>: the building blocks of life. Magnetite (an iron oxide) found in the sample has been linked to chemical reactions crucial for the evolution of life. As Dr Daniel Glavin, Osiris-Rex sample analyst, <a href="https://www.nbcnews.com/science/space/nasa-unveils-asteroid-sample-reveal-details-life-earth-rcna119903">summarised</a>: “We picked the right asteroid. And not only that, we brought back the right sample.”</p>
<h2>What next?</h2>
<p>As well as helping answer the big questions of how we and our planet came to be here, finding water on asteroids is also destined to be a part of our future. Water can be broken down into hydrogen and oxygen, which can then be used as rocket fuel. While still some way off, spaceship <a href="https://en.wikipedia.org/wiki/Orbital_propellant_depot">refuelling stations</a> are moving out of the realms of science fiction and into reality.</p>
<p>There’s only so much fuel you can take with you on a rocket. Far better to take just what you need to get off the planet and then <a href="https://www.space.com/water-rich-asteroids-space-exploration-fuel.html">fuel up in space</a> for the rest of your journey.</p>
<p>Water can also be used for life support in future bases on the Moon and Mars. So it’s crucial to understand where we can access water in space, and how to extract it. The water on asteroids is one potential source.</p>
<p>Asteroids, once known best for their likely part in the demise of dinosaurs, are enjoying some positive time in the spotlight, showcasing their part in humanity’s past, present and future.</p><img src="https://counter.theconversation.com/content/215484/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lucinda King 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>Studying the sample could help answer how water arrived on Earth and how life started.Lucinda King, Space Projects Manager & Mission Design Lead, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2155472023-10-12T15:56:56Z2023-10-12T15:56:56ZNasa’s Psyche mission is set for launch – here’s how it could unveil the interior secrets of planets<figure><img src="https://images.theconversation.com/files/553482/original/file-20231012-25-cvqpz6.jpeg?ixlib=rb-1.1.0&rect=165%2C130%2C7716%2C4314&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Falcon Heavy rocket with Psyche.</span> <span class="attribution"><span class="source">Nasa</span></span></figcaption></figure><p>It’s unlikely to be a bad omen, but Nasa’s mission Psyche is currently due to launch on Friday 13 October. Lifting off at 10.19 EDT on a SpaceX Falcon Heavy rocket, it faces a perilous journey and isn’t scheduled for arrival at its namesake asteroid, <a href="https://science.nasa.gov/solar-system/asteroids/16-psyche/">16 Pscyhe</a>, until 2029. </p>
<p>Asteroid 16 Psyche (meaning “soul” in Greek) was discovered in 1852 and is named after an ancient Greek princess who married Eros (the namesake of another asteroid). It orbits the Sun in the main asteroid belt between Mars and Jupiter, at approximately three times the distance from the Sun as Earth. It is a massive M-type asteroid (M stands for “metal-rich”), over 230km across. </p>
<p>Astronomers have to be careful with the term metal though, as in stellar physics “metallicity” means anything heavier than helium. In this case though, we are talking about metals such as iron and cobalt. </p>
<p>To give an idea of scale, if the Sun was shrunk down to the size of an official NBA basketball, then the asteroid’s diameter would be about the same size as the thickness of three pieces of paper (0.3mm), and located at a distance of 161 metres away.</p>
<p>As you can see, a mission to an object so small is not straightforward, although smaller objects have been visited – for example the recent sample return of <a href="https://science.nasa.gov/mission/osiris-rex/">OSIRIS-REX from asteroid Bennu</a> or the <a href="https://science.nasa.gov/mission/hayabusa-2/">Hayabusa 2 mission to 162173 Ryugu</a>. </p>
<p>To accomplish this remarkable voyage, the Psyche spacecraft, once launched, will use solar-electric propulsion. This works by using an electrically charged gas that’s accelerated out of the rocket nozzle by a powerful electric field. This form of propulsion, unlike a chemical rocket, produces very modest thrust. But it can operate continuously over many months or even years, while using comparatively little fuel. </p>
<p>The technology is very useful for long-distance interplanetary missions, but it does require a decent amount of sunlight for the spacecraft’s solar panels to generate the necessary electrical power. <a href="https://science.nasa.gov/mission/lucy/">Lucy</a>, another recently launched Nasa mission to asteroids in the outer Solar System, uses the same propulsion.</p>
<h2>Mission goals</h2>
<p>So what makes this particular asteroid interesting? Planets are born in “<a href="https://aasnova.org/2016/12/19/selections-from-2016-gaps-in-hl-taus-protoplanetary-disk/">protoplanetary disks</a>” through a process called accretion. This involves small bits of material gradually acquiring more mass from gravitational attraction and collision with other nearby material. </p>
<p>Technically, this is an ongoing process as the Earth sweeps up some 100 tons of natural debris every day as it orbits the Sun. However, the bulk of a planet’s mass is acquired within the first few million years of its existence. </p>
<p>This is typically an extremely violent epoch in which catastrophic collisions between young worlds are common. Needless to say, not every <a href="https://www.science.org/doi/10.1126/science.aam6036">planet to be</a> survives to full planethood. And 16 Psyche may be an <a href="https://link.springer.com/article/10.1007/s11214-022-00880-9">example</a> of such as “stunted” planet. </p>
<p>If there’s enough internal radioactive decay and heat released by countless impacts during planetary formation, a young world will melt and undergo a process called “differentiation”, in which heavier material sinks to the core and lighter material floats to the surface. </p>
<p>There are several models of formation for 16 Psyche, but the simplest one consistent with present evidence is that 16 Psyche appears to have undergone differentiation, but subsequently <a href="https://link.springer.com/article/10.1007/s11214-022-00880-9#Sec22">suffered a catastrophic impact</a> with another young world – obliterating the outer layers, leaving a remnant dense metal-rich core exposed to space.</p>
<p>A key science objective of the Psyche mission will be to distinguish which of these models is most likely correct.</p>
<p>There are two main reasons for visiting Psyche. One is the scientific interest in visiting an object that could be similar to the iron core of a planet – including the Earth. The second is to found out whether it is possible to mine the metals – with <a href="https://www.forbes.com/sites/bridaineparnell/2017/05/26/nasa-psyche-mission-fast-tracked/#49cf598b4ae8">Forbes calling it a “quadrillion-dollar asteroid”</a>. </p>
<p>Venturing into the centre of a planet to directly study its core is <a href="https://www.sciencefocus.com/planet-earth/what-is-at-earths-core">impossible with our current technology</a>. However, visiting an exposed planetary core provides an excellent opportunity to test our current models of planetary formation. </p>
<p>The Psyche spacecraft carries a number of scientific instruments such as an imager for mapping the surface of the asteroid, a gravity experiment to help to determine the world’s interior structure, and a spectrometer for investigating the mineral content of the asteroid’s surface.</p>
<p>One of the instruments is a magnetometer which is designed to try and detect whether 16 Psyche has a magnetic field. This is useful because any remnant magnetic field could demonstrate that Psyche’s interior was once indeed molten and underwent differentiation.</p>
<p>As long as the spacecraft reaches the asteroid safely, there are great discoveries to look forward to. It will certainly provide a wealth of data for scientists to analyse back on Earth for years to come.</p><img src="https://counter.theconversation.com/content/215547/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The asteroid is interesting from a scientific perspective as well as a commercial one.Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of BirminghamIan Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2143202023-10-12T12:29:48Z2023-10-12T12:29:48ZAstronomers have learned lots about the universe − but how do they study astronomical objects too distant to visit?<figure><img src="https://images.theconversation.com/files/551236/original/file-20230929-19-43qoyt.jpg?ixlib=rb-1.1.0&rect=11%2C8%2C1905%2C663&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Telescopes at the Cerro Tololo Inter-American Observatory near La Serena, Chile.</span> <span class="attribution"><a class="source" href="https://noirlab.edu/public/images/iotw2107a/">Guillaume Doyen/CTIO/NOIRLab/NSF/AURA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>NASA’s <a href="https://science.nasa.gov/mission/osiris-rex">OSIRIS-REx spacecraft</a> flew by Earth on Sept. 24, 2023, dropping off its sample of dust and pebbles <a href="https://theconversation.com/7-years-billions-of-kilometres-a-handful-of-dust-nasa-just-brought-back-the-largest-ever-asteroid-sample-214151">gathered from the surface</a> of near-Earth asteroid Bennu.</p>
<p>Analysis of this sample will help scientists understand how the solar system formed and from what sorts of materials. Scientists will begin their analysis in the <a href="https://ares.jsc.nasa.gov">same facility</a> that analyzed rocks and dust from the Apollo lunar landings.</p>
<p><a href="https://scholar.google.com/citations?hl=en&user=BUAUD4YAAAAJ&view_op=list_works&sortby=pubdate">As an astronomer</a> studying how planets form around distant stars, I felt excited watching the broadcast of that Bennu sample descending to the Utah desert – and a little envious. Those of us who study distant young solar systems can’t send robotic spacecraft to get a closer look at them, let alone grab a sample for laboratory analysis. Instead, we rely on remote observations. </p>
<p>But what astronomers can measure using telescopes is not what we really want to know – instead, we calculate the properties we’re interested in studying by observing and interpreting apparent properties from afar.</p>
<h2>Astronomers’ tools</h2>
<p>Asteroids are like fossils – they’re composed of rocky material from the formation and early evolution of a solar system and they are preserved nearly unchanged. That’s how the pristine Bennu samples will help astronomers learn about our solar system’s formation.</p>
<p>Over the past several decades, astronomers have learned that <a href="https://www.planetary.org/articles/0416-the-birth-of-the-wanderers">disks of gas and dust</a> called protoplanetary disks orbit young stars. Observing these disks – located many light years outside our solar system – can help astronomers understand the early planet formation process, but they’re too distant to send a sample-return mission like OSIRIS-REx to directly measure what the <a href="https://public.nrao.edu/blogs/what-is-a-debris-disk/">dust and asteroids in these systems</a> are made of.</p>
<p>All that astronomers like me can do is observe those distant regions of the universe remotely, using telescopes here on Earth or in orbit near Earth. But even with limited tools and techniques, we’ve still managed to learn quite a bit about them.</p>
<h2>Distance and luminosity</h2>
<p>The <a href="https://www.eso.org/public/news/eso1611/">closest protoplanetary systems</a> are a few hundred light years from the Sun, but we can’t directly measure distances that large. Instead, we have to determine distance indirectly using precise <a href="https://www.space.com/30417-parallax.html">measurements of parallax</a> – small changes in the apparent position of the star caused by our changing perspective as Earth orbits the Sun.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/iwlMmJs1f5o?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video illustration of determining distances to stars using measurements of parallax. Las Cumbres Observatory.</span></figcaption>
</figure>
<p>Once we know their distances from Earth, we can determine another essential physical property of protoplanetary disks: their luminosities and the luminosities of their stars.</p>
<p><a href="https://earthsky.org/astronomy-essentials/stellar-luminosity-the-true-brightness-of-stars/">Luminosity</a> is an object’s power output measured in watts. The luminosity of a star like our Sun is in <a href="https://www.space.com/57-stars-formation-classification-and-constellations.html">the hundreds of trillions of trillions of watts</a>. Just as sunlight influences weather and the chemistry of planetary atmospheres in our solar system, the luminosity of a young star directly affects the material in its protoplanetary disk. Luminosity can alter the size and composition of dust particles that will later form asteroids and planetary cores.</p>
<p>But brightness does not directly indicate luminosity. The measured brightness of a star or any luminous object decreases with the square of its distance from us. We measure the apparent brightness of a star, or how bright it looks in a digital image, and then <a href="https://earthsky.org/astronomy-essentials/stellar-luminosity-the-true-brightness-of-stars/">calculate its luminosity</a> from this observed brightness and the star’s distance.</p>
<h2>Color and temperature</h2>
<p>Luminosity also depends on temperature – warmer objects are usually more luminous – but we can’t directly measure the temperatures of distant systems. Astronomers <a href="https://www.atnf.csiro.au/outreach/education/senior/astrophysics/photometry_colour.html">determine temperature</a> using precise measurements of the apparent color of a star and of the gas and dust orbiting in its planet-forming disk. </p>
<p>The color images of celestial objects that you see from observatories like the Hubble or James Webb space telescopes are <a href="https://www.scientificamerican.com/article/are-the-james-webb-space-telescopes-pictures-real/">composites of multiple images</a> taken through a series of colored filters.</p>
<p>For astronomers, colors are numbers describing the brightness of an object at a particular wavelength compared with its brightness at another wavelength. Warmer objects emit more blue light relative to red light, so their color looks more blue and the corresponding number is smaller. Astronomers measure color in even more detail by passing starlight through a small prism installed in the telescope’s camera. This prism disperses the light into a spectrum.</p>
<p>The spectrum of light from a star and its surrounding material isn’t a smooth rainbow of color. Sharp bright and dark features in the spectra indicate the presence and relative abundances of atoms, molecules and even minerals. These chemical elements emit or absorb light in unique and recognizable <a href="https://www.astronomy.com/science/how-do-scientists-determine-the-chemical-compositions-of-the-planets-and-stars/">combinations of colors</a>.</p>
<h2>Measurement and interpretation</h2>
<p>Can you see a theme emerging? Astronomers can measure only a handful of apparent properties: brightness, color, position in the sky, shape, angular size and how each of these changes with time. These are the same properties each of us measures with our senses to navigate our surroundings in everyday life. They’re nothing exotic or special.</p>
<p>And yet everything astronomers know about distant solar systems and their formation we have derived from measurements of these familiar and unremarkable apparent properties. The rich and detailed descriptions that we’ve come to expect in astronomy and astrophysics come from applying our understanding of chemistry and physics to these measurements.</p>
<p>The arrival of the Bennu sample is exciting because it is “real.” In the coming months and years, scientists will examine this dust to inform our studies not only of asteroids and interplanetary dust, but also of interstellar dust in solar systems farther afield. I am eager to see what these new details will teach us about cosmic dust, some of the primary building blocks of planets everywhere.</p><img src="https://counter.theconversation.com/content/214320/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Keller has received funding from the National Aeronautics and Space Administration. </span></em></p>Controlled experiments are impossible in astronomy, as are direct measurements of physical properties of objects outside our solar system. So how do astronomers know so much about them?Luke Keller, Professor of Physics and Astronomy, Ithaca CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2134022023-09-27T13:56:24Z2023-09-27T13:56:24ZMeteorite discovery: unusual finds by South African farmer add to space rock heritage<figure><img src="https://images.theconversation.com/files/549742/original/file-20230922-19-t7wiqi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A digital composite of a meteor shower speeding towards Earth.</span> <span class="attribution"><span class="source">Adastra</span></span></figcaption></figure><p>Meteorites – fragments of rock that have fallen to Earth from space in spectacularly fiery meteors – have been the subject of public fascination, awe, <a href="https://theconversation.com/how-ancient-cultures-explained-comets-and-meteors-100982">myths</a> and even <a href="https://owlcation.com/social-sciences/The-Worship-of-Meteorites-in-Ancient-Cultures">religious worship</a> for thousands of years. </p>
