tag:theconversation.com,2011:/africa/topics/venus-3099/articlesVenus – The Conversation2024-01-29T16:38:10Ztag:theconversation.com,2011:article/2221732024-01-29T16:38:10Z2024-01-29T16:38:10ZNasa’s Mars helicopter Ingenuity has ended its mission – its success paves the way for more flying vehicles on other planets and moons<figure><img src="https://images.theconversation.com/files/571847/original/file-20240129-15-v0glwl.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2270%2C1360&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Ingenuity helicopter on Mars.</span> <span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/27421/ingenuity-at-two-years-on-mars/">NASA/JPL-Caltech/ASU/MSSS</a></span></figcaption></figure><p>It is difficult to emphasise the significance of the milestone surpassed by Nasa’s Mars helicopter, Ingenuity. </p>
<p>The little (1.8kg) helicopter <a href="https://mars.nasa.gov/resources/25608/nasas-perseverance-rover-lands-successfully-on-mars/">touched down with the Perseverance rover in 2021</a>. On 25 January, Nasa announced that the flying vehicle <a href="https://www.nasa.gov/news-release/after-three-years-on-mars-nasas-ingenuity-helicopter-mission-ends/">had to perform an emergency landing</a> which damaged one of its rotors and ended its mission. </p>
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<p>This reminds us that space exploration is still difficult to do. But Ingenuity’s three years on Mars proved that powered, controlled flight on Mars was possible. </p>
<p>The little helicopter lasted for far longer than had been planned and flew higher and further than many had envisaged. Beyond this Martian experiment, the rotorcraft’s success paves the way for other missions using flying vehicles to explore planets and moons.</p>
<p>The first landings on the Moon were static. The year 1969 was probably the most important one for space exploration, when <a href="https://www.nasa.gov/mission/apollo-11/">Apollo 11</a> and <a href="https://www.nasa.gov/mission/apollo-12/">Apollo 12</a> brought astronauts to the lunar surface, but 1970 was the year for planetary exploration. </p>
<p>In 1970, we had the <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1970-060A">first soft landing on another planet</a>, Venus. The first robotic sample delivered to Earth from the Moon. And the first robot rover to drive around another body (also the Moon). </p>
<p>Since then, following over 50 years of planetary exploration and technology development, there have only been a small number of successful surface missions, and even fewer were able to move. Venus was visited by a dozen static landers between 1970 and 1985, and never again. </p>
<h2>From rovers to helicopters</h2>
<p>Mars was only successfully landed on three times between 1971 and 1976 before the <a href="https://mars.nasa.gov/mars-exploration/missions/pathfinder/">Pathfinder lander</a> and Sojourner rover arrived in 1997. The European Huygens spacecraft then landed on Titan, the moon of Saturn, in 2005. </p>
<p>These attempts at reaching the surface are rare, extremely difficult, and, historically, the landers were hardly ever mobile. Yet the Nasa <a href="https://mars.nasa.gov/mer/mission/overview/">Mars rovers Spirit, Opportunity</a>, <a href="https://mars.nasa.gov/msl/home/">Curiosity</a>, and <a href="https://mars.nasa.gov/mars2020/">Perseverance</a> have all exceeded their designs and travelled further and further.</p>
<p>And Ingenuity flew.</p>
<p>It wasn’t the first spacecraft to fly. Those would be the balloons deployed by the <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1984-128F">Soviet Vega 1 and 2 missions</a>, which floated over Venus in 1985. But Ingenuity had control, cameras, and connectivity. It took photos of its rover and of Mars from an entirely new perspective. It commanded the world’s attention and captured our hearts.</p>
<p>In Moscow, I had the chance to see models and replicas of the Vega balloons and the first lunar rover. They made a stronger impression on me than the Mars rover twins being used at Nasa’s Jet Propulsion Laboratory (JPL) in California. The Soviet missions were more audacious and different, and they were from generations ago, before my time and long before my career as a planetary scientist.</p>
<p>Ingenuity was audacious, original and completely new. The photos it took, of Perseverance, finding technology discarded from the descent module that carried it down to Mars and of the Martian vistas from a bird’s eye view, were breathtaking. Meanwhile, Perseverance also took videos of Ingenuity flying in the air. Nothing like it had ever seen before.</p>
<figure class="align-center ">
<img alt="CGI image of a silver drone with eight propellers over the Martian surface" src="https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=380&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=380&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=380&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=478&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=478&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571881/original/file-20240129-23-b4r2m2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=478&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An artist’s impression of the Dragonfly spacecraft in flight.</span>
<span class="attribution"><a class="source" href="https://dragonfly.jhuapl.edu/Gallery/">NASA/Johns Hopkins APL/Steve Gribben</a></span>
</figcaption>
</figure>
<h2>Future flights</h2>
<p>Ingenuity had a rough ride getting there, however. The entire Mars 2020 mission (of Perseverance, Ingenuity and their transport systems) was sudden. </p>
<p>Following Nasa’s withdrawal from the joint European Space Agency ExoMars programme, which included a Mars rover mission, the US space agency started developing one on its own. This rover, later named Perseverance, went from announcement to concept to development and launch in just seven-and-a-half years.</p>
<p>And Ingenuity wasn’t included onboard at first. As an idea, it was proposed late in the development phase of Mars 2020, and faced serious opposition. It added extra complexity, cost, risk and new failure modes. It was also driven by an engineering objective, with the possibility of a little outreach – the opportunity to communicate the mission’s science and engineering to the public – on the side.</p>
<p>Ingenuity wasn’t intended to last for very long. It was designed to prove helicopter flight in the thin Mars atmosphere. It targeted five short flights over a month. Possible outcomes included hard landings, toppling over, losing power if its solar panels were covered in dust, or losing communication when it was far from the rover (this happened several times). </p>
<figure class="align-center ">
<img alt="Large silver balloon being launched in the desert." src="https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/571874/original/file-20240129-25-1d0l8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Aerial robotic balloons, or aerobots, like this Nasa prototype, could one day explore Venus.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/news/jpls-venus-aerial-robotic-balloon-prototype-aces-test-flights">Nasa / JPL-Caltech</a></span>
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<p>But it went way beyond expectations, surviving three years on the Martian surface, even through a dusty season, and making 72 flights. Much of its success was aided by the communication network that now exists at Mars. </p>
<p>Ingenuity receives instructions and transmits data to Perseverance, which communicates with a fleet of satellites that include the European ExoMars Trace Gas Orbiter, Nasa’s Maven spacecraft, and the Mars Reconnaissance Orbiter. These, in turn, communicate with two deep space networks on Earth, systems of radio antennas around the world that command and track spacecraft. </p>
<p>It took 50 years of planetary exploration to get here, but already we can see the impact on future exploration that Ingenuity’s mission is having. The next interplanetary rotorcraft will be the <a href="https://dragonfly.jhuapl.edu/">Dragonfly mission to Saturn’s moon Titan</a>. </p>
<p>It will be a very different from Ingenuity. It will weigh about a ton and fly with eight rotors. It is a huge vehicle designed to fly in Titan’s thick atmosphere. </p>
<p>One of the next Red Planet missions will be Mars Sample Return, aiming to collect sample containers of Martian soil being prepared and cached by Perseverance. This has been planned to be carried out with use of a rover, but the success of Ingenuity has led to the idea – and now the development – of <a href="https://mars.nasa.gov/msr/spacecraft/sample-recovery-helicopters/">a helicopter</a> to do that. </p>
<p>The future that Ingenuity has opened up for us is exciting. We’ll see helicopters on Mars and Venus, more balloons on Venus, swimming vehicles under the icy moons of Jupiter and Saturn, and maybe even an aeroplane or two.</p><img src="https://counter.theconversation.com/content/222173/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Olsen in an employee of the University of Oxford and receives funding from the UK Space Agency in support of Mars science.</span></em></p>Among the missions being planned is a huge helicopter drone to explore Saturn’s moon Titan.Kevin Olsen, UKSA Mars Science Fellow, Department of Physics, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2011882023-06-05T01:08:59Z2023-06-05T01:08:59Z5 incredible craters that will make you fall in love with the grandeur of our Solar System<figure><img src="https://images.theconversation.com/files/525076/original/file-20230509-23-xn5f6x.jpeg?ixlib=rb-1.1.0&rect=120%2C63%2C1644%2C1014&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Occator crater, Ceres.</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia20180-occator-in-false-color">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</a></span></figcaption></figure><p>Impact cratering happens on every solid body in the Solar System. In fact, it is the dominant process affecting the surfaces on most extraterrestrial bodies today. </p>
<p>On Earth, however, such craters are often lost over time by active geological processes, but elsewhere in the Solar System there are some truly majestic examples of impact craters preserved for all to see.</p>
<p>Here, we pick our highlights of what the Solar System has to offer.</p>
<h2>1. South Pole–Aitken basin, the Moon</h2>
<p>Our first crater is a big one: the biggest, deepest and oldest impact crater on the Moon. It is 2,500km diameter, 6.2 to 8.2km deep and formed roughly 4.2 billion years ago. As the name suggests, it is at the south pole on the far side of the Moon, although the crater rim can be seen from Earth as a dark mountain range, just on the border between the light and dark side of the moon.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A rainbow coloured image of a textured circle with red around the edges and blue in the middle" src="https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=587&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=587&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=587&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=738&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=738&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525071/original/file-20230509-15-2ly6rr.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=738&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 colour-coded topographical image taken by NASA’s Lunar Orbiter Laser Altimeter, showing the South Pole–Aitken basin in blue.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lola-20100409-aitken.html">NASA/Goddard</a></span>
</figcaption>
</figure>
<p>It is a prime site favoured by lunar scientists to visit and learn about our Moon’s geology. The depth excavated by the crater is almost as deep as the deepest ocean trenches on Earth. It gives us a unique view of the interior of the Moon’s crust, with 4.2 billion years of history exposed. </p>
<p>In 2019, a rover from the Chinese space agency, Chang'e 4, <a href="https://www.planetary.org/space-missions/change-4">touched down in the basin</a> and carried out the first scientific experiments there. One of the most interesting of these was the <a href="https://www.universetoday.com/141229/theres-life-on-the-moon-chinas-lander-just-sprouted-the-first-plants/">Lunar Micro Ecosystem</a>, a collection of seeds and insect eggs designed to see if life could flourish in a tiny biosphere on the surface.</p>
<h2>2. Unnamed Crater (S1094b), Mars</h2>
<p>There are many famous craters on Mars, from the homes of Mars rovers (<a href="https://mars.nasa.gov/msl/home/">Gale Crater for Curiosity</a> or <a href="https://mars.nasa.gov/mars2020/">Jezero for Perseverance</a>) to the hypothesised source regions of Mars meteorites (<a href="https://www.higp.hawaii.edu/%7Epmm/Tooting_Crater.html">Tooting</a> or <a href="https://www.jpl.nasa.gov/images/pia12840-terrain-model-of-mars-mojave-crater">Mojave</a>). But one of the newest craters on the red planet is actually quite a dramatic one. </p>
<figure class="align-center ">
<img alt="An animation of a grey landscape where a dark splash mark suddenly appears" src="https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526069/original/file-20230515-124665-1wa14a.gif?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">The impact event on Mars on Christmas Eve 2021.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/Malin Space Science Systems/Peter Grindrod</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While Mars rovers claim all the glory for exploring the Martian surface, the satellites orbiting Mars have been making discoveries of their own for decades. NASA’s Mars Reconnaissance Orbiter (MRO) was launched in 2005 but is still operational, and its 16+ years of Mars’s surface images allow us to make comparisons year on year, highlighting differences between data sets. </p>
<p>On Christmas Eve 2021, NASA’s InSight mission detected a large “Marsquake” on the red planet, which MRO data later helped to identify as <a href="https://doi.org/10.1126/science.abq7704">a new impact on the other side of Mars</a>.</p>
<p>The vibrant, fresh impact ejecta (“blankets” of material thrown aside by the impact) can be seen clearly from space using the context camera data aboard the orbiter, and thanks to InSight we even know what it <a href="https://youtu.be/17hsIedHKx8">sounded like</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two greyscale images of a textured surface, on the right one there are dark streaks visible in a concentric pattern" src="https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525068/original/file-20230509-23-bnnzdk.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&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 before-and-after comparison of the location on Mars’s Amazonis Planitia where a meteoroid impacted on December 24 2021.</span>
<span class="attribution"><a class="source" href="https://mars.nasa.gov/resources/27087/context-camera-views-an-impact-crater-in-amazonis-planitia/">NASA/JPL-Caltech/MSSS</a></span>
</figcaption>
</figure>
<h2>3. Enki Catena, Ganymede</h2>
<p>Enki Catena is a chain crater on Ganymede, one of the Galilean satellites of Jupiter. At latest count, <a href="https://astronomy.com/news/2023/02/jupiter-now-has-92-moons">Jupiter has more than 90 moons</a>, a mini planetary system of its own.</p>
<p>Jupiter’s gravity creates tidal forces which shape the moons and give us some of the most interesting geological features we have yet found, from the volcanoes of Io to the subsurface ocean of Europa. There are also strings of craters found on two of the moons, Callisto and Ganymede.</p>
<p>These crater chains were first spotted when the Voyager 1 spacecraft gave us some of the first pictures of the surface of these moons in 1979. They were thought to potentially be collapsed lava tubes, features that have been observed on Mars and the Moon.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A textured grey surface with a line-shaped scoop taken out of it" src="https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=609&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=609&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=609&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=766&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=766&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521137/original/file-20230416-24-ynnjdo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=766&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Chain of impact craters Enki Catena on Ganymede.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/pia01610">NASA/JPL/Brown University</a></span>
</figcaption>
</figure>
<p>However, their origin remained under debate until the Shoemaker-Levy 9 comet was observed as it smashed into Jupiter. The comet was seen <a href="https://www.nature.com/articles/365731a0">breaking into multiple pieces</a> and this gave an idea as to how these chains might form – the gravity from Jupiter pulls apart objects into many pieces that all impact close together.</p>
<p>Enki Catena is a chain of 13 craters which crosses from an area of dark to bright terrain on Ganymede. It is 162km in length and about 10km wide. </p>
<p>The <a href="https://sci.esa.int/web/juice">European Space Agency’s Juice mission</a> will visit the Jovian system in the 2030s and allow us to see the surfaces in greater detail than ever before. We might even find more of these crater chains.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-much-anticipated-juice-mission-to-jupiter-launches-today-heres-what-it-might-discover-203669">The much-anticipated JUICE mission to Jupiter launches today. Here's what it might discover</a>
</strong>
</em>
</p>
<hr>
<h2>4. Occator Crater, Ceres</h2>
<p>Ceres is the largest body in the main asteroid belt between Mars and Jupiter. It is large and round enough to be considered a “dwarf planet” (along with Pluto and three less famous examples, Eris, Makemake and Haumea).</p>
<p><iframe id="tc-infographic-852" class="tc-infographic" height="400px" src="https://cdn.theconversation.com/infographics/852/1843fe3dc0b49b387d1fc0ea9b551efa73cdb7cb/site/index.html" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>The Occator crater on Ceres is impressive because it contains a bright spot in the centre that has been observed both from space, and from Earth at Mauna Kea Observatory, Hawaii. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A grey image with a round circle in the middle, dotted with several white spots" src="https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525555/original/file-20230511-19-lkluwg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Occator crater with its bright spots as imaged by the Dawn mission.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/jpl/occator-crater-and-ceres-brightest-spots">NASA</a></span>
</figcaption>
</figure>
<p>NASA’s Dawn mission entered an orbit around Ceres in 2015, and imaged the bright spot in Occator crater known as “Spot 5”. It’s a three kilometre wide dome covered in bright salts on the crater floor, likely resulting from hydrothermal activity.</p>
<p>Occator crater itself is 92km in diameter and 3km deep. Simulations indicate that the impactor (the space rock that created the crater) was rougly 5km across, striking Ceres between 20–25 million years ago.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A dark bowl-shaped depression with what looks like white ice spread in the middle" src="https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=349&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=349&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=349&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=439&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=439&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525556/original/file-20230511-11888-acngdy.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=439&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 mosaic from NASA’s Dawn spacecraft combines images obtained from altitudes as low as 22 miles (35 km) above Ceres’ surface.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/1074/mosaic-of-cerealia-facula/">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI</a></span>
</figcaption>
</figure>
<h2>5. Aurelia, Venus</h2>
<p>Venus is <a href="https://www.nasa.gov/feature/why-is-venus-called-earths-evil-twin-we-asked-a-nasa-scientist-episode-32">sometimes called Earth’s twin</a>. It is when it comes to size, but the surface images we have of Venus show the planets have very different features.</p>
<p>The best such images were taken in the 1990s by NASA’s Magellan spacecraft. Venus has a thick cloudy atmosphere, and visible-light cameras can’t see through to the surface. Magellan was equipped with a radar which can “see” the surface – but the images can be harder to interpret. </p>
<p>In radar, dark terrain is very smooth and bright terrain is very rough. This makes impact craters stand out really well in radar images. The ejecta are very rough, especially against the surrounding volcanic plains, so they appear bright in the images.</p>
<p>This is Aurelia, a 32km impact crater on Venus. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A greyscale image with a bright white semicircular shape standing out against a dark background" src="https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/521138/original/file-20230416-18-3lnwor.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"></a>
<figcaption>
<span class="caption">Aurelia crater on Venus, imaged by Magellan in 1996.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/?IDNumber=PIA00239">NASA/JPL</a></span>
</figcaption>
</figure>
<p>You can see it stands out against the grey plains that surround it. The black terrain on the edges of the bright white ejecta are smooth flows of rock that melted when the impact hit.</p>
<p>Speaking of volcanoes on Venus, recently a group from the University of Alaska Fairbanks used this Magellan data to find the first active volcano on <a href="https://www.nasa.gov/feature/jpl/nasa-s-magellan-data-reveals-volcanic-activity-on-venus/">Venus</a></p>
<p>NASA has <a href="https://solarsystem.nasa.gov/planets/venus/exploration/#otp_future_missions">three Venus missions in development</a> over the next 10 years, so hopefully soon we will know much more about our enigmatic twin.</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>
<img src="https://counter.theconversation.com/content/201188/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>If we could go sightseeing across our cosmic neighbourhood, these would be some of the best highlights.Helen Brand, Senior Beamline Scientist - Powder Diffraction, Australian Nuclear Science and Technology OrganisationNatasha Stephen, Director of Science & Engagement, The Geological Society of London, and Honorary Lecturer, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2019312023-03-16T14:34:43Z2023-03-16T14:34:43ZVenus: proof of active volcanoes – at last<figure><img src="https://images.theconversation.com/files/515632/original/file-20230315-711-ry6ind.jpg?ixlib=rb-1.1.0&rect=5%2C640%2C3988%2C1958&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A perspective view across Maat Mons on Venus, based on Magellan radar data</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/images/pia00106-venus-3-d-perspective-view-of-maat-mons">Nasa/JPL</a></span></figcaption></figure><p>Venus is almost the same size, mass and density as Earth. So it should be generating heat in its interior (by the decay of radioactive elements) at much the same rate as the Earth does. On Earth, one of the main ways in which this heat leaks out is via volcanic eruptions. During an average year, at least 50 volcanoes erupt.</p>
<p>But despite decades of looking, we’ve not seen clear signs of volcanic eruptions on Venus – until now. A new study by geophysicist <a href="https://uaf.edu/experts/robert-herrick.php">Robert Herrick</a> of the University of Alaska, Fairbanks, which he reported this week at the Lunar & Planetary Science Conference in Houston and <a href="http://www.science.org/doi/10.1126/science.abm7735">published in the journal Science</a>, has at last caught one of the planet’s volcanoes in the act.</p>
<p>It’s not straightforward to study Venus’s surface because it has a dense atmosphere including an unbroken cloud layer at a height of 45-65km that is opaque to most wavelengths of radiation, including visible light. The only way to get a detailed view of the ground from above the clouds is by radar directed downward from an orbiting spacecraft. </p>
<figure class="align-center ">
<img alt="The globe of Venus shrouded in cloud" src="https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515735/original/file-20230316-20-gx1sqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Venus seen in ultraviolet light by Japan’s Akatsuki spacecraft in December 2016. The surface cannot be seen.</span>
<span class="attribution"><span class="source">Courtesy of ISAS/JAXA</span></span>
</figcaption>
</figure>
<p>A technique known as aperture synthesis is used to build up an image of the surface. This combines the varying strength of the radar echos bounced back from the ground – including the time delay between transmission and receipt, plus slight shifts in frequency corresponding to whether the spacecraft is getting closer to or further from the origin of a particular echo. The resulting image looks rather like a black and white photograph, except that the brighter areas usually correspond to rougher surfaces and the darker areas to smoother surfaces.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=368&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=368&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=368&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515738/original/file-20230316-18-re3tcw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">140 km wide Magellan radar image of Venus showing lava flows (bright because they are rough) that have begun to encroach on an older impact crater.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>Nasa’s Magellan probe orbited Venus from August 1990 to October 1994 and used this sort of radar technique to map the planet’s surface with a spatial resolution of about a hundred metres at best. It showed that over 80% of the surface is covered by lava flows, but just how recently the youngest of them were erupted, and whether any eruptions continue today, remained a mystery for the next three decades. </p>
<p>There have been <a href="https://astronomynow.com/2016/10/19/recently-active-lava-flows-from-volcano-idunn-mons-on-venus/">various hints of activity</a> provided by spacecraft peering into, and sometimes through, the clouds – suggesting that the rocks there are so young that their minerals have not yet been altered by reaction with the acidic atmosphere and so are freshly erupted lava. <a href="https://eos.org/research-spotlights/evidence-for-volcanoes-on-venus">Thermal anomalies</a> that could correspond to active lava flows have also been detected, as have temporary local hiccups in the <a href="https://www.lpi.usra.edu/planetary_news/2022/01/18/estimates-of-eruption-frequency-suggest-ongoing-volcanic-activity-on-venus/">atmospheric sulphur dioxide concentration</a> – another potential sign of volcanic eruptions. But none of these was fully convincing.</p>
<h2>Volcanic vent spotted</h2>
<p>The new study now seems to have settled the matter, by revealing changes on the surface that really have to be a result of volcanic activity. The authors spent hundreds of hours comparing Magellan radar images of parts of Venus that had been imaged more than once to look for new or changed features on the surface. </p>
<p>They concentrated on the most promising volcanic regions, and eventually spotted an example where details on an image recorded in October 1991 are different to those on an image from February of the same year. The changes they saw are best explained by a volcanic eruption within that time window. </p>
<p>Using radar images to verify surface changes is tricky because the appearance of even an unchanging surface can differ according to surface slopes and direction of view. However, the researchers performed simulations to verify that the observed changes could not result from these things.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=258&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=258&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=258&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=324&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=324&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515635/original/file-20230315-3305-69ahd6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=324&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Close-ups of the active volcanic vent north of the summit of Maat Mons in February and October 1991. Between those dates the vent enlarged and changed shape, and new lava flows seem to emerged.</span>
