tag:theconversation.com,2011:/us/topics/dawn-mission-14256/articlesDawn mission – The Conversation2016-09-02T10:42:21Ztag:theconversation.com,2011:article/646272016-09-02T10:42:21Z2016-09-02T10:42:21ZCeres asteroid may have an ‘ice volcano’ and other signs of water, NASA mission reveals<figure><img src="https://images.theconversation.com/files/136403/original/image-20160902-20217-4yfkat.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ceres' Haulani Crater shows evidence of landslides from its crater rim</span> <span class="attribution"><span class="source">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</span></span></figcaption></figure><p>The arrival of <a href="https://theconversation.com/dawn-breaks-over-distant-ceres-and-perhaps-reveals-signs-of-habitability-38967">NASA’s Dawn mission</a> at the huge asteroid “1 Ceres” in early 2015 has turned out to have been well worth waiting for. This dwarf planet is the largest body in the asteroid belt between Mars and Jupiter and was the first to be discovered. But, until recently, we have only had information from ground and space-based telescopes, which have given us tantalising glimpses of a dark, possibly water-rich object.</p>
<p>Now the Dawn space probe has sent back a bumper harvest of findings, summarised in six new research papers published in a special issue of the journal Science. We now have a map of Ceres that reveals unusual minerals, a surface peppered with craters, and water in the form of ice and possibly an outer atmosphere of vapour. There’s also enough uncertainty in the results to sow the seeds for future research.</p>
<p>The data provides a global geological map of the asteroid showing that its entire surface appears to be <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4279">covered in phyllosilicates</a>, an important group of clay minerals. Two specific clays are identified: one that is magnesium-rich, the second an ammonium-rich species. There seems to be little or no pattern to the distribution of the two minerals – they are both almost everywhere.</p>
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<span class="caption">Dawn over Ceres.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</span></span>
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<p>This ubiquity is what is important. The minerals could not have been formed in a local event, such as an impact into an ice-filled crater. They must have been produced by planet-wide alteration, presumably implying there must have been volumes of water. It is clear that enormous quantities of liquid water are not present on Ceres now. But the signal of water-ice <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf3010">has been detected</a> in at least one crater.</p>
<p>Because the temperature of Ceres is relatively warm (between -93°C and -33°C), water-ice exposed at the surface would rapidly convert into a gas in such a low-pressure environment. So the discovered traces of water-ice suggest some underground ice was recently exposed and that there must be some mechanism to explain how the surface was disturbed in this way. Some researchers <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4286">think that the answer</a> is cryovolcanism, where subsurface layers of mixed ice and minerals percolate slowly to the surface through cracks and fractures, or more swiftly following an impact. If the minerals are chlorides, then a low temperature brine can keep the subsurface layer mobile.</p>
<h2>Ice flows</h2>
<p>As well as a geological map of Ceres, we also have a picture of Ceres’ <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4332">global geomorphology</a> (its surface features). This shows that the surface of Ceres is peppered with impact craters, although the craters <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4759">are not distributed evenly</a> over the surface. Much more interesting are the three distinct types of mineral flow across the landscape, produced by the movement of ice-rich material, landslides or blankets of ejected particles following impact into ice-rich material. The distribution of the flow types varies with latitude – and the researchers think this means different surface layers of the asteroid contain different amounts of ice.</p>
<p>One of the <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4219">most remarkable results</a> is the detection of a sudden burst of highly energetic electrons over a period of around a week in June 2015, coinciding with a solar proton storm. The researchers think the protons fired out by the sun interacted with particles in Ceres’ weak atmosphere, creating a shock wave that accelerated the electrons. Based on <a href="http://onlinelibrary.wiley.com/doi/10.1002/2015GL067451/full">observations by the Hubble Space Telescope</a>, Ceres is believed to have a tenuous exosphere (outer atmosphere) of water vapour. <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aaf4219">The results</a> from Dawn suggest that this may indeed be the case.</p>