<p>In recent decades they’ve become a cosmic <a href="https://www.britannica.com/topic/Rosetta-Stone">Rosetta Stone</a> for scientists investigating the birth throes of our solar system and the organic life it hosts. Meteorites are therefore <a href="https://www.sahra.org.za/archaeology-palaeontology-and-meteorites/">rightly classified</a> by many countries as an integral part of communal natural heritage and are sought after by museums and private collectors.</p>
<p>South Africa, where I research meteorites, is one such country. In late 2021, my colleagues and I were alerted to an exceptional opportunity. Gideon Lombaard, a farmer in the Northern Cape province, reached out to us because he suspected that he had found two meteorite fragments. If proved true, these would be the first meteorite discoveries in South Africa in over 40 years. </p>
<p>After subjecting the fragments to a range of tests, we were able to show that the two fragments, despite being found only a kilometre apart, were unrelated – that is, they must have come from different meteor events.</p>
<p>In August, the <a href="https://meteoritical.org/">Meteoritical Society’s</a> nomenclature committee, which adjudicates all new meteorite submissions, formally accepted our proposal that the two fragments were different meteorites. They approved our suggested names – <a href="https://www.lpi.usra.edu/meteor/metbull.php?sea=&sfor=names&ants=&nwas=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=South+Africa&srt=name&categ=All&mblist=All&rect=&phot=&strewn=&snew=0&pnt=Normal%20table&code=79964">Brierskop</a> and <a href="https://www.lpi.usra.edu/meteor/metbull.php?sea=&sfor=names&ants=&nwas=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=South+Africa&srt=name&categ=All&mblist=All&rect=&phot=&strewn=&snew=0&pnt=Normal%20table&code=79963">Wolfkop</a> – after landmarks near their discovery sites. </p>
<p>Mr Lombaard’s double discovery raises South Africa’s tally of confirmed meteorites to 51 – the highest in sub-Saharan Africa. Namibia has 18 confirmed meteorites, <a href="https://theconversation.com/rare-meteorite-recovery-in-botswana-can-help-reveal-secrets-of-outer-space-99678">Botswana</a> 12, Zimbabwe four, and Lesotho and eSwatini one each. But, compared with the over 14,000 meteorites recovered from the Sahara desert, the number of recovered southern African meteorites is extremely small. A concerted national meteorite education awareness and search programme could thus reap great benefits. </p>
<h2>What is a meteorite?</h2>
<p>A meteorite is a piece of rocky space debris that survives collision with Earth. Meteorites are usually discovered by someone who notices an unusual rock while out walking (called a “find”). However, around 2% of meteorites are classified as “falls” because they are retrieved after witnessed meteor fireball events.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/secrets-revealed-of-dash-cam-meteorite-that-rocked-russia-19923">Secrets revealed of 'dash-cam' meteorite that rocked Russia</a>
</strong>
</em>
</p>
<hr>
<p>The meteorite family comprises several different types of rocks. A very small proportion of the <a href="https://www.lpi.usra.edu/meteor/">approximately 72,000 meteorites recovered globally</a> to date are actually pieces blasted off the surfaces of the moon and Mars by giant impacts. The overwhelming majority appear to have originated in the asteroid belt that lies between the orbits of Mars and Jupiter. They are the shrapnel from past collisions between some of these asteroids that were ejected into orbits that have ended up crossing Earth’s path.</p>
<h2>Discovery and forensics</h2>
<p>Finding meteorites is not easy, which makes Mr Lombaard’s twin discoveries all the more significant. Because they originate in outer space, meteorites commonly contain iron in either metal or sulphide forms, both of which begin to deteriorate rapidly when they come into contact with free oxygen and water. </p>
<p>It is thus not surprising that nearly 80% of all meteorites have been found where arid climates aid their preservation, namely Antarctica and the Sahara desert. Meteorites typically become coated in a dark fusion crust during their fiery passage through the atmosphere. That makes the white Antarctic ice and the pale-coloured Sahara bedrock and sand perfect backdrops for searchers.</p>
<p>Mr Lombaard discovered the two meteorites during routine farming activities. The Brierskop meteorite is a 21.19g chondrite which he found on 18 September 2018. Chondrites are the oldest rocks in our solar system, dating back 4.567 billion years. It was only after he found the Wolfkop stone (also a chondrite, weighing 90.26g) 1km away from the Brierskop site on 27 August 2021 that he reached out to determine whether these were, as he suspected, meteorites. Contacting an expert is the best approach if you think you’ve found a meteorite.</p>
<p>The initial pictures he sent were very promising; our primary task was then to establish whether they represented two pieces from a single fall or had originated from separate falls.</p>
<p>Our analysis, which involved slicing a small piece from each stone and grinding it down to produce an ultra-thin wafer through which light from a microscope could pass, was able to show that the meteorites have distinct differences.</p>
<p>Brierskop contains less iron metal and less iron in its main silicate minerals than Wolfkop. The chondrules (particles in the rock) are much better preserved in Brierskop, indicating that they experienced less heating in the parent asteroid before the impact collision that liberated it. We then used the greater oxidation (rust) of the Wolfkop stone to suggest that its fall predated that of the Brierskop meteorite.</p>
<h2>South Africa’s meteorite heritage</h2>
<p>The <a href="https://www.gov.za/documents/national-heritage-resources-act">South African Heritage Act</a> No. 25 of 1999 classifies South African meteorites as national heritage items that cannot be damaged, removed, exported or traded without a permit issued by the South African Heritage Agency. The Meteoritical Society also requires that meteorites are properly stored and conserved at accredited institutions such as museums and universities for future research. Wolfkop and Brierskop are now stored at the University of the Witwatersrand in Johannesburg, which is an accredited repository.</p>
<p>An average of between 10 and 50 meteorites are estimated to hit Earth’s surface every day. Technology will help drive new discoveries. In recent years an increasing number of countries have installed camera networks (such as NASA’s <a href="https://www.seti.org/cams">CAMS</a>) designed to record the trajectories of meteor fireballs that can then be triangulated to try to locate the fall site. The power of citizen science is also being harnessed in many places in the form of volunteer ground searches for fallen meteorites. </p>
<p>Prior to the two recent discoveries, the <a href="https://www.lpi.usra.edu/meteor/">Meteoritical Bulletin Database</a> listed 49 meteorites as having been satisfactorily proved to be from South African sites. Mr Lombaard’s double find takes the country’s meteorite inventory above 50. There’s no doubt that more are just waiting to be found.</p><img src="https://counter.theconversation.com/content/213402/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Lawrence Gibson receives funding from the NRF. </span></em></p>Meteorites are usually discovered by someone who notices an unusual rock while out walking.Roger Lawrence Gibson, Professor of Structural Geology and Metamorphic Petrology, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2141512023-09-25T22:49:19Z2023-09-25T22:49:19Z7 years, billions of kilometres, a handful of dust: NASA just brought back the largest-ever asteroid sample<figure><img src="https://images.theconversation.com/files/549936/original/file-20230925-15-fs9o2u.jpg?ixlib=rb-1.1.0&rect=1221%2C886%2C2502%2C1772&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/gsfc/53210429686/in/album-72177720310727975/">NASA</a></span></figcaption></figure><p>After a journey of billions of kilometres, NASA’s <a href="https://www.nasa.gov/press-release/nasa-s-first-asteroid-sample-has-landed-now-secure-in-clean-room">OSIRIS-REx mission has culminated</a> in a small black capsule blazing through the sky before touching down in the Utah desert. </p>
<p>Inside is likely to be the largest ever sample of dust and rock returned from an asteroid. Extracted and brought back with great technical ingenuity from an asteroid called Bennu, scientists will now study in search of clues about the origins of the Solar System and life itself.</p>
<p>The seven-year mission took OSIRIS-REx to a near-Earth carbon-rich asteroid, which it orbited for two and a half years, mapping its surface and measuring properties such as its density and spin. This “rubble pile” asteroid also has a (very) small chance of one day impacting Earth, so getting intricate measurements of its orbit and other dynamics was also a mission goal. </p>
<h2>The origins of the Solar System – and life</h2>
<p>Most asteroids are the rocky leftovers of failed planets and destructive collisions in the early Solar System, orbiting in a belt between Mars and Jupiter. They vary drastically in size, shape and composition, and finding out what they are made of can help us learn more about how the planets formed.</p>
<p>These primitive bodies – some more than 4.5 billion years old – can also shed light on the origins of life, because they tell us about the distribution of water, minerals and other elements such as carbon. </p>
<p>There is also an element of self-interest in studying these asteroids, to understand the risk they may pose if they are heading Earth’s way. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-solar-system-is-filled-with-asteroids-that-are-particularly-hard-to-destroy-new-study-finds-197413">Our Solar System is filled with asteroids that are particularly hard to destroy, new study finds</a>
</strong>
</em>
</p>
<hr>
<p>Using telescopes on Earth, we can get a rough idea of what an asteroid’s surface is made of. However, to do an in-depth chemical analysis we need to get hold of some actual samples.</p>
<p>Most of the asteroid samples we have are meteorites – lumps of space rock that have crashed into Earth. There are more than 70,000 meteorites in collections around the world, but we know the origins of less than 0.1% of them.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-pristine-chunk-of-space-rock-found-within-hours-of-hitting-earth-can-tell-us-about-the-birth-of-the-solar-system-194725">A pristine chunk of space rock found within hours of hitting Earth can tell us about the birth of the Solar System</a>
</strong>
</em>
</p>
<hr>
<p>What’s more, we know the samples we have are not very representative of the kinds of asteroids in space. Part of the reason for this is that some kinds of asteroids are better than others at surviving the fiery descent through the atmosphere. </p>
<p>But some meteorites don’t appear to correspond to any known type of asteroid. So where do they come from?</p>
<p>Using dedicated camera networks such as Australia’s <a href="https://dfn.gfo.rocks/">Desert Fireball Network</a> we can observe incoming asteroids, recover meteorite samples and track their paths back through space to determine their origins. This process can <a href="https://theconversation.com/a-pristine-chunk-of-space-rock-found-within-hours-of-hitting-earth-can-tell-us-about-the-birth-of-the-solar-system-194725">deliver relatively uncontaminated samples to the lab</a>.</p>
<p>Even still, linking a meteorite to a known parent asteroid, or even a type of asteroid observed via telescope, is very difficult. </p>
<h2>Bringing pieces of space back to Earth</h2>
<p>Sample return missions are the gold standard for analysing the makeup of extraterrestrial bodies. They can bring pieces from a different planet or asteroid back to Earth to study. </p>
<p>The first such mission was to the Moon, bringing back lunar samples for analysis. We learned the Moon was made from the same material as the Earth, and that it likely formed from the orbiting debris after a giant impact.</p>
<p>Sample return missions are technically very challenging. Not only does a spacecraft have to travel hundreds of millions of kilometres from Earth, but it has to match speed with the target (not just zoom past), find a safe landing site, touch down to collect a sample (without crashing), stow the sample in a sealed capsule, take off again, and return to Earth. Much of this process needs to be autonomous, as the time delay for communications with Earth is too long for remote control. </p>
<p>Other than the lunar samples returned by the Apollo missions, OSIRIS-REx is the fourth mission to return extraterrestrial material back to Earth. </p>
<p>NASA’s <a href="https://www.jpl.nasa.gov/missions/stardust">Stardust mission</a>, launched in 1999, returned microscopic samples from the trail of comet Wild-2. The <a href="https://pdssbn.astro.umd.edu/data_sb/missions/hayabusa/index.shtml">Hayabusa mission</a>, launched in 2003 by the Japanese space agency, JAXA, returned less than 1 milligram from asteroid Itokawa. JAXA’s <a href="https://www.hayabusa2.jaxa.jp/en/">Hayabusa2</a> (launched 2014) returned 5.4 grams of sample from asteroid Ryugu. </p>
<p>NASA estimates OSIRIS-REx has brought back around 250 grams from asteroid Bennu, by far the largest sample yet recovered. We will know for sure once the sample is carefully examined at Johnson Space Centre over the coming days.</p>
<h2>The sound of fireballs</h2>
<p>We and our colleagues at Curtin University are heavily involved in the global effort to find out what asteroids are really made of, having participated in or analysed samples from all of these sample return missions and leading the <a href="https://gfo.rocks/">Global Fireball Observatory</a>. </p>
<p>There are <a href="https://www.curtin.edu.au/news/media-release/curtin-ready-to-analyse-rare-asteroid-rocks-from-epic-nasa-mission/">six OSIRIS-REx mission scientists from Curtin</a> (including one of us – Nick Timms), and they will be among those receiving the first wave of samples in the coming weeks. </p>
<p>The re-entry of the capsule also had its own incredible science value. It was essentially a human-made fireball. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-hayabusa2-spacecraft-is-about-to-drop-a-chunk-of-asteroid-in-the-australian-outback-151280">The Hayabusa2 spacecraft is about to drop a chunk of asteroid in the Australian outback</a>
</strong>
</em>
</p>
<hr>
<p>Fireballs, or really bright shooting stars from large space rocks, are quite rare and impossible to predict. This is why we use dedicated camera networks to observe large areas of sky (The Desert Fireball Network observes nearly three million square kilometres of Australian skies every night). </p>
<p>When objects from outer space enter the atmosphere, travelling much faster than the speed of sound, they ignite the air to create a fireball and also trigger other less-studied phenomena such as shockwaves – which can be hazardous.</p>
<p>A sample return is a great opportunity to set out seismic sensors and other instruments to analyse the shockwave, which can tell us more about the physics of re-entry and why some meteorites survive while others don’t make it. This was done for the <a href="https://dfn.gfo.rocks/hayabusa.html">Hayabusa2 sample return</a> in 2020, and researchers from <a href="https://www.seismosoc.org/news/preparing-a-seismoacoustic-welcome-as-osiris-rex-capsule-returns-to-earth/">Sandia Labs</a> and the <a href="https://www.unisq.edu.au/news/2023/09/nasa-mission">University of Southern Queensland</a> had detectors set up in Utah for the OSIRIS-REx return. </p>
<h2>What’s next?</h2>
<p>Like Hayabusa2, the OSIRIS-REx spacecraft itself isn’t finished yet. Both of these spacecraft dropped their precious samples to Earth and have continued on with the aim of future asteroid fly-bys. </p>