<span class="attribution"><span class="source">Nasa/JPL</span></span>
</figcaption>
</figure>
<p>The paired images show an initially near circular volcanic crater about 1.5km across that between February and October doubled in size by extending eastwards. It also became shallower, and the authors suggest that the crater is a volcanic vent that partially collapsed and was largely filled by fresh lava during October. </p>
<p>There are probably also new lava flows extending several kilometres down slope, northwards of the crater, which either flooded over the crater rim or leaked out of an associated fissure. The active crater sits high on Maat Mons, one of Venus’s largest volcanoes whose summit is 5km above the surrounding plains.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=296&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=296&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=296&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=372&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=372&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515755/original/file-20230316-24-qkc7jr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=372&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Maat Mons. The arrow points to the location of the volcanic vent that erupted in 1991, which is too small to show up at this scale.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<h2>Future missions</h2>
<p>Most planetary scientists already expected Venus to be volcanically active. The focus of attention will now surely turn to how often, and at how many sites, are eruptions occurring on Venus. The biggest surprise in all this is that it took so long for someone to find the evidence for surface changes that had been lurking in the Magellan data for 30 years.</p>
<p>The likelihood of finding and studying ongoing volcanism is one of the main drivers for Nasa’s <a href="https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus">Veritas</a> mission and Esa’s <a href="https://www.esa.int/Science_Exploration/Space_Science/ESA_selects_revolutionary_Venus_mission_EnVision">EnVision</a> mission (both approved in 2021). Each will carry a better imaging radar than Magellan. EnVision is intended to reach its orbit about Venus in 2034. Originally Veritas should have been there several years beforehand, but there have been <a href="https://spacenews.com/delayed-nasa-venus-mission-looks-for-a-reprieve/">delays to the schedule</a>.</p>
<p>With Nasa’s <a href="https://ssed.gsfc.nasa.gov/davinci/mission">DaVinci</a> mission likely to arrive year or two ahead of them, providing optical images from below the clouds during its descent, we are in for an exciting time about ten years from now. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/venus-has-very-few-volcanoes-weirdly-this-might-be-why-its-as-hot-as-hell-78363">Venus has very few volcanoes – weirdly, this might be why it's as hot as hell</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/201931/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Rothery is Professor of Planetary Geosciences at the Open University. He is co-leader of the European Space Agency's Mercury Surface and Composition Working Group, and a Co-Investigator on MIXS (Mercury Imaging X-ray Spectrometer) that is now on its way to Mercury on board the European Space Agency's Mercury orbiter BepiColombo. He has received funding from the UK Space Agency and the Science & Technology Facilities Council for work related to Mercury and BepiColombo, and from the European Commission under its Horizon 2020 programme for work on planetary geological mapping (776276 Planmap). He is author of Planet Mercury - from Pale Pink Dot to Dynamic World (Springer, 2015), Moons: A Very Short Introduction (Oxford University Press, 2015) and Planets: A Very Short Introduction (Oxford University Press, 2010). He is Educator on the Open University's free learning Badged Open Course (BOC) on Moons and its equivalent FutureLearn Moons MOOC, and chair of the Open University's level 2 course on Planetary Science and the Search for Life.</span></em></p>Decades old images reveal that a volcano erupted on Venus in 1991.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2004542023-03-15T13:37:40Z2023-03-15T13:37:40ZCurious Kids: How are planets created?<figure><img src="https://images.theconversation.com/files/511620/original/file-20230222-16-c8nmnb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Eight planets, including Earth, revolve around our Sun.</span> <span class="attribution"><span class="source">Illustration by Tobias Roetsch/Future Publishing via Getty Images</span></span></figcaption></figure><p><em>Curious Kids is a <a href="https://theconversation.com/africa/topics/curious-kids-36782">series</a> for children in which we ask experts to answer questions from kids.</em></p>
<p><strong>How are planets created? - (Saba, 6, Kenya)</strong></p>
<p>Thanks for asking such an interesting question, Saba. When you talk about planets you’re probably thinking of the planets in our solar system – the ones orbiting (circling around) our sun. There are eight of these <a href="https://solarsystem.nasa.gov/planets/overview/#otp_planets_of_our_solar_system">planets</a>. One of them is where you and I live: Earth. The others are Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune.</p>
<p>There are many, many more planets way beyond our solar system and our galaxy, the Milky Way. Scientists like us, known as astronomers, have found <a href="https://www.planetary.org/worlds/exoplanets">over 5,000 planets</a> around other stars. We estimate that there may be trillions across the Universe.</p>
<p>How did they come into being? It all starts with a cloud of gas and dust.</p>
<h2>Gas and dust</h2>
<p>These clouds of gas and dust are called nebulae. They float around in space much like the clouds in our sky. There are some regions with more clouds and some with fewer and astronomers can see these using telescopes.</p>
<p>Nebulae contain gases like hydrogen, helium and carbon. When a nebula becomes dense enough its gravity pulls it together into a very dense core. This is a bit like the water in your bath swirling around the drain before getting sucked down. As the cloud gets dense it heats up. When it gets dense and hot enough the atoms – tiny building blocks for all the matter in the world – in the nebula start to fuse.</p>
<p>This process is called nuclear fusion and produces a lot of energy. And the cloud lights up like a firework. This is how a new star is born, just like our Sun was <a href="https://spaceplace.nasa.gov/sun-age/en/">4.5 billion years ago</a>.</p>
<p>A small amount of gas and dust remains around new stars in a spinning disc. Planets are formed from this disc of material.</p>
<h2>Protoplanets</h2>
<p>As the disc rotates, the material in it, small bits of rock and ice, lump together and get bigger and bigger. That forms what we call planetesimals, which collide with each other like bumper cars, creating even larger bodies known as protoplanets.</p>
<p>The protoplanets keep growing. While this is happening, they can attract gases from the surrounding disc, creating a thick atmosphere. This process is called accretion and it is how gas giant planets like Jupiter and Saturn are formed. If a protoplanet forms from heavier elements in the outer solar system it can create an ice giant. The planets Neptune and Uranus are ice giants.</p>
<p>Even after the planet is formed it can keep changing over time through processes such as volcanic activity, tectonic movement, and erosion. On Earth, mountains like Mount Kilimanjaro in Tanzania – the country next door to Kenya – formed from large volcanoes. And even larger mountains like the Himalayas have formed from tectonic plates colliding. Tectonic plates are big pieces of the Earth’s outer layer; sometimes they crash into each other and that creates things like mountains.</p>
<h2>Millions of years</h2>
<p>The way I’ve described this makes it sound as though planets are formed quickly. But the process which begins with those clouds of gas and dust takes millions of years to transform into the beautiful and diverse worlds we see in our Solar System and beyond.</p><img src="https://counter.theconversation.com/content/200454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Cunnama receives funding from the National Research Foundation and the South African Astronomical Observatory. </span></em></p>It all starts with a cloud of gas and dust.Daniel Cunnama, Science Engagement Astronomer, South African Astronomical Observatory, South African Astronomical ObservatoryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1977352023-02-08T13:43:00Z2023-02-08T13:43:00ZDon’t underestimate Cupid – he’s not the chubby cherub you associate with Valentine’s Day<figure><img src="https://images.theconversation.com/files/508485/original/file-20230206-31-17810f.jpg?ixlib=rb-1.1.0&rect=6%2C6%2C1013%2C787&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">'Cupid and Psyche' by Italian sculptor Antonio Canova</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/stature-of-cupid-and-psyche-embracing-from-the-villa-news-photo/517391898?phrase=cupid%20and%20psyche&adppopup=true">Bettmann via Getty Images</a></span></figcaption></figure><p>Ah, Valentine’s Day: that Hallmark holiday of greeting cards and chocolates, its bloody origins almost entirely forgotten over the last 2,000 years! </p>
<p>What began as a Christian feast day honoring two or three early Christian martyrs – <a href="https://theconversation.com/the-real-st-valentine-was-no-patron-of-love-90518">the original “Valentines</a>” – is now associated with flocks of winged cherubic Cupids, whose innocuous-looking bows and arrows symbolize gentle romance instead of death-dealing war. Somehow, the phrase “struck by Cupid’s arrow” is supposed to be exciting rather than excruciating.</p>
<p><a href="https://theconversation.com/what-the-mythical-cupid-can-teach-us-about-the-meaning-of-love-and-desire-176760">The original Cupid</a> was the son of Venus, Roman goddess of love and beauty. He himself was a Roman deity associated with lust and love, based on the Greek Eros. In Greece and Rome, both figures were depicted as handsome young men, not as winged infants.</p>
<p>But ancient poets and artists also imagined a troop of “Erotes” or “Cupidines” as attendants of these gods. The Romans portrayed them as winged infants, <a href="https://uncpress.org/book/9781469628400/inventing-the-renaissance-putto/">or “putti</a>,” as they became known in Italian Renaissance art. These, in turn, became the chubby cherubs of today’s valentines.</p>
<p>Despite envisioning the god with a troop of adorable attendants, even the Romans understood that Cupid had a darker, more dangerous side – one whose power you wouldn’t want to dismiss.</p>
<h2>Small but mighty</h2>
<p>The archer god Apollo found this out the hard way, as the poet Ovid told in his epic of A.D. 8, “Metamorphoses.” Having just <a href="https://www.poetryintranslation.com/PITBR/Latin/Metamorph.php#anchor_Toc64105469">slain the dragon of Delphi with 1,000 arrows,</a> Apollo provoked the fierce fury of Venus’ son by mocking Cupid’s seemingly toylike weapons.</p>
<figure class="align-right ">
<img alt="A painting in black and white shows a winged naked figure talking with a man in a tunic." src="https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=761&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=761&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=761&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=957&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=957&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508469/original/file-20230206-21-fnxjey.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=957&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">‘Cupid and Apollo’ by Pontormo (attributed to the School of Andrea del Sarto)</span>
<span class="attribution"><a class="source" href="https://kress.nga.gov/Detail/objects/2916">Samek Art Museum at Bucknell University/National Art Gallery</a></span>
</figcaption>
</figure>
<p>Cupid swiftly took his revenge. He pierced Apollo’s heart with a golden arrow, causing him to fall passionately in love with the nymph Daphne. But Daphne was a sworn virgin, and Cupid shot her with a lead arrow, intensifying her loathing for all things amorous. </p>
<p>She fled from Apollo’s advances. The desperate deity pursued her relentlessly, until Daphne’s father <a href="http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0028%3Abook%3D1%3Acard%3D452">turned her into a laurel tree to save her</a>. Cupid’s arrows, however diminutive, were more powerful than Apollo’s.</p>
<h2>The unseen spouse</h2>
<p>But the most famous characterization of Cupid in Latin literature appears in the work of Apuleius, who lived during the second century in what is now Algeria. He wrote <a href="https://www.poetryintranslation.com/PITBR/Latin/TheGoldenAssIV.php#anchor_Toc347999726">a story about Psyche</a>, a princess so exceedingly beautiful that mortals worshipped her as if she were the goddess of love herself.</p>
<p>Enraged by jealousy, Venus commanded her son to make Psyche fall in love with the most wretched man possible. But an oracle told the royal family that their daughter was destined to marry “a savage, untamed creature” that flew about tormenting everyone with fire – and they abandoned her on a cliff to meet this terrifying fate.</p>
<p>Instead, Psyche found herself borne by a gentle breeze to an elaborate palace inhabited by invisible servants. That night, an “unknown husband arrived and made Psyche his wife,” departing before sunrise.</p>
<p>Her unseen spouse continued to visit nightly, and Psyche was soon overjoyed to find herself pregnant. But she also became increasingly lonely. Her mysterious husband agreed that <a href="https://www.poetryintranslation.com/PITBR/Latin/TheGoldenAssV.php">her sisters could visit</a> – as long as she did not try to “investigate his appearance.” She happily agreed, telling him, “Whoever you are I love you deeply. Not even Cupid could compare to you.”</p>
<p>But when Psyche’s two older sisters visited, they became envious of her luxurious life. “She must be married to a god!” they intuited – unlike Psyche, who remained inexplicably clueless. Hoping to break up the marriage, they offered a false explanation for her husband’s secrecy: He must be a monstrous serpent intent on devouring her and her unborn child.</p>
<p>A horrified Psyche believed them, despite her intimate physical knowledge of her spouse – his “perfumed locks, tender cheeks, and warm chest.” Armed with a dagger, she prepared to kill her husband as he slept. But first, ignoring his repeated warnings, she gazed at him by the light of an oil lamp. Here, halfway through the story, the audience finally finds out his identity: none other than Cupid himself!</p>
<figure class="align-center ">
<img alt="A statue of a naked woman looking down at a sleeping man on display in a park in autumn." src="https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/508488/original/file-20230206-19-2byobp.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">Psyche finally gets a good look at her husband. ‘Cupid and Psyche’ by Giulio Kartar.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/marble-sculpture-cupid-and-psyche-royalty-free-image/471366765?phrase=cupid%20and%20psyche&adppopup=true">leoaleks/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>At the sight, Psyche “fell in love with Love.” But a drop of scalding oil awakened Cupid. Utterly dismayed at his wife’s betrayal, he flew away – but first explained: “I have disobeyed my mother’s orders to fill you with passion for some vile wretch. I flew to you as your lover instead.”</p>
<h2>Love lost – and found</h2>
<p>The rest of the narrative involves Psyche’s long, arduous quest to win Cupid back. Though despairing and exhausted, Psyche willingly submitted herself to a series of brutal tasks imposed by Venus, only to fall into a deathlike slumber just before completing them.</p>
<p>And where is Cupid during all this? If he is characterized as a powerful, dangerous force in the first half of the story, the second half depicts him as a helpless mama’s boy. He flew back to Venus’ palace, where his mother – furious that he had secretly married Psyche – scolded him righteously, screamed that he had embarrassed her, and locked him in his room. </p>
<p>Finally, recalling his love for Psyche, Cupid escaped out the window and saved her from eternal slumber. Then he made a savvy deal with Jupiter, king of the gods: Psyche could be made immortal, clearing the way for her to “officially” marry Cupid in an arrangement that even satisfied Venus.</p>
<h2>Complex vision of love</h2>
<p>Apuleius’ story is rare in focusing on a female character and how love and desire affect her. The audience follows Psyche through several rites of passage. Initially, as an unmarried girl, she has not fulfilled her expected <a href="https://www.pbs.org/empires/romans/empire/weddings.html">role of wife and mother</a>. As a frightened bride, she has no say in whom she marries – an experience common for young wives in ancient Roman society. Love does not enter the picture.</p>
<p>But Apuleius’ portrayal of Psyche’s situation suggests a lesson Roman writers of the day wanted readers to believe: that young married women eventually come to desire and love their husbands. Although that process can be long and difficult, wives and husbands both adjust to their roles over time. The birth of Psyche’s child, “Pleasure,” at the end of the story results in harmony all around, an idealized image of marriage. </p>
<p>Ovid and Apuleius remind us that the original Cupid is not the benign little bearer of valentines but an elemental force of human nature – a “savage, untamed creature” that lights the fires of passion in unpredictable ways. Whereas Apollo’s lust for Daphne’s visible beauty remained unsated, Psyche eventually enjoyed sex with her unseen husband. Apollo learned that longing isn’t always mutual, while Psyche realized that love and trust must be earned. </p>
<p>Apuleius’s story suggests that Cupid and all the intense emotions he represents, once tempered, can provide the basis for a loving, long-lasting relationship. In short, both stories contain valuable lessons about the nature of romance.</p><img src="https://counter.theconversation.com/content/197735/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Debbie Felton 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>Ancient Greece and Rome may have handed down the image of rosy-cheeked Cupids, but their myths about him explore the messier – sometimes scarier – sides of love.Debbie Felton, Professor of Classics, UMass AmherstLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1915342022-09-29T16:12:59Z2022-09-29T16:12:59ZVenus: the trouble with sending people there<figure><img src="https://images.theconversation.com/files/487253/original/file-20220929-25-a6bvkz.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C4096%2C4071&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA/JPL</span></span></figcaption></figure><p>Venus, often called <a href="https://www.esa.int/ESA_Multimedia/Images/2019/05/Earth_s_evil_twin">Earth’s “evil twin” planet</a>, formed closer to the Sun and has since evolved quite differently from our own planet. It has a <a href="https://www.space.com/venus-runaway-greenhouse-effect-earth-next.html">“runaway” greenhouse effect</a> (meaning heat is completely trapped), a thick carbon-dioxide-rich atmosphere, no magnetic field and a surface hot enough to melt lead. </p>
<p>Several uncrewed scientific missions will study how and why that happened in the next decade. But now some scientists <a href="https://www.theguardian.com/science/2022/sep/25/target-venus-not-mars-for-first-crewed-mission-to-another-planet-experts-say">want to send a crewed mission</a> there as well for a flyby. Is that a good idea?</p>
<p>With a slightly smaller diameter than Earth, Venus orbits closer to the Sun. This means that any water on the surface would have evaporated shortly after its formation, starting its greenhouse effect. Early and sustained volcanic eruptions created lava plains and increased the carbon dioxide in the atmosphere – starting the runaway greenhouse effect, which increased the temperature from just a little higher than Earth’s to its current high value of 475°C. </p>
<p>While the Venus year is shorter than ours (225 days), its rotation is very slow (243 days) and “retrograde” – the other way round to Earth. The slow rotation is related to a lack of magnetic field, resulting in a continuing loss of atmosphere.
Venus’ atmosphere “super-rotates” faster than the planet itself. Images from many missions show V-shaped patterns of clouds, composed of sulphuric acid droplets. </p>
<p>Despite the harsh conditions, some scientists have speculated that Venus’ clouds might at some altitudes harbour habitable conditions. Recent measurements apparently <a href="https://theconversation.com/venus-could-it-really-harbour-life-new-study-springs-a-surprise-145981">showing phosphine</a> – a potential sign of life as it is continuously produced by microbes on Earth – in Venus’ clouds have been strongly debated. Clearly, we need more measurements and exploration to work out where it comes from.</p>
<h2>Future missions</h2>
<p>What we know about Venus so far has been gathered from several past probes. In 1970-82, for example, the Soviet <a href="https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1970-060A">Venera 7-14 probes</a> were able to land on Venus’ harsh surface, survive for up to two hours and send back images and data. But there are remaining questions about how Venus evolved so differently from Earth, which are also relevant for understanding which planets orbiting other stars may harbour life.</p>
<p>The next decade promises to be a bonanza for Venus scientists. In 2021, Nasa <a href="https://theconversation.com/nasa-has-announced-two-missions-to-venus-by-2030-heres-why-thats-exciting-162133">selected two missions</a>, <a href="https://www.jpl.nasa.gov/missions/veritas">Veritas</a> and <a href="https://ntrs.nasa.gov/api/citations/20170002022/downloads/20170002022.pdf">DaVinci+,</a> due for launch in 2028-30. The European Space Agency <a href="https://www.esa.int/Science_Exploration/Space_Science/ESA_selects_revolutionary_Venus_mission_EnVision">selected EnVision</a> for launch in the early 2030s. These are complementary, uncrewed missions which will give us deeper understanding of Venus’ environment and evolution.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of craters on Venus seen by Venus Nasa's Magellan probe." src="https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/487252/original/file-20220929-1555-oz5asc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Craters on Venus seen by Venus Nasa’s Magellan probe.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>Veritas will map Venus’ surface to determine the geological history, rock composition and the importance of early water. DaVinci+ includes an orbiter and a small probe that will descend through the atmosphere and measure its composition, study the planet’s formation and evolution and determine whether it ever had an ocean. EnVision will study the planet’s surface, subsurface and atmospheric trace gases. It will use radar to map the surface with better resolution than ever before.</p>
<p>India also plans an uncrewed mission, <a href="https://www.space.com/india-venus-orbiter-shukrayaan-2024-launch">Shukrayaan-1</a>, and Russia has proposed <a href="https://www.esa.int/About_Us/ESA_Permanent_Mission_in_Russia/Venera-D">Venera-D</a>.</p>
<h2>Do we need crewed flybys?</h2>
<p>The idea of a crewed flyby of Venus <a href="http://spaceflighthistory.blogspot.com/2017/05/apollo-ends-at-venus-1967-proposal-for.html">was suggested in the late 1960s</a>, and involved using an Apollo capsule to fly people around the planet. But this idea ended when Apollo finished. Now, the Artemis project to fly around the Moon, and other ideas of crewed missions, have led to the idea being floated again, most recently in <a href="https://www.sciencedirect.com/science/article/pii/S0094576520307554">journal papers</a> and at a recent meeting of the <a href="https://www.iafastro.org/">International Astronautical Federation</a>, an advocacy organisation, in September 2022. </p>
<p>The idea would be to fly a crewed spacecraft around Venus and return to Earth. This would allow scientists to test deep-space techniques such as how to operate a crewed mission with significant time delays when communicating with Earth. It could therefore prepare us for a more complex, crewed mission to Mars. However, the crew wouldn’t do any landing or actual atmosphere investigation at Venus – the conditions are way too harsh.</p>
<p>The researchers who back this idea argue that you could also use Venus’ gravity to alter the spacecraft’s course for Mars, which could save time and energy compared with going directly from Earth to Mars. That’s because the latter option would require the orbits of the two planets to be aligned, meaning you’d have to wait for the right moment both on the way there and back. However, as a crewed mission to Mars would be highly complex, going directly from Earth to Mars would keep designs simpler.</p>
<p>Sending humans to a planet that may harbour living organisms also won’t make it easier to find them. It is risky – we may end up contaminating the atmosphere before we discover any life. The best way to look for biochemical signs of life is with uncrewed probes. There would also be significant thermal challenges and higher radiation from solar flares due to closer proximity to the Sun.</p>
<p>And, unfortunately, with a flyby mission like this, only a few hours of data would be possible on the inbound and outbound trajectories. It would be a highly expensive venture, which would no doubt produce some amazing imagery and useful additional data. However, this would add little to the detailed and much longer bespoke studies currently planned. I, therefore, believe the likelihood of a crewed mission to Venus is very unlikely. </p>
<p>There have also been conceptual, more far-fetched studies – including sending <a href="https://theconversation.com/nasa-wants-to-send-humans-to-venus-heres-why-thats-a-brilliant-idea-104961">crewed airships to hover in Venus’ atmosphere</a>, rather than just flying by. This is a nice idea, which may achieve more science than a flyby, but it remains a distant and unrealistic concept for now. </p>
<p>For the moment, we only carry out crewed exploration in low-Earth orbit. The Artemis project, however, aims to fly people around the Moon and build a station, called Gateway, in lunar orbit. This is being designed to do science, enable crewed landings on the Moon and crucially to test deep space techniques such as refuelling and operating in a remote environment that could in the long run help get us to Mars without doing training at Venus.</p><img src="https://counter.theconversation.com/content/191534/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Coates receives funding from UKSA and STFC (UK). </span></em></p>Some scientists are keen to send humans to Venus on a flyby.Andrew Coates, Professor of Physics, Deputy Director (Solar System) at the Mullard Space Science Laboratory, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1852702022-06-23T14:22:16Z2022-06-23T14:22:16ZCosmic dust from Venus is inspiring new air pollution-busting technology<figure><img src="https://images.theconversation.com/files/470562/original/file-20220623-52339-jw2nyz.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3089&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Venus has a thick, toxic atmosphere filled with carbon dioxide.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/thick-clouds-over-planet-venus-3d-1313293106">Jurik Peter/Shutterstock</a></span></figcaption></figure><p>Reducing carbon emissions from roads, railways and shipping requires implementing a range of solutions simultaneously. As far as cars are concerned, cutting the number of journeys altogether (by making it easier for people to walk and cycle and improving public transport), changing the fuel in vehicles and making the most of those vehicles already on the road must all play a part. None of these solutions are sufficient on their own.</p>
<p>In 2030, the sale of new diesel and petrol passenger cars <a href="https://www.gov.uk/government/news/government-takes-historic-step-towards-net-zero-with-end-of-sale-of-new-petrol-and-diesel-cars-by-2030">will be outlawed</a> in the UK. The future of passenger motoring will be electric. But recent <a href="https://theconversation.com/electric-car-supplies-are-running-out-and-could-drastically-slow-down-the-journey-to-net-zero-182787">problems supplying parts</a> and the <a href="https://academic.oup.com/cje/article/44/4/953/5859377?login=true">high carbon cost of manufacturing</a> electric vehicles could delay the climate benefits of this transition.</p>