<p>Together, this new set of information shows that Ceres is a world that has been shaped by a series of events, with a strong crust of magnesium- and ammonium-bearing phyllosilicates overlying an interior of briny ice and hydrated minerals. What other hidden secrets will be revealed as research continues on the trove of data from Ceres? Questions still remain about the variety of mineral deposits, the depth of the subsurface ice-rock layer, and, of course, the potential for organic material on the minor planet. The harvest from Ceres so far has been rich and promises to keep us busy for years to come.</p><img src="https://counter.theconversation.com/content/64627/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Monica Grady is a Trustee of Lunar Mission One and receives funding from the STFC and the EU.</span></em></p>The latest data from the Dawn space probe points to underground ice flows and a water vapour atmosphere.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/492742015-12-22T20:15:45Z2015-12-22T20:15:45ZAfter eight years, NASA’s Dawn probe brings dwarf planet Ceres into closest focus<figure><img src="https://images.theconversation.com/files/106933/original/image-20151222-27863-xoz6fr.jpg?ixlib=rb-1.1.0&rect=0%2C136%2C1024%2C763&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ceres, as seen by NASA's Dawn spacecraft on December 10, around a crater chain called Gerber Catena.</span> <span class="attribution"><a class="source" href="http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20186">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>More than a thousand times farther from Earth than the moon, farther even than the sun, an extraordinary extraterrestrial expedition is taking place. <a href="http://dawn.jpl.nasa.gov">NASA’s Dawn spacecraft</a> is exploring dwarf planet Ceres, which orbits the sun between Mars and Jupiter. The probe has just reached the closest point it ever will, and is now beginning to collect its most detailed pictures and other measurements on this distant orb.</p>
<p>Ceres is a remnant from the <a href="http://www.jpl.nasa.gov/blog/2014/12/ceres-curiosities-the-mysterious-world-comes-into-view">dawn of our solar system</a> nearly 4.6 billion years ago. All the data Dawn is now sending back will provide insight into Ceres’ history and geology, including the presence of water, past or present. Scientists believe that by studying Ceres, we can unlock some of the secrets of the epoch in which planets, including our own, formed.</p>
<p>But this mission isn’t only for scientists. Discovering the nature of an uncharted world is a thrill that can be shared by anyone who has ever gazed up at the night sky in wonder, been curious about the universe and Earth’s place in it, or felt the lure of a bold adventure into the unknown. </p>
<p>I happen to fall into all those categories. I fell in love with space at the age of four, and I knew by the fourth grade that I wanted to earn a doctorate in physics. (It was a few more years before I did.) My passion for the exploration of space and the grandeur of scientific discovery and understanding has never wavered. It’s a dream come true for me to be the mission director and chief engineer on Dawn at JPL.</p>
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<figcaption><span class="caption">False color video of Ceres from distance of 2,700 miles, courtesy of Dawn.</span></figcaption>
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<h2>Ceres before Dawn</h2>
<p>Named for the <a href="https://en.wikipedia.org/wiki/Ceres_(mythology)">Roman goddess of agriculture and grain</a>, Ceres was the <a href="http://dawnblog.jpl.nasa.gov/2014/12/29/dawn-journal-december-29">first dwarf planet discovered</a>, in 1801. That’s 129 years before Pluto – and in fact, both were originally considered planets, only later to be designated dwarf planets.</p>
<p>Although Ceres appeared as little more than a fuzzy blob of light amidst the stars, scientists determined that it’s the behemoth of the main asteroid belt between Mars and Jupiter – nearly 600 miles in diameter. Its surface area is more than a third of the area of the continental US. Before Dawn’s arrival, Ceres was the largest object between the sun and Pluto that a spacecraft had not visited.</p>
<p>Since well before Dawn, we’ve had telescopic evidence that Ceres harbors water. While it’s mostly in the form of ice, scientists have good reason to believe an underground ocean once circulated. The question of whether reservoirs still lurk beneath the alien surface remains open. Dawn’s studies of Ceres may even provide hints about how Earth acquired its own supply of that precious liquid billions of years ago.</p>
<h2>Dawn en route to Ceres</h2>
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<span class="caption">Dawn launches at dawn on September 27 2007, headed for the asteroid belt.</span>
<span class="attribution"><span class="source">NASA</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>In 2007, we launched Dawn from Cape Canaveral, and it will never again visit its erstwhile planetary home. In 2011, it became the only spacecraft ever to orbit an object in the main asteroid belt, devoting 14 months to scrutinizing <a href="http://www.jpl.nasa.gov/blog/2013/1/the-giant-asteroid-a-retrospective">protoplanet Vesta</a>. Dawn showed us this second most massive resident of the belt is more closely related to the terrestrial planets (including Earth) than to the much smaller chunks of rock that are typical of asteroids.</p>