<p>The mission, now renamed “<a href="https://blogs.nasa.gov/osiris-rex/2023/09/24/osiris-rex-spacecraft-departs-for-new-mission/">OSIRIS-APEX</a>”, has already begun to redirect itself towards an asteroid called Apophis, which it will intercept not long after the asteroid zooms past Earth in April 2029.</p><img src="https://counter.theconversation.com/content/214151/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eleanor K. Sansom receives funding from the International Centre for Radio Astronomy Research and is supported by the Space Science and Technology Centre at Curtin University and the Australian Research Council (DP230100301).</span></em></p><p class="fine-print"><em><span>Nick Timms received funding from the Australian Research Council (ARC) Linkage Infrastructure, Equipment, and Facilities (LIEF) scheme and is supported by the Space Science and Technology Centre at Curtin University.</span></em></p>NASA’s OSIRIS-REx mission has delivered pieces of asteroid Bennu, which scientists hope will offer a window into the early era of the Solar System billions of years ago.Eleanor K. Sansom, Research Associate, Curtin UniversityNick Timms, Associate Professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2140802023-09-21T19:31:10Z2023-09-21T19:31:10ZA Nasa spacecraft is on course to deliver material from an asteroid to Earth – here’s what we could learn<figure><img src="https://images.theconversation.com/files/549564/original/file-20230921-21-76lpa0.png?ixlib=rb-1.1.0&rect=7%2C0%2C2470%2C1406&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/osiris-rex-artists-concept">Nasa/GSFC</a></span></figcaption></figure><p>Around 15 years ago, I was on a <a href="https://www.esa.int/">European Space Agency</a> (Esa) committee, looking at Esa’s strategy for proposed forthcoming space missions. Under consideration was a mission to an asteroid. Over dinner, one of the committee members, an astrophysicist, quizzed me on why we needed to visit one of these objects. </p>
<p>“Nasa has already been to one and the Japanese Space Agency to another. Why do you need to go to another one? They’re all the same aren’t they, just lumps of rock?” My deliberately less-than-polite response was: “Why do astronomers keep wanting to launch more telescopes into space to look at stars? They’re all the same aren’t they, just balls of burning gas?” Our meal continued in frosty silence.</p>
<p>The misconception that asteroids are “just lumps of rock” doesn’t stand up to scrutiny, given the rich harvest of information about asteroid diversity that has come from studying meteorites. Meteorites have taught us about the origin and evolution of the Solar System.</p>
<p>We can measure the ages of meteorites and identify the volatiles – water- and carbon-containing chemicals – that some contain. Volatiles are important for understanding how the building blocks of life were delivered to Earth.</p>
<p>But there are gaps in our knowledge, so we need to study samples directly taken from asteroids – in part because meteorites are often contaminated with compounds from Earth’s environment. This means we can’t always be sure that the volatiles in them came from the asteroid itself, or from Earth. </p>
<p>We also don’t fully understand the relationship of specific meteorite types to different classes of asteroids. This affects our understanding of how volatiles were distributed in the early Solar System and therefore what types of objects could have delivered life’s building blocks to Earth. Hence the need for sample return missions.</p>
<p>On Sunday 24 September, a Nasa spacecraft called Osiris-Rex will fly past Earth and release a capsule containing a haul of dust and rock, which it collected from the surface of the asteroid Bennu in 2020. <a href="https://www.nasa.gov/nasalive">Under the watching eyes</a> of nervous scientists, the capsule will parachute down to a test range in Utah, where it will be retrieved and taken to a sample-curation facility in Houston.</p>
<h2>A rich heritage</h2>
<p>The previous missions mentioned by my astrophysicist colleague were <a href="https://solarsystem.nasa.gov/missions/near-shoemaker/in-depth/#:%7E:text=NASA's%20NEAR%20was%20the%20first,Moon%2C%20Mars%2C%20and%20Venus.">Nasa’s Near-Shoemaker spacecraft</a>, which operated from 1996 to 2001, and the <a href="https://www.isas.jaxa.jp/en/missions/spacecraft/past/hayabusa.html">Japanese space agency’s (Jaxa) Hayabusa mission</a>, which lasted from 2003 to 2005.</p>
<p>Hayabusa brought a few milligrams of material to Earth from the asteroid Itokawa. This allowed us, for the first time, to <a href="https://www.nature.com/articles/s41598-018-30192-4">measure an asteroid’s age</a> –- an important first step in understanding relationships between asteroids and meteorites. </p>
<p>The two most recent asteroid missions are <a href="https://www.isas.jaxa.jp/en/missions/spacecraft/current/hayabusa2.html">Jaxa’s Hayabusa2 mission</a> to the asteroid Ryugu and <a href="https://www.nasa.gov/osiris-rex">Nasa’s Osiris-Rex mission</a> to Bennu. The missions both orbited carbonaceous asteroids, which are rich in volatiles. The orbiting spacecraft helped confirm that Ryugu and Bennu are both water-rich asteroids, with abundant clay and carbonate minerals.</p>
<p>The asteroids have very low densities, suggesting they are objects called “rubble piles”. These contain significant amounts of empty space beneath the surface. Rubble piles formed from debris thrown into space when their bigger parent bodies were hit by another object. The rubble eventually came together to form an asteroid of its own.</p>
<h2>Watery history</h2>
<p>Results from analysis of samples from Ryugu were published in <a href="https://www.nature.com/articles/s41550-021-01550-6">December 2021</a>. They showed that the Ryugu material is very similar in composition to what we call CI meteorites. This is important because CI-related materials are extremely fragile and easily weathered. </p>
<p>As a result, few survive their passage through the Earth’s atmosphere. Now that we can link these rare meteorites more definitively to the class of asteroids Ryugu belongs to, we can expand our understanding of the processes that asteroids went through as they evolved.</p>
<p>In the past, temperatures on some asteroids were just high enough for liquid water to exist. The reaction of the original minerals with water transformed them into more complex mixtures. <a href="https://www.nature.com/articles/s41550-022-01863-0">Evidence suggests the</a> parent asteroid for Ryugu was altered by water between two million and five million years after the Solar System formed.</p>
<p>An important aim of Hayabusa2 was to analyse organics (carbon-containing chemicals) in the sample. There’s overlap between organics and volatiles. Both categories include compounds that could have been important for the origin of life.</p>
<figure class="align-center ">
<img alt="Bennu" src="https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/549599/original/file-20230921-25-rz88v4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bennu has been likened to a spinning top in space.</span>
<span class="attribution"><a class="source" href="https://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4857">Nasa's Scientific Visualization Studio</a></span>
</figcaption>
</figure>
<p>There were around 20,000 species (types) of <a href="https://www.science.org/doi/10.1126/science.abn9033">organic compound present in the Ryugu material</a>. This opened our eyes to the sheer complexity of organic compounds in primitive asteroids. </p>
<p>So what’s still left to learn from Bennu? For a start, Osiris-Rex observed bright regions on Bennu’s surface. These were interpreted as <a href="https://www.science.org/doi/full/10.1126/science.abc3557">thick veins of the mineral carbonate</a>. </p>
<p>These were not seen on Ryugu’s surface, although individual grains were found during <a href="https://www.nature.com/articles/s41561-023-01226-y">lab analysis of the samples</a>. This could suggest that alteration by water took place under different conditions on Bennu.</p>
<p>If the ages of alteration by water are different between Ryugu and Bennu, it could mean one of the asteroids underwent a longer process of alteration. This would suggest that their parent bodies formed in different parts of the Solar System.</p>
<p>Like Ryugu, Bennu is very dark. <a href="https://www.science.org/doi/10.1126/science.aaw0422">Analysis of Ryugu from orbit</a> suggested that a process called space weathering may have helped darken and dehydrate the asteroid’s surface. However, lab analysis of the Ryugu sample revealed the presence of clay minerals, showing that water was in fact <a href="https://theconversation.com/material-from-asteroid-ryugu-starts-to-give-up-secrets-of-early-solar-system-173884">abundant on the asteroid</a>. If the same effect is observed for Bennu, there are implications for the search for water on asteroids.</p>
<p>Bennu is recognised as a potentially hazardous asteroid, meaning there is a one in 3,000 chance of it hitting us in 150-200 years’ time.</p>
<p>By the time the global community of planetary scientists has analysed all the available material from Bennu, it is unlikely that any aspect of its formation, evolution and orbital history, composition and components will be unknown, allowing an effective “Earth
rescue” <a href="https://theconversation.com/nasa-is-crashing-a-spacecraft-into-an-asteroid-to-test-a-plan-that-could-one-day-save-earth-from-catastrophe-190888">mission to be launched</a>.</p><img src="https://counter.theconversation.com/content/214080/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady is Professor of Planetary and Space Sciences at The Open University. She is Chancellor of Liverpool Hope University and Senior Research Fellow at the Natural History Museum. She receives funding from the Science and Technology Facilities Council and the UK Space Agency. She tweets @MonicaGrady and orbits the Sun as Asteroid (4731) Monicagrady</span></em></p>Missions to asteroids are opening up the secrets of the Solar SystemMonica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2132712023-09-13T14:00:06Z2023-09-13T14:00:06ZFlowering plants survived the dinosaur-killing asteroid – and may outlive us<figure><img src="https://images.theconversation.com/files/547777/original/file-20230912-15-mm7cp3.jpg?ixlib=rb-1.1.0&rect=53%2C44%2C5937%2C3943&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/pink-rose-flower-pastel-ink-creative-1336421165">Zamurovic Brothers/Shutterstock</a></span></figcaption></figure><p>If you looked up 66 million years ago you might have seen, for a split second, a bright light as a mountain-sized asteroid burned through the atmosphere and smashed into Earth. <a href="https://www.nature.com/articles/s41586-022-04446-1">It was springtime</a> and the literal end of an era, the <a href="https://www.usgs.gov/youth-and-education-in-science/mesozoic">Mesozoic</a>. </p>
<p>If you somehow survived the initial impact, you would have witnessed the devastation that followed. Raging firestorms, megatsunamis, and <a href="https://pubmed.ncbi.nlm.nih.gov/11539442/">a nuclear winter</a> lasting months to years. The 180-million-year reign of non-avian dinosaurs was over in the blink of an eye, as well as at least <a href="https://www.science.org/doi/abs/10.1126/science.215.4539.1501?casa_token=DrtWs804WZsAAAAA:4SB3Ih2f1Ffnvilw9c8jxUViVd3IvyUVQRQ9PHOIezMQ7O5K9fR3a_nTWZWVKDJ94uKgsCBUfMH7Kg">75% of the species</a> who shared the planet with them. </p>
<p>Following this event, known as the <a href="https://www.britannica.com/science/K-T-extinction">Cretaceous-Paleogene mass extinction</a> (K-Pg), a new dawn emerged for Earth. Ecosystems bounced back, but the life inhabiting them was different.</p>
<p>Many iconic pre-K-Pg species can only be seen in a museum. The formidable <em>Tyrannosaurus rex</em>, the <em>Velociraptor</em>, and the winged dragons of the <em>Quetzalcoatlus</em> genus could not survive the asteroid and are confined to deep history. But if you take a walk outside and smell the roses, you will be in the presence of ancient lineages that blossomed in the ashes of K-Pg. </p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513999/original/file-20230307-18-3frmra.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em>Many people think of plants as nice-looking greens. Essential for clean air, yes, but simple organisms. A step change in research is shaking up the way scientists think about plants: they are far more complex and more like us than you might imagine. This blossoming field of science is too delightful to do it justice in one or two stories.</em>
<em><a href="https://theconversation.com/topics/plant-curious-137238?utm_source=TCUK&utm_medium=linkback&utm_campaign=PlantCurious2023&utm_content=InArticleTop">This article is part of a series, Plant Curious</a>, exploring scientific studies that challenge the way you view plantlife.</em></p>
<hr>
<p>Although the living species of roses are not the same ones that shared Earth with <em>Tyrannosaurus rex</em>, their lineage (family Rosaceae) <a href="https://www.nature.com/articles/s41467-020-17116-5">originated tens of millions of years</a> before the asteroid struck.</p>
<p>And the roses are an not unusual angiosperm (flowering plant) lineage in this regard. Fossils and genetic analysis suggest that the <a href="https://www.nature.com/articles/s41559-020-1241-3">vast majority of angiosperm families</a> originated before the asteroid. </p>
<p>Ancestors of the ornamental orchid, magnolia and passionflower families, grass and potato families, the medicinal daisy family, and the herbal mint family all shared Earth with the dinosaurs. In fact, the explosive evolution of angiosperms into the roughly 290,000 species today may have been facilitated by K-Pg. </p>
<p>Angiosperms seemed to have taken advantage of the fresh start, similar to the early members of our own lineage, <a href="https://www.cell.com/current-biology/pdf/S0960-9822(23)00767-4.pdf">the mammals</a>. </p>
<figure class="align-center ">
<img alt="Purple flower growing out of a crack in the pavement" src="https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547779/original/file-20230912-35629-s73lh2.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">Flowers are surprisingly resilient.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/purple-flower-growing-on-crack-street-776381272">PopTika/Shutterstock</a></span>
</figcaption>
</figure>
<p>However, it’s not clear how they did it. Angiosperms, so fragile compared with dinosaurs, cannot fly or run to escape harsh conditions. They rely on sunlight for their existence, which was blotted out. </p>
<h2>What do we know?</h2>
<p>Fossils in different regions tell different versions of events. It is clear there was high angiosperm turnover (species loss and resurgence) <a href="https://www.science.org/doi/full/10.1126/science.abf1969?casa_token=s5xuTGC7SpAAAAAA%3AJHgkvkmunfwRZLpwfcoumaus-20jehSJ4vDnlJa8LRzFqco_pveiJVbdvHm1h2P3SXvHckDRN5ERuw">in the Amazon</a> when the asteroid hit, and a decline in plant-eating insects <a href="https://www.pnas.org/doi/10.1073/pnas.042492999#:%7E:text=The%20most%20specialized%20associations%2C%20which,associations%20regained%20their%20Cretaceous%20abundances">in North America</a> which suggests a loss of food plants. But other regions, <a href="https://www.sciencedirect.com/science/article/abs/pii/S0034666723001021?via%3Dihub">such as Patagonia</a>, show no pattern. </p>
<p>A study in 2015 analysing angiosperm fossils of 257 <a href="https://www.britannica.com/science/genus-taxon">genera</a> (families typically contain multiple genera) found K-Pg had <a href="https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.13247">little effect</a> on extinction rates. But this result is difficult to generalise across the <a href="https://academic.oup.com/sysbio/article/71/2/301/6275244">13,000 angiosperm genera</a>. </p>
<p>My colleague Santiago Ramírez-Barahona, from the Universidad Nacional Autónoma de México, and I took a new approach to solving this confusion in a study we <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2023.0314">recently published</a> in Biology Letters. We analysed large angiosperm family trees, which previous work mapped from mutations in DNA sequences from 33,000-73,000 species. </p>
<p>This way of tree-thinking has laid the groundwork for major insights about the evolution of life, since the first family tree was scribbled by Charles Darwin. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scribble of a diagram with handwritten notes to the sides and underneath" src="https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=978&fit=crop&dpr=1 600w, https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=978&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=978&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1229&fit=crop&dpr=1 754w, https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1229&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/547814/original/file-20230912-25-6n0182.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1229&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Charles Darwin’s first diagram of an evolutionary tree from 1837.</span>
</figcaption>
</figure>
<p>Although the family trees we analysed did not include extinct species, their shape contains clues about how extinction rates changed through time, through the way the branching rate ebbs and flows. </p>
<p>The extinction rate of a lineage, in this case angiosperms, can be estimated using mathematical models. The one we used compared ancestor age with estimates for how many species should be appearing in a family tree according to what we know about the evolution process. </p>