<p>To make best use of existing petrol and diesel burning vehicles – and the carbon that was invested in creating them – drivers and manufacturers can reduce the emissions of a family of compounds called nitrogen oxides, which are <a href="https://climatenexus.org/wp-content/uploads/2015/09/HumanHealthEffectsofAirPollutionKampaandCastanas.pdf">linked to respiratory diseases</a>, through better treatment of exhaust fumes. This way, the communities most blighted by air pollution can at least be protected before harmful vehicle emissions are finally eradicated.</p>
<p>My research team is developing a new generation of catalytic converters – the devices fitted to exhaust pipes to reduce the release of toxic gases. Inspired by chemistry observed on the surface of extremely hot planets such as Venus, we have <a href="https://doi.org/10.1016/j.jastp.2016.08.011">produced a synthetic material</a> that could improve air quality. </p>
<h2>From Venus to vehicle exhausts</h2>
<p>The Sun’s light destroys carbon dioxide (CO₂) in the atmospheres of planets, producing carbon monoxide (CO). Not fast enough to avert climate change, but enough that atmospheres like Venus should contain far more CO than we observe there.</p>
<p>Our group studies the effects of meteoric material (dust arriving from space) in atmospheres. An iron silicate powder we made which replicates this dust <a href="https://doi.org/10.1016/j.icarus.2017.06.005">can speed up</a> the conversion of CO to CO₂. This is what the first catalytic converters in cars were designed to do, since CO is a toxic gas. </p>
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<img alt="A series of metal chambers and pipes on the underside of a car." src="https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470558/original/file-20220623-51616-f12k26.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">
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<span class="caption">Catalytic converters turn toxic gases generated in petrol and diesel engines into safer alternatives.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/catalytic-converter-exhaust-system-modern-car-1651656655">Ulianenko Dmitrii/Shutterstock</a></span>
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<p>That got us thinking about whether this material could help with other problems, such as nitrogen oxide pollution, which <a href="https://www.theguardian.com/environment/2021/mar/04/uk-has-broken-air-pollution-limits-for-a-decade-eu-court-finds">exceeds legal limits</a> in the air of many UK cities. Poor air quality from vehicle exhausts costs <a href="https://www.eea.europa.eu/publications/air-quality-in-europe-2021/health-impacts-of-air-pollution">tens of thousands of lives annually</a>. </p>
<p>We’ve found that not only can the powder <a href="https://www.sciencedirect.com/science/article/abs/pii/S138589472103391X">simultaneously clean up</a> CO and nitrogen oxide emissions, but it can convert nitrogen dioxide (NO₂, a harmful gas which is specifically regulated) to harmless molecular nitrogen (N₂) and water at room temperature.</p>
<p>Catalysts for processing nitrogen oxide (NOx) emissions installed in modern diesel vehicles only work at exhaust temperatures above 150°C. Even if your car uses an additive fluid to reduce nitrogen oxide emissions, it’s unlikely to work while driving slowly when the exhaust is cooler. This is when vehicles emit the most NO₂ – often in traffic jams where the most polluted air can accumulate.</p>
<p>When the electricity grid is decarbonised and sufficiently robust to charge millions of electric vehicles, catalytic converters capable of removing nitrogen oxides may still be important. For example, the natural gas fuel in industrial furnaces <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/824592/industrial-fuel-switching.pdf">is likely to be replaced</a> with hydrogen. </p>
<p>Unlike buses and cars running on hydrogen, which produce energy via a reaction in a fuel cell, larger applications such as furnaces in steelworks will burn hydrogen fuel directly. This high-temperature combustion will convert molecular nitrogen in the air to nitrogen oxide pollution, which will need to be removed.</p>
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Read more:
<a href="https://theconversation.com/hydrogen-where-is-low-carbon-fuel-most-useful-for-decarbonisation-147696">Hydrogen: where is low-carbon fuel most useful for decarbonisation?</a>
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<p>That’s why we’re excited to be developing a prototype emissions converter that can work in most situations, with the potential to radically reduce toxic emissions from combustion engines and other sources in the future.</p><img src="https://counter.theconversation.com/content/185270/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander James is a listed inventor on the patent protecting intellectual property on LowCat. He and his team received funding from the Science and Technology Funding Council.</span></em></p>New catalytic converters can remove toxic chemicals from the exhaust fumes of combustion-engine cars.Alexander James, Research Fellow in Atmospheric Chemistry, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1812412022-05-19T20:01:31Z2022-05-19T20:01:31ZWhat’s it like to be on Venus or Pluto? We studied their sand dunes and found some clues<figure><img src="https://images.theconversation.com/files/458386/original/file-20220418-22-1t0v2e.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C4045%2C5085&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sand blown by wind into ripples within Victoria Crater at Meridiani Planum on Mars, as photographed by NASA's Mars Reconnaissance Orbiter on October 3, 2006.</span> <span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA08813">NASA/JPL-Caltech/University of Arizona/Cornell/Ohio State University</a></span></figcaption></figure><p>What is it like to be on the surface of Mars or Venus? Or even further afield, such as on Pluto, or Saturn’s moon Titan? </p>
<p>This curiosity has driven advances in space exploration since Sputnik 1 was launched <a href="https://www.nationalgeographic.org/thisday/oct4/ussr-launches-sputnik/">65 years</a> ago. But we’re only beginning to scratch the surface of what is knowable about other planetary bodies in the Solar System.</p>
<p>Our <a href="https://doi.org/10.1038/s41550-022-01669-0">new study</a>, published today in Nature Astronomy, shows how some unlikely candidates – namely sand dunes – can provide insight into what weather and conditions you might experience if you were standing on a far-off planetary body. </p>
<h2>What’s in a grain of sand?</h2>
<p>English poet William Blake <a href="https://www.poetryfoundation.org/poems/43650/auguries-of-innocence">famously wondered</a> what it means “to see a world in a grain of sand”. </p>
<p>In our research, we took this quite literally. The idea was to use the mere presence of sand dunes to understand what conditions exist on a world’s surface. </p>
<p>For dunes to even exist, there are a pair of “<a href="https://theconversation.com/exo-earths-and-the-search-for-life-elsewhere-a-brief-history-33096">Goldilocks</a>” criteria that must be satisfied. First is a supply of erodible but durable grains. There must also be winds fast enough to make those grains hop across the ground – but not fast enough to carry them high into the atmosphere.</p>
<p>So far, the direct measurement of winds and sediment has only been possible on Earth and Mars. However, we have observed wind-blown sediment features on multiple other bodies (and even <a href="https://doi.org/10.1073/pnas.1612176114">comets</a>) by satellite. The very presence of such dunes on these bodies implies the Goldilocks conditions are met.</p>
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<img alt="" src="https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/460205/original/file-20220428-18-ofmyhl.png?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">
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<span class="caption">Windblown features on (from top left, clockwise) Earth, Mars, Titan, Venus, Pluto and Triton have been imaged by satellites.</span>
<span class="attribution"><span class="source">Nature Astronomy/Image adapted from Gunn and Jerolmack (2022)</span></span>
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<p>Our work focused on Venus, Earth, Mars, Titan, Triton (Neptune’s largest moon) and Pluto. Unresolved debates about these bodies have gone on for decades. </p>
<p>How do we square the apparent wind-blown features on Triton’s and Pluto’s surfaces with their thin, tenuous atmospheres? Why do we see such prolific sand and dust activity on Mars, despite measuring winds that seem too weak to sustain it? </p>
<p>And does Venus’s thick and stiflingly hot atmosphere move sand in a similar way to how air or water move on Earth?</p>
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<img alt="Mars ripples" src="https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/461935/original/file-20220509-7428-n5ash3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Windblown ripples on the Bagnold Dunes on Mars were photographed by the rover Curiosity.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/MSSS</span></span>
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<h2>Furthering the debate</h2>
<p>Our study offers predictions for the winds required to move sediment on these bodies, and how easily that sediment would break apart in those winds. </p>
<p>We constructed these predictions by piecing together results from a host of other research papers, and testing them against all the experimental data we could get our hands on.</p>
<p>We then applied the theories to each of the six bodies, drawing on telescope and satellite measurements of variables including gravity, atmospheric composition, surface temperature, and the strength of sediments.</p>
<p>Studies before ours have looked at either the wind speed threshold required to move sand, or the strength of various sediment particles. Our work combined these together – looking at how easily particles could break apart in sand-transporting weather on these bodies.</p>
<p>For example, we know Titan’s equator has sand dunes – but we aren’t sure of what sediment encircles the equator. Is it pure <a href="https://www.pnas.org/doi/10.1073/pnas.0608561103">organic haze</a> raining down from the atmosphere, or is it mixed with denser ice?</p>
<p>As it turns out, we discovered loose aggregates of organic haze would disintegrate upon collision if they were blown by the winds at Titan’s equator. </p>
<p>This implies Titan’s dunes probably aren’t made of purely organic haze. To build a dune, sediment must be blown around in the wind for a long time (some of Earth’s dune sands are a <a href="https://doi.org/10.1038/ngeo985">million years</a> old).</p>
<p>We also found wind speeds would have to be excessively fast on Pluto to transport either methane or nitrogen ice (which is what Pluto’s dune sediments were hypothesised to be). This calls into question whether “dunes” on Pluto’s plain, <a href="https://www.nasa.gov/feature/scientists-probe-mystery-of-pluto-s-icy-heart">Sputnik Planitia</a>, are dunes at all.</p>
<p>They may instead be <a href="https://doi.org/10.1016/j.earscirev.2020.103350">sublimation waves</a>. These are dune-like landforms made from the sublimation of material, instead of sediment erosion (such as those seen on Mars’s north polar cap).</p>
<p>Our results for Mars suggest more dust is generated from wind-blown sand transport on Mars than on Earth. This suggests our models of the Martian atmosphere may not be effectively capturing Mars’s strong “<a href="https://earthobservatory.nasa.gov/images/41161/katabatic-winds-rake-terra-nova-bay">katabatic</a>” winds, which are cold gusts that blow downhill at night.</p>
<h2>Potential for space exploration</h2>
<p>This study comes at an interesting stage of space exploration.</p>
<p>For Mars, we have a relative abundance of observations; five space agencies are conducting active missions in orbit, or in situ. Studies such as ours help inform the objectives of these missions, and the paths taken by rovers such as <a href="https://www.youtube.com/watch?v=4czjS9h4Fpg">Perseverance</a> and <a href="https://theconversation.com/on-its-first-try-chinas-zhurong-rover-hit-a-mars-milestone-that-took-nasa-decades-161078">Zhurong</a>.</p>
<p>In the outer reaches of the Solar System, Triton has not been observed in detail since the NASA Voyager 2 flyby in 1989. There is currently a <a href="https://doi.org/10.3847/PSJ/abf654">mission proposal</a> which, if selected, would have a probe launched in 2031 to study Triton, before annihilating itself by flying into Neptune’s atmosphere.</p>
<p>Missions planned to Venus and Titan in the coming decade will revolutionise our understanding of these two. NASA’s <a href="https://www.nasa.gov/dragonfly/dragonfly-overview/index.html">Dragonfly</a> mission, slated to leave Earth in 2027 and arrive on Titan in 2034, will land an uncrewed helicopter on the moon’s dunes.</p>
<p>Pluto was observed during a 2015 <a href="https://www.youtube.com/watch?v=NEdvyrKokX4">flyby</a> by NASA’s ongoing New Horizons mission, but there are no plans to return.</p>
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<a href="https://theconversation.com/jupiter-saturn-uranus-neptune-why-our-next-visit-to-the-giant-planets-will-be-so-important-and-just-as-difficult-175918">Jupiter, Saturn, Uranus, Neptune: why our next visit to the giant planets will be so important (and just as difficult)</a>
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<img src="https://counter.theconversation.com/content/181241/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Gunn received funding from the National Aeronautics and Space Agency. </span></em></p>There are many bodies in the solar system we can’t easily access. But observations of their winds and sediments reveal a surprising amount.Andrew Gunn, Lecturer, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1767382022-02-17T11:04:44Z2022-02-17T11:04:44ZCurious Kids: could we change other planets in the Solar System so we could live on them?<figure><img src="https://images.theconversation.com/files/446785/original/file-20220216-25-1t0fpbr.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3744%2C2492&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/futuristic-astronaut-on-another-planet-image-317943374">Lia Koltyrina/Shutterstock</a></span></figcaption></figure><p><strong>Can we terraform other planets so that the human race can spread around the Solar System? – Xander, aged 14, Eindhoven, The Netherlands</strong></p>
<p>Of the eight planets in the Solar System, we live on Earth, and for good reasons. It has the perfect conditions for life.</p>
<p>Right now, though, we are sculpting Earth’s surface by deforestation, and <a href="https://climatekids.nasa.gov/climate-change-meaning/">changing its atmosphere</a> by adding carbon dioxide, methane and other greenhouse gases. These changes have resulted in global warming, which might lead us to worry that in the future, Earth may not be such a good place for us to live. </p>
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<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a> that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a> and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.</em></p>
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<p>Perhaps this ability to change a planet could make somewhere else in the Solar System suitable for us to live. This planet engineering is called “<a href="https://www.nasa.gov/press-release/goddard/2018/mars-terraforming">terraforming</a>”.</p>
<p>In our Solar System, the most similar planets to Earth are Mars, which is a bit further from the Sun, and Venus, which is a bit closer to the Sun. However, they are still very different to Earth.</p>
<p>There are a lot of ways in which these planets are different to Earth. One is the gases that are in the atmosphere. Both the atmosphere of Mars and that of Venus are mainly made of carbon dioxide. Neither planet’s atmosphere contains any amounts of oxygen to speak of, which means that right now, we wouldn’t be able to breathe on either planet. </p>
<figure class="align-center ">
<img alt="Red rocky terrain" src="https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446790/original/file-20220216-10384-9yftm.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An enhanced colour image of the surface of Mars taken by the Imager for Mars Pathfinder.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-PIA00979">NASA/JPL/USGS</a></span>
</figcaption>
</figure>
<p>Mars is generally considered the most promising planet to terraform. However, as well as being made mostly of carbon dioxide, the <a href="https://mars.nasa.gov/all-about-mars/facts/">atmosphere on Mars</a> is very thin. It doesn’t press down on the planet with the same weight that the atmosphere on Earth does. </p>
<p>This pressure from the atmosphere is what keeps water on Earth liquid – so we can drink it, and plants can use it to grow. Nearly all of the water on Mars is ice, except for a bit of <a href="https://mars.nasa.gov/all-about-mars/facts/">water vapour</a> in the atmosphere. </p>
<p>In order to create an atmosphere that we could breathe in, and to create enough pressure to keep water liquid, we would need to pump a lot of air into Mars’ atmosphere – a mixture of nitrogen and oxygen – until the atmosphere was about as heavy as Earth’s.</p>
<figure class="align-left ">
<img alt="Round beige planet in space" src="https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446792/original/file-20220216-19-gjdte4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mars.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-PIA04591">NASA/JPL/Malin Space Science Systems</a></span>
</figcaption>
</figure>
<p>It might be possible to find this nitrogen and oxygen on Mars, which has soil that has been found to contain significant <a href="https://www.jpl.nasa.gov/news/curiosity-rover-finds-biologically-useful-nitrogen-on-mars">amounts of nitrate</a> – a molecule of one nitrogen and three oxygen atoms. </p>
<p>But there would be problems with doing this, including taking nutrients out of the soil that might be needed to grow plants.</p>
<p>Mars is also a very cold place, with an average temperature of <a href="https://www.space.com/16907-what-is-the-temperature-of-mars.html">about -60°C</a>. </p>
<p>To change this, we would need to help its atmosphere trap heat. This is called the greenhouse effect. We could do this by pumping more carbon dioxide and methane into it (methane has been found on Mars). This would warm Mars and melt much of its ice, creating a water cycle like in Earth’s climate. Mars would have seas, rivers and rainfall like Earth.</p>
<h2>Mars or Venus?</h2>
<p>Alternatively, we could think about terraforming Venus. The gravity of Venus is quite similar to that on Earth, but for reasons not fully understood it has an atmosphere almost a hundred times <a href="https://solarsystem.nasa.gov/planets/venus/overview/">heavier than Earth’s</a>. The weight of the atmosphere pressing down on us would crush us. </p>
<p>To reduce the weight of the atmosphere on Venus to be more like Earth’s atmosphere, we would need to remove the carbon dioxide and some of the nitrogen.</p>
<figure class="align-center ">
<img alt="yellow coloured mountain" src="https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/446791/original/file-20220216-27-cja80p.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A three-dimensional perspective view of Maat Mons, a volcano on Venus, taken by NASA Magellan.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-PIA00254">NASA/JPL</a></span>
</figcaption>
</figure>
<p>Unfortunately, if we knew how to remove carbon dioxide from the atmosphere on such massive scale, we would be better off doing that on Earth in order to slow down global warming.</p>
<p>Mars and Venus have reached a natural state that differs from Earth’s. If we turn them into Earth-like planets it means taking them out of balance. Left alone, they would change again. A terraformed Mars or Venus would require constant effort to maintain.</p>
<p>It would be far simpler and easier to build an artificial space colony, big enough to hold a whole ecosystem made up of plants, animals and other forms of life. We could then even possibly travel to another star system, where we might find a planet more like Earth. But we do not have the ability to do this, yet. </p>
<p>Until then, the best kind of terraforming would be to reduce humankind’s imprint on Earth.</p><img src="https://counter.theconversation.com/content/176738/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacco van Loon 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>Humans might one day be able to live somewhere else in the Universe.Jacco van Loon, Astronomer, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1660462021-08-23T10:48:52Z2021-08-23T10:48:52ZThe five most impressive geological structures in the solar system<figure><img src="https://images.theconversation.com/files/417379/original/file-20210823-13-aqa2uc.jpg?ixlib=rb-1.1.0&rect=9%2C0%2C1581%2C1505&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ligeia Mare on Titan.</span> <span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Ligeia_Mare#/media/File:Ligeia_Mare_in_false_color_(PIA17031).jpg">NASA/JPL-Caltech/ASI/Cornell -</a></span></figcaption></figure><p>When we talk about amazing geological features, we often limit ourselves to those on Earth. But as a geologist, I think that’s crazy – there are so many structures on other worlds that can excite and inspire, and that can put processes on our own planet into perspective.</p>
<p>Here, in no particular order, are the five geological structures in the solar system (excluding Earth) that most impress me.</p>
<h2>The grandest canyon</h2>
<p>I left out the solar system’s biggest volcano, <a href="https://theconversation.com/monster-volcanoes-on-mars-how-space-rocks-are-helping-us-solve-their-mysteries-85045">Olympus Mons</a> on Mars, so I could include that planet’s most spectacular canyon, <a href="https://www.space.com/20446-valles-marineris.html">Valles Marineris</a>. Being 3,000km long, hundreds of kilometres wide and up to eight kilometres deep, this is best seem from space. If you were lucky enough to stand on one rim, the opposite rim would be way beyond the horizon. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of Marineris seen in a colour-coded topographic view." src="https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=191&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=191&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=191&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=240&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=240&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416017/original/file-20210813-17-1pochz0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=240&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Valles Marineris seen in a colour-coded topographic view as if from 5,000 km above the surface (left), and imaged by the High Resolution Stereo Camera on Esa’s Mars Express (right).</span>
<span class="attribution"><span class="source">Google Earth and NASA/USGS/ESA/DLR/FU Berlin (G. Neukum)</span></span>
</figcaption>
</figure>
<p>It was probably initiated by fracturing when an adjacent volcanic region (called <a href="https://astronomynow.com/tag/tharsis-volcanic-dome/">Tharsis</a>) began to bulge upwards, but was widened and deepened by a series of catastrophic floods that climaxed more than 3 billion years ago.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">Plate tectonics: new findings fill out the 50-year-old theory that explains Earth's landmasses</a>
</strong>
</em>
</p>
<hr>
<h2>Venus’ fold mountains</h2>
<p>We are going to learn a lot more about Venus in the 2030s when <a href="https://theconversation.com/nasa-has-announced-two-missions-to-venus-by-2030-heres-why-thats-exciting-162133">two Nasa missions</a> and <a href="https://www.esa.int/Science_Exploration/Space_Science/ESA_selects_revolutionary_Venus_mission_EnVision">one from Esa (European Space Agency)</a> arrive. Venus is nearly the same size, mass and density as the Earth, causing <a href="https://theconversation.com/venus-has-very-few-volcanoes-weirdly-this-might-be-why-its-as-hot-as-hell-78363">geologists to puzzle</a> over why it lacks Earth-style plate tectonics and why (or indeed whether) it has comparatively little active volcanism. How does the planet get its heat out?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Image of the fold mountains on Venus." src="https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=438&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=438&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=438&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416030/original/file-20210813-25-ofb1wa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fold mountains in Ovda Regio, Venus. The insert is a similar view of part of the Applachians in central Pennsylvania.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>I find it reassuring that at least some aspects of Venus’ geology look familiar. For example, the northern margin of the highlands named <a href="https://www.jpl.nasa.gov/images/venus-ovda-regio">Ovda Regio</a> looks strikingly similar, apart from the lack of rivers cutting through the eroded, fold-like pattern, to “fold mountains” on Earth such as the <a href="https://www.nationalgeographic.org/encyclopedia/fold-mountain/">Appalachians</a>, which are the result of a <a href="https://www.nationalgeographic.org/encyclopedia/fold-mountain/">collision between continents</a>.</p>
<h2>Blasted Mercury</h2>
<p>I’m cheating a little with my next example, because it is both one of the solar system’s largest impact basins and an explosive volcano within it. Mercury’s 1,550km diameter <a href="https://solarsystem.nasa.gov/resources/2266/mercurys-caloris-basin/">Caloris basin</a> was formed by a major asteroid impact about 3.5 billion years ago, and soon after that its floor was flooded by lavas. </p>
<p>Some time later, a series of explosive eruptions blasted kilometres-deep holes through the solidified lavas near the edge of the basin where the lava cap was thinnest. These sprayed volcanic ash particles out over a range of tens of kilometres. One such deposit, named Agwo Facula, surrounds the explosive vent that I have chosen as my example. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Images of Mercury's Caloris basin." src="https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=298&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=298&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=298&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=374&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=374&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416045/original/file-20210813-13-osbbma.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=374&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Right: most of Mercury’s Caloris basin, its floor covered by dull, orange lava. Brighter orange patches are remnants of explosive eruptions. Lower left: close-up inside the red box of an explosive volcanic deposit. Upper left: details of the vent interior.</span>
<span class="attribution"><span class="source">NASA/JHUAPL/CIW</span></span>
</figcaption>
</figure>
<p>Explosive eruptions are driven by the force of expanding gas, and are a <a href="https://theconversation.com/mysterious-red-spots-on-mercury-get-names-but-what-are-they-95114">surprising find on Mercury</a>, whose proximity to the Sun was previously expected to have starved it of such volatile substances – the heat would have made them boil off. Scientists suspect that there were in fact several explosive eruptions, possibly spaced over a prolonged timescale. This means that gas-forming volatile materials (whose composition will remain uncertain until <a href="https://theconversation.com/europe-blasts-off-to-mercury-heres-the-rocket-science-104641">Esa’s BepiColombo</a> mission starts work in 2026) were repeatedly available in Mercury’s magmas.</p>
<h2>The tallest cliff?</h2>
<p>In soil or vegetation-rich regions on Earth, cliffs offer the largest exposures of clean rock. Although <a href="https://www.bbc.co.uk/news/uk-england-dorset-56773648">dangerous to approach</a>, they reveal an uninterrupted cross-section of rock and can be great for fossil hunting. Because geologists love them so much, I give you the seven kilometres-high <a href="https://spaceplace.nasa.gov/cliff-jumping/en/">Verona Rupes</a>. This is a feature on Uranus’s small moon <a href="https://solarsystem.nasa.gov/moons/uranus-moons/miranda/in-depth/">Miranda</a> that is often described as “the tallest cliff in the solar system”, including on a <a href="https://science.nasa.gov/verona-rupes-tallest-known-cliff-solar-system">recent Nasa website</a>. This even goes so far as to remark that if you were careless enough to take a tumble off the top, it would take you 12 minutes to fall to the bottom. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Images of Verona Rupes." src="https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=592&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=592&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=592&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=744&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=744&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415845/original/file-20210812-15866-1l1jbhp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=744&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Verona Rupes, about 50km long and several km high, but not actually so cliff-like as it appears as seen by Voyager 2 during its 1986 flyby.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/mysterious-red-spots-on-mercury-get-names-but-what-are-they-95114">Mysterious red spots on Mercury get names – but what are they?</a>
</strong>
</em>
</p>
<hr>
<p>This is nonsense, because Verona Rupes is nowhere near vertical. The only images we have of it are from <a href="https://solarsystem.nasa.gov/missions/voyager-2/in-depth/">Voyager 2</a>, captured during its 1986 fly by of Uranus. It is undeniably impressive, being almost certainly a geological fault where one block of Miranda’s icy crust (the outermost “shell” of the planet) has moved downwards against the adjacent block. </p>
<p>However, the obliqueness of the view is deceptive, making it impossible to be sure of the face’s steepness – it probably slopes at less than 45 degrees. If you stumbled at the top, I doubt you’d even slide to the bottom. The face appears to be very smooth in the best, but rather low resolution image that we have, but at Miranda’s -170°C daytime temperature, water-ice has a <a href="https://www.zmescience.com/science/ice-slippery-h-bonds-8731058/">high friction</a> and is not slippery at all.</p>
<h2>Titan’s drowned coastline</h2>
<p>For my final example I could happily have chosen virtually anywhere on Pluto, but instead I have opted for a hauntingly Earth-like coastline on Saturn’s largest moon, <a href="https://theconversation.com/flying-on-saturns-moon-titan-what-we-could-discover-with-nasas-new-dragonfly-mission-119823">Titan</a>. Here, a large depression in Titan’s water-ice “bedrock” hosts a sea of liquid methane named <a href="https://www.esa.int/ESA_Multimedia/Images/2013/06/Ligeia_Mare">Ligeia Mare</a>.</p>
<p>Valleys carved by methane rivers draining into the sea have evidently become flooded as the sea level rose. This complexly indented coastline reminds me strongly of Oman’s <a href="https://www.bbc.com/travel/article/20120323-omans-sleepy-peninsula">Musandam peninsula</a>, on the south side of the Straits of Hormuz. There, the local crust has been warped downwards because of the ongoing collision between Arabian and the Asian mainlands. Has something similar happened on Titan? We don’t know yet, but the way that the coastal geomorphology changes around Ligeia Mare suggests to me that its drowned valleys are more than a straightforward result of rising liquid levels.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Images of Ligeia Mare and The Musandam peninsula side by side." src="https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=319&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=319&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=319&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=401&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=401&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416316/original/file-20210816-28-tx30nn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=401&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: Part of Titan’s Ligeia Mare, showing a coastline with valleys drowned by a sea of liquid methane. Right: The Musandam peninsula, Arabia, where coastal valleys are similarly drowned, but by a saltwater sea.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/ASI/Cornell and Expedition 63, International Space Station (ISS)</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/titan-first-global-map-uncovers-secrets-of-a-potentially-habitable-moon-of-saturn-126985">Titan: first global map uncovers secrets of a potentially habitable moon of Saturn</a>
</strong>
</em>
</p>
<hr>
<p>Rock and liquid water on Earth, frigid water-ice and liquid methane on Titan - it makes little difference. Their mutual interactions are the same, and so we see geology repeating itself on different worlds.</p><img src="https://counter.theconversation.com/content/166046/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Rothery is Professor of Planetary Geosciences at the Open University. He is co-leader of the European Space Agency's Mercury Surface and Composition Working Group, and a Co-Investigator on MIXS (Mercury Imaging X-ray Spectrometer) that is now on its way to Mercury on board the European Space Agency's Mercury orbiter BepiColombo. He has received funding from the UK Space Agency and the Science & Technology Facilities Council for work related to Mercury and BepiColombo, and from the European Commission under its Horizon 2020 programme for work on planetary geological mapping (776276 Planmap). He is author of Planet Mercury - from Pale Pink Dot to Dynamic World (Springer, 2015), Moons: A Very Short Introduction (Oxford University Press, 2015) and Planets: A Very Short Introduction (Oxford University Press, 2010). He is Educator on the Open University's free learning Badged Open Course (BOC) on Moons and its equivalent FutureLearn Moons MOOC, and chair of the Open University's level 2 course on Planetary Science and the Search for Life.</span></em></p>From the tallest cliff in the solar system to its largest impact basin, geological processes on other worlds are very similar to those on our own planet.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1641602021-07-12T20:08:22Z2021-07-12T20:08:22ZHow to see tonight’s conjunction of Venus and Mars in the evening sky<figure><img src="https://images.theconversation.com/files/410725/original/file-20210712-70807-123snvl.jpg?ixlib=rb-1.1.0&rect=209%2C270%2C1792%2C843&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">SolarSystemScope</span> <span class="attribution"><a class="source" href="https://www.solarsystemscope.com/">SolarSystemScope</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Venus has returned to our evening skies and is looking lovely in the north-west after sunset. Tonight, July 13, it will pair up with the red planet Mars and just above the two planets will be the waxing crescent Moon.</p>
<p>Wherever you are in Australia, find a location that has a good view of the north-west horizon to see the <a href="https://earthsky.org/astronomy-essentials/definition-conjunction-astronomy/">conjunction</a>. Venus will be visible during dusk, but you need to wait until the sky darkens to have a chance to see faint Mars. </p>
<p>Mars will appear just above and to the left of Venus. The best viewing opportunity will be from about 6:30pm , with the planets setting an hour later. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=476&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=476&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410279/original/file-20210708-23-1v2nuy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=476&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Look towards the north-west horizon after sunset on July 13 to see Venus, Mars and the crescent Moon.</span>
<span class="attribution"><span class="source">Museums Victoria/Stellarium</span></span>
</figcaption>
</figure>
<p>Venus is dazzling, so it is easy to see why it’s known as the “evening star”. Just look towards the north-west horizon after sunset and you can’t miss it.</p>
<p>Mars, on the other hand, is looking fairly faint. The red planet has been in the north-west sky for the past few months and while it was bright and red earlier in the year, it has been fading quite considerably as its orbit takes it away from Earth.</p>
<p>On Tuesday evening, the pair will appear so close together, they will fit within the field of view of a telescope or pair of binoculars. Yet in reality, they are millions of kilometres apart – Venus will be around 210 million km from Earth and Mars a more distant 370 million km.</p>
<h2>The eyes of Buwadjarr</h2>
<p>Aboriginal Australians have witnessed close pairings of Venus and Mars for thousands of years and for the Euahlayi people of northern New South Wales it has particular significance. </p>
<p>This cosmic pairing represents the eyes of <a href="https://en.wikipedia.org/wiki/Baiame">Buwadjarr</a>, the supreme creation ancestor. As one Euahlayi elder (who chose not to be named) told <a href="https://researchers.mq.edu.au/en/publications/the-astronomy-of-the-kamilaroi-and-euahlayi-peoples-and-their-nei">researchers</a>: </p>
<blockquote>
<p>During the day, the eyes of Maliyan (the eaglehawk) are the eyes of [Buwadjarr]. During the night, Maliyan’s eyes are Venus and Mars, which become the eyes of [Buwadjarr]. Because one is red (Mars), and one is blue and green (Venus).</p>
</blockquote>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/aboriginal-traditions-describe-the-complex-motions-of-planets-the-wandering-stars-of-the-sky-97938">Aboriginal traditions describe the complex motions of planets, the 'wandering stars' of the sky</a>
</strong>
</em>
</p>
<hr>
<p>Euahlayi people would have seen <a href="https://www.skyatnightmagazine.com/advice/skills/green-flash-venus-what-is-how-see/">Venus flash green</a>, which is an interesting phenomenon that occurs as Venus is setting and its bright light is scattered by the Earth’s atmosphere. When it does this it also twinkles. Elders describe the planet as an old man who told a crude joke and is animatedly laughing to himself.</p>
<p>The event is also linked to ceremony. Euahlayi people follow part of <a href="https://theconversation.com/how-ancient-aboriginal-star-maps-have-shaped-australias-highway-network-55952">a Songline</a> mapped out in the stars to travel to a place near Quilpie, 430 km northwest of Goodooga in western Queensland. Bringing with them a green and blue opal, representing Venus, they meet the local Maranganji people, who provide a red stone signifying Mars. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-ancient-aboriginal-star-maps-have-shaped-australias-highway-network-55952">How ancient Aboriginal star maps have shaped Australia's highway network</a>
</strong>
</em>
</p>
<hr>
<h2>The original Goldilocks planets</h2>
<p>Venus and Mars are Earth’s closest neighbours and yet they evolved so differently to our planet – one too hot and the other too cold.</p>
<p>Billions of years ago, it’s likely this trio of rocky planets all had oceans covering their surfaces. But on our two neighbours, those oceans have dried up.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=227&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=227&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=227&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=285&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=285&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410278/original/file-20210708-26673-12insf5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=285&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Meet the neighbours: Venus and Mars.</span>
<span class="attribution"><a class="source" href="https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Venus_compared_to_Earth">ESA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For Venus, new <a href="https://theconversation.com/venus-was-once-more-earth-like-but-climate-change-made-it-uninhabitable-150445">modelling suggests that volcanic activity</a> could have been the likely cause. Over a short period of time, so much carbon dioxide was pumped into the atmosphere that it could not be re-absorbed by the rocks. This triggered a runaway greenhouse effect and turned Venus into the hot, hellish world we know today.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/venus-was-once-more-earth-like-but-climate-change-made-it-uninhabitable-150445">Venus was once more Earth-like, but climate change made it uninhabitable</a>
</strong>
</em>
</p>
<hr>
<p>For Mars it’s a different story. Back when water was flowing on Mars, the planet was much warmer because its atmosphere was more substantial. However over billions of years, the solar wind made up of particles from the Sun has blown away much of that atmosphere. Mars doesn’t have a magnetic field like Earth to deflect the solar wind and the planet’s low gravity makes it easier for the gases to escape.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410281/original/file-20210708-17-16180jh.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">Artist’s rendition of a solar storm hitting Mars and stripping ions from the upper atmosphere.</span>
<span class="attribution"><span class="source">NASA/GSFC</span></span>
</figcaption>
</figure>
<p>The atmosphere is now so thin that liquid water can no longer exist on the Martian surface. Some water may have <a href="https://theconversation.com/why-is-there-so-little-water-left-on-mars-163333">escaped along with the atmosphere</a>, but the majority seems to be locked up in the Martian rocks and frozen underground. </p>
<h2>Leo, the lion</h2>
<p>As you observe the planets and in particular the Moon, you may notice an arrangement of stars that looks like an upside-down question mark. That’s the mane of Leo, the lion.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=855&fit=crop&dpr=1 600w, https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=855&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=855&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1074&fit=crop&dpr=1 754w, https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1074&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/410284/original/file-20210708-15-17qvyam.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1074&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Leo, with Leo Minor above, as depicted in Urania’s Mirror, a set of constellation cards published in London c.1825.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Leo is one of the original Greek constellations and also one of the 12 constellations of the zodiac. The zodiac is a band of constellations that maps the path of the Sun (known as the <a href="https://www.space.com/5417-ecliptic-zodiac-work.html">ecliptic</a>), and therefore the Moon and planets can be found passing through these constellations throughout the year. </p>
<p>From our vantage point in the southern hemisphere, Leo appears upside-down. In fact, all the constellations, and even the Moon, are viewed “upside-down”, <a href="https://www.sciencealert.com/the-moon-is-upside-down-in-the-northern-southern-hemisphere-and-how-did-we-not-know-this">because we live on a sphere</a>. </p>
<p>The brightest star in the constellation of Leo is Regulus, often called the “little king”. </p>
<p>In Wardaman astronomy (from west of Katherine, Northern Territory), Regulus is called Moroborronggo. Uncle Yidumduma Bill Harney describes it as the creation dog. Right now, we are seeing Moroborronggo setting in the west, but back in April when the star is seen rising in the east at sunset, it brings special significance as it marks the start of the <a href="http://www.bom.gov.au/iwk/calendars/wardaman.shtml">Wardaman calendar</a>, when the monsoon rains begin to ease. </p>
<hr>
<p><em>An earlier version of this article used a name that has been changed out of respect for Indigenous customs. The Conversation regrets any offence caused.</em></p><img src="https://counter.theconversation.com/content/164160/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duane W. Hamacher receives funding from the Australian Research Council, the Laby Foundation, the Pierce Bequest, and the Indigenous Knowledge Institute at the University of Melbourne. He is also president of the Australian Association for Astronomy in Culture (Triple-AC), a charitable not-for-profit organisation.</span></em></p><p class="fine-print"><em><span>Tanya Hill 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>Mars, Venus and the crescent Moon will all come together in the sky just after sunset on Tuesday.Tanya Hill, Honorary Fellow of the University of Melbourne and Senior Curator (Astronomy), Museums Victoria Research InstituteDuane Hamacher, Associate Professor, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1629842021-06-21T19:12:11Z2021-06-21T19:12:11ZThe surface of Venus is cracked and moves like ice floating on the ocean – likely due to tectonic activity<figure><img src="https://images.theconversation.com/files/407495/original/file-20210621-27-8cz1kb.png?ixlib=rb-1.1.0&rect=28%2C19%2C1249%2C685&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">New research suggests that Venus' crust is broken into large blocks – the dark reddish–purple areas – that are surrounded by belts of tectonic structures shown in lighter yellow–red.
</span> <span class="attribution"><a class="source" href="https://astrogeology.usgs.gov/search/map/Venus/Magellan/Venus_Magellan_LeftLook_mosaic_global_75m">Paul K. Byrne/NASA/USGS</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>Much of the brittle, upper crust of Venus is broken into fragments that jostle and move – and the slow churning of Venus’ mantle beneath the surface might be responsible. My colleagues and I arrived at this finding using <a href="https://astrogeology.usgs.gov/search/map/Venus/Magellan/Venus_Magellan_LeftLook_mosaic_global_75m">decades-old radar data</a> to explore how the surface of Venus interacts with the interior of the planet. We describe it in a <a href="https://doi.org/10.1073/pnas.2025919118">new study published</a> in the Proceedings of the National Academy of Sciences on June 21, 2021.</p>
<p><a href="https://scholar.google.com/citations?user=Lb6BrKEAAAAJ&hl=en&oi=ao">Planetary scientists like me</a> have long known that Venus has <a href="https://arstechnica.com/science/2017/04/on-venus-tectonics-without-the-plates/">a plethora of tectonic landforms</a>. Some of these formations are long, thin belts where the crust has been pushed together to form ridges or pulled apart to form troughs and grooves. In many of these belts there’s evidence that pieces of the crust have moved side to side, too.</p>
<p>Our new study shows, for the first time, that these bands of ridges and troughs often mark the boundaries of flat, low-lying areas that themselves show relatively little deformation and are individual blocks of Venus’ crust that have shifted, rotated and slid past each other over time – and may have done so in the recent past. It’s a little like <a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">Earth’s plate tectonics</a> but on a smaller scale and more closely resembles <a href="https://www.oceanpolaire.org/en/polar-encyclopaedia/encyclopedie-polaire-en-c1/#">pack ice that floats atop the ocean</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A person standing on an ice chunk with a large ridge of ice in front of them." src="https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407455/original/file-20210621-62599-1w5g1ia.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">Where ice chunks collide, the ice is thrust upwards to create ridges much like what researchers think happens on Venus.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Pressure_ridge_--_where_two_ice_floes_meet.jpg#/media/File:Pressure_ridge_--_where_two_ice_floes_meet.jpg">Ben Holt and Susan Digby/WikimediaCommons</a></span>
</figcaption>
</figure>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial photo of pack ice with large block of ice floating on the sea and small cracks showing water between chunks of ice." src="https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407456/original/file-20210621-34789-1ggbcf2.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">The crust of Venus is fractured into large pieces that behave more like chunks of ice floating on the ocean.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Sea_ice_near_coast_of_Labrador_-a.jpg#/media/File:Sea_ice_near_coast_of_Labrador_-a.jpg">Endlisnis/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Researchers have hypothesized that – <a href="https://people.earth.yale.edu/sites/default/files/files/Bercovici/17_MantlConvection-ESEG2011-2_0.pdf">just like Earth’s mantle</a> – the mantle of Venus swirls with currents as it’s heated from below. My colleagues and I modeled the sluggish but powerful movement of Venus’ mantle and showed that it is sufficiently forceful to fragment the upper crust everywhere we’ve found these lowland blocks. </p>
<h2>Why it matters</h2>
<p>A major question about Venus is whether the planet has active volcanoes and tectonic faulting today. It’s essentially the same size, composition and age as Earth – so why wouldn’t it be geologically alive?</p>
<p>But no mission to Venus has yet conclusively shown the planet to be active. There’s tantalizing but ultimately inconclusive evidence that <a href="https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Venus_is_alive_geologically_speaking">volcanic eruptions have taken place there in the geologically recent past</a> – and are perhaps even ongoing. The case for tectonic activity – the creaking, breaking and folding of the planet’s crust – is on even less solid ground.</p>
<p>Showing that Venus’ geological engine is still running would have huge implications for understanding the composition of the planet’s mantle, where and how volcanism might be taking place today and how the very crust itself is formed, destroyed and replaced. Because our study suggests that some of this jostling of the crust is geologically recent, we may have taken a big step forward in understanding if Venus really is active today.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A red–hued image of the surface of Venus showing a large darker piece of the surface surrounded by lighter colors against the backdrop of space." src="https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407309/original/file-20210619-27-tggglg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The largest block of lowlands the team found – the dark red shape in the center of this radar image – is about the size of Alaska and surrounded by ridges and deformations that show up as lighter colors.</span>
<span class="attribution"><a class="source" href="https://astrogeology.usgs.gov/search/map/Venus/Magellan/Venus_Magellan_LeftLook_mosaic_global_75m">Paul K. Byrne/NASA/USGS</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>What still isn’t known</h2>
<p>It’s not clear just how widespread these crustal fragments are. My colleagues and I have found 58 so far, but that’s almost certainly a low estimate.</p>
<p>We also don’t yet know when these crustal blocks first formed, nor how long they’ve been moving around on Venus. Determining when the crust’s fragmentation and jostling occurred is key – especially if planetary scientists want to understand this phenomenon in relation to the planet’s suspected recent volcanic activity. Figuring that out would give us vital information on how the planet’s surface features reflect the geological turmoil within.</p>
<h2>What’s next</h2>
<p>This initial study has allowed my colleagues and me to make our best guess yet about how Venus’ vast lowlands have been deformed, but we need much higher-resolution radar images and topographic data to build on this work. Luckily, that’s <a href="https://theconversation.com/nasa-is-returning-to-venus-to-learn-how-it-became-a-hot-poisonous-wasteland-and-whether-the-planet-was-ever-habitable-in-the-past-162140">exactly what scientists are going to get</a> in the coming years, with <a href="https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus/">NASA</a> and the <a href="https://www.esa.int/Science_Exploration/Space_Science/ESA_selects_revolutionary_Venus_mission_EnVision">European Space Agency</a> both recently announcing new missions bound for Venus later this decade. It’ll be worth the wait to get a better understanding of Earth’s enigmatic neighbor.</p>
<p>[<em>The Conversation’s science, health and technology editors pick their favorite stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-favorite">Weekly on Wednesdays</a>.]</p><img src="https://counter.theconversation.com/content/162984/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul K. Byrne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers used decades-old radar data and found that some low-lying areas of Venus’ crust are moving and jostling. This evidence is some of the strongest yet of tectonic activity on Venus.Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1621402021-06-14T12:24:18Z2021-06-14T12:24:18ZNASA is returning to Venus to learn how it became a hot poisonous wasteland – and whether the planet was ever habitable in the past<figure><img src="https://images.theconversation.com/files/405981/original/file-20210611-4750-1cpfjcv.png?ixlib=rb-1.1.0&rect=17%2C0%2C1862%2C1080&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Two new NASA missions hope to answer important questions about Venus' past.</span> <span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/486/hemispheric-view-of-venus/">NASA/JPL/USGS</a></span></figcaption></figure><p>NASA is finally headed back to Venus. On June 2, 2021, NASA Administrator Bill Nelson announced that the agency had selected two winners of <a href="https://www.nasa.gov/press-release/nasa-selects-four-possible-missions-to-study-the-secrets-of-the-solar-system">its latest Discovery class spacecraft mission competition</a>, and both are headed to the second planet from the Sun. </p>
<p><a href="https://scholar.google.com/citations?user=Lb6BrKEAAAAJ&hl=en&oi=ao">I’m a planetary scientist</a> and a <a href="https://meas.sciences.ncsu.edu/people/pkbyrne/">self-confessed Venus evangelist</a>, and here’s why I’m so excited that humanity is going back to Venus.</p>
<p>This is the first time since the <a href="https://solarsystem.nasa.gov/missions/magellan/in-depth/">Magellan mission</a> in 1989 that NASA has committed to sending spacecraft to study the shrouded planet just next door. With the data these two Venus missions – called VERITAS and DAVINCI+ – will collect, planetary scientists can start tackling one of the biggest mysteries in the solar system: Why is Venus, a planet almost the same size, density and age of Earth, so very different from the world humanity calls home?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Venus divided in half with green–yellow clouds on the left and an artists impression of what it might have looked like with oceans, clouds and life on the right." src="https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404967/original/file-20210608-25-4hdwvd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Venus might once have been covered in oceans and clouds and could have supported life.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2017/spanning-disciplines-in-the-search-for-life-beyond-earth">NASA/JPL-Caltech/Ames</a></span>
</figcaption>
</figure>
<h2>An Earth gone wrong?</h2>
<p><a href="https://solarsystem.nasa.gov/planets/venus/overview/">Venus</a> is a rocky planet about the same size as Earth, but despite these similarities, it is a brutal place. Although only a little closer to the Sun than Earth, a <a href="http://www.pas.rochester.edu/%7Eblackman/ast104/vgreenhouse.html">runaway greenhouse effect</a> means that it’s extremely hot at the surface – about 870 F (465 C), roughly the temperature of a self-cleaning oven. The pressure at the surface is a crushing 90 times the pressure at sea level on Earth. And to top it off, there are sulfuric acid clouds covering the entire planet that corrode anything passing through them. </p>
<p>But perhaps the most fascinating aspect of Venus is that <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">it may have once looked a lot like Earth</a>. Recent climate models suggest that in the past the planet could have had liquid water oceans and a mild climate. It may have been habitable for as long as 3 billion years before succumbing to some sort of climate catastrophe that triggered the runaway greenhouse. The goal of these two new missions to Venus is to try to determine if Venus really was Earth’s twin, why it changed and whether, in general, large rocky planets become habitable oases like Earth… or scorched wastelands like Venus.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A square satellite with two long solar panels above a tan–colored Venus." src="https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404968/original/file-20210608-121132-xqszsb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The VERITAS mission will send a craft carrying a powerful radar system into orbit above Venus.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/news/nasa-selects-investigations-for-future-key-planetary-mission">NASA/JPL–Caltech</a></span>