<p>It also compared the number of species in a family tree with estimates of how long it takes for a new species to evolve. This gives us a net diversification rate - how fast new species are appearing, adjusted for the number of species that have disappeared from the lineage. </p>
<p>The model generates time bands, such as a million years, to show how extinction rate varies through time. And the model allowed us to identify time periods that had high extinction rates. It can also suggest times in which major shifts in species creation and diversification have occurred as well as when there may have been a mass extinction event. It shows how well the DNA evidence supports these findings too. </p>
<p>We found that extinction rates seem to have been remarkably constant over the last 140-240 million years. This finding highlights how resilient angiosperms have been over hundreds of millions of years. </p>
<p>We cannot ignore the <a href="https://www.cambridge.org/core/journals/cambridge-prisms-extinction/article/endcretaceous-plant-extinction-heterogeneity-ecosystem-transformation-and-insights-for-the-future/D74EBD512E4261E4C28BB7AF024E80B9">fossil evidence</a> showing that many angiosperm species did disappear around K-Pg, with some locations hit harder than others. But, as our study seems to confirm, the lineages (families and orders) to which species belonged carried on undisturbed, creating life on Earth as we know it. </p>
<p>This is different to how non-avian dinosaurs fared, who disappeared in their entirety: their entire branch was pruned. </p>
<p>Scientists believe <a href="https://genome.cshlp.org/content/24/8/1334.short">angiosperm resilience</a> to the K-Pg mass extinction (why only leaves and branchlets of the angiosperm tree were pruned) may be explained by their ability to adapt. For example, their evolution of new seed-dispersal and pollination mechanisms. </p>
<p>They can also <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2017.0912">duplicate their entire genome</a> (all of the DNA instructions in an organism) which provides a second copy of every single gene on which selection can act, potentially leading to new forms and greater diversity.</p>
<p>The sixth mass extinction event <a href="https://www.science.org/doi/full/10.1126/sciadv.1400253">we currently face</a> may follow a similar trajectory. A worrying number of angiosperm species are already threatened with extinction, and their demise will probably lead to the end of life as we know it. </p>
<p>It’s true angiosperms may blossom again from a stock of diverse survivors - and they may outlive us.</p><img src="https://counter.theconversation.com/content/213271/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jamie Thompson received PhD funding from Roger and Sue Whorrod (University of Bath alumni and philanthropists).</span></em></p>The fossil record tells conflicting stories about what happened to flowering plants after the asteroid.Jamie Thompson, Postdoctoral Evolutionary Biologist, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2127892023-09-06T12:07:36Z2023-09-06T12:07:36ZHave we really found the first samples from beyond the Solar System? The evidence is not convincing<figure><img src="https://images.theconversation.com/files/546217/original/file-20230904-27-c5k7ta.jpg?ixlib=rb-1.1.0&rect=89%2C89%2C4167%2C2744&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/pacific-ocean-view-santa-monica-pier-345950342">Frank Romeo/Shutterstock</a></span></figcaption></figure><p>Avi Loeb, an astrophysicist at Harvard University in the US, has published a <a href="https://projects.iq.harvard.edu/galileo/news/spherule-analysis-finds-evidence-extrasolar-composition">press release</a> claiming that some of the 700 or so spherical metallic fragments (spherules) <a href="https://theconversation.com/physicist-who-found-spherical-meteor-fragments-claims-they-may-come-from-an-alien-spaceship-heres-what-to-make-of-it-209101">he recovered</a> from the bottom of the Pacific Ocean, just off the coast of Papua New Guinea, are from beyond the Solar System.</p>
<p>The discovery was quite interesting because, although such spherules are distributed globally, it is not easy to recover them from the depths of the ocean bed – requiring a dredging operation with a powerful magnet. But Loeb has speculated that the spherules may be related to the passage of an interstellar meteor, IM1, which burned up over the South Pacific Ocean in January, 2014. He has even hypothesised that the spherules are actually debris from an alien spacecraft. I commented at the time that <a href="https://theconversation.com/physicist-who-found-spherical-meteor-fragments-claims-they-may-come-from-an-alien-spaceship-heres-what-to-make-of-it-209101">I’d need firm analytical evidence</a> to accept such interpretations. </p>
<p>Loeb has now provided a very <a href="https://arxiv.org/abs/2308.15623">detailed set of analytical data</a> of 57 spherules in an article submitted to a journal. But it has not yet been subject to the peer review that academics require before they accept research as legitimate. However, the paper has been subject to <a href="https://twitter.com/Deschscoveries/status/1697538023666397513">much scrutiny</a> on social media.</p>
<figure class="align-center ">
<img alt="Loeb next to image of spherule" src="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Loeb next to image of spherule.</span>
<span class="attribution"><span class="source">NewsNation/Youtube</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Loeb’s analyses were carried out using well known techniques and state-of-the art equipment, so there are no concerns that the analyses are faulty. Indeed, most of the spherules do appear to come from outside our own planet, as shown by their abundances of elements such as nickel, magnesium and manganese, which match those of meteorites. </p>
<p>Such particles are referred to as “cosmic spherules” and normally come from asteroids within our Solar System. Loeb’s material is, in fact, similar in nature to cosmic spherules <a href="https://www.sciencedirect.com/science/article/pii/S0016703717305495">that have been found</a> in sediments and ice cores. </p>
<p>A few of the spherules stand out because they have more unusual elemental compositions. These are named “BeLaU” particles by Loeb because they are rich in beryllium, lanthanum and uranium. Loeb rules out them being natural, terrestrial material, or extraterrestrial material from within the Solar System, on the basis of their iron isotope compositions. Isotopes are versions of an element with the same number of particles called protons in the nucleus, but different numbers of particles called neutrons, giving them different atomic masses. </p>
<p>His conclusions are a little inconsistent. The BeLaU spherules do indeed have a very different iron isotopic composition from some terrestrial and Solar System bodies, specifically those that have been through the process of melting and cooling as they formed. In other words, they do not match planetary objects, such as the Earth, Mars or the Moon. But that does not rule out their coming from bodies that have not been through a planetary formation process, such as the asteroids from which cosmic spherules originate.</p>
<p>Most cosmic spherules have been produced by ablation, the process by which material is eroded from a surface by friction. The friction is generated by interaction with air as a meteorite passes through the atmosphere at high velocity. This imparts unusual iron isotope compositions to the particles. The BeLaU spherules have iron isotope compositions in the same range as cosmic spherules. This could imply that they are indeed from within the Solar System. </p>
<p>Although Loeb acknowledges this, he still concludes that the BeLaU material has an interstellar origin.</p>
<h2>Other explanations</h2>
<p>It is interesting to join Loeb and speculate on potential origins for the spherules. In his paper, he says the samples “could have originated from a highly differentiated magma ocean of a planet with an iron core outside the solar system or from more exotic sources”. This is unlikely – iron meteorites from within the Solar System are the most affected by melting and do not have similar compositions to the BeLaU spherules.</p>
<p>Other possibilities that Loeb considers are supernovas (infinitely hot exploding stars) and cool, luminous stars (known as “asymptotic giant branch” stars, where cool is still incredibly hot). A supernova results from the catastrophic implosion of a stellar source, producing bursts of neutrons to form new elements. </p>
<p>The isotopic composition of those elements has been measured in many grains found in meteorites. Such grains are older than the Sun and could be regarded as interstellar. But they differ from the spherules described by Loeb because they are very small – only a few microns at most. Loeb’s samples are millimetre to centimetre sized. </p>
<p>I have another, equally speculative, suggestion. The Marshall Islands are only a few hundred kilometres or so from the region where Loeb searched. The Islands were the site of <a href="https://ahf.nuclearmuseum.org/ahf/location/marshall-islands/">67 nuclear tests</a> by the US between 1946 and 1958, causing radiation damage. The spherules could be fallout from these tests – a type of human-generated supernova. </p>
<figure class="align-center ">
<img alt="Marshall islands nuclear test." src="https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/546216/original/file-20230904-15-zdhoxe.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">Marshall islands nuclear test.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Castle_Bravo_Blast.jpg">United States Department of Energy</a></span>
</figcaption>
</figure>
<p>I think there are more analyses that could be done to test Loeb’s hypothesis. For example: look for spherules in the beach sands and ocean floor around Bikini Atoll and Enewetak, where the nuclear tests took place.</p>
<p>Another obvious test is to measure the oxygen isotopic composition of the spherules. This parameter is based on the three stable isotopes of oxygen. The ratios between those can be used to conclusively determine whether material is terrestrial or extraterrestrial. </p>
<p>An oxygen isotope signature can be traced even following weathering and alteration of samples. Similarly, it would be informative to see whether there are gases trapped in the spherules. Analysis of noble gases (especially xenon) in the spherules could indicate if they came from a supernova or other type of star. </p>
<p>Assuming the spherules are not radioactive, I would be happy to facilitate their analysis. Our <a href="https://www.open.ac.uk/research/engagement/facilities">laboratories at The Open University</a> specialise in the analysis of miniscule amounts of extraterrestrial material, specifically in <a href="https://www.nature.com/articles/s41550-022-01824-7">oxygen isotope composition</a>. We also have a long history of analysis of <a href="https://iopscience.iop.org/article/10.1086/507176">xenon in interstellar grains</a>.</p>
<p>I am afraid that I come to the same conclusion that I did last time: Loeb has recovered some interesting particles, but none of the evidence he presents is sufficiently convincing to infer that the materials are either connected with IM1, or are from an alien spaceship.</p><img src="https://counter.theconversation.com/content/212789/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady is Professor of Planetary and Space Sciences at the Open University, Chancellor of Liverpool Hope University and Honorary Senior Research Fellow at The Natural History Museum. She receives funding from the Science and Technology Facilities Council and the UK Space Agency. She tweets as @MonicaGrady</span></em></p>Could spherical metallic fragments be from a nuclear test?Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2122552023-08-29T20:13:02Z2023-08-29T20:13:02ZSahara space rock 4.5 billion years old upends assumptions about the early Solar System<figure><img src="https://images.theconversation.com/files/544957/original/file-20230828-123419-925u5r.jpeg?ixlib=rb-1.1.0&rect=0%2C8%2C5505%2C4467&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/Category:Erg_Chech_002#/media/File:Erg_Chech_002_%E2%80%94_5x_Macro_-2_(50866963572).jpg">Steve Jurvetson / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>In May 2020, some unusual rocks containing distinctive greenish crystals were found in the Erg Chech sand sea, a dune-filled region of the Sahara Desert in southern Algeria.</p>
<p>On close inspection, the rocks turned out to be from outer space: lumps of rubble <a href="https://www.pnas.org/doi/full/10.1073/pnas.2026129118">billions of years old</a>, left over from the dawn of the Solar System.</p>
<p>They were all pieces of a meteorite known as Erg Chech 002, which is the oldest volcanic rock ever found, having melted long ago in the fires of some now-vanished ancient protoplanet.</p>
<p>In <a href="https://doi.org/10.1038/s41467-023-40026-1">new research</a> published in Nature Communications, we analysed lead and uranium isotopes in Erg Chech 002 and calculated it is some 4.56556 billion years old, give or take 120,000 years. This is one of the most precise ages ever calculated for an object from space – and our results also cast doubt on some common assumptions about the early Solar System.</p>
<h2>The secret life of aluminium</h2>
<p>Around 4.567 billion years ago, our Solar System formed from a vast cloud of gas and dust. Among the many elements in this cloud was aluminium, which came in two forms.</p>
<p>First is the stable form, aluminium-27. Second is aluminium-26, a radioactive isotope mainly produced by exploding stars, which decays over time into magnesium-26.</p>
<p>Aluminium-26 is very useful stuff for scientists who want to understand how the Solar System formed and developed. Because it decays over time, we can use it to date events – particularly within the first four or five million years of the Solar System’s life. </p>
<p>The decay of aluminium-26 is also important for another reason: we think it was the main source of heat in the early Solar System. This decay influenced the melting of the small, primitive rocks that later clumped together to form the planets.</p>
<h2>Uranium, lead and age</h2>
<p>However, to use aluminium-26 to understand the past, we need to know whether it was spread around evenly or clumped together more densely in some places than in others.</p>
<p>To figure that out, we will need to calculate the absolute ages of some ancient space rocks more precisely.</p>
<p>Looking at aluminium-26 alone won’t let us do that, because it decays relatively quickly (after around 705,000 years, half of a sample of aluminium-26 will have decayed into magnesium-26). It’s useful for determining the relative ages of different objects, but not their absolute age in years.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-pristine-chunk-of-space-rock-found-within-hours-of-hitting-earth-can-tell-us-about-the-birth-of-the-solar-system-194725">A pristine chunk of space rock found within hours of hitting Earth can tell us about the birth of the Solar System</a>
</strong>
</em>
</p>
<hr>
<p>But if we combine aluminium-26 data with data about uranium and lead, we can make some headway.</p>
<p>There are two important isotopes of uranium (uranium-235 and uranium-238), which decay into different isotopes of lead (lead-207 and lead-206, respectively). </p>
<p>The uranium isotopes have much longer half-lives (710 million years and 4.47 billion years, respectively), which means we can use them to directly figure out how long ago an event happened.</p>
<h2>Meteorite groups</h2>
<p>Erg Chech 002 is what is known as an “ungrouped achondrite”. </p>
<p>Achondrites are rocks formed from melted planetesimals, which is what we call solid lumps in the cloud of gas and debris that formed the Solar System. The sources of many achondrites found on Earth have been identified. </p>
<figure class="align-center ">
<img alt="A small rock sitting against a ruler." src="https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=423&fit=crop&dpr=1 600w, https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=423&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=423&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/544965/original/file-20230828-123419-jo6a9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Achondrite meteorites like Erg Chech 002 offer clues about the early years of the Solar System.</span>
<span class="attribution"><span class="source">Yuri Amelin</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Most belong to the so-called Howardite-Eucrite-Diogenite clan, which are believed to have originated from Vesta 4, one of the largest asteroids in the Solar System. Another group of achondrites is called angrites, which all share an unidentified parent body. </p>
<p>Still other achondrites, including Erg Chech 002, are “ungrouped”: their parent bodies and family relationships are unknown.</p>
<h2>A clumpy spread of aluminium</h2>
<p>In our study of Erg Chech 002, we found it contains a high abundance of lead-206 and lead-207, as well as relatively large amounts of undecayed uranium-238 and uranium-235. </p>