</figcaption>
</figure>
<h2>Fresh eyes on Venus</h2>
<p>What might come as a surprise is that in the 1960s and 1970s <a href="https://nssdc.gsfc.nasa.gov/planetary/chronology_venus.html">Venus was the central focus of space exploration</a> like <a href="https://theconversation.com/bringing-mars-rocks-back-to-earth-on-feb-18-perseverance-rover-landed-safely-on-mars-a-lead-scientist-explains-the-tech-and-goals-153851">Mars is today</a>. The U.S. and Soviet Union sent more than 30 spacecraft in total to the second planet from the Sun. But since 1989, only two missions have gone to Venus, and both were focused on studying the atmosphere – the European Space Agency’s <a href="http://www.esa.int/Science_Exploration/Space_Science/Venus_Express">Venus Express</a> and Japan’s <a href="https://akatsuki.isas.jaxa.jp/en/">Akatsuki</a>. </p>
<p>In contrast, the VERITAS and DAVINCI+ missions will take a holistic view by exploring the geological and climatological history of Venus as a whole, in two very different but complementary ways.</p>
<p>The thick, global layer of sulfuric acid clouds covering Venus make it almost impossible to see the surface with normal cameras. That’s why the <a href="https://www.jpl.nasa.gov/news/veritas-exploring-the-deep-truths-of-venus">VERITAS orbiter</a> – short for “Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy” – will carry a powerful radar system. This radar can peer through the clouds and gather images and topographic data up to 10 times higher-resolution than any previous mission to Venus. This will allow scientists to look for clues about Venus’ earlier climate that may be preserved in rock formations on the surface and might also answer whether the planet is geologically active today. And, finally, this exciting mission will use a special, infrared camera to peer through the atmosphere at very specific wavelengths to take the <a href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11502/1150208/The-Venus-Emissivity-Mapper-VEM--advanced-development-status-and/10.1117/12.2567634.short?SSO=1">first global measurements of what Venus’ rocks are made of</a> – something scientists know very little about.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A circular probe with sampling equipment on it falling towards Venus." src="https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404969/original/file-20210608-28218-1wf5tz8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The DAVINCI+ probe will fall through the Venus atmosphere collecting samples and snapping photos before it ultimately collides with the Alpha Regio region.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/feature/goddard/2021/nasa-to-explore-divergent-fate-of-earth-s-mysterious-twin-with-goddard-s-davinci">NASA GSFC visualization by CI Labs Michael Lentz and others</a></span>
</figcaption>
</figure>
<p>VERITAS’ stablemate is <a href="https://www.nasa.gov/feature/goddard/2021/nasa-to-explore-divergent-fate-of-earth-s-mysterious-twin-with-goddard-s-davinci">DAVINCI+</a>, or “Deep Atmosphere Venus Investigation of Noble gases, Chemistry and Imaging.” The DAVINCI+ mission also involves an orbiter, but the real star of the show will be the meter-wide atmospheric probe. The probe will drop into Venus’ atmosphere and free-fall through the thick clouds for about an hour before reaching the surface. </p>
<p>On the way down, it will take samples of the atmosphere, specifically measuring a variety of gases including argon, krypton and xenon. Different climate histories for Venus would lead to different ratios of these noble gases in the atmosphere – and so by analyzing these ratios, scientists will be able to work out how much water the planet formed with, and even how much water it has lost over the past 4.5 billion years. </p>
<p>But that’s not all the probe will do. Just before impacting crash landing into an area called <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103515001438">Alpha Regio</a> that has some of the oldest rocks on the planet, the probe will take infrared images of the surface as it comes into view through the gloom of the lower atmosphere. Those images will be the first ever taken from above the surface but below the cloud deck, showing planetary scientists Venus as never before.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An artists impression of an exoplanet around a different star." src="https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=340&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=340&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=340&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=427&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=427&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404970/original/file-20210608-144041-1xqktto.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=427&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Studying Venus can offer valuable insight into how other rocky, potentially habitable planets in the galaxy – like Kepler-186f, seen here in an artist’s rendition – might evolve.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/ames/kepler/nasas-kepler-discovers-first-earth-size-planet-in-the-habitable-zone-of-another-star">NASA Ames/SETI Institute/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>Now is the time to go back to Venus</h2>
<p><a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">I have argued before for returning to Venus</a>, so to say I’m enthusiastic about these missions is an understatement. Venus may hold the key to understanding the past – and possibly the future – of Earth. As astronomers discover <a href="https://www.nasa.gov/feature/goddard/2020/nasa-planet-hunter-finds-its-1st-earth-size-habitable-zone-world">more and more Earth-size worlds around other stars</a>, they need to understand whether the outcome we see on Earth – blue skies, water oceans and even a thriving biosphere – is the norm, or if the hellish, barren wastelands of Venus are the rule.</p>
<p>[<em>Over 100,000 readers rely on The Conversation’s newsletter to understand the world.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=100Ksignup">Sign up today</a>.]</p>
<p>Several decades of <a href="https://mars.nasa.gov/mars-exploration/missions/historical-log/">sustained Mars exploration</a> have shown that each mission answers earlier questions and also raises new ones. I don’t know what surprises VERITAS and DAVINCI+, scheduled to launch in the late 2020s, will uncover at Venus, but I do know they’ll discover aspects of the planet that no one had ever imagined. Scientists and mission teams across the world have worked hard to realize a “<a href="https://doi.org/10.1038/d41586-019-01730-5">Decade of Venus</a>,” and it’s starting to pay off. In fact, only a week after NASA’s announcement, the European Space Agency <a href="http://www.esa.int/Science_Exploration/Space_Science/ESA_selects_revolutionary_Venus_mission_EnVision">declared its plans for a Venus mission, too</a>. With these new missions, it’s my guess – my hope – that we’re at the start of a new, golden age of Venus exploration.</p><img src="https://counter.theconversation.com/content/162140/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul K. Byrne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Two new NASA missions – VERITAS and DAVINCI+ – are headed to Venus. The missions will use radar and a probe to learn about Earth’s hard-to-study and potentially prophetic neighbor.Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1621922021-06-07T09:59:19Z2021-06-07T09:59:19ZNasa has just rejected missions to moons of Jupiter and Neptune – here’s what we would have found out<figure><img src="https://images.theconversation.com/files/404489/original/file-20210604-27-1ybuyah.png?ixlib=rb-1.1.0&rect=114%2C45%2C2378%2C1363&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A volcanic eruption on Jupiter's moon Io.</span> <span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/1039/galileo-sees-io-erupt/?category=moons/jupiter-moons_io">NASA/JPL/DLR</a></span></figcaption></figure><p>It’s been 30 years since Nasa last visited Venus, with <a href="https://theconversation.com/astronomers-spot-strange-bow-like-structure-in-venus-atmosphere-71347">the Magellan orbiter</a> in 1990. Now, <a href="https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus/">two new missions</a> have been selected to explore the deadly atmosphere, crushing pressures and volcanic landscape. </p>
<p>The process dates back to February 2020, when Nasa announced that four missions were to undergo a nine-month peer-review process for feasibility. They were all part of the <a href="https://www.nasa.gov/planetarymissions/discovery.html">Discovery program</a>, started by Nasa in 1992 to bring together scientists and engineers to create exciting, groundbreaking missions. Set aside from the flagship missions – such as <a href="https://theconversation.com/curiosity-catches-a-whiff-of-methane-on-mars-and-a-possibility-of-past-life-35595">Curiosity</a> and <a href="https://theconversation.com/uk/search?q=perseverance">Perseverance</a> – the missions operating under Discovery have taken unique and innovative approaches to exploring the solar system.</p>
<p>The two winning Venus missions, <a href="https://theconversation.com/nasa-has-announced-two-missions-to-venus-by-2030-heres-why-thats-exciting-162133">Davinci and Veritas</a>, have been awarded US$500 million (£354 million) and will be launched some time between 2028 and 2030. But the competition was tough from the two losing missions, which would have gone to <a href="https://www.nasa.gov/planetarymissions/io-volcano-observer">Io</a> and <a href="https://www.nasa.gov/feature/jpl/proposed-nasa-mission-would-visit-neptunes-curious-moon-triton">Triton</a>, respectively moons of Jupiter and Neptune. So what are we missing out on as a result?</p>
<h2>Exploring Jupiter’s bizarre moon</h2>
<p>Io is a strange moon – even among moons, which are strange to begin with. As Jupiter’s innermost moon, orbiting a mere 350,000 km above the cloud tops, it gives Io an extreme <a href="https://www.youtube.com/watch?v=9qHrzs6Mbp4">heating mechanism</a> that makes it the <a href="https://ui.adsabs.harvard.edu/abs/2004Icar..169..140L/abstract">most volcanically active</a> object in the solar system, sporting over four hundred volcanoes. </p>
<p>You might think, given we live on a planet with a fair share of volcanoes, that we’d have a good idea of where all this heat is coming from. In fact, according to Alfred McEwen, principal investigator on the proposed Io Volcanic Explorer or IVO mission, we’re still profoundly ignorant of how it actually works.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/nasa-has-announced-two-missions-to-venus-by-2030-heres-why-thats-exciting-162133">Nasa has announced two missions to Venus by 2030 – here's why that's exciting</a>
</strong>
</em>
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<p>IVO was designed to perform multiple fly-bys of the moon and use a suite of instruments to map the activity on and below the surface. By collecting information on Io’s magnetic and gravitational fields, taking videos of the enormous lava eruptions and analysing the gas and dust escaping from the moon, IVO would help scientists learn how Io’s heat is generated and lost.</p>
<p>All of this information is crucial – not just for awesome videos of space volcanoes – because this kind of extreme activity is believed to be an <a href="https://www.nasa.gov/planetarymissions/io-volcano-observer">important aspect</a> of planetary formation and evolution. By understanding the processes that drive change on Io, we can ultimately learn more about how planets and moons came to be.</p>
<h2>The ice giants</h2>
<p>The least explored and understood planets are Uranus and Neptune, and they are home to some of the most bizarre things in the solar system. Uranus has an axial tilt – the angle of its axis of rotation compared to the plane it orbits the Sun – so extreme that it spins on its side. This is thought to be the result of a <a href="http://icc.dur.ac.uk/giant_impacts/">giant collision</a> in the solar system’s past. </p>
<p>Meanwhile, Neptune is home to the <a href="https://www.nasa.gov/feature/jpl/proposed-nasa-mission-would-visit-neptunes-curious-moon-triton">only large moon</a> that orbits backwards around its parent planet, the curious Triton. The peculiar orbital arrangement isn’t where the oddities end. The plane in which Triton orbits is offset by an extreme 23 degrees compared to Neptune’s, and it is believed to have moved to <a href="https://ui.adsabs.harvard.edu/abs/2006Natur.441..192A/abstract">Neptune from the Kuiper Belt</a>, the region beyond Neptune’s orbit filled with icy leftovers from the solar system’s formation. </p>
<figure class="align-center ">
<img alt="A diagram showing the surface of Triton and what the Trident mission was aiming to do." src="https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=628&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=628&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=628&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=789&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=789&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404488/original/file-20210604-25-vy73f1.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=789&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">What the Trident mission would’ve done.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/thumbnails/image/pia23874-1041.jpg">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<p>Triton also has an <a href="https://ui.adsabs.harvard.edu/abs/1992AdSpR..12k.113L/abstract">active ionosphere</a> – a layer of charged particles in its atmosphere ten times more active than any other moon, which isn’t powered by the Sun – as well as a constantly changing and dynamic surface, coated in what might be nitrogen snow. When <a href="https://solarsystem.nasa.gov/moons/neptune-moons/triton/in-depth/">Voyager 2 photographed the moon</a>, it discovered cryovolcanoes – geysers erupting ice and gas up to 8km high, which might indicate a subsurface ocean. </p>
<p>The proposed Trident mission would have explored these many strange things about the moon. It proposed a three-pronged approach using instruments to measure the magnetic field of Triton. It would have identified the presence and structure of a subsurface ocean. High resolution infrared cameras would have allowed the spacecraft to image the entire surface, using the sunlight reflected from Neptune, showing scientists what had changed since the last visit in 1989. Finally, the spacecraft would have tried to discover how Triton’s surface remains so dynamic and young.</p>
<p>Ultimately, Trident and IVO lost out to the Venus missions. It would have been fascinating to once again explore the outer reaches of the solar system, or see the colossal volcanoes of Io. But Venus is a fascinating planet, with mysteries and potential all of its own.</p><img src="https://counter.theconversation.com/content/162192/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ashley Spindler 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>When two missions to Venus were announced, two others missed out.Ashley Spindler, STFC Innovation Fellow, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1621332021-06-04T12:34:51Z2021-06-04T12:34:51ZNasa has announced two missions to Venus by 2030 – here’s why that’s exciting<figure><img src="https://images.theconversation.com/files/404327/original/file-20210603-13-1xi0iqy.jpeg?ixlib=rb-1.1.0&rect=23%2C31%2C1012%2C1008&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/topics/solarsystem/features/pia00104.html">NASA/JPL</a></span></figcaption></figure><p>For decades, the exploration of our solar system left one of our neighbouring planets, Venus, largely unexplored. Now, things are about to change.</p>
<p>In the latest announcement from Nasa’s <a href="https://www.nasa.gov/planetarymissions/discovery.html">solar system exploration program</a>, two missions have been given the go-ahead – and they’re both bound for <a href="https://www.nasa.gov/press-release/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus">Venus</a>. The two ambitious missions will launch between 2028 and 2030.</p>
<p>This marks a considerable change in direction for Nasa’s planetary science division, which hasn’t sent a mission to the planet since 1990. It’s exciting news for space scientists like me.</p>
<p>Venus is a hostile world. Its atmosphere contains sulphuric acid and the surface temperatures is hot enough to melt lead. But it has not always been this way. It is thought Venus started out <a href="https://theconversation.com/nasa-wants-to-send-humans-to-venus-heres-why-thats-a-brilliant-idea-104961">very similar to the Earth</a>. So what happened?</p>
<p>While on Earth, carbon is <a href="https://www.bgs.ac.uk/discovering-geology/climate-change/the-carbon-story/">mainly trapped in rocks</a>, on Venus it has escaped into the atmosphere – making it roughly 96% carbon dioxide. This has led to a runaway greenhouse effect, pushing surface temperatures up to 750 kelvin (470°C or 900°F). </p>
<p>The planet’s history makes it an excellent place to study the greenhouse effect and to learn how to manage it on Earth. We can use models which plot the atmospheric extremes of Venus, and compare the results to what we see back home. </p>
<p>But, the extreme surface conditions are one of the reasons planetary exploration missions have avoided Venus. The high temperature means a very high pressure of 90 bars (equivalent to <a href="https://www.planetary.org/articles/every-picture-from-venus-surface-ever">roughly one kilometre</a> underwater) which is enough to instantly crush most planetary landers. It might not come as a surprise, then, that missions to Venus haven’t always gone to plan.</p>
<figure class="align-center ">
<img alt="Black and white photo showing a rocky surface of Venus." src="https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=126&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=126&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=126&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=158&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=158&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404329/original/file-20210603-13-x58sza.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=158&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Photo of the surface of Venus taken by the Venera 9 lander.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Venera_9#/media/File:Foto_de_Venera_9.png">Wikimedia/Ted Stryk</a></span>
</figcaption>
</figure>
<p>Most of the exploration done so far was carried out by the then Soviet Union between the 1960s and the 1980s. There are some notable exceptions, such as <a href="https://solarsystem.nasa.gov/missions/pioneer-venus-1/in-depth/">Nasa’s Pioneer Venus mission</a> in 1972 and the European Space Agency’s <a href="https://www.esa.int/Enabling_Support/Operations/Venus_Express">Venus Express</a> mission in 2006. </p>
<p>The first landing happened in 1970, when the Soviet Union’s Venera 7 crashed due to the parachute melting. But it managed to transmit 20 minutes of data back to Earth. The first surface images were taken by Venera 9, followed by <a href="https://www.planetary.org/articles/every-picture-from-venus-surface-ever">Veneras 10, 13 and 14</a>.</p>
<h2>The descent mission</h2>
<p>The first of the two selected Nasa missions will be known as Davinci+ (a shortening of Deep Atmosphere of Venus Investigations of Noble Gases, Chemistry and Imaging). It includes a descent probe, meaning it will be dropped through the atmosphere, taking measurements as it goes. The descent has three stages with the first investigating the entire atmosphere.</p>
<p>The probe will be looking at the composition of the atmosphere in detail, providing information on each layer as it falls. We know sulphuric acid is <a href="http://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Acid_clouds_and_lightning">confined to cloud layers</a> at around 50km (30 miles) up, and we know that the atmosphere is 97% carbon dioxide. But studying trace elements can provide information on how the atmosphere ended up in this state. The second stage will be looking at lower altitudes to measure weather properties such as wind speed, temperature and pressure in detail.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/venus-was-once-more-earth-like-but-climate-change-made-it-uninhabitable-150445">Venus was once more Earth-like, but climate change made it uninhabitable</a>
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<p>The last stage take surface images in high resolution. While this is very common for Mars, it has always been a challenge on Venus. The thick cloud layer means visible light is reflected, so observing from Earth or from orbit isn’t practical. The intense surface conditions also mean rovers are impractical. One suggestion has been <a href="https://theconversation.com/nasa-wants-to-send-humans-to-venus-heres-why-thats-a-brilliant-idea-104961">a balloon mission</a>. </p>
<p>We have a low resolution image of the surface of Venus, thanks to Nasa’s Magellan mission in 1990, which mapped the surface using radar. The Davinci probe will take surface images using infrared light during its descent. These pictures will not only allow better planning for future missions but also help scientists investigate how the surface formed.</p>
<figure> <img src="https://cdn.theconversation.com/static_files/files/1597/Venus.gif?1622734777"><figcaption>The surface of Venus seen in radio waves, taken from the Magellan mission.</figcaption></figure>
<h2>Mapping the surface</h2>
<p>The second mission is called Veritas, short for Venus Emissivity, Radio science, InSAR, Topography and Spectroscopy. This will be a more standard planetary mission. The orbiter will carry <a href="https://www.universetoday.com/147027/more-details-on-nasas-veritas-mission-which-could-go-to-venus/">two instruments on board</a> to map the surface, complementing the detailed infrared observations from Davinci. </p>
<p>The first of these is a camera that observes in a range of wavelengths. It can see through the Venusian clouds, to investigate atmospheric and ground composition. This task is very difficult, as the surface temperature causes the reflected light to have a very broad range of wavelengths. Veritas will compensate for this using techniques often used to study the atmospheres of exoplanets.</p>
<p>The wavelength camera will also look for signs of water vapour. The Venus Express mission showed that the main elements escaping the Venusian atmosphere <a href="https://sci.esa.int/web/venus-express/-/54068-7-water-loss">are hydrogen and oxygen</a>, so if there’s any water it will be in tiny amounts, or deep under the surface.</p>
<p>The second instrument is a radar and utilises a technique used extensively on Earth observation satellites. A very large active radio receiver – important for high resolution images – is simulated using radio pulses pointed at <a href="https://earthdata.nasa.gov/learn/backgrounders/what-is-sar">different angles</a>
in front of the spacecraft. The high resolution radar images will create a more detailed map to investigate the surface evolution of Venus, as well as determine if there is any tectonic or volcanic activity.</p>
<figure class="align-center ">
<img alt="Computer-generated view of the surface of Venus" src="https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404328/original/file-20210603-23-1t20lqy.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The surface of Venus.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/multimedia/imagegallery/image_feature_358.html">NASA/JPL</a></span>
</figcaption>
</figure>
<p>These missions could also add evidence to a theory that the Venusian surface completely melted and reformed 500 million years ago. This came about to explain the lack of meteorite impacts on the surface, but so far no evidence has been found a volcanic lava layer which would result from such <a href="https://www.newscientist.com/article/dn10427-venuss-surface-may-be-much-older-than-thought">resurfacing</a>.</p>
<p>It is exciting that Nasa has turned its planetary mission view towards Venus. For any budding astronauts I’m afraid the chance of <a href="https://theconversation.com/nasa-wants-to-send-humans-to-venus-heres-why-thats-a-brilliant-idea-104961">sending a human there</a> any time soon is non-existent. But, the information that can be gained from Earth’s largely forgotten sister will be of very high value for understanding our world.</p><img src="https://counter.theconversation.com/content/162133/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>Nasa’s sending its first missions to Earth’s twin since 1990.Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1620802021-06-04T01:47:36Z2021-06-04T01:47:36ZNASA is returning to Venus, where surface temperatures are 470°C. Will we find life when we get there?<figure><img src="https://images.theconversation.com/files/404401/original/file-20210604-13-128m0ja.jpg?ixlib=rb-1.1.0&rect=194%2C26%2C3400%2C2365&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>NASA has selected two missions, dubbed DAVINCI+ and VERITAS, to study the “<a href="https://www.jpl.nasa.gov/news/nasa-selects-2-missions-to-study-lost-habitable-world-of-venus">lost habitable</a>” world of Venus. Each mission will receive approximately US$500 million for development and both are expected to launch between 2028 and 2030.</p>
<p>It had long been thought there was no life on Venus, due to its extremely high temperatures. But late last year, scientists studying the planet’s atmosphere announced the surprising (and somewhat <a href="https://www.nature.com/articles/s41550-020-1174-4">controversial</a>) <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091327">discovery</a> of phosphine. On Earth, this chemical is produced primarily by living organisms.</p>
<p>The news sparked renewed interest in Earth’s “<a href="https://www.space.com/venus-earth-twin-evolution-life-search.html#">twin</a>”, prompting NASA to plan state-of-the-art missions to look more closely at the planetary environment of Venus — which could hint at life-bearing conditions. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/if-there-is-life-on-venus-how-could-it-have-got-there-origin-of-life-experts-explain-146407">If there is life on Venus, how could it have got there? Origin of life experts explain</a>
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<h2>Conditions for life</h2>
<p>Ever since the Hubble Space Telescope revealed the sheer number of nearby galaxies, astronomers have become obsessed with searching for exoplanets in other star systems, particularly ones that appear habitable. </p>
<p>But there are certain criteria for a planet to be considered habitable. It must have a suitable temperature, atmospheric pressure similar to Earth’s and availabile water. </p>
<p>In this regard, Venus probably wouldn’t have attracted much attention if it were outside our solar system. Its skies are filled with thick clouds of sulphuric acid (which is dangerous for humans), the land is a desolate backdrop of extinct volcanoes and 90% of the surface is covered in red hot lava flows.</p>
<p>Despite this, NASA will search the planet for environmental conditions that may have once supported life. In particular, any evidence that Venus may have once had an ocean would change all our existing models of the planet.</p>
<p>And interestingly, conditions on Venus are far less harsh at a height of about 50km above the surface. In fact, the pressure at these higher altitudes eases so much that conditions become much more Earth-like, with breathable air and balmy temperatures. </p>
<p>If life (in the form of microbes) does exist on Venus, this is probably where it would be found.</p>
<h2>The DAVINCI+ probe</h2>
<p>NASA’s DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission has several science goals, relating to:</p>
<p><strong>Atmospheric origin and evolution</strong></p>
<p>It will aim to understand the atmospheric origins on Venus, focusing on how it first formed, how it evolved and how (and why) it is different from the atmospheres of Earth and Mars.</p>
<p><strong>Atmospheric composition and surface interaction</strong></p>
<p>This will involve understanding the history of water on Venus and the chemical processes at work in its lower atmosphere. It will also try to determine whether Venus ever had an ocean. Since life on Earth started in our oceans, this would become the starting point in any search for life. </p>