<p>Measuring the ratios of all the lead and uranium isotopes was what helped us to estimate the age of the rock with such unprecedented accuracy.</p>
<p>We also compared our calculated age with previously published aluminium-26 data for Erg Chech 002, as well as data for various other achondrites. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-asteroids-made-of-a-sample-returned-to-earth-reveals-the-solar-systems-building-blocks-176548">What are asteroids made of? A sample returned to Earth reveals the Solar System's building blocks</a>
</strong>
</em>
</p>
<hr>
<p>The comparison with a group of achondrites called volcanic angrites was particularly interesting. We found that the parent body of Erg Chech 002 must have formed from material containing three or four times as much aluminium-26 as the source of the angrites’ parent body.</p>
<p>This shows aluminium-26 was indeed distributed quite unevenly throughout the cloud of dust and gas which formed the solar system. </p>
<p>Our results contribute to a better understanding of the Solar System’s earliest developmental stages, and the geological history of burgeoning planets. Further studies of diverse achondrite groups will undoubtedly continue to refine our understanding and enhance our ability to reconstruct the early history of our Solar System.</p><img src="https://counter.theconversation.com/content/212255/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Evgenii Krestianinov 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 of the meteorite Erg Chech 002 makes it one of the most precisely dated space objects and changes our understanding of how elements were spread around the cloud of dust that formed the Sun and planets.Evgenii Krestianinov, PhD candidate, Research School of Earth Sciences, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2069132023-08-17T12:34:23Z2023-08-17T12:34:23ZNASA’s Psyche mission to a metal world may reveal the mysteries of Earth’s interior<figure><img src="https://images.theconversation.com/files/539847/original/file-20230727-19-gbh5t6.jpg?ixlib=rb-1.1.0&rect=5%2C11%2C3982%2C2646&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An illustration of the asteroid Psyche, orbiting between Mars and Jupiter.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/psyche-asteroid-in-space-royalty-free-image/1286927980?phrase=Psyche&adppopup=true">24K-Production/iStock via Getty Images Plus</a></span></figcaption></figure><p>French novelist Jules Verne delighted 19th-century readers with the tantalizing notion that a <a href="https://etc.usf.edu/lit2go/222/the-journey-to-the-center-of-the-earth/">journey to the center of the Earth</a> was actually plausible. </p>
<p>Since then, scientists have long acknowledged that Verne’s literary journey was only science fiction. The extreme temperatures of the Earth’s interior – around 10,000 degrees Fahrenheit (5,537 Celsius) at the core – and the accompanying crushing pressure, which is millions of times more than at the surface, <a href="https://www.youtube.com/watch?v=NXFBJr8XRlQ">prevent people from venturing down very far</a>. </p>
<p>Still, there are a few things <a href="https://education.nationalgeographic.org/resource/core/">known about the Earth’s interior</a>. For example, geophysicists discovered that the core consists of a solid sphere of iron and nickel that comprises 20% of the Earth’s radius, surrounded by a shell of molten iron and nickel that spans an additional 15% of Earth’s radius.</p>
<p>That, and the rest of our knowledge about our world’s interior, was learned indirectly – either by studying <a href="https://climate.nasa.gov/news/3105/earths-magnetosphere-protecting-our-planet-from-harmful-space-energy/">Earth’s magnetic field</a> or the way earthquake waves <a href="https://www.snexplores.org/article/explainer-seismic-waves-come-different-flavors">bounce off different layers</a> below the Earth’s surface. </p>
<p>But indirect discovery has its limitations. How can scientists find out more about our planet’s deep interior?</p>
<p><a href="http://jimbell.sese.asu.edu/">Planetary scientists like me</a> think the best way to learn about inner Earth is in outer space. NASA’s <a href="https://www.jpl.nasa.gov/missions/psyche">robotic mission to a metal world</a> is scheduled for liftoff on Oct. 5, 2023. That mission, the spacecraft traveling there, and the world it will explore all have the same name – Psyche. And for six years now, I’ve been <a href="https://psyche.asu.edu/mission/the-team/">part of NASA’s Psyche team</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/y__vwRQ3PVg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">It’s a mission of ‘firsts.’</span></figcaption>
</figure>
<h2>About the asteroid Psyche</h2>
<p><a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/overview/?">Asteroids are small worlds</a>, with some the size of small cities and others as large as small countries. They are the leftover building blocks from our solar system’s early and violent period, <a href="https://solarsystem.nasa.gov/solar-system/our-solar-system/in-depth/#:%7E:">a time of planetary formation</a>. </p>
<p>Although most are rocky, icy or a combination of both, perhaps 20% of asteroids are worlds made of metal, and similar in composition to the Earth’s core. So it’s tempting to imagine that these metallic asteroids are pieces of the cores of once-existing planets, ripped apart by ancient cosmic collisions with each other. Maybe, by studying these pieces, scientists could find out directly what a planetary core is like. </p>
<p><a href="https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/16-psyche/in-depth/">Psyche</a> is the largest-known of the metallic asteroids. Discovered in 1852, Psyche has the width of Massachusetts, a squashed spherical shape reminiscent of a pincushion, and an orbit between Mars and Jupiter in the main asteroid belt. An amateur astronomer can see Psyche with a backyard telescope, but it appears only as a pinpoint of light.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/TgVorJfM8BM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">An artist’s rendition of Psyche, a spectacular metallic world.</span></figcaption>
</figure>
<h2>About the Psyche mission</h2>
<p>In early 2017, NASA approved the US$1 billion <a href="https://www.nasa.gov/psyche">mission to Psyche</a>. To do its work, there’s no need for the uncrewed spacecraft to land – instead, it will orbit the asteroid repeatedly and methodically, starting from 435 miles (700 kilometers) out and then going down to 46 miles (75 km) from the surface, and perhaps even lower. </p>
<p>Once it arrives in August 2029, the probe will spend 26 months mapping the asteroid’s geology, topography and gravity; it will search for evidence of a magnetic field; and it will compare the asteroid’s composition with what scientists know, or think we know, about Earth’s core.</p>
<p>The central questions are these: Is Psyche really an exposed planetary core? Is the asteroid one big bedrock boulder, a rubble pile of smaller boulders, or something else entirely? Are there clues that the previous outer layers of this small world – the crust and mantle – were violently stripped away long ago? And maybe the most critical question: Can what we learn about Psyche be extrapolated to solve some of the mysteries about the Earth’s core? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Technicians, inside a clean room and dressed in white garb, examine the Psyche spacecraft." src="https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/542041/original/file-20230809-23-wqfx53.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">NASA’s Psyche spacecraft, undergoing final tests in a clean room at a facility near Florida’s Kennedy Space Center.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA25952">NASA/Frank Michaux</a></span>
</figcaption>
</figure>
<h2>About the spacecraft Psyche</h2>
<p>The probe’s body is about the same size and mass as a large SUV. Solar panels, stretching a bit wider than a tennis court, power the cameras, spectrometers and other systems. </p>
<p>A SpaceX Falcon Heavy rocket will <a href="https://techcrunch.com/2020/02/28/spacex-wins-the-117-million-launch-contract-to-explore-psyches-heavy-metal-asteroid/">take Psyche off the Earth</a>. The rest of the way, Psyche will <a href="https://www.nasa.gov/feature/jpl/solar-electric-propulsion-makes-nasa-s-psyche-spacecraft-go">rely on ion propulsion</a> – the gentle pressure of ionized xenon gas jetting out of a nozzle provides a continuous, reliable and low-cost way to propel spacecraft out into the solar system.</p>
<p>The journey, a slow spiral of 2.5 billion miles (4 billion km) that includes a gravity-assist flyby past Mars, <a href="https://www.cnn.com/2023/06/05/world/nasa-psyche-mission-october-launch-scn/index.html">will take nearly six years</a>. Throughout the cruise, the Psyche team at NASA’s Jet Propulsion Laboratory in Pasadena, California, and here at Arizona State University in Tempe, will stay in regular contact with the spacecraft. Our team will send and receive data using <a href="https://www.nasa.gov/directorates/heo/scan/services/networks/deep_space_network/about">NASA’s Deep Space Network</a> of giant radio antennas. </p>
<p>Even if we learn that Psyche is not an ancient planetary core, we’re bound to significantly add to our body of knowledge about the solar system and the way planets form. After all, Psyche is still unlike any world humans have ever visited. Maybe we can’t yet journey to the center of the Earth, but robotic avatars to places like Psyche can help unlock the mysteries hidden deep inside the planets – including our own.</p><img src="https://counter.theconversation.com/content/206913/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jim Bell works for Arizona State University, the lead academic institution responsible for the Pyche mission. He is also a member of the Board of Directors of The Planetary Society. He receives funding from NASA.</span></em></p>Liftoff to the distant asteroid is scheduled for Oct. 5, 2023 – the beginning of a six-year journey to one of the most unusual objects in the solar system.Jim Bell, Professor of Earth and Space Exploration, Arizona State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2095932023-08-10T03:24:09Z2023-08-10T03:24:09ZNew evidence suggests the world’s largest known asteroid impact structure is buried deep in southeast Australia<figure><img src="https://images.theconversation.com/files/542059/original/file-20230810-25-7n4kt.png?ixlib=rb-1.1.0&rect=43%2C0%2C2600%2C1005&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Google Maps</span></span></figcaption></figure><p><em>Acknowledgment: I’d like to thank my colleague Tony Yeates, who originated the view of the Deniliquin multi-ring structure as an impact structure – and who was instrumental to this work.</em></p>
<p>In <a href="https://www.sciencedirect.com/science/article/abs/pii/S0040195122002487">recent research</a> published by myself and my colleague Tony Yeates in the journal Tectonophysics, we investigate what we believe – based on many years of experience in asteroid impact research – is the world’s largest known impact structure, buried deep in the earth in southern New South Wales.</p>
<p>The Deniliquin structure, yet to be further tested by drilling, spans up to 520 kilometres in diameter. This exceeds the size of the near-300km-wide <a href="https://en.wikipedia.org/wiki/Vredefort_impact_structure">Vredefort</a> impact structure in South Africa, which to date has been considered the world’s largest.</p>
<h2>Hidden traces of Earth’s early history</h2>
<p>The history of Earth’s bombardment by asteroids is largely concealed. There are a few reasons for this. The first is erosion: the process by which gravity, wind and water slowly wear away land materials through time. </p>
<p>When an asteroid strikes, it creates a crater with an uplifted core. This is similar to how a drop of water splashes upward from a transient crater when you drop a pebble in a pool. </p>
<p>This central uplifted dome is a key characteristic of large impact structures. However, it can erode over thousands to millions of years, making the structure difficult to identify.</p>
<p>Structures can also be buried by sediment through time. Or they might disappear as a result of subduction, wherein tectonic plates can collide and slide below one another into Earth’s mantle layer.</p>
<p>Nonetheless, new geophysical discoveries are unearthing signatures of impact structures formed by asteroids that may have reached tens of kilometres across – heralding a paradigm shift in our understanding of how Earth evolved over eons. These include pioneering discoveries of impact “ejecta”, which are the materials thrown out of a crater during an impact. </p>
<p><a href="https://www.sciencedirect.com/science/article/abs/pii/S1387647317300714">Researchers think</a> the oldest layers of these ejecta, found in sediments in early terrains around the world, might signify the tail end of the Late Heavy Bombardment of Earth. The <a href="https://www.sciencedirect.com/science/article/abs/pii/S1387647317300714">latest evidence</a> suggests Earth and the other planets in the Solar System were subject to intense asteroid bombardments until about 3.2 billion years ago, and sporadically since.</p>
<p>Some large impacts are correlated with mass extinction events. For example, the <a href="https://en.wikipedia.org/wiki/Alvarez_hypothesis">Alvarez hypothesis</a>, named after father and son scientists Luis and Walter Alvarez, explains how non-avian dinosaurs were wiped out as a result of a large asteroid strike some 66 million years ago.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/we-found-the-worlds-oldest-asteroid-strike-in-western-australia-it-might-have-triggered-a-global-thaw-130192">We found the world's oldest asteroid strike in Western Australia. It might have triggered a global thaw</a>
</strong>
</em>
</p>
<hr>
<h2>Uncovering the Deniliquin structure</h2>
<p>The Australian continent and its predecessor continent, <a href="https://en.wikipedia.org/wiki/Gondwana">Gondwana</a>, have been the target of numerous asteroid impacts. These have resulted in at least 38 confirmed and 43 potential impact structures, ranging from relatively small craters to large and completely buried structures.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=649&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=649&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541853/original/file-20230809-24-hpgo51.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=649&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This map shows the distribution of circular structures of uncertain, possible or probable impact origin on the Australian continent and offshore. Green dots represent confirmed impact craters. Red dots represent confirmed impact structures that are more than 100km wide, whereas red dots inside white circles are more than 50km wide. Yellow dots represent likely impact structures.</span>
<span class="attribution"><span class="source">Andrew Glikson and Franco Pirajno</span></span>
</figcaption>
</figure>
<p>As you’ll recall with the pool and pebble analogy, when a large asteroid hits Earth, the underlying crust responds with a transient elastic rebound that produces <a href="https://www.lpi.usra.edu/publications/books/CB-954/CB-954.pdf">a central dome</a>. </p>
<p>Such domes, which can slowly erode and/or become buried through time, may be all that’s preserved from the original impact structure. They represent the deep-seated “root zone” of an impact. Famous examples are found in the Vredefort impact structure and the 170km-wide <a href="https://en.wikipedia.org/wiki/Chicxulub_crater">Chicxulub crater</a> in Mexico. The latter represents the impact that caused the extinction of the dinosaurs.</p>
<p>Between 1995 and 2000, Tony Yeates suggested magnetic patterns beneath the Murray Basin in New South Wales <a href="https://www.aseg.org.au/publications/preview-old">likely represented</a> a massive, buried impact structure. An analysis of the region’s updated geophysical data between 2015 and 2020 confirmed the existence of a 520km diameter structure with a seismically defined dome at its centre.</p>
<p>The Deniliquin structure has all the features that would be expected from a large-scale impact structure. For instance, magnetic readings of the area reveal a symmetrical rippling pattern in the crust around the structure’s core. This was likely produced during the impact as extremely high temperatures created intense magnetic forces.</p>
<p>A central low magnetic zone corresponds to 30km-deep deformation above a seismically defined mantle dome. The top of this dome is about 10km <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL065345">shallower than the top</a> of the regional mantle.</p>