<p><strong>Surface properties</strong></p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=941&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=941&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=941&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1183&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1183&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404153/original/file-20210603-13-1s1g1d0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1183&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An artist’s concept of the NASA DAVINCI+ probe descending in stages to the surface of Venus.</span>
<span class="attribution"><span class="source">NASA/GSFC</span></span>
</figcaption>
</figure>
<p>This aspect of the mission will provide insights into geographically complex <a href="https://en.wikipedia.org/wiki/Tessera_(Venus)">tessera</a> regions on Venus (which have highly deformed terrain), and will investigate their origins and tectonic, volcanic and weathering history. </p>
<p>These findings could shed light on how Venus and Earth began similarly and then diverged in their evolution. </p>
<p>The DAVINCI+ spacecraft, upon arrival at Venus, will drop a spherical probe full of sensitive instruments through the planet’s atmosphere. During its descent, the probe will sample the air, constantly measuring the atmosphere as it falls and returning the measurements back to the orbiting spacecraft. </p>
<p>The probe will carry a mass spectrometer, which can measure the mass of different molecules in a sample. This will be used to detect any <a href="https://www.britannica.com/science/noble-gas">noble gases</a> or other trace gases in Venus’s atmosphere. </p>
<p>In-flight sensors will also help measure the dynamics of the atmosphere, and a camera will take high-contrast images during the probe’s descent. Only four spacecraft have ever returned <a href="https://www.planetary.org/articles/every-picture-from-venus-surface-ever">images from the surface of Venus</a>, and the last such photo was taken in 1982. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404157/original/file-20210603-23-1k94i8z.jpeg?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">Maat Mons is the highest shield volcano on Venus and the second-highest mountain on the planet.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<h2>VERITAS</h2>
<p>Meanwhile, the <a href="https://www.jpl.nasa.gov/news/veritas-exploring-the-deep-truths-of-venus">VERITAS</a> (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) mission will map surface features to determine the planet’s geologic history and further understand why it developed so differently to Earth. </p>
<p>Historical geology provides important information about ancient changes in climate, volcanic eruptions and earthquakes. This data can be used to anticipate the possible size and frequency of future events. </p>
<p>The mission will also seek to understand the internal geodynamics that shaped the planet. In other words, we may be able to build a picture of Venus’s continental plate movements and compare it with Earth’s.</p>
<p>In parallel with DAVINCI+, VERITAS will take planet-wide, high-resolution topographic images of Venus’s surface, mapping surface features including mountains and valleys.</p>
<p>At the same time, the <a href="https://doi.org/10.1117/12.2025582">Venus Emissivity Mapper</a> (VEM) instrument on board the orbiting VERITAS spacecraft will map emissions of gas from the surface, with such accuracy that it will be able to detect near-surface water vapour. Its sensors are so powerful they will be able to see through the thick clouds of sulphuric acid.</p>
<h2>Key insight into conditions on Venus</h2>
<p>The most exciting thing about these two missions is the orbit-to-surface probe. In the 1980s, four landers made it to the surface of Venus, but could only operate for two days due to crushing pressure. The pressure there is 93 bar, which is the same as being 900m below sea level on Earth.</p>
<p>Then there’s the lava. Many lava flows on Venus stretch for several hundred kilometres. And this lava’s mobility may be enhanced by the planet’s average surface temperature of about 470°C.</p>
<p>Meanwhile, <a href="https://geology.com/stories/13/venus-volcanoes/">“shield” volcanoes</a> on Venus are an impressive 700km wide at the base, but only about 5.5km high on average. The largest shield volcano on Earth, <a href="https://www.arcgis.com/apps/MapTour/index.html?appid=d9eabc7a3c64462bb964d1d4bbd765de">Mauna Loa</a> in Hawaii, is only 120km wide at the base.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Idunn Mons volcano on Venus." src="https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=336&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=336&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=336&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=422&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=422&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404398/original/file-20210604-23-1xjmzpq.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=422&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are only three bodies in our solar system with confirmed active fire volcanoes: Earth, Mars and Jupiter’s Io moon. But recent research has proposed Idunn Mons (pictured), a volcanic peak on Venus, may still be active.</span>
<span class="attribution"><span class="source">EarthSky</span></span>
</figcaption>
</figure>
<p>The information obtained from DAVINCI+ and VERITAS will provide crucial insight into not only how Venus formed, but how any rocky, life-giving planet forms. Ideally, this will equip us with valuable markers to look for when searching for habitable worlds outside our solar system. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/venus-was-once-more-earth-like-but-climate-change-made-it-uninhabitable-150445">Venus was once more Earth-like, but climate change made it uninhabitable</a>
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</p>
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<img src="https://counter.theconversation.com/content/162080/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gail Iles does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Venus wouldn’t attract much attention if it were outside our solar system. Its skies are filled with sulphuric acid, its land abounds with extinct volcanoes and its surface is mostly red hot lava.Gail Iles, Senior Lecturer in Physics, RMIT UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1554472021-04-06T04:48:28Z2021-04-06T04:48:28ZClimate explained: rising carbon emissions (probably) won’t make the Earth uninhabitable<figure><img src="https://images.theconversation.com/files/389486/original/file-20210315-24-b9l6t3.jpg?ixlib=rb-1.1.0&rect=1149%2C0%2C4841%2C3035&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock/Jurik Peter </span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to <a href="mailto:climate.change@stuff.co.nz">climate.change@stuff.co.nz</a></em></p>
<hr>
<blockquote>
<p><strong>Even with all humanity’s carbon emissions to date, there’s a lot less carbon dioxide in Earth’s atmosphere than Venus, and Earth is further away from the Sun. But if carbon emissions continue at the current rate, is there any risk of reaching a tipping point at which a runaway greenhouse effect takes over, making Earth uninhabitable for any form of life?</strong></p>
</blockquote>
<p>When sunlight enters the Earth’s atmosphere, some is reflected back to space by clouds, some is reflected by bright surfaces such as ice and snow and some is absorbed by the land surface and ocean.</p>
<p>To maintain a balance, the Earth emits energy back to space in the form of infrared, or longwave, radiation. Some longwave radiation is absorbed in the atmosphere by heat-trapping gases, such as carbon dioxide.</p>
<p>This is the well-known <a href="https://theconversation.com/climate-explained-what-earth-would-be-like-if-we-hadnt-pumped-greenhouse-gases-into-the-atmosphere-141194">greenhouse effect</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-what-earth-would-be-like-if-we-hadnt-pumped-greenhouse-gases-into-the-atmosphere-141194">Climate Explained: what Earth would be like if we hadn't pumped greenhouse gases into the atmosphere</a>
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<hr>
<p>As is already well established, concentrations of carbon dioxide have increased over the past 250 years, <a href="http://berkeleyearth.org/january-2021-temperature-update/">causing the average surface temperature to increase</a>.</p>
<p>One consequence of increasing atmospheric carbon dioxide concentrations is that, as the atmosphere warms, it can contain more water vapour. Since <a href="https://www.nasa.gov/topics/earth/features/vapor_warming.html">water vapour</a> is itself a greenhouse gas, this can create an amplifying effect.</p>
<p>In general, as surface temperature increases, the Earth emits more longwave radiation to space to maintain the energy balance. But there is a limit to how much longwave radiation can be emitted.</p>
<p>If the atmosphere becomes completely saturated with water vapour, the Earth’s surface and lower atmosphere warm up, but further increases in emission of longwave radiation are not possible.</p>
<h2>The runaway greenhouse</h2>
<p>This is termed a <a href="https://royalsocietypublishing.org/doi/10.1098/rsta.2012.0004" title="The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres">runaway greenhouse</a> and would mean the Earth would become lethally hot and unable to cool itself by emitting heat to space.</p>
<p>Ultimately, this is the fate of the Earth. In billions of years from now the Sun will become brighter and grow into a Red Dwarf. As the Sun’s luminosity increases, the Earth will become hotter and its oceans will evaporate.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/p24SQlhJVZo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">We’re doomed … but not for billions of years.</span></figcaption>
</figure>
<p>The hot and steamy atmosphere will ensure the Earth is just as uninhabitable to current life-forms as Venus is today.</p>
<p>But could we bring such a situation about on a shorter timeframe through continued carbon dioxide emissions? The good news is, probably not.</p>
<h2>We’re safe, for now</h2>
<p><a href="https://www.pnas.org/content/115/41/10293" title="Earth’s outgoing longwave radiation linear due to H2O greenhouse effect">Previous research</a> has found that, due to differences in the properties of water vapour and carbon dioxide as greenhouse gases, adding carbon dioxide to the atmosphere is likely insufficient to trigger a runaway greenhouse. </p>
<p>Atmospheric carbon dioxide is currently around <a href="https://www.co2.earth/daily-co2">416 parts per million (ppm)</a> – up from <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide">approximately 280 ppm</a> since the first industrial revolution began, some 250 years ago.</p>
<p>In geological terms, this is a very large increase to take place over a short period of time. Yet human emissions of carbon dioxide are considered <a href="https://www.nature.com/articles/ngeo1892" title="Low simulated radiation limit for runaway greenhouse climates">insufficient</a> to trigger a runaway greenhouse, given the fossil fuel reserves available.</p>
<p>The Earth should be safe from a runaway greenhouse developing for <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL058376" title="Delayed onset of runaway and moist greenhouse climates for Earth">at least another 1.5 billion years</a>.</p>
<h2>But then …</h2>
<p>The caveat to all the above is that the models scientists use to study future climate are built based on past, known conditions. It is therefore difficult to predict how certain parts of the climate system might operate under extremely high greenhouse gas emissions scenarios.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Clouds hiding the Sun but with rays of light emerging from behind top." src="https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/389498/original/file-20210315-21-ia3ukf.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">Clouds can reflect sunlight back to space.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/scheendijk/15242655742/">Flickr/scheendijk</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For example, clouds can reflect sunlight back to space, or they can trap heat emitted by the Earth. In a warming world, scientists are still unclear on the <a href="https://theconversation.com/why-clouds-are-the-missing-piece-in-the-climate-change-puzzle-140812">role clouds will play</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/expect-the-new-normal-for-nzs-temperature-to-get-warmer-153291">Expect the new normal for NZ's temperature to get warmer</a>
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</em>
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<p>While a runaway greenhouse would make Earth completely uninhabitable to life as we know it, the losses that may accrue from just a few degrees Celsius of global warming are serious and must not be discounted.</p>
<p><a href="https://theconversation.com/au/topics/sea-level-rise-6790">Sea level rise</a>, increased frequency and intensity of <a href="https://theconversation.com/au/topics/extreme-weather-3799">extreme weather</a> events, threats to endangered species and unique <a href="https://theconversation.com/existential-threat-to-our-survival-see-the-19-australian-ecosystems-already-collapsing-154077">ecosystems</a> are just a few of the many reasons we have to be concerned.</p>
<p>The silver lining is we (probably) don’t need to worry about becoming like our neighbour Venus any time soon.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/o-KMLF-OPtg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">We’re not heading this way just yet.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/155447/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Revell receives funding from the Royal Society of New Zealand Marsden Fund, the Deep South National Science Challenge and the Ministry for Business, Innovation and Employment.</span></em></p>The Earth should be safe (and habitable) for a few billions of years, but we still need to worry about the impact now of just a few degrees of global warming.Laura Revell, Senior Lecturer in Environmental Physics, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1504452020-12-13T13:04:34Z2020-12-13T13:04:34ZVenus was once more Earth-like, but climate change made it uninhabitable<figure><img src="https://images.theconversation.com/files/373102/original/file-20201204-23-kssues.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3500&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's rendering of the surface of Venus.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of 450°C (the temperature of an oven’s self-cleaning cycle) and an atmosphere dominated by carbon dioxide (96 per cent) with a density 90 times that of Earth’s. </p>
<p>Venus is a very strange place, totally uninhabitable, except perhaps in the clouds some 60 kilometres up where <a href="https://doi.org/10.1038/s41550-020-1174-4">the recent discovery of phosphine may suggest floating microbial life</a>. But the surface is totally inhospitable.</p>
<p>However, Venus once likely had an Earth-like climate. According to recent climate modelling, for much of its history <a href="https://doi.org/10.1002/2016GL069790">Venus had surface temperatures similar to present day Earth</a>. It likely also had oceans, rain, perhaps snow, maybe continents and plate tectonics, and even more speculatively, perhaps even surface life. </p>
<p>Less than one billion years ago, the climate dramatically changed due to a runaway greenhouse effect. It can be speculated that an intensive period of volcanism pumped enough carbon dioxide into the atmosphere to cause this great climate change event that <a href="https://doi.org/10.1029/2019JE006276">evaporated the oceans and caused the end of the water cycle</a>.</p>
<h2>Evidence of change</h2>
<p>This hypothesis from the climate modellers inspired Sara Khawja, a master’s student in my group (co-supervised with geoscientist Claire Samson), to look for <a href="https://doi.org/10.1038/s41467-020-19336-1">evidence in Venusian rocks for this proposed climatic change event</a>. </p>
<p>Since the early 1990s, my Carleton University research team — and more recently my Siberian team at Tomsk State University — have been mapping and interpreting the geological and tectonic history of Earth’s remarkable sister planet.</p>
<p>Soviet Venera and Vega missions of the 1970s and 1980s did land on Venus and take pictures and evaluated the composition of the rocks, before <a href="https://doi.org/10.1016/j.pss.2007.09.005">the landers failed due to the high temperature and pressure</a>. However, our most comprehensive view of the surface of Venus has been provided by <a href="https://nssdc.gsfc.nasa.gov/planetary/magellan.html">NASA’s Magellan spacecraft in the early 1990s</a>, which used radar to see through the dense cloud layer and produce detailed images of more than 98 per cent of Venus’s surface.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/yUrIzPRI4GE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A visualization of Venus’s surface produced by radar on board the Magellan spacecraft.</span></figcaption>
</figure>
<h2>Ancient rocks</h2>
<p>Our search for geological evidence of the great climate change event led us to focus on the oldest type of rocks on Venus, called tesserae, which have a complex appearance suggestive of a long, complicated geological history. We thought that these oldest rocks had the best chance of preserving evidence of water erosion, which is a such an important process on Earth and should have occurred on Venus prior to the great climate change event. </p>
<p>Given poor resolution altitude data, we used an indirect technique to try to recognize ancient river valleys. We demonstrated that younger lava flows from the surrounding volcanic plains had filled valleys in the margins of tesserae. </p>
<p>To our astonishment these tesserae valley patterns were very similar to river flow patterns on Earth, leading to our suggestion that <a href="https://doi.org/10.1038/s41467-020-19336-1">these tesserae valleys were formed by river erosion during a time with Earth-like climatic conditions</a>. My <a href="http://research.earthsci.carleton.ca/ernst-lab">Venus research groups at Carleton and Tomsk State universities</a> are studying the post-tesserae lava flows for any geological evidence of the transition to extremely hot conditions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="rock surface of Venus" src="https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373126/original/file-20201204-15-1cmblr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A portion of Alpha Regio, a topographic upland on the surface of Venus, was the first feature on Venus to be identified from Earth-based radar.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/infographics/resource.view.php?id=502&catId=">(Jet Propulsion Laboratory, NASA)</a></span>
</figcaption>
</figure>
<h2>Earth analogies</h2>
<p>In order to understand how volcanism on Venus could produce such a change in climate, we can look to Earth history for analogues. We can find analogies in super-eruptions like <a href="https://doi.org/10.1130/G47384.1">the last eruption at Yellowstone that occurred 630,000 years</a>. </p>
<p>But such volcanism is small compared to large igneous provinces (LIPs) that occur approximately every 20-30 million years. These eruption events can release enough carbon dioxide to cause <a href="https://doi.org/10.1016/j.palaeo.2017.03.014">catastrophic climate change on Earth</a>, including mass extinctions. To give you a sense of scale, consider that <a href="https://www.wiley.com/en-us/Large+Igneous+Provinces%3A+A+Driver+of+Global+Environmental+and+Biotic+Changes-p-9781119507451">the smallest LIPs produce enough magma to cover all of Canada to a depth of about 10 metres</a>. The largest known LIP produced enough magma that would have covered an area the size of Canada to a depth of nearly eight kilometres. </p>
<p>The LIP analogues on Venus include individual volcanoes that are up to 500 kilometres across, extensive lava channels that reach up to 7,000 kilometres long, and there are also associated rift systems — where the crust is pulling apart — up to 10,000 kilometres long.</p>
<p>If LIP-style volcanism was the cause of the great climate change event on Venus, then could similar climate change happen on Earth? We can imagine a scenario many millions of years in the future when multiple LIPs randomly occurring at the same time could cause Earth to have such runaway climate change leading to conditions like present-day Venus.</p><img src="https://counter.theconversation.com/content/150445/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Richard Ernst receives relevant funding from a Canadian government grant (NSERC Discovery program), and a Russian government grant (Mega-Grant program)</span></em></p>A severe climate change event on Venus may have transformed an Earth-like climate to the current uninhabitable-to-humans state.Richard Ernst, Scientist-in-Residence, Earth Sciences, Carleton University (also a professor at Tomsk State University, Russia), Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1515102020-12-07T13:08:37Z2020-12-07T13:08:37ZThree scientists on what we learned from the Arecibo radio telescope<figure><img src="https://images.theconversation.com/files/373089/original/file-20201204-23-5mfera.jpg?ixlib=rb-1.1.0&rect=738%2C194%2C4291%2C2952&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Large radio telescope dish in Arecibo national observatory.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/large-radio-telescope-dish-arecibo-national-1263118288">Shutterstock/photospirit</a></span></figcaption></figure><p>Astronomers are mourning the loss of the world’s second largest radio telescope in Puerto Rico. The US National Science Foundation <a href="https://www.bbc.co.uk/news/world-us-canada-55147973">said</a> the Arecibo telescope’s 900-tonne instrument platform fell onto a reflector dish some 450ft (137 metres) below – just weeks after it was announced that the telescope would be dismantled due to safety fears.</p>
<p>It was a sad and dramatic end for this magnificent telescope (once famously scaled <a href="https://www.youtube.com/watch?v=6HFkF8904Uw">by James Bond</a>) which was the largest in the world <a href="https://www.nature.com/articles/d41586-019-02790-3">until 2019</a>. It has given so much to humanity from the start of its observations in <a href="https://www.naic.edu/ao/history">1963</a> and we all have reasons to be grateful and to celebrate. </p>
<p>We are three scientists from different fields. But we all had the good fortune of working with Arecibo in one way or another. Here are our personal perspectives and a brief list of some of its most significant discoveries.</p>
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</figure>
<h2>Philippe Blondel – ‘the message’ and Venus</h2>
<p>Surprising as it may seem, I discovered Arecibo thanks to a <a href="https://www.okapi.fr/">French journal</a> for curious children. In a 1974 issue of Okapi, it was explained how radio telescopes were used to listen to stars, to image planets and even to send interstellar radio messages. It was the year the <a href="https://en.wikipedia.org/wiki/Arecibo_message">Arecibo message</a> was broadcast into space.</p>
<p>The message was made up of basic numbers, chemistry, biology and the Earth’s location in 1,679 bits (less than a tweet). It will reach its target star system in 25,000 years – proving, if proof were needed, that Arecibo’s work will live on long after its physical demise.</p>
<p>Arecibo was also the telescope that gave us the first high-resolution <a href="https://astronomynow.com/2015/03/10/venus-revealed-in-high-resolution-radar-images-from-earth/">radar images of Venus</a>. It managed to pierce through the heavy clouds that had always limited the view of traditional optical telescopes. In 1970, it took pictures of the highly reflective Alpha and Beta regions and huge <a href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA00149">Maxwell Montes</a> mountain chains, 11km high. Then in 1988, by measuring light across several polarisations, Arecibo showed how complex the surface of Earth’s “<a href="https://www.esa.int/ESA_Multimedia/Images/2019/05/Earth_s_evil_twin#:%7E:text=Welcome%20to%20Venus.,and%20a%20sweltering%20470%C2%BAC%20surface.&text=It%20is%20a%20natural%20phenomenon%20that%20helps%20regulate%20a%20planet's%20temperature.">evil twin</a>” (almost the same size but plagued with a poisonous atmosphere of carbon dioxide and a sweltering 470ºC surface) really was. The different terrains were seen in glorious detail and helped prepare and extend the results of the <a href="https://solarsystem.nasa.gov/missions/magellan/in-depth/">Magellan mission</a>.</p>
<figure class="align-center ">
<img alt="Black and white image of venus" src="https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=322&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=322&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373093/original/file-20201204-21-1ojlk37.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=322&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Radar image of Venus taken by Arecibo. Many features, including mountain ranges, volcanic domes and craters can be seen.</span>
<span class="attribution"><a class="source" href="https://public.nrao.edu/gallery/arecibo-gbt-image-of-venus-2/">Campbell et al., (NRAO/AUI/NSF); NAIC</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Arecibo revealed how the intricate patterns of geological structures criss-cross to form tesserae (which look similar to parquet floors) that are <a href="https://uapress.arizona.edu/book/venus-ii">unique to Venus</a> and are not seen anywhere else in the solar system.</p>
<h2>Karen Masters – hydrogen</h2>
<p>A new, state-of-the-art seven pixel camera was installed at Arecibo in 2004 while I was completing my PhD in extragalactic radio astronomy. Radio pixels are very big and that camera is the size of a large refrigerator (it definitely won’t fit in your pocket). It was used to, among other things, detect hydrogen. Hydrogen is the most abundant element in the universe and it emits a characteristic radio signal, known as the “<a href="http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/h21.html">21cm line</a>”.</p>
<figure class="align-center ">
<img alt="Woman and baby daughter stand in front of radio telescope." src="https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373094/original/file-20201204-19-ahgruw.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">Karen Masters with her baby daughter at the Arecibo radio telescope in 2008.</span>
<span class="attribution"><span class="source">Karen Masters</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Many galaxies have more than enough hydrogen to be detected this way. And a detection means we can also measure how fast these galaxies are rotating and how far away they are. Arecibo’s observations of galaxies in the <a href="https://en.wikipedia.org/wiki/Perseus-Pisces_Supercluster">Pisces-Perseus supercluster</a> won Martha Haynes and Riccardo Giovanelli the <a href="http://www.nasonline.org/programs/awards/henry-draper-medal.html">1989 Henry Draper medal</a> for the first three dimensional map of this massive string like structure of galaxies. </p>
<p>Because Arecibo was so big it could detect the faintest traces of hydrogen in galaxies – the record for the most distant detections <a href="https://academic.oup.com/mnras/article/446/4/3526/2891907">was broken by Arecibo</a> and the Arecibo camera was used to complete <a href="http://egg.astro.cornell.edu/alfalfa/epo/index.php">a survey</a> which discovered numerous, tiny hydrogen-rich galaxies. These discoveries challenged our understanding of how galaxies form. </p>
<h2>Carole Mundell – The dynamic universe</h2>
<p>Although I began my career as a radio astronomer mapping hydrogen in nearby galaxies, my research interests now focus on high energy, time-variable and transient phenomena in the dynamic universe. For me, Arecibo will remain a pioneering and enduring icon in <a href="https://astronomy.ac.uk/msc/timedomain">time-domain</a> astrophysics (the study of how astronomical objects change with time).</p>
<p>From its early work on <a href="https://theconversation.com/uk/topics/pulsars-1324">pulsars</a> to recent breakthroughs in the study of mysterious radio flashes, the telescope has probed fundamental laws of physics and motivated new discoveries with other facilities around the world. </p>
<figure class="align-center ">
<img alt="Colour image of the Crab Nebula" src="https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373285/original/file-20201207-23-1mxpjx2.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">A composite image of the Crab Nebula showing the X-ray (blue) and optical (red) images superimposed.</span>
<span class="attribution"><a class="source" href="https://hubblesite.org/contents/media/images/2002/24/1248-Image.html">NASA/CXC/ASU/J. Hester et al</a></span>