<p>Magnetic measurements also show evidence of “radial faults”: fractures that radiate from the centre of a large impact structure. This is further accompanied by small magnetic anomalies which may represent igneous “dikes”, which are sheets of magma injected into fractures in a pre-existing body of rock. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=565&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=565&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=565&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=710&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=710&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541855/original/file-20230809-27-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=710&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This ‘total magnetic intensity’ image of the Deniliquin impact structure portrays its 520km-diameter multi-ring pattern, the central core, radial faults and the location of shallow drill holes.</span>
<span class="attribution"><a class="source" href="https://www.sciencedirect.com/science/article/abs/pii/S0040195122002487">Data from Geoscience Australia, published in Glikson and Yeates, 2022</a></span>
</figcaption>
</figure>
<p>Radial faults, and igneous sheets of rocks that form within them, are typical of large impact structures and can be found in the Vredefort structure and the <a href="https://journals.uair.arizona.edu/index.php/maps/article/viewFile/14921/14892">Sudbury impact structure</a> in Canada.</p>
<p>Currently, the bulk of the evidence for the Deniliquin impact is based on geophysical data obtained from the surface. For proof of impact, we’ll need to collect physical evidence of shock, which can only come from drilling deep into the structure.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/these-5-spectacular-impact-craters-on-earth-highlight-our-planets-wild-history-197618">These 5 spectacular impact craters on Earth highlight our planet's wild history</a>
</strong>
</em>
</p>
<hr>
<h2>When did the Deniliquin impact happen?</h2>
<p>The Deniliquin structure was likely located on the eastern part of the Gondwana continent, prior to it splitting off into several continents (including the Australian continent) much later.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/541858/original/file-20230809-21-qpfxif.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&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 Deniliquin structure was likely created in eastern Gondwana during the Late Ordovician.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s41598-022-08941-3#rightslink">Zhen Qiu et al, 2022</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The impact that caused it may have occurred during what’s known as the Late Ordovician mass extinction event. Specifically, I think it may have triggered what’s called the <a href="https://www.britannica.com/science/Ordovician-Silurian-extinction">Hirnantian glaciation stage</a>, which lasted between 445.2 and 443.8 million years ago, and is also defined as the <a href="https://www.sciencedirect.com/science/article/abs/pii/S1342937X23000655">Ordovician-Silurian extinction event</a>. </p>
<p>This huge glaciation and mass extinction event <a href="https://www.britannica.com/science/Ordovician-Silurian-extinction">eliminated</a> about 85% of the planet’s species. It was more than double the scale of the <a href="https://en.wikipedia.org/wiki/Alvarez_hypothesis">Chicxulub impact</a> that killed off the dinosaurs. </p>
<p>It is also possible the Deniliquin structure is older than the Hirnantian event, and may be of an early Cambrian origin (about 514 million years ago). The next step will be to gather samples to determine the structure’s exact age. This will require drilling a deep hole into its magnetic centre and dating the extracted material. </p>
<p>It’s hoped further studies of the Deniliquin impact structure will shed new light on the nature of early <a href="https://www.livescience.com/37584-paleozoic-era.html">Paleozoic</a> Earth.</p><img src="https://counter.theconversation.com/content/209593/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>Research on the Deniliquin structure points to an asteroid impact that would have been more than double the scale of the one that killed the dinosaurs.Andrew Glikson, Adjunct professor, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2088382023-08-03T23:40:36Z2023-08-03T23:40:36Z‘City killers’ and half-giraffes: how many scary asteroids really go past Earth every year?<figure><img src="https://images.theconversation.com/files/539914/original/file-20230728-3774-n34t6e.png?ixlib=rb-1.1.0&rect=270%2C43%2C1587%2C910&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://eyes.nasa.gov/apps/asteroids/#/asteroids/">NASA/Eyes on Asteroids</a></span></figcaption></figure><p>Asteroids are chunks of rock left over from the formation of our <a href="https://solarsystem.nasa.gov/solar-system/our-solar-system/overview/">Solar System</a>. Approximately half a billion asteroids with sizes greater than four metres in diameter orbit the Sun, travelling through our Solar System at speeds up to about 30 kilometres per second – about the same speed as Earth.</p>
<p>Asteroids are certainly good at capturing the public imagination. This follows <a href="https://www.space.com/best-asteroid-movies">many Hollywood movies</a> imagining the destruction they could cause if a big one hits Earth.</p>
<p>Almost every week we see <a href="https://www.9news.com.au/asteroid">online headlines</a> describing asteroids the size of a “bus”, “truck”, “vending machine”, “<a href="https://www.abc.net.au/adelaide/programs/afternoons/half-a-giraffe/13800376">half the size of a giraffe</a>”, or indeed a whole giraffe. We have also had headlines warning of “city killer”, “planet killer” and “God of Chaos” asteroids.</p>
<p>Of course, the threats asteroids pose are real. Famously, about 65 million years ago, life on Earth was brought to its knees by what was likely the impact of a big asteroid, <a href="https://www.nhm.ac.uk/discover/how-an-asteroid-caused-extinction-of-dinosaurs.html">killing off most dinosaurs</a>. Even a four-metre object (half a giraffe, say) travelling at a relative speed of up to 60 kilometres per second is going to pack a punch. </p>
<p>But beyond the media labels, what are the risks, by the numbers? How many asteroids hit Earth and how many can we expect to zip past us?</p>
<h2>What is the threat of a direct hit?</h2>
<p>In terms of asteroids hitting Earth, and their impact, the graphic below from NASA summarises the general risks.</p>
<p>There are far more small asteroids than large asteroids, and small asteroids cause much less damage than large asteroids.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=306&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=306&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=306&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534980/original/file-20230630-14093-2ehxuy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Asteroid statistics and the threats posed by asteroids of different sizes. NEOs are near-Earth objects, any small body in the Solar System whose orbit brings it close to our planet.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>So, Earth experiences frequent but low-impact collisions with small asteroids, and rare but high-impact collisions with big asteroids. In most cases, the smallest asteroids largely break up when they hit Earth’s atmosphere, and don’t even make it down to the surface.</p>
<p>When a small asteroid (or meteoroid, an object smaller than an asteroid) hits Earth’s atmosphere, it produces a spectacular “fireball” – a very long-lasting and bright version of a shooting star, or meteor. If any surviving bits of the object hit the ground, they are called meteorites. Most of the object burns up in the atmosphere.</p>
<h2>How many asteroids fly right past Earth?</h2>
<p>A very simplified calculation gives you a sense for how many asteroids you might expect to come close to our planet.</p>
<p>The numbers in the graphic above estimate how many asteroids could hit Earth every year. Now, let’s take the case of four-metre asteroids. Once per year, on average, a four-metre asteroid will intersect the surface of Earth. </p>
<p>If you doubled that surface area, you’d get two per year. Earth’s radius is 6,400km. A sphere with twice the surface area has a radius of 9,000km. So, approximately once per year, a four-metre asteroid will come within 2,600km of the surface of Earth – the difference between 9,000km and 6,400km.</p>
<p>Double the surface area again and you could expect two per year within 6,400km of Earth’s surface, and so on. This tallies pretty well with <a href="https://en.wikipedia.org/wiki/List_of_asteroid_close_approaches_to_Earth">recent records of close approaches</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/asteroid-2023-bu-just-passed-a-few-thousand-kilometres-from-earth-heres-why-thats-exciting-198656">Asteroid 2023 BU just passed a few thousand kilometres from Earth. Here's why that's exciting</a>
</strong>
</em>
</p>
<hr>
<p>A few thousand kilometres is a pretty big distance for objects a handful of metres in size, but most of the asteroids covered in the media are passing at much, much larger distances.</p>
<p>Astronomers consider anything passing closer than the Moon – approximately 300,000km – to be a “close approach”. “Close” for an astronomer is not generally what a member of the public would call “close”.</p>
<p>In 2022 there <a href="https://en.wikipedia.org/wiki/List_of_asteroid_close_approaches_to_Earth_in_2022">were 126 close approaches</a>, and in 2023 we’ve had <a href="https://en.wikipedia.org/wiki/List_of_asteroid_close_approaches_to_Earth_in_2023">50 so far</a>.</p>
<p>Now, consider really big asteroids, bigger than one kilometre in diameter. The same highly simplified logic as above can be applied. For every such impact that could threaten civilisation, occurring once every half a million years or so, we could expect thousands of near misses (closer than the Moon) in the same period of time. </p>
<p>Such an event will occur in 2029, when <a href="https://www.spacereference.org/asteroid/153814-2001-wn5">asteroid 153814 (2001 WN5)</a> will pass 248,700km from Earth.</p>
<h2>How do we assess threats and what can we do about it?</h2>
<p>Approximately 95% of asteroids of size greater than one kilometre are estimated to have already been discovered, <a href="https://cneos.jpl.nasa.gov/about/search_program.html">and the skies are constantly being searched for the remaining 5%</a>. When a new one is found, astronomers take extensive observations to assess any threat to Earth.<br>
The <a href="https://en.wikipedia.org/wiki/Torino_scale">Torino Scale</a> categorises predicted threats up to 100 years into the future, the scale being from 0 (no hazard) to 10 (certain collision with big object).</p>
<p>Currently, all known objects have a rating of zero. No known object to date has had a rating above 4 (a close encounter, meriting attention by astronomers).</p>
<p><iframe id="tc-infographic-895" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/895/b083d2a58aef50aa5cf9eccf3e83e7853ef8df45/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>So, rather than hearing about giraffes, vending machines, or trucks, what we really want to know from the media is the rating an asteroid has on the Torino Scale.</p>
<p>Finally, technology has advanced to the point we have a chance to do something if we ever do face a big number on the Torino Scale. Recently, the DART mission collided a spacecraft into an asteroid, changing its trajectory. In the future, it is plausible that such an action, with enough lead time, could help to protect Earth from collision.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/nasas-asteroid-deflection-mission-was-more-successful-than-expected-an-expert-explains-how-192334">NASA's asteroid deflection mission was more successful than expected. An expert explains how</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/208838/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steven Tingay is affiliated with the Australian Labor Party.</span></em></p>Barely a week goes by without headlines about a giant asteroid coming past Earth. Here’s what really makes an asteroid pass notable – it’s not just size.Steven Tingay, John Curtin Distinguished Professor (Radio Astronomy), Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2102182023-08-03T12:24:52Z2023-08-03T12:24:52ZMost Americans support NASA – but don’t think it should prioritize sending people to space<figure><img src="https://images.theconversation.com/files/539322/original/file-20230725-21-7pchup.jpg?ixlib=rb-1.1.0&rect=58%2C0%2C7802%2C3971&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Artemis I Launch in November 2022. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasahqphoto/52503151166/">NASA/Bill Ingalls</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Most Americans (69%) believe it is essential that the United States continue to be a world leader in space. But only a subsection of that group believes NASA should prioritize sending people to the Moon, according to <a href="https://www.pewresearch.org/science/2023/07/20/americans-views-of-space-u-s-role-nasa-priorities-and-impact-of-private-companies/">a new report</a> released by the Pew Research Center. The study surveyed over 10,000 U.S. adults on their attitudes toward NASA and their expectations for the space industry over the next few decades.</p>
<p>As scholars who study <a href="https://scholar.google.com/citations?user=aESo-coAAAAJ&hl=en">international relations in space</a> and the <a href="https://airandspace.si.edu/people/staff/teasel-muir-harmony">history of the space program</a>, we are interested in understanding how Americans view space activities, and how their perspectives might affect the future of both U.S. and global space developments.</p>
<h2>US dominance in space</h2>
<p>The United States’ most visible effort to maintain world leadership in space is arguably its <a href="https://www.nasa.gov/specials/artemis/">Artemis Program</a> to <a href="https://theconversation.com/returning-to-the-moon-can-benefit-commercial-military-and-political-sectors-a-space-policy-expert-explains-209300">land humans on the Moon</a> by late 2024. The U.S. has emphasized international cooperation, bringing in Europe, Japan and Canada as partners in the program.</p>
<p>With China and Russia <a href="https://www.space.com/china-russia-moon-base-ilrs">undertaking a parallel effort</a> to land people on the Moon, many see a competitive element to these plans as well.</p>
<p>One of the most striking features of the recent poll is how similar it looks to earlier public opinion polling, especially <a href="https://www.pewresearch.org/science/2018/06/06/majority-of-americans-believe-it-is-essential-that-the-u-s-remain-a-global-leader-in-space">one conducted in 2018</a>. The popularity of NASA has remained consistently high for decades, frequently with a favorability rating between 60% and 70%, far higher than many other federal agencies. But the specific priorities of the U.S. space program have often been at odds with public opinion. </p>
<p>While 65% of Americans said <a href="https://www.pewresearch.org/science/2023/07/20/americans-views-of-space-u-s-role-nasa-priorities-and-impact-of-private-companies/">in the new Pew survey</a> it was essential that NASA continue to be involved in space exploration, only 12% said that sending human astronauts to the Moon should be NASA’s top priority. Although somewhat at odds with the national space agenda, this valuation is not new. Even during the 1960s, when NASA undertook Project Apollo, Americans ranked solving problems on Earth – such as pollution, poverty and national beautification – <a href="https://doi.org/10.1111/ssqu.12473">above landing humans on the Moon</a>.</p>
<p>Most Americans for the majority of the 1960s responded in public opinion polls that the Apollo program <a href="https://doi.org/10.1016/S0265-9646(03)00039-0">was not worth its high budget</a>. Over time, however, the <a href="https://nap.nationalacademies.org/read/18801/chapter/3#29">Apollo program has grown in popularity</a>. </p>
<p>Between 1989 and 1995, polling revealed that the public thought the U.S. space program should <a href="https://doi.org/10.1016/S0265-9646(03)00039-0">focus on robotic spacecraft</a> as opposed to crewed missions. This position began to change in the mid-1990s with docking of the space shuttle with the Russian space station and several blockbuster space-themed films. </p>
<p>Despite <a href="https://doi.org/10.1111/ssqu.12473">moderate public support</a>, human spaceflight consistently receives the majority share of <a href="https://www.planetary.org/space-policy/nasa-budget">U.S. civilian space funding</a>, suggesting that public opinion and the national space agenda stand apart. The most recent poll results underscore how <a href="https://nap.nationalacademies.org/read/18801/chapter/2#2">a combination of rationales</a> – including advancing science, national stature, geopolitics, economic interests and national security – rather than public opinion alone have shaped national space priorities throughout time.</p>
<h2>Planetary defense</h2>
<p>Additionally, the recent poll explored people’s expectations for the space industry. It found 60% of people believed NASA’s top priority should be monitoring asteroids that could hit the Earth. NASA does have national responsibility for this job – referred to as planetary defense – but the office receives <a href="https://ww2.aip.org/fyi/2023/fy23-budget-outcomes-nasa">less than 1% of NASA’s budget</a>, or US$138 million out of $25.4 billion in 2023.</p>
<p>Even with its relatively modest budget, the office has made significant progress. This included the <a href="https://www.nasa.gov/planetarydefense/dart/dart-news">Double Asteroid Redirect Test</a> – the world’s <a href="https://dart.jhuapl.edu/Mission/index.php">first planetary defense experiment</a>. <a href="https://theconversation.com/nasa-successfully-shifted-an-asteroids-orbit-dart-spacecraft-crashed-into-and-moved-dimorphos-192317">DART intentionally</a> <a href="https://apnews.com/article/nasa-dart-asteroid-updates-b6cfccd90a0450c3cce6048af61a1c01">crashed into an asteroid</a> in September 2022 to understand how the impact would change the asteroid’s orbit. The results of the test could help scientists understand how to deflect asteroids that threaten the Earth.</p>
<p><iframe id="QXuaj" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/QXuaj/3/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Private enterprise in space</h2>
<p>Private activity in space goes back to the 1960s, with the creation of commercial <a href="https://history.nasa.gov/satcomhistory.html">communication satellite companies</a> and growth of large <a href="https://www.theverge.com/2019/12/11/20981714/spacex-commercial-spaceflight-space-industry-decade-nasa-business">defense contractors</a>. However, many experts view the wave of companies that started in the 2000s as marking an important change.</p>
<p>While earlier companies often relied heavily on the government to set requirements and fund projects, these “<a href="https://www.nationalacademies.org/news/2022/03/new-space-ecosystem-should-be-leveraged-to-provide-transformative-science-advancements-says-new-report">new space</a>” companies set their own priorities and often see the government as only one of many customers.</p>
<p>These companies are bringing new capabilities to the market. For example, <a href="https://www.planet.com/">Planet</a> collects daily images of the Earth, <a href="https://www.umbra.com/">Umbra</a> uses radar to take pictures at night and through clouds, <a href="https://astroscale.com/">Astroscale</a> is demonstrating the ability to remove debris from space, and <a href="https://www.astrobotic.com/">Astrobotic</a> is developing a commercial Moon lander.</p>
<p>Many Americans view private activity in space positively, but a large portion have not yet formed an opinion. While 48% of Americans surveyed said private companies are doing a good job building rockets and spacecraft that are safe and reliable, another 39% were unsure. Similarly, 47% of Americans said private companies are making important contributions to space exploration, but another 40% were unsure. </p>
<p><iframe id="0cdOM" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/0cdOM/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Companies like <a href="https://www.cbsnews.com/news/spacex-commercial-flight-space-station-launch-private-citizens-saudis-axiom/">SpaceX</a>, <a href="https://www.space.com/blue-origin-ns-21-space-tourist-mission">Blue Origin</a> and <a href="https://www.cbsnews.com/news/virgin-galactic-rocketplane-first-commercial-sub-orbital-flight-to-space/">Virgin Galactic</a> are <a href="https://theconversation.com/spacex-inspiration4-mission-sent-4-people-with-minimal-training-into-orbit-and-brought-space-tourism-closer-to-reality-167611">beginning to take tourists into space</a>. Doing so in a safe and sustainable way will be essential to the future perception of this industry. Priorities include carefully designing safety systems and procedures and carrying out careful analysis of any <a href="https://spacenews.com/blue-origin-continues-investigation-into-new-shepard-anomaly/">anomolies</a> that occur during flight.</p>
<p>Overall, Americans are optimistic about the future of space activity. The poll found 55% of Americans expect people will routinely travel to space as tourists within the next 50 years.</p>
<h2>Militarization of space</h2>
<p>A significant portion of Americans (44%) see a more militaristic future for space. They believe the U.S. will definitely or probably fight against other nations in space sometime in the next 50 years. Warfare could include the destruction or disabling of U.S. or other nations’ strategic satellites. </p>
<p>By some definitions, conflict in space has <a href="https://theconversation.com/war-in-ukraine-highlights-the-growing-strategic-importance-of-private-satellite-companies-especially-in-times-of-conflict-188425">already occurred</a>. At the outset of the Ukraine War, Russia carried out a <a href="https://www.technologyreview.com/2022/05/10/1051973/russia-hack-viasat-satellite-ukraine-invasion/">cyberattack against the ViaSat satellite network</a> used by the Ukrainian military. Russia also regularly <a href="https://www.space.com/russia-jamming-gps-signals-ukraine">jams GPS signals</a> in Ukraine. However, no nation has ever physically attacked another nation’s satellite in space.</p>
<p>There is <a href="https://www.armscontrol.org/act/2021-12/focus/small-step-toward-asat-ban">no ban on anti-satellite weapons</a>, but in December 2022, 155 nations <a href="https://spacenews.com/united-nations-general-assembly-approves-asat-test-ban-resolution/">passed a United Nations General Assembly resolution</a> calling for a halt to one type of anti-satellite testing. In addition, the United Nations’ <a href="https://meetings.unoda.org/open-ended-working-group-on-reducing-space-threats-2022">open-ended working group on reducing space threats</a> has been meeting since 2022 to help avoid conflict in space.</p>
<h2>Space debris</h2>
<p>Americans are also concerned about space debris – 69% think there will definitely or probably be a major problem with debris in space by 2073. Space debris can include defunct satellites, discarded rocket bodies, or pieces of satellites resulting from accidental collisions or anti-satellite tests.</p>
<p>There is reason for concern. The number of objects in space has grown rapidly, from just over 1,000 in 2013 to <a href="https://www.ucsusa.org/resources/satellite-database">6,718 satellites today</a>. Many countries have <a href="https://spacenews.com/satellite-operators-criticize-extreme-megaconstellation-filings/">announced plans for new large constellations</a> of satellites, with some experts predicting there could be <a href="https://www.gao.gov/products/gao-22-105166">60,000 satellites in orbit by 2030</a>.</p>
<p>Right now the United States maintains the most advanced <a href="https://nsarchive.gwu.edu/briefing-book/intelligence/2023-03-13/whats-there-where-it-and-whats-it-doing-us-space-surveillance">system for monitoring space objects</a>. It shares <a href="https://www.space-track.org/">information and collision warnings</a> with satellite operators all over the world, but there are no rules that require those operators to take action. As space traffic increases, this ad hoc system will need to change.</p>
<p>The United States is developing a new <a href="https://spacenews.com/commerce-department-outlines-plans-for-basic-space-traffic-management-service/">Traffic Coordination System for Space</a> that will improve data sharing and coordination with commercial and international partners. Countries have been working within the United Nations to develop and implement guidelines for the <a href="https://www.unoosa.org/oosa/en/ourwork/topics/long-term-sustainability-of-outer-space-activities.html">long-term sustainability</a> of outer space activities. </p>
<p>Still, the U.S. will need to coordinate with countries around the world to ensure satellite technology doesn’t outpace safety and give organizations like NASA the ability to continue leading activities in space.</p><img src="https://counter.theconversation.com/content/210218/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mariel Borowitz receives funding from the National Air and Space Administration (NASA), the Department of Defense (DoD), and the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Teasel Muir-Harmony 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>A new survey catalogs Americans’ expectations about the future of space, from NASA to SpaceX. Two space policy experts describe how these results stack up against the current state of space affairs.Mariel Borowitz, Associate Professor of International Affairs, Georgia Institute of TechnologyTeasel Muir-Harmony, Curator of the Apollo Collection, Smithsonian National Air and Space Museum and Affiliate Adjunct, Georgetown UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2091012023-07-07T14:12:35Z2023-07-07T14:12:35ZPhysicist who found spherical meteor fragments claims they may come from an alien spaceship – here’s what to make of it<figure><img src="https://images.theconversation.com/files/536320/original/file-20230707-25-qnitc7.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6586%2C2997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anybody out there?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-space-galaxy-stars-universe-filled-1995429968">Triff/Shutterstock</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Avi Loeb, a physicist from Harvard University in the US, <a href="https://www.independent.co.uk/news/world/americas/avi-loeb-interstellar-object-aliens-b2369534.html">has recovered</a> 50 tiny spherical iron fragments from the bottom of the Pacific Ocean that he claims may be material from an interstellar alien spaceship. </p>
<p>Loeb is linking his finding with the passage of a fireball in January 2014. The meteor was observed by sensors of the US Department of Defense that track all objects entering the Earth’s atmosphere. It was recorded as travelling faster than most meteors and eventually broke up over the South Pacific Ocean near Papua New Guinea. </p>
<p>Data on the object is held by Nasa’s <a href="https://cneos.jpl.nasa.gov/">Centre for Near Earth Object Studies</a> (CNEOS). The meteor’s official name is CNEOS 20140108, and is also referred to as IM1 (for interstellar meteor).</p>
<figure class="align-center ">
<img alt="Loeb next to image of spherule" src="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=385&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=385&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536316/original/file-20230707-21-5ea08a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=385&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Loeb next to image of spherule.</span>
<span class="attribution"><span class="source">NewsNation/Youtube</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>There is a very large scientific leap from observing a fireball to claiming it is an alien spaceship. What is the evidence on which Loeb bases the claim? And how likely is it to be true? </p>
<h2>‘Oumuamua, an interstellar comet</h2>
<p>We have already had at least one visitor from interstellar space - the comet <a href="https://theconversation.com/discovery-of-cigar-shaped-asteroid-from-outer-space-could-help-unveil-secrets-of-extrasolar-worlds-87873">'Oumuamua</a>. The appearance of 1I/2017U1, the official name for 'Oumuamua, was certainly an unusual event. The object was observed in 2017 as it was leaving the Solar System. Its <a href="https://legacy.ifa.hawaii.edu/info/press-releases/interstellar/interstellar_orbit.pdf">trajectory</a> is different from the near-circular orbits of the planets and elliptical orbits of comets.</p>
<p>The comet’s path was traced back, with scientists discovering that it had come from well beyond the outermost fringes of the Solar System. Scientists were excited but also intrigued - although its shape was not captured on camera, the way that light reflected from it as it rotated suggested that it had an odd shape like a cigar when viewed side-on or a plate when viewed from the top.</p>
<figure class="align-center ">
<img alt="'Oumuamua" src="https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&rect=42%2C22%2C1235%2C768&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/536103/original/file-20230706-23-ul92t8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">‘Oumuamua.</span>
<span class="attribution"><span class="source">ESO/M. Kornmesser</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In a thoughtful <a href="https://blogs.scientificamerican.com/observations/how-to-search-for-dead-cosmic-civilizations/">article written in 2018</a>, Loeb speculated that 'Oumuamua might be artificial, rather than natural in origin – the product of an alien civilisation. He suggested that we should keep searching for interstellar debris in the Solar System. </p>
<p>In pursuit of such debris, Loeb’s team interrogated the CNEOS database, looking for objects with unusual orbital characteristics. That’s when they found CNEOS 20140108 and, based on its high velocity, suggested it was an <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ac8eac/pdf">interstellar meteor</a> – giving it the more manageable name of IM1. </p>
<p>Modelling the path of the fireball, Loeb identified a specific area of the South Pacific where he believed debris from IM1 would be deposited. Following a dredging operation in the area with a powerful magnet, he now claims to have found <a href="https://www.independent.co.uk/news/world/americas/avi-loeb-interstellar-object-aliens-b2369534.html">material from IM1</a>.</p>
<p>But what are the chances that he has found genuine interstellar debris at all, never mind a spaceship?</p>
<h2>Cosmic spherules?</h2>
<p>The metallic spherules that have been recovered are each about half a millimetre in diameter. It isn’t impossible for them to be of extraterrestrial origin: several previous expeditions have recovered spherules from space from the seabed.</p>
<p>The first expedition to find such samples was HMS Challenger in 1872-76. Material dredged from the ocean floor <a href="https://www.nhm.ac.uk/content/dam/nhmwww/discover/challenger/challenger-6-two-column.jpg.thumb.768.768.jpg">contained</a> many metallic droplets, described at the time, quite accurately, as “cosmic spherules”. Droplets from space are spherical because they solidify from molten material torn from the surface of meteorites as they traverse the atmosphere.</p>
<p>Subsequent expeditions throughout the 20th century have also found cosmic spherules at the bottom of the ocean, but it has become harder to identify them. This is because, in the 150 years since the Challenger expedition, the amount of pollution has increased on Earth. </p>
<p>In 1872, the industrial revolution was in its infancy in Europe and practically non-existent in the southern hemisphere. Hence pollution such as “fly ash” (waste from burning coal) and particles from vehicles was minimal. Many of these pollutants are also spherical in appearance and metallic in composition.</p>
<p>Today, products from industrial processes and vehicles are everywhere. So, without an actual analysis of the composition of the spherules and a comparison with analyses of meteorites (and common terrestrial pollutants), it is not possible to identify any as extraterrestrial.</p>
<h2>Interstellar?</h2>
<p>But Loeb doesn’t just think the material is from space, he thinks it is from interstellar space – arguing <a href="https://www.dailymail.co.uk/sciencetech/article-12243125/Harvards-Avi-Loeb-says-50-microscopic-spherules-recovered-Pacific-alien-probe.html">“this could be the first time humans put their hands on interstellar material”</a>. </p>
<p>This is simply not true. We have an abundance of interstellar material on Earth. Some of it is almost certainly on the ocean floor, but not in the form collected by Loeb. </p>
<p>The interstellar material to which I am referring comes in several different varieties. It is well known by astronomers that the interstellar medium - the space between stars - is not empty, but contains several different molecules, many of which are organic (made up of chains or rings of carbon). A portion of these molecules got mixed into the region of space where the Solar System was starting to form. </p>
<p>Stars themselves have also contributed material to the interstellar medium, as they evolved or exploded as supernovas. Some of this material comes as tiny diamonds or sapphires - rare mementoes of stars that lived and died before the Sun was born. These grains became part of the dust cloud that collapsed to form the Solar System, and were eventually carried to Earth in meteorites.</p>
<h2>Alien spacecraft?</h2>
<p>Loeb’s evidence for an extraterrestrial source for the material – never mind an interstellar origin – is rather shaky. He has found metallic spherules. For me (and many others) to accept that these spherules are extraterrestrial, I’d need firm analytical evidence. What is their composition? What is their age? Can we rule out terrestrial pollutants? Can we rule out debris from extraterrestrial material from within the Solar System? </p>