</figcaption>
</figure>
<p>Highlights include <a href="https://www.naic.edu/ao/legacy-discoveries">the 1968 discovery</a> of clear evidence of a pulsar with a rotation period of 33 milliseconds in the Crab Nebula (this confirmed earlier suggestions by pulsar pioneer <a href="https://royalsociety.org/people/jocelyn-bell-burnell-11066/">Joceyln Bell Burnell</a> that the nebula appeared to be flashing). And the 1974 discovery of the <a href="https://www.naic.edu/ao/legacy-discoveries">first binary pulsar</a> (pulsars locked in orbit around a common centre of mass). </p>
<p>The measurements, taken by Russell Hulse and Joseph Taylor, confirmed the loss of energy due to gravitational radiation predicted in Einstein’s General Theory of Relativity. They had used the telescope to find a new type of pulsar which opened up new possibilities for the study of gravitation and led to their 1993 <a href="https://www.nobelprize.org/prizes/physics/1993/summary/">Nobel Prize in Physics</a>. </p>
<p>Decades of Arecibo pulsar monitoring data continue to be mined by astronomers and in <a href="https://www.nasa.gov/multimedia/imagegallery/image_feature_574.html">1992 the first exoplanet</a> was discovered around a pulsar. </p>
<p>In 2016, Arecibo discovered the first repeating <a href="https://iopscience.iop.org/article/10.1088/0004-637X/790/2/101">Fast Radio Burst</a> (very short-lived flashes of intense cosmic radio waves). The origin of these bursts is still unknown but is likely lie at cosmic distances beyond our Milky Way galaxy. The Arecibo discovery <a href="https://theconversation.com/message-from-aliens-or-colliding-objects-the-hunt-for-enigmatic-radio-bursts-is-about-to-get-real-55965">heralded a new international race</a> to solve this mystery. </p>
<p>Today, generations of astronomers around the world are grateful to the engineers who realised the dream of the world’s largest radio telescope and ensured it remained a world-leading facility. Arecibo’s discoveries still stand out and its long scientific legacy is secure.</p><img src="https://counter.theconversation.com/content/151510/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Karen Masters is a member of the Committee on Radio Frequencies of the National Academy of Sciences, and on the advisory board for the Green Bank Radio Observatory. </span></em></p><p class="fine-print"><em><span>Carole Mundell and Philippe Blondel 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 Arecibo radio telescope has collapsed but its amazing discoveries will live on.Philippe Blondel, Senior Lecturer, Department of Physics, University of BathCarole Mundell, Professor of Extragalactic Astronomy, Head of the Astrophysics Group, University of BathKaren Masters, Associate Professor of Physics and Astronomy, Haverford CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1509342020-11-26T05:06:36Z2020-11-26T05:06:36ZAncient Earth had a thick, toxic atmosphere like Venus – until it cooled off and became liveable<figure><img src="https://images.theconversation.com/files/371399/original/file-20201125-29-1q9llhb.jpg?ixlib=rb-1.1.0&rect=0%2C68%2C1920%2C1112&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Tobias Stierli / NCCR PlanetS</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Earth is the only planet we know contains life. Is our planet special? Scientists over the years have mulled over what factors are essential for, or beneficial to, life. The answers will help us identify other potentially inhabited planets elsewhere in the galaxy.</p>
<p>To understand what conditions were like in Earth’s early years, our research tried to recreate the chemical balance of the boiling magma ocean that covered the planet billions of years ago, and conducted experiments to see what kind of atmosphere it would have produced. Working with colleagues in France and the United States, we <a href="https://advances.sciencemag.org/content/6/48/eabd1387">found</a> Earth’s first atmosphere was likely a thick, inhospitable soup of carbon dioxide and nitrogen, much like what we see on Venus today.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/if-there-is-life-on-venus-how-could-it-have-got-there-origin-of-life-experts-explain-146407">If there is life on Venus, how could it have got there? Origin of life experts explain</a>
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</em>
</p>
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<h2>How Earth got its first atmosphere</h2>
<p>A rocky planet like Earth is born through a process called “accretion”, in which initially small particles clump together under the pull of gravity to form larger and larger bodies. The smaller bodies, called “planetesimals”, look like asteroids, and the next size up are “planetary embryos”. There may have been many planetary embryos in the early Solar System, but the only one that still survives is Mars, which is not a fully fledged planet like Earth or Venus.</p>
<p>The late stages of accretion involve giant impacts that release enormous amounts of energy. We think the last impact in Earth’s accretion involved a Mars-sized embryo hitting the growing Earth, spinning off our Moon, and melting most or all of what was left. </p>
<p>The impact would have left Earth covered in a global sea of molten rock called a “magma ocean”. The magma ocean would have leaked hydrogen, carbon, oxygen and nitrogen gases, to form Earth’s first atmosphere. </p>
<h2>What the first atmosphere was like</h2>
<p>We wanted to know exactly what kind of atmosphere this would have been, and how it would have changed as it, and the magma ocean beneath, cooled down. The crucial thing to understand is what was happening with the element oxygen, because it controls how the other elements combine. </p>
<p>If there was little oxygen around, the atmosphere would have been rich in hydrogen (H₂), ammonia (NH₃) and carbon monoxide (CO) gases. With abundant oxygen, it would have been made of a much friendlier mix of gases: carbon dioxide (CO₂), water vapour (H₂O) and molecular nitrogen (N₂).</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/the-rise-and-fall-of-oxygen-18954">The rise and fall of oxygen</a>
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</em>
</p>
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<p>So we needed to work out the chemistry of oxygen in the magma ocean. The key was to determine how much oxygen was chemically bonded to the element iron. If there’s a lot of oxygen, it bonds to iron in a 3:2 ratio, but if there is less oxygen we see a 1:1 ratio. The actual ratio may vary between these extremes. </p>
<p>When the magma ocean eventually cooled down, it became Earth’s mantle (the layer of rock beneath the planet’s crust). So we made the assumption that the oxygen-iron bonding ratios in the magma ocean would have been the same as they are in the mantle today. </p>
<p>We have plenty of samples of the mantle, some brought to the surface by volcanic eruptions and others by tectonic processes. From these, we could work out how to put together a matching mix of chemicals in the laboratory.</p>
<h2>In the lab</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=844&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=844&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=844&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1061&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1061&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371409/original/file-20201126-25-17e307k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1061&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the experiments we levitated a miniature magma ocean on a stream of gases, kept molten by the heat of a powerful laser. This allowed us to calibrate the chemical reaction between iron and oxygen in the magma and relate this to the composition of the atmosphere.</span>
<span class="attribution"><span class="source">IPGP</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We determined this atmosphere was composed of CO₂ and H₂O. Nitrogen would have been in its elemental form (N₂) rather than the toxic gas ammonia (NH₃). </p>
<p>But what would have happened when the magma ocean cooled down? It seems the early Earth cooled enough for the water vapour to condense out of the atmosphere, forming oceans of liquid water like we see today. This would have left an atmosphere with 97% CO₂ and 3% N₂, at a total pressure roughly 70 times today’s atmospheric pressure. Talk about a greenhouse effect! But the Sun was <a href="https://en.wikipedia.org/wiki/Faint_young_Sun_paradox#Carbon_dioxide_as_a_greenhouse_gas">less than three-quarters</a> as bright then as it is now. </p>
<h2>How Earth avoided the fate of Venus</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=616&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=616&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=616&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=774&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=774&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371429/original/file-20201126-17-8z655k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=774&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 ultraviolet view shows bands of clouds in the atmosphere of Venus.</span>
<span class="attribution"><a class="source" href="http://www.darts.isas.jaxa.jp/pub/doi/VCO-00003.html">ISAS / JAXA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>This ratio of CO₂ to N₂ is strikingly like the present atmosphere on Venus. So why did Venus, but not Earth, retain the hellishly hot and toxic environment we observe today? </p>
<p>The answer is that Venus was too close to the Sun. It simply never cooled down enough to form water oceans. Instead, the H₂O in the atmosphere stayed as water vapour and was slowly but inexorably lost to space. </p>
<p>On the early Earth, the water oceans instead slowly but steadily drew down CO₂ from the atmosphere by reaction with rock – a reaction known to science for the past 70 years as the “<a href="https://pubs.geoscienceworld.org/msa/ammin/article/104/10/1365/573790/Carbonation-and-the-Urey-reaction">Urey reaction</a>”, after the Nobel prizewinner who discovered it – and reducing atmospheric pressure to what we observe today. </p>
<p>So, although both planets started out almost identically, it is their different distances from the Sun that put them on divergent paths. Earth became more conducive to life while Venus became increasingly inhospitable.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ancient-minerals-on-earth-can-help-explain-the-early-solar-system-46991">Ancient minerals on Earth can help explain the early solar system</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/150934/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Antony Burnham receives funding from the Australian Synchrotron. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357.</span></em></p><p class="fine-print"><em><span>Hugh O'Neill received funding from the Australian Research Council (grant FL130100066)</span></em></p>Unlike our hellish neighbour Venus, Earth was far enough from the Sun for liquid water to form and create a more hospitable environment for life.Antony Burnham, Research Fellow, Research School of Earth Sciences, Australian National UniversityHugh O'Neill, Professor, Research School of Earth Sciences, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1464072020-09-20T19:42:37Z2020-09-20T19:42:37ZIf there is life on Venus, how could it have got there? Origin of life experts explain<figure><img src="https://images.theconversation.com/files/358781/original/file-20200918-18-1xkxztj.jpg?ixlib=rb-1.1.0&rect=71%2C35%2C5919%2C3458&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The <a href="https://theconversation.com/life-on-venus-traces-of-phosphine-may-be-a-sign-of-biological-activity-146093">recent discovery of phosphine</a> in the atmosphere of Venus is exciting, as it may serve as a potential sign of life (among other possible explanations). </p>
<p>The researchers, who <a href="https://www.nature.com/articles/s41550-020-1174-4">published their findings in Nature Astronomy</a>, couldn’t really explain how the phosphine got there. </p>
<p>They explored all conceivable possibilities, including lightning, volcanoes and even delivery by meteorites. But each source they modelled couldn’t produce the amount of phosphine detected.</p>
<p>Most phosphine in Earth’s atmosphere is produced by living microbes. So the possibility of life on Venus producing phosphine can’t be ignored. </p>
<p>But the researchers, led by UK astronomer Jane Greaves, say their discovery “is not robust evidence for life” on Venus. Rather, it’s evidence of “anomalous and unexplained chemistry”, of which biological processes are just one possible origin.</p>
<p>If life were to exist on Venus, how could it have come about? Exploring the origins of life on Earth might shed some light.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/life-on-venus-traces-of-phosphine-may-be-a-sign-of-biological-activity-146093">Life on Venus? Traces of phosphine may be a sign of biological activity</a>
</strong>
</em>
</p>
<hr>
<h2>The ingredients for life (as we know it)</h2>
<p>Understanding how life formed on Earth not only helps us understand our own origins, but could also provide insight into the key ingredients needed for life, as we know it, to form. </p>
<p>The details around the origins of life on Earth are still shrouded in mystery, with <a href="https://www.scientificamerican.com/article/lifes-origins-by-land-or-sea-debate-gets-hot/">multiple competing scientific theories</a>. But most theories include a common set of environmental conditions considered vital for life. These are: </p>
<p><strong>Liquid water</strong></p>
<p>Water is needed to dissolve the molecules needed for life, to facilitate their chemical reactions. Although other solvents (such as methane) have been suggested to potentially support life, water is most likely. This is because it <a href="http://sitn.hms.harvard.edu/uncategorized/2019/biological-roles-of-water-why-is-water-necessary-for-life/">can dissolve a huge range of different molecules</a> and is found throughout the universe.</p>
<p><strong>Mild temperatures</strong> </p>
<p>Temperatures higher than 122°C destroy most complex organic molecules. This would make it almost impossible for carbon-based life to form in very hot environment. </p>
<p><strong>A process to concentrate molecules</strong> </p>
<p>As the origin of life would have required a large amount of organic molecules, a process to concentrate organics from the diluted surrounding environment would be required – either through absorption onto mineral surfaces, evaporation or floating on top of water in oily slicks. </p>
<p><strong>A complex natural environment</strong></p>
<p>For life to have originated, there would have had to be a complex natural environment wherein a diverse range of conditions (temperature, pH and salt concentrations) could create chemical complexity. Life itself is incredibly complex, so even the most primitive versions would need a complex environment to originate.</p>
<p><strong>Trace metals</strong></p>
<p>A range of trace metals, amassed through water-rock interactions, would be needed to promote the formation of organic molecules.</p>
<p>So if these are the conditions required for life, what does that tell us about the likelihood of life forming on Venus? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photo of Venus" src="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358787/original/file-20200918-14-6vka30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Venus has 90 times the atmospheric pressure of Earth.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<h2>It’s unlikely today …</h2>
<p>The possibility of life as we know it forming on the surface of present-day Venus is incredibly low. An average surface temperature above 400°C means the surface can’t possibly have liquid water and this heat would also destroy most organic molecules. </p>
<p>Venus’s milder upper atmosphere, however, has temperatures low enough for water droplets to form and thus could potentially be suitable for the formation of life. </p>
<p>That said, this environment has its own limitations, such as clouds of sulfuric acid which would destroy any organic molecules not protected by a cell. For example, on Earth, molecules such as DNA are rapidly destroyed by acidic conditions, although some <a href="https://sciencing.com/types-bacteria-living-acidic-ph-9296.html">bacteria can survive</a> in extremely acidic environments.</p>
<p>Also, the constant falling of water droplets from Venus’s atmosphere down to its extremely hot surface would destroy any unprotected organic molecules in the droplets. </p>
<p>Beyond this, with no surfaces or mineral grains in the Venusian atmosphere on which organic molecules could concentrate, any chemical building blocks for life would be scattered through a diluted atmosphere – making it incredibly difficult for life to form. </p>
<h2>… but possibly less unlikely in the past</h2>
<p>Bearing all this in mind, if atmospheric phosphine is indeed a sign of life on Venus, there are three main explanations for how it could have formed. </p>
<p>Life may have formed on the planet’s surface when its conditions were very different to now. </p>
<p>Modelling suggests the surface of early Venus was very similar to early Earth, with lakes (or even oceans) of water and <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">mild conditions</a>. This was before a runaway greenhouse effect turned the planet into the hellscape it is today.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Computer generated surface view of Eistla Regio region on Venus." src="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=587&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=587&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358782/original/file-20200918-16-1s8z2gp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=587&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 is a computer-generated picture of the Eistla Regio region on Venus’s surface.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>If life formed back then, it might have adapted to spread into the clouds. Then, when intense climate change boiled the oceans away – killing all surface-based life – microbes in the clouds would have become the last outpost for life on Venus.</p>
<p>Another possibility is that life in Venus’s atmosphere (if there is any) came from Earth. </p>
<p>The planets of our inner solar system have been documented to exchange materials in the past. When meteorites crash into a planet, they can send that planet’s rocks hurtling into space where they occasionally intersect with the orbits of other planets.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/meteorites-from-mars-contain-clues-about-the-red-planets-geology-130104">Meteorites from Mars contain clues about the red planet's geology</a>
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<p>If this happened between Earth and Venus at some point, the rocks from Earth may have contained microbial life that could have adapted to Venus’s highly acidic clouds (similar to Earth’s acid-resistant bacteria).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Rendered image of meteorite hitting Earth." src="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=483&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=483&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358784/original/file-20200918-16-7blw0k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=483&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">If rocks from Earth containing microbial life entered Venus’s orbit in the past, this life may have adapted to Venus’s atmospheric conditions.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A truly alien explanation</h2>
<p>The third explanation to consider is that a truly alien form of life (life as we <em>don’t</em> know it) could have formed on Venus’s 400°C surface and survives there to this day. </p>
<p>Such a foreign life probably wouldn’t be carbon-based, as nearly all complex carbon molecules break down at extreme temperatures. </p>
<p>Although carbon-based life produces phosphine on Earth, it’s impossible to say <em>only</em> carbon-based life can produce phosphine. Therefore, even if totally alien life exists on Venus, it may produce molecules that are still recognisable as a potential sign of life. </p>
<p>It’s only through further missions and research that we can find out whether there is, or was, life on Venus. As prominent scientist Carl Sagan <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114207/#:%7E:text=non%2Dlocal%20perception-,Introduction,et%20al.%2C%201999">once said</a>: “extraordinary claims require extraordinary evidence”. </p>
<p>Luckily, two of the <a href="https://www.nasa.gov/press-release/nasa-selects-four-possible-missions-to-study-the-secrets-of-the-solar-system">four finalist proposals</a> for NASA’s next round of funding for planetary exploration are focused on Venus.</p>
<p>These include VERITAS, an orbiter proposed to map the surface of Venus, and DAVINCI+, proposed to drop through the planet’s skies and sample different atmospheric layers on the way down.</p><img src="https://counter.theconversation.com/content/146407/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Steller receives funding from a Research Training Program scholarship provided by the Australian government. </span></em></p><p class="fine-print"><em><span>Martin Van Kranendonk receives funding from the Australian Research Council and BHP. </span></em></p>Considering what we know about the key ingredients for life’s formation on Earth, here are three explanations for how this process may have occurred on our sister planet.Luke Steller, PhD Student, UNSW SydneyMartin Van Kranendonk, Professor and Head of School, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1461852020-09-18T12:07:59Z2020-09-18T12:07:59ZThe detection of phosphine in Venus’ clouds is a big deal – here’s how we can find out if it’s a sign of life<figure><img src="https://images.theconversation.com/files/358693/original/file-20200917-16-6y1m7g.png?ixlib=rb-1.1.0&rect=93%2C1%2C1005%2C671&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A radar mosaic image of Venus.</span> <span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/stellar_items/image_files/3_feature_1600x900_venus.jpg">NASA.gov</a></span></figcaption></figure><p>On Sept. 14, 2020, a new planet was added to the list of potentially habitable worlds in the Solar System: Venus. </p>
<p><a href="https://en.wikipedia.org/wiki/Phosphine">Phosphine</a>, a toxic gas made up of one phosphorus and three hydrogen atoms (PH₃), <a href="https://news.mit.edu/2019/phosphine-aliens-stink-1218">commonly produced by organic life forms</a> but otherwise difficult to make on rocky planets, <a href="https://doi.org/10.1038/s41550-020-1174-4">was discovered in the middle layer of the Venus atmosphere.</a> This raises the tantalizing possibility that something is alive on our planetary neighbor. With this discovery, Venus joins the exalted ranks of Mars and the icy moons Enceladus and Europa among planetary bodies where life may once have existed, or perhaps might even still do so today.</p>
<p>I’m a planetary scientist and something of a <a href="https://twitter.com/ThePlanetaryGuy/status/1306052714074443776?s=20">Venus evangelical</a>. This discovery is one of the most exciting made about Venus in a very long time — and opens up a new set of possibilities for further exploration in search of life in the Solar System. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358687/original/file-20200917-20-1mupw8q.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Venus as seen in the infrared by the Japanese Akatsuki spacecraft. The warm colors are from the hot lower atmosphere glowing through the cooler cloud layers above. Image credit: JAXA/ISAS/DARTS/Damia Bouic.</span>
<span class="attribution"><a class="source" href="https://planetary.s3.amazonaws.com/web/assets/pictures/20180113_ir2_20160927_090331_226_l2b_v10_PRGB.jpg">JAXA/ISAS/DARTS/Damia Bouic</a></span>
</figcaption>
</figure>
<h2>Atmospheric mysteries</h2>
<p>First, it’s critical to point out that this detection does not mean that astronomers have found alien life in the clouds of Venus. Far from it, in fact. </p>
<p>Although the discovery team identified phosphine at Venus <a href="https://alma-telescope.jp/en/news/press/venus-202009">with two different telescopes</a>, helping to confirm the initial detection, phosphine gas can result from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity. </p>
<p>However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than those processes are capable of generating, allowing the team to <a href="http://astrobiology.com/2020/09/phosphine-on-venus-cannot-be-explained-by-conventional-processes.html">rule out</a> numerous inorganic possibilities. But our understanding of the chemistry of Venus’ atmosphere is sorely lacking: Only a handful of missions have plunged through the inhospitable, <a href="https://solarsystem.nasa.gov/planets/venus/overview/">carbon dioxide-dominated atmosphere</a> to take samples among the global layer of <a href="https://www.esa.int/Science_Exploration/Space_Science/Venus_Express/Acid_clouds_and_lightning">sulfuric acid clouds</a>.</p>
<p>So we planetary scientists are faced with two possibilities: Either there is some sort of life in the Venus clouds, generating phosphine, or there is unexplained and unexpected chemistry taking place there. How do we find out which it is?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358689/original/file-20200917-20-gnavh2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A model of the Soviet Vega 1 spacecraft at the Udvar-Hazy Center, Dulles International Airport. Vega 1 carried a balloon to Venus on its way to visit Halley’s Comet in 1985.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/5/52/Vega_model_-_Udvar-Hazy_Center.JPG">Daderot</a></span>
</figcaption>
</figure>
<p>First and foremost, we need more information about the abundance of PH₃ in the Venus atmosphere, and we can learn something about this from Earth. Just as the discovery team did, existing telescopes capable of detecting phosphine around Venus can be used for follow-up observations, to both definitively confirm the initial finding and figure out if the amount of PH₃ in the atmosphere changes with time. In parallel, there is now a huge opportunity to carry out lab work to better understand the types of chemical reactions that might be possible on Venus — for which we have <a href="https://twitter.com/PlanetDr/status/1306308300397596672?s=20">very limited information</a> at present.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358692/original/file-20200917-22-2c69qg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antennas of the Atacama Large Millimeter/submillimeter Array telescope, on the Chajnantor Plateau in the Chilean Andes. The telescope was used to confirm the initial detection of phosphine in Venus’ atmosphere.</span>
<span class="attribution"><a class="source" href="https://cdn.eso.org/images/screen/ann13016a.jpg">ESO/C. Malin.</a></span>
</figcaption>
</figure>
<h2>Once more unto the breach</h2>
<p>But measurements on and from Earth can take us only so far. To really get to the heart of this mystery, <a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">we need to go back to Venus</a>. Spacecraft equipped with spectrometers that can detect phosphine from orbit could be dispatched to the second planet with the express purpose of characterizing where, and how much, of this gas is there. Because spacecraft <a href="https://en.wikipedia.org/wiki/Pioneer_Venus_Orbiter">can survive for many years in Venus’ orbit</a>, we could obtain continuous observations with a dedicated orbiter over a much longer period than with telescopes on Earth.</p>
<p>But even orbital data can’t tell us the whole story. To fully get a handle on what’s happening at Venus, we have to actually get into the atmosphere. <a href="https://solarsystem.nasa.gov/resources/2197/aerial-platforms-for-the-scientific-exploration-of-venus/">And that’s where aerial platforms come in</a>. Capable of operating above much of the acidic cloud layer – where the temperature and pressure are almost Earthlike – for potentially months at a time, balloons or <a href="https://www.northropgrumman.com/vamp/">flying wings</a> could take detailed atmospheric composition measurements there. These craft could even carry the kinds of instruments <a href="https://www.lpi.usra.edu/opag/meetings/apr2019/presentations/Schulte.pdf">being developed to look for life on Europa</a>. At that point, humanity might finally be able to definitively tell if we share our Solar System with Venusian life.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1827&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1827&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1827&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=2296&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=2296&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358694/original/file-20200917-14-1qga7x5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=2296&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A concept for an aerial platform at Venus. Two connected balloons could take turns to inflate, allowing the balloon to control the altitude at which it floats. An instrument package would then hang from below the balloons.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/system/resources/detail_files/2197_Venus_Aerial_Platforms_Final_Report_Summary_Report_10_25_2018-1.jpg">NASA/JPL-Caltech</a></span>