<p>The first question, about composition, has been answered: analysis of the spherules shows them to be <a href="https://www.dailymail.co.uk/sciencetech/article-12259813/EXCL-Harvard-scientists-say-UFO-crashed-ocean-2014-appears-artificial-origin.html">mainly iron with a few trace metals</a>.</p>
<p>We know meteors from our Solar System contain iron and nickel, echoing the relative abundances of these metals in the Sun. But the spherules apparently contain “negligible” amounts of nickel - thus indicating that they are almost certainly not from meteors within the Solar System. This does not, however, prove they are interstellar - it merely makes it more likely that they’re terrestrial pollutants.</p>
<p>The most convincing evidence would be to measure an age for the spherules greater than that of the Sun - which would identify them as interstellar.</p>
<p>And that would be amazing, but it would not necessarily identify them as having an artificial, rather than natural origin. I am not sure what evidence would be sufficiently convincing for this - maybe the autograph of the alien engineer who built the spacecraft?</p><img src="https://counter.theconversation.com/content/209101/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady receives funding from the STFC and the UK Space Agency. She is Professor of Planetary and Space Sciences at the Open University, Chancellor of Liverpool Hope University and Senior Researcher at the Natural History Museum. She tweets as @MonicaGrady</span></em></p>There is a very large scientific leap from observing a fireball to claiming it as an alien spaceship.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2030612023-04-18T04:57:04Z2023-04-18T04:57:04ZFrom platypus to parsecs and milliCrab: why do astronomers use such weird units?<figure><img src="https://images.theconversation.com/files/520396/original/file-20230412-22-m6601g.jpg?ixlib=rb-1.1.0&rect=0%2C308%2C2000%2C1356&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA / ESA / J. Hester / A. Loll</span></span></figcaption></figure><p>You may have heard about an asteroid set to fly near Earth that is <a href="https://www.jpost.com/science/article-735881">the size of 18 platypus</a>, or maybe the one that’s <a href="https://www.jpost.com/science/article-735473">the size of 33 armadillos</a>, or even one <a href="https://www.jpost.com/science/article-735299">the size of 22 tuna fish</a>. </p>
<p>These outlandish comparisons are the invention of Jerusalem Post journalist Aaron Reich (who <a href="https://twitter.com/aaronreich?lang=en">bills himself</a> as “creator of the <a href="https://www.jpost.com/science/article-708238">giraffe metric</a>”), but real astronomers sometimes measure celestial objects with units that are just as strange. </p>
<p>The idea of a planet that’s <a href="https://www.nature.com/articles/nature17448">85% the mass of Earth</a> seems straightforward. But what about a pulsar-wind nebula with a brightness of a few milliCrab? That’s where things get weird.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A top down image of a platypus swimming." src="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.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"></a>
<figcaption>
<span class="caption">A platypus that is approximately 1/18th of the size of Asteroid 2023 FH7.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Platypus#/media/File:Platypus.jpg">Stefan Kraft / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Why do astronomers use such strange units?</h2>
<p>The basic problem is that lots of things in space are way too big for our familiar units. </p>
<p>Take my whippet Astro, who is 94cm long. Earth’s radius is about 638 million cm, or 7.5 million Astros. </p>
<p>Jupiter’s radius is 11.2 Earths, or 85 million Astros. That number of Astros is a bit ridiculous, which is why we adjust our unit choice to one that makes more sense. </p>
<figure class="align-center ">
<img alt="A white whippet with a brown splotch over his eye is lying down in the grass with a blue sky with puffy clouds in the background. He's staring off into the distance." src="https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Astro the whippet contemplating the wonders of the Universe (probably).</span>
<span class="attribution"><span class="source">Laura Driessen</span></span>
</figcaption>
</figure>
<p>At an even larger scale, consider the star Betelguese: its radius is 83,000 Earths, or 764 times the radius of the Sun. So if we want to talk about how big Betelgeuse is, it’s much more convenient to use the radius of the Sun as our unit, instead of the radius of Earth (or to describe it as 632 billion Astros).</p>
<h2>Heavy stuff</h2>
<p>If we want to measure how heavy an asteroid is, we could <a href="https://www.jpost.com/science/article-733651">do it with camels</a> – but in space we’re more interested in mass than in weight. Mass is a measure of how much stuff something is made of. </p>
<p>On Earth the weight of an object, like Astro, depends on the mass of Astro and the gravitational force pulling him down to the ground. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-mass-49299">Explainer: what is mass?</a>
</strong>
</em>
</p>
<hr>
<p>We can think of weight in terms of how hard it is to lift an 18kg Astro off the ground. This would be easy to do on Earth, even easier somewhere with lower gravity like the Moon, and much harder somewhere with higher gravity like Jupiter. </p>
<p>On the other hand, Astro’s mass is how much stuff he’s made of – and it’s the same no matter which planet he’s on. </p>
<p>Astronomers use Earth and the Sun as handy units to measure mass. For example, the Andromeda galaxy is approximately <a href="https://arxiv.org/abs/2211.15928">three trillion times</a> the mass of the Sun (or 3×10<sup>41</sup> – that’s a 3 followed by 41 zeros – Astros).</p>
<h2>Astronomical units and parsecs</h2>
<p>Astronomers also use comparisons to measure how far apart things are. The Sun and Earth are 149 million kilometres apart, and we give this distance a name: an astronomical unit (AU). </p>
<p>For an even twistier unit of distance, we use the parsec (insert Han Solo <a href="https://starwars.fandom.com/wiki/Kessel_Run">Kessel run</a> joke here). Parsec is short for “parallax second”, and if you remember your trigonometry, this is the length of the hypotenuse of a right-angle triangle when the angle is 1 arcsecond (1/3,600 degrees) and the “opposite” side of the triangle is 1 AU. </p>
<p>Parsecs are handy for measuring even bigger distances because 1 parsec = 206,265 AU. For example, the centre of our very own galaxy, the Milky Way, is about 8,000 parsecs away from Earth, or 1.6 million AU.</p>
<h2>Magnitudes</h2>
<p>If we want to measure how bright something is, astronomical units of measurement get even weirder. In the second century BC, the ancient Greek astronomer Hipparchus looked up at space and gave the brightest stars a value of 1 and the faintest stars a value of 6. </p>
<p>Notice here that a brighter star has a lower number. We call these brightness values “magnitudes”. The Sun has an apparent magnitude of –26! </p>
<figure class="align-center ">
<img alt="A image of the Sun as an orange ball with dark spots and bright loops." src="https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An image of the Sun taken by NASA’s Solar Dynamics Observatory.</span>
<span class="attribution"><span class="source">NASA/SDO</span></span>
</figcaption>
</figure>
<p>Even more confusing than a negative brightness, each single step in magnitude is a 2.512 times difference in brightness. The star Vega has an apparent magnitude of 0, which is two and a bit times brighter than the star Antares with an apparent magnitude of 1.</p>
<h2>At last, the milliCrab</h2>
<p>The light we see with our eyes is, for obvious reasons, called “visible” light. The light we use to take pictures of your bones is called X-ray light. </p>
<p>When astronomers use X-ray light to observe the sky we sometimes measure brightness in “Crabs”. </p>
<p>The Crab is a rapidly spinning neutron star (or pulsar) in the remains of an exploded star that is extremely bright when we look at it using our X-ray telescopes. It’s so bright in X-ray light that astronomers have been using it to <a href="https://ui.adsabs.harvard.edu/abs/2005SPIE.5898...22K/abstract">calibrate their telescopes</a> since the 1970s. </p>
<figure class="align-center ">
<img alt="A bright, multi-coloured supernova remnant with dusty, wispy filaments and something resembling a tornado (the pulsar wind nebula) in the centre." src="https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Image of the Crab Nebula where red is radio from the Very Large Array, yellow is infra-red from the Spitzer Space Telescope, green is visible from the Hubble Space Telescope, and blue and purple are X-ray from the XMM-Newton and Chandra X-ray Observatories respectively.</span>
<span class="attribution"><span class="source">NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al.; A. Loll et al.; T. Temim et al.; F. Seward et al.; VLA/NRAO/AUI/NSF; Chandra/CXC; Spitzer/JPL-Caltech; XMM-Newton/ESA; and Hubble/STScI</span></span>
</figcaption>
</figure>
<p>So every X-ray astronomer knows how bright a Crab is. And if we’re talking about a particular object, say a <a href="https://ui.adsabs.harvard.edu/abs/2019ApJ...885...48G/abstract">black hole binary system called GX339-4</a>, and it’s only five thousandths as bright as the Crab, we say it’s 5 milliCrab bright.</p>
<p>But buyer beware! The brightness of the Crab is different depending on what energy of X-ray light you’re looking at, and it also <a href="https://ui.adsabs.harvard.edu/abs/2011ApJ...727L..40W/abstract">changes over time</a>.</p>
<p>Whether we use lions or tigers or Crabs, astronomers make sure to define the units we’re using. There’s no use using an armadillo, or even your local whippet, unless you’ve made sure the definition is clear.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beating-heart-of-the-crab-nebula-62282">Beating heart of the Crab Nebula</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/203061/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Nicole Driessen is part of MeerTRAP, which is supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No 694745).</span></em></p>An asteroid ‘the size of 33 armadillos’ might be a flight of fancy, but real astronomers measure celestial objects with units that are just as strange.Laura Nicole Driessen, Postdoctoral researcher in radio astronomy, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2019602023-03-21T19:12:29Z2023-03-21T19:12:29ZNew asteroid sample study offers further hints of space origin for the building blocks of life on Earth<figure><img src="https://images.theconversation.com/files/516537/original/file-20230321-16-wajyqt.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C1997%2C1616&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">MASCOT / DLR / JAXA</span></span></figcaption></figure><p>How did life come about? The answer to this question goes to the very heart of our existence on planet Earth. </p>
<p>Did life simply arise from chemical reactions among organic compounds in a primordial soup left after Earth clumped together from space rubble? If so, where did the organic compounds come from?</p>
<p>Some of the so-called “building blocks of life” may have been surprisingly common in the early Solar System.</p>
<p>A team of Japanese and American scientists led by Yasuhiro Oba has analysed samples taken from the asteroid Ryugu in 2018 by the Hayabusa2 mission and found uracil, one of the five key bases of the RNA and DNA molecules that are crucial to life as we know it. Their <a href="https://www.nature.com/articles/s41467-023-36904-3">study</a> is published today in Nature Communications.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-hayabusa2-spacecraft-is-about-to-drop-a-chunk-of-asteroid-in-the-australian-outback-151280">The Hayabusa2 spacecraft is about to drop a chunk of asteroid in the Australian outback</a>
</strong>
</em>
</p>
<hr>
<h2>Building blocks</h2>
<p>At the most basic level, the development of life is a matter of combining simple organic molecules into increasingly complex compounds that can participate in the myriad reactions associated with a living organism. </p>
<p>Simple amino acids are believed to act as building blocks in the construction of these more complex molecules. But this isn’t just a simple random combination exercise. </p>
<p>The largest “chunk” of the human genome, chromosome 1, is made up of 249 million base pairs (the rungs on the twisted ladder of the DNA molecule). Each base pair is made of two bases: either guanine and cytosine, or adenine and thymine. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-rna-15169">Explainer: what is RNA?</a>
</strong>
</em>
</p>
<hr>
<p>Building from the simple base pair chemicals to a full strand of DNA is a massive undertaking. A strand of DNA also has a complex structure, which varies from one individual to another. Life on Earth uses the structure of DNA to memorise the construction of the life form involved. </p>
<p>Alongside DNA, life uses a molecule called RNA for making proteins and doing other odds jobs inside cells. RNA is also made of a long string of bases: guanine, cytosine and adenine (like DNA), but instead of thymine it has uracil – which is what turned up in the sample from Ryugu.</p>
<h2>Ryugu</h2>
<p>Ryugu is what’s called a C-type or carbonaceous asteroid. These are the most common type in the asteroid belt, making up about 75% of the asteroids we can see. </p>
<p>The Hayabusa2 mission established that C-type asteroids like Ryugu are the source of a kind of rare meteorite sometimes found on Earth, called a carbonaceous chondrite.</p>
<p>Uracil and other organic molecules have previously been found in these meteorites, but there has been no way to rule out the possibility that some of the molecules had a terrestrial origin. The meteorite samples could have been contaminated here on Earth, or their chemistry might have been changed by heating as they fell through the atmosphere.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-asteroids-made-of-a-sample-returned-to-earth-reveals-the-solar-systems-building-blocks-176548">What are asteroids made of? A sample returned to Earth reveals the Solar System's building blocks</a>
</strong>
</em>
</p>
<hr>
<p>However, since the Ryugu sample was taken from the surface of an asteroid and brought back in a tightly sealed container, scientists are confident it is free of contamination or any effects of coming to Earth.</p>
<p>Furthermore, the presence of these amino acids on Ryugu shows that even on asteroid surfaces, exposed to solar wind, micrometeorites and cosmic rays, organic molecules can survive transportation through the solar system.</p>
<p>A huge variety of different organic compounds have <a href="https://www.science.org/doi/10.1126/science.abn9033">already been found</a> in Ryugu samples. </p>
<p>Many organic molecules, such as amino acids, come in two forms: left-handed and right-handed. Life on Earth relies on left-handed amino acids, but both forms are equally common in Ryugu samples – which indicates the molecules found on Ryugu are not signs of life. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/is-there-life-through-the-looking-glass-the-riddle-of-lifes-single-handedness-48819">Is there life through the looking-glass? The riddle of life's single-handedness</a>
</strong>
</em>
</p>
<hr>
<h2>The big picture</h2>
<p>The Solar System formed around 4.57 billion years ago from a molecular dust cloud that was exposed to UV radiation and particle bombardment from protons. </p>
<p>The molecular cloud contained simple molecules such as methane (CH₄), water (H₂O) and ammonia (NH₃). These would have been fragmented by the radiation, and the fragments would have reassembled into more complex molecules such as amino acids.</p>
<p>C-type asteroids like Ryugu are believed to have formed so far from the Sun that the water and carbon dioxide they contain would have remained frozen. However, as the asteroids warmed up and the ice melted, liquid water would have been able to react with the rocks and minerals.</p>
<p>Whether these conditions led to the creation of more complex organic molecules is an open question, but certainly these conditions would be conducive to further reactions. In addition, these conditions could affect the survival of different compounds. </p>
<p>The Hayabusa2 samples from Ryugu provide a new context for understanding the origin of organic compounds that may have been the start of life on Earth. It is still a big step from having these organic compounds available to early Earth, and the formation of life itself.</p><img src="https://counter.theconversation.com/content/201960/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Trevor Ireland receives funding from The Australian Research Council for research into the Ryugu samples. He is affiliated with the Hayabusa2 mission.</span></em></p>The discovery of a key component of RNA in samples from asteroid Ryugu adds weight to the theory that basic organic molecules may have arrived on Earth from outer space.Trevor Ireland, Professor, School of Earth and Environmental Sciences, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.