</figcaption>
</figure>
<h2>A new dawn for Venus exploration?</h2>
<p>Thirty-one years have elapsed since the United States last sent a dedicated mission to Venus. That could soon change as NASA considers two of four missions in the late 2020s targeting Venus. One, called <a href="https://science.jpl.nasa.gov/projects/VERITAS/">VERITAS</a>, would carry a powerful radar to peer through the thick clouds and return unprecedented high-resolution images of the surface. The other, <a href="https://www.nasa.gov/feature/goddard/2020/nasa-goddard-team-selected-to-design-concept-for-probe-of-mysterious-venus-atmosphere">DAVINCI+</a>, would plunge through the atmosphere, sampling the air as it descended, perhaps even able to sniff any phosphine present. NASA plans to pick at least one mission in April 2021.</p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p><a href="https://theconversation.com/why-we-need-to-get-back-to-venus-115355">I have argued before for a return to Venus</a>, and will continue to do so. Even without this latest scientific discovery, Venus is a compelling exploration target, with tantalizing evidence that the planet <a href="https://www.nasa.gov/feature/goddard/2016/nasa-climate-modeling-suggests-venus-may-have-been-habitable">once had oceans</a> and perhaps even suffered a hellish fate at the hands of <a href="https://eos.org/research-spotlights/how-long-was-venus-habitable">its own volcanic eruptions</a>. </p>
<p>But with the detection of a <a href="https://www.liebertpub.com/doi/full/10.1089/ast.2018.1954?journalCode=ast">potential biomarker</a> in Venus’ atmosphere, we now have yet another major reason to return to the world ancient Greek astronomers called Phosphorus — a name for Venus that, it turns out, is wonderfully prescient.</p><img src="https://counter.theconversation.com/content/146185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul K. Byrne does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>News that Venus may harbor life has swept the globe. So how do we find out for sure? A planetary scientist explains what’s next.Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1463582020-09-18T11:50:53Z2020-09-18T11:50:53ZThe four most promising worlds for alien life in the solar system<figure><img src="https://images.theconversation.com/files/358659/original/file-20200917-14-1qdn4n4.jpg?ixlib=rb-1.1.0&rect=36%2C36%2C1238%2C782&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">NASA's Curiosity Rover takes a selfie on Mars in June, 2018.</span> <span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA22486">NASA/JPL-Caltech/MSSS</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The Earth’s biosphere contains all the known ingredients necessary for life as we know it. Broadly speaking these are: liquid water, at least one source of energy, and an inventory of biologically useful elements and molecules.</p>
<p>But the recent discovery of possibly biogenic phosphine <a href="https://theconversation.com/venus-could-it-really-harbour-life-new-study-springs-a-surprise-145981">in the clouds of Venus</a> reminds us that at least some of these ingredients exist elsewhere in the solar system too. So where are the other most promising locations for extra-terrestrial life?</p>
<h2>Mars</h2>
<p>Mars is one of the most Earth-like worlds in the solar system. It has a 24.5-hour day, polar ice caps that expand and contract with the seasons, and a large array of surface features that were sculpted by water during the planet’s history.</p>
<figure class="align-center ">
<img alt="Red planet Mars in space with polar ice caps visible" src="https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358594/original/file-20200917-24-fwl0h9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mars has polar ice caps.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/0/02/OSIRIS_Mars_true_color.jpg">ESA & MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The detection of <a href="https://www.sciencemag.org/news/2018/07/liquid-water-spied-deep-below-polar-ice-cap-mars">a lake beneath</a> the southern polar ice cap and methane in the Martian atmosphere (which varies with the seasons and even the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083800">time of day</a>) make Mars a very interesting candidate for life. Methane is significant as it can be produced by biological processes. But the actual source for the methane on Mars is not yet known.</p>
<p>It is possible that life may have gained a foothold, given the <a href="https://advances.sciencemag.org/content/4/6/eaar3330">evidence</a> that the planet once had a much more benign environment. Today, Mars has a very thin, dry atmosphere comprised almost entirely of carbon dioxide. This offers scant protection from solar and cosmic radiation. If Mars has managed to retain some reserves of water beneath its surface, it is not impossible that life may still exist. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/life-on-mars-europe-commits-to-groundbreaking-mission-to-bring-back-rocks-to-earth-128328">Life on Mars? Europe commits to groundbreaking mission to bring back rocks to Earth</a>
</strong>
</em>
</p>
<hr>
<h2>Europa</h2>
<p>Europa was discovered by Galileo Galilei in 1610, along with Jupiter’s three other larger moons. It is slightly smaller than Earth’s moon and orbits the gas giant at a distance of some 670,000km once every 3.5 days. Europa is constantly squeezed and stretched by the competing gravitational fields of Jupiter and the other <a href="https://www.universetoday.com/44796/galilean-moons/">Galilean moons</a>, a process known as tidal flexing. </p>
<p>The moon is believed to be a geologically active world, like the Earth, because the strong tidal flexing heats its rocky, metallic interior and keeps it partially molten.</p>
<figure class="align-center ">
<img alt="Jupiter's white with brown streaks moon Europa in space," src="https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358637/original/file-20200917-14-1hfzvc8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Europa’s icy surface is a good sign for alien hunters.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA19048">NASA/JPL-Caltech/SETI Institute</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The surface of Europa is a vast expanse of water ice. Many scientists think that beneath the frozen surface is a layer of liquid water – a global ocean – which is prevented from freezing by the heat from flexing and which maybe over 100km deep. </p>
<p>Evidence for this ocean includes geysers erupting through <a href="https://www.nature.com/articles/s41550-019-0933-6">cracks in the surface ice</a>, a <a href="http://ffden-2.phys.uaf.edu/webproj/212_spring_2015/Justin_Long/Justin_Long/magnetic.html">weak magnetic field</a> and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103599961870?via%3Dihub">chaotic terrain</a> on the surface, which could have been deformed by ocean currents swirling beneath. This icy shield insulates the subsurface ocean from the extreme cold and vacuum of space, as well as Jupiter’s ferocious radiation belts.</p>
<p>At the bottom of this ocean world it is conceivable that we might find <a href="https://oceanservice.noaa.gov/facts/vents.html">hydrothermal vents</a> and ocean floor volcanoes. On Earth, such features often support very rich and diverse ecosystems.</p>
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Read more:
<a href="https://theconversation.com/europa-there-may-be-life-on-jupiters-moon-and-two-new-missions-will-pave-the-way-for-finding-it-122551">Europa: there may be life on Jupiter's moon and two new missions will pave the way for finding it</a>
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</em>
</p>
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<h2>Enceladus</h2>
<p>Like Europa, <a href="https://solarsystem.nasa.gov/moons/saturn-moons/enceladus/in-depth/">Enceladus</a> is an ice-covered moon with a subsurface ocean of liquid water. Enceladus orbits Saturn and first came to the attention of scientists as a potentially habitable world following the <a href="https://solarsystem.nasa.gov/resources/806/bursting-at-the-seams-the-geyser-basin-of-enceladus/">surprise discovery</a> of enormous geysers near the moon’s south pole.</p>
<p>These jets of water escape from large cracks on the surface and, given Enceladus’ weak gravitational field, spray out into space. They are clear evidence of an underground store of liquid water.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"906891543780323328"}"></div></p>
<p>Not only was water detected in these geysers but also an array of organic molecules and, crucially, tiny grains of rocky silicate particles that can only be present if the sub-surface ocean water was in physical contact with the rocky ocean floor at a <a href="https://solarsystem.nasa.gov/missions/cassini/science/enceladus/">temperature of at least 90˚C</a>. This is very strong evidence for the existence of hydrothermal vents on the ocean floor, providing the chemistry needed for life and localised sources of energy. </p>
<h2>Titan</h2>
<p>Titan is the largest moon of Saturn and the only moon in the solar system with a substantial atmosphere. It contains a thick orange haze of complex organic molecules and a methane weather system in place of water – complete with seasonal rains, dry periods and surface sand dunes created by wind.</p>
<figure class="align-center ">
<img alt="Yellow/orange moon Titan in space" src="https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/358645/original/file-20200917-16-17xgwya.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Titan’s atmosphere makes it look like a fuzzy orange ball.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA14602">NASA/JPL-Caltech/Space Science Institute</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The atmosphere consists mostly of nitrogen, an important chemical element used in the construction of proteins in all known forms of life. Radar observations have detected the presence of <a href="https://theconversation.com/titan-first-global-map-uncovers-secrets-of-a-potentially-habitable-moon-of-saturn-126985">rivers and lakes</a> of liquid methane and ethane and possibly the presence of cryovolcanoes – volcano-like features that erupt liquid water rather than lava. This suggests that Titan, like Europa and Enceladus, has a sub-surface reserve of liquid water.</p>
<p>At such an enormous distance from the Sun, the surface temperatures on Titan are a frigid -180˚C – way too cold for liquid water. However, the bountiful chemicals available on Titan has raised speculation that lifeforms – potentially with fundamentally different chemistry to terrestrial organisms – <a href="https://www.space.com/8547-strange-discovery-titan-leads-speculation-alien-life.html">could exist</a> there.</p><img src="https://counter.theconversation.com/content/146358/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gareth Dorrian does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The clouds of Venus may harbour alien life. But where else?Gareth Dorrian, Post Doctoral Research Fellow in Space Science, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1460932020-09-14T19:50:32Z2020-09-14T19:50:32ZLife on Venus? Traces of phosphine may be a sign of biological activity<figure><img src="https://images.theconversation.com/files/357810/original/file-20200914-14-hd6f47.jpg?ixlib=rb-1.1.0&rect=6%2C18%2C1376%2C1364&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">JAXA / ISAS / DARTS / Damia Bouic</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The discovery that the atmosphere of Venus absorbs a precise frequency of microwave radiation has just <a href="https://doi.org/10.1038/s41550-020-1174-4">turned planetary science on its head</a>. An international team of scientists used radio telescopes in Hawaii and Chile to find signs that the clouds on Earth’s neighbouring planet contain tiny quantities of a molecule called phosphine.</p>
<p>Phosphine is a compound made from phosphorus and hydrogen, and on Earth its only natural source is tiny microbes that live in oxygen-free environments. It’s too early to say whether phosphine is also a sign of life on Venus – but no other explanation so far proposed seems to fit. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ePoDG00VydE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows how methane was detected in the atmosphere of Mars. The process is the same for finding phosphine on Venus.</span></figcaption>
</figure>
<h2>What makes an atmosphere?</h2>
<p>The molecular makeup of a planet’s atmosphere normally depends on what its parent star is made of, the planet’s position in its star’s system, and the chemical and geological processes that take place given these conditions. </p>
<p>There is phosphine in the atmospheres of Jupiter and Saturn, for example, but there it’s not a sign of life. Scientists think it is formed in the deep atmosphere at high pressures and temperatures, then dredged into the upper atmosphere by a strong convection current. </p>
<p>Although phosphine quickly breaks down into phosphorus and hydrogen in the top clouds of these planets, enough lingers – 4.8 parts per million – to be observable. The phosphorus may be what gives clouds on Jupiter a reddish tinge.</p>
<p>Things are different on a rocky planet like Venus. The new research has found fainter traces of phosphine in the atmosphere, at 20 parts per billion. </p>
<p>Lightning, clouds, volcanoes and meteorite impacts might all produce some phosphine, but not enough to counter the rapid destruction of the compound in Venus’s highly oxidising atmosphere. The researchers considered all the chemical processes they could think of on Venus, but none could explain the concentration of phosphine. What’s left? </p>
<p>On Earth, phosphine is only produced by microbial life (and by various industrial processes) – and the concentration in our atmosphere is in the parts per trillion range. The much higher concentration on Venus cannot be ignored. </p>
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<strong>
Read more:
<a href="https://theconversation.com/we-asked-astronomers-are-we-alone-in-the-universe-the-answer-was-surprisingly-consistent-132088">We asked astronomers: are we alone in the Universe? The answer was surprisingly consistent</a>
</strong>
</em>
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<h2>Signs of life?</h2>
<p>To determine whether the phosphine on Venus is really produced by life, chemists and geologists will be trying to identify other reactions and processes that could be alternative explanations. </p>
<p>Meanwhile, biologists will be trying to better understand the microbes that live in Venus-like conditions on Earth – high temperatures, high acidity, and high levels of carbon dioxide – and also ones that produce phosphine. </p>
<p>When Earth microbes produce phosphine, they do it via an “anaerobic” process, which means it happens where no oxygen is present. It has been observed in places such as activated sludge and sewage treatment plants, but the exact collection of microbes and processes is not well understood. </p>
<p>Biologists will also be trying to work out whether the microbes on Earth that produce phosphine could conceivably do it under the harsh Venusian conditions. If there is some biological process producing phosphine on Venus, it may be a form of “life” very different from what we know on Earth.</p>
<p>Searches for life beyond Earth have often skipped over Venus, because its surface temperature is around 500°C and the atmospheric pressure is almost 100 times greater than on Earth. Conditions are <a href="https://www.liebertpub.com/doi/10.1089/ast.2017.1783">more hospitable for life</a> as we know it about 50 kilometres off the ground, although there are still vast clouds of sulfuric acid to deal with.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-the-idea-of-alien-life-now-seems-inevitable-and-possibly-imminent-115643">Why the idea of alien life now seems inevitable and possibly imminent</a>
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<h2>Molecular barcodes</h2>
<p>The researchers found the phosphine using spectroscopy, which is the study of how light interacts with molecules. When sunlight passes through Venus’s atmosphere, each molecule absorbs very specific colours of this light. </p>
<p>Using telescopes on Earth, we can take this light and split it into a massive rainbow. Each type of molecule present in Venus’ atmosphere produces a distinctive pattern of dark absorption lines in this rainbow, like an identifying barcode. </p>
<figure class="align-center ">
<img alt="A rainbow image of stripes fading from red through the visible spectrum to blue, with narrow black lines." src="https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357805/original/file-20200914-14-2hyaac.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 full visible spectrum of sunlight, showing the dark ‘barcodes’ that indicate the presence of different atoms and molecules.</span>
<span class="attribution"><a class="source" href="https://solarsystem.nasa.gov/resources/390/the-solar-spectrum/">N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF</a></span>
</figcaption>
</figure>
<p>This barcode is not always strongest in visible light. Sometimes it can only be detected in the parts of the electromagnetic spectrum that are invisible to the human eye, such as UV rays, microwave, radio waves and infrared. </p>
<p>The barcode of carbon dioxide, for example, is most evident in the infrared region of the spectrum. </p>
<p>While phosphine on Jupiter was first detected in infrared, for Venus observations astronomers used radio telescopes: the <a href="https://www.almaobservatory.org/en/home/">Atacama Large Millimeter/submillimeter Array</a> (ALMA) and <a href="https://www.eaobservatory.org/jcmt/about-jcmt/">James Clerk Maxwell Telescope</a> (JCMT), which can detect the barcode of phosphine in millimetre wavelengths.</p>
<h2>New barcodes, new discoveries</h2>
<p>The discovery of phosphine on Venus relied not only on new observations, but also a more detailed knowledge of the compound’s barcode. Accurately predicting the barcode of phosphine across all relevant frequencies took <a href="http://www.tampa.phys.ucl.ac.uk/ftp/eThesis/ClaraSousaSilva2015.pdf">the whole PhD</a> of astrochemist Clara Sousa-Silva in the <a href="https://www.ucl.ac.uk/exoplanets/research/spectroscopy-exoplanets">ExoMol group</a> at University College London in 2015. </p>
<p>She used computational quantum chemistry – basically putting her molecule into a computer and solving the equations that describe its behaviour – to predict the strength of the barcode at different colours. She then tuned her model using available experimental data before making the <a href="https://arxiv.org/abs/1410.2917">16.8 billion lines of phosphine’s barcode</a> available to astronomers. </p>
<p>Sousa-Silva originally thought her data would be used to study Jupiter and Saturn, as well as weird stars and distant “hot Jupiter” exoplanets. </p>
<p>More recently, she led the detailed consideration of <a href="https://arxiv.org/abs/1910.05224">phosphine as a biosignature</a> – a molecule whose presence implies life. This analysis demonstrated that, on small rocky exoplanets, phosphine should not be present in observable concentrations unless there was life there as well. </p>
<p>But she no doubt wouldn’t have dreamed of a phone call from an astronomer who has discovered phosphine on our nearest planetary neighbour. With phosphine on Venus, we won’t be limited to speculating and looking for molecular barcodes. We will be able to send probes there and hunt for the microbes directly.</p><img src="https://counter.theconversation.com/content/146093/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 discovery of phosphine in the acidic clouds of Venus can’t be explained by any known chemical or geological processes.Laura McKemmish, Lecturer, UNSW SydneyBrendan Paul Burns, Senior Lecturer, UNSW SydneyLucyna Kedziora-Chudczer, Program Manager / Adjunct Research Fellow, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1459812020-09-14T15:02:27Z2020-09-14T15:02:27ZVenus: could it really harbour life? New study springs a surprise<figure><img src="https://images.theconversation.com/files/357667/original/file-20200911-14-1avt61v.jpg?ixlib=rb-1.1.0&rect=21%2C14%2C1576%2C883&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Composite image of Venus from data from NASA's Magellan spacecraft and Pioneer Venus Orbiter.</span> <span class="attribution"><span class="source">NASA/JPL-Caltech</span></span></figcaption></figure><p>Earth’s sister planet, Venus, has not been regarded as a high priority in the search for life. Its surface temperature of around 450°C is thought to be hostile to even the hardiest of micro-organisms, and its thick, sulphurous and acidic atmosphere has kept the surface almost completely free from visiting spacecraft.</p>
<p>We have only had the briefest of glimpses of a barren landscape from the two <a href="https://www.space.com/18551-venera-13.html">Russian landers</a> that made it down to the ground back in the 1980s. So it’s no wonder that a report <a href="https://www.nature.com/articles/s41550-020-1174-4">published in Nature Astronomy</a> that the upper levels of Venus’ atmosphere contain a molecule that is a potential signature of life, comes as something of a shock.</p>
<p>The <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Phosphine">molecule in question</a> is PH₃ (phosphine). It is a highly reactive and flammable, extremely smelly toxic gas, found (among other places) in heaps of <a href="https://phys.org/news/2019-12-smelly-poisonous-molecule-sure-fire-extraterrestrial.html">penguin dung and the bowels of badgers and fish</a>. </p>
<p>It is present in Earth’s atmosphere in only trace quantities – less than around a few parts per trillion – because it is rapidly destroyed by the process of <a href="https://www.bbc.co.uk/bitesize/guides/zqd2mp3/revision/4">oxidation</a>. The fact that this molecule is nevertheless present in our oxidising atmosphere is because it is continuously produced by microbes. So phosphine in the atmosphere of a rocky planet <a href="https://www.liebertpub.com/doi/abs/10.1089/ast.2018.1954">is proposed to be</a> a strong signature for life.</p>
<p>It shouldn’t be stable in the atmosphere of a planet like Venus where it would be rapidly oxidised unless, like on Earth, there is a constant new supply. So why were the authors of the study looking for phosphine in such an unpromising environment? And are they certain that they have found it?</p>
<p>Reading between the lines of the report, it seems that the team was not expecting to find phosphine. Indeed, they actively seemed to be looking for its absence. Venus was to supply the “baseline atmosphere” of a rocky planet, free from a phosphine biosignature. Scientists investigating rocky exoplanets would then be able to compare the atmospheres of these bodies with that of Venus, to identify any potential phosphine biosignature.</p>
<h2>Detective work</h2>
<p>So to find a global concentration of the molcule around 1,000 times higher than that of Earth was something of a surprise. In fact, it caused the authors to conduct one of the most detailed forensic dissections of their own data that I’ve seen.</p>
<p>The first set of data was acquired in June 2017 using the <a href="https://www.eaobservatory.org/jcmt/about-jcmt/">James Clerk Maxwell Telescope (JCMT)</a> in Hawaii. It unambiguously indicated the presence of phosphine, so a second set of data was recorded, using a different instrument on a different telescope. </p>
<p>These observations were taken in March 2019, at higher spectral resolution, using the <a href="https://www.eso.org/public/unitedkingdom/teles-instr/alma/">Atacama Large Millimetre Array (ALMA)</a> in Chile. The two datasets were almost indistinguishable. Phosphine is present in Venus’ atmosphere, with a patchy distribution across the mid-latitudes, decreasing towards the poles.</p>
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Read more:
<a href="https://theconversation.com/nasa-wants-to-send-humans-to-venus-heres-why-thats-a-brilliant-idea-104961">NASA wants to send humans to Venus – here's why that's a brilliant idea</a>
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<p>But where has it come from? The feedstock for phosphine is <a href="https://www.rsc.org/periodic-table/element/15/phosphorus">phosphorus</a>, an element with a well understood chemistry that underpins many possible chemical reactions. Phosphorus in Venus’ atmosphere was measured by the (former Soviet Union) <a href="https://stardust.jpl.nasa.gov/comets/vega.html">Vega probes</a> and found to occur as the oxidised molecule P₄O₆. </p>
<p>In looking to explain the presence of phosphine, astronomer <a href="https://www.cardiff.ac.uk/people/view/913804-greaves-jane">Jane Greaves</a> from the University of Cardiff and her team used the Vega data and modelled almost 100 different chemical reactions in the atmosphere to see if they could recreate the phosphine they’d found. </p>
<p>Despite doing this over a range of conditions (pressure, temperature, reactant concentration), they found none was viable. They even considered reactions below the surface, but Venus would have to have volcanic activity at least two hundred times greater than that of Earth to produce sufficient phosphine in this way. </p>
<figure class="align-center ">
<img alt="Picture of Venus' surface." src="https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/357694/original/file-20200911-22-1q0ejk0.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">Computer-generated perspective view of Latona Corona and Dali Chasma on Venus using Magellan radar data.</span>
<span class="attribution"><span class="source">NASA/JPL</span></span>
</figcaption>
</figure>
<p>What about a meteorite bringing the substance to Venus? They considered this too, but found it wouldn’t lead to the amounts of phosphine the data indicated. What’s more, there is no evidence of a recent, large impact that might have enhanced atmospheric phosphorus concentrations. The team also considered whether reactions with lightning or the solar wind could create phosphine in the atmosphere but discovered only negligible quantities would be produced this way.</p>
<p>Where does that leave us then? Phosphine is present in Venus’ atmosphere at concentrations way above the level that can be explained by non-biological processes. Does that mean there are microbes present in Venus’ atmosphere, sailing through the clouds in aerosol droplets – a Venus fly-trap at the micro-scale? </p>
<p>The authors do not claim to have found evidence for life, only for “anomalous and unexplained chemistry”. But, as Sherlock Holmes said to Dr Watson: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.” </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/mars-2020-the-hunt-for-life-on-the-red-planet-is-about-to-get-serious-143698">Mars 2020: the hunt for life on the red planet is about to get serious</a>
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<p>The presence of methane as a biosignature in Mars’ atmosphere is still <a href="https://theconversation.com/methane-on-mars-a-new-discovery-or-just-a-lot-of-hot-air-114656">hotly debated</a>. It may be that astrobiologists searching for life beyond Earth now have an additional atmospheric biosignature about which to argue. </p>
<p>The European Space Agency is currently considering a <a href="https://envisionvenus.eu/envision/">mission to Venus</a> that would determine its geological and tectonic history, including observation of potential volcanic gases. This would yield a better idea of the species that are added to Venus’ atmosphere. The new study should boost the case for selection of the mission.</p><img src="https://counter.theconversation.com/content/145981/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady works for the Open University and is Chancellor of Liverpool Hope University and a Senior Research Fellow at the Natural History Museum. She has received funding from the STFC and the UK Space Agency. Follow her on Twitter @MonicaGrady</span></em></p>Scientists don’t claim to have evidence of life on Venus but they have ruled out pretty much everything else.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.