<p>The unique capability to travel to worlds beyond Mars, enter orbit and maneuver extensively and then depart for yet another destination is achieved with advanced ion propulsion. The technology spent much of its history in the domain of sci-fi, including Star Trek and Star Wars. (Darth Vader’s TIE Fighter is named for its twin ion engines.) But what may have seemed only science fiction is science fact. Without its three ion engines (note that Dawn does the TIE Fighters one better), Dawn’s mission wouldn’t be possible. </p>
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<figcaption><span class="caption">A gridded ion thruster uses electrical energy to create, accelerate and neutralize positively charged ions to generate thrust.</span></figcaption>
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<p>The ion engines use xenon gas, a chemical cousin of helium and neon. With electrical power from Dawn’s large solar panels, the xenon is given an electrical charge in a process called ionization. The engines use high voltage to accelerate the ions. They’re then shot out of the engines at up to 90,000 mph. When the ions leave the spacecraft at this fantastically high speed, it’s pushed in the opposite direction. Dawn’s ion propulsion system is exceptionally efficient – 10 times as efficient as conventional spacecraft propulsion. It’s comparable to your car getting 250 miles per gallon.</p>
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<span class="caption">Artist’s conception of the Dawn spacecraft arriving at Ceres. The engine’s xenon ions glow with blue light.</span>
<span class="attribution"><a class="source" href="http://photojournal.jpl.nasa.gov/catalog/PIA18921">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<h2>Dawn drops into Cerean orbit</h2>
<p>Finally, after a journey of more than seven years and three billion miles, our interplanetary ambassador reached Ceres on March 6 2015, and <a href="http://www.jpl.nasa.gov/blog/2015/3/we-did-it-dawn-arrives-at-dwarf-planet-ceres">gracefully entered</a> the dwarf planet’s permanent gravitational embrace.</p>
<p>Mission controllers at JPL then piloted the craft to three orbits at successively lower altitudes, so we could first obtain an overview and then gain better and better views of this vast unexplored territory. And Dawn has just performed the penultimate act in its grand celestial choreography. It’s spent the last seven weeks maneuvering to its lowest altitude. Orbiting now about 240 miles above the exotic terrain of rock and ice, Dawn is closer to Ceres than the International Space Station is to Earth.</p>
<h2>Dawn brings Ceres into focus</h2>
<p>Included in the spacecraft’s suite of sophisticated sensors is a camera that has already taken 10,000 pictures of alien landscapes on Ceres. Following from Ceres’ own name, features Dawn discovers are named for agricultural deities and festivals from around the world.</p>
<p>We see rugged terrain and smooth areas, sometimes with streaks of material that’s flowed across it. There are craters large and small, created by billions of years of assaults in the rough-and-tumble neighborhood of the asteroid belt. We see mountains and valleys, huge fissures in the ground and <a href="http://dawn.jpl.nasa.gov/news/news-detail.html?id=4785">bright spots that glow</a> with a mysterious luster, reflecting much more sunlight than most of the dark surface.</p>
<p>The most striking of these shining regions, inside the 55-mile-wide Occator Crater (named for the Roman deity of harrowing), is so bright that the Hubble Space Telescope detected a hint of it a decade ago. Dawn’s pictures to date have been more than 200 times sharper than Hubble’s. The images we’re starting to get back now will be even better, revealing 850 times the detail that Hubble had provided.</p>
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<span class="caption">Dawn took this image in its low-altitude mapping orbit from an approximate distance of 240 miles (385 kilometers) from Ceres on December 10.</span>
<span class="attribution"><a class="source" href="http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20185">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>Dawn has shown us a mountain named Ahuna Mons that towers more than 20,000 feet in an otherwise unremarkable area, comparable to the elevation of North America’s tallest peak, Mt Denali. (Ahuna is a celebration of thanksgiving for the harvest among the Sumis of northeast India.) Bright streaks seem to suggest some unidentified material once flowed down the steep slopes of Ahuna Mons. While scientists have not yet determined what forces and processes shaped this conical mountain, it doesn’t take a geologist to notice its resemblance to terrestrial volcanic cones. Imagine what it might have been like to witness an eruption of some strange combination of water and other chemicals on this cold, distant world.</p>
<p>Beyond photos, Dawn will take a great many other measurements from its new orbital perch before its mission concludes in 2016. It will measure radiation to help scientists determine what types of atoms are present on Ceres. It will use infrared light to identify the minerals on Ceres’ surface. And it will gauge subtle variations in the gravitational field to reveal the interior structure of the dwarf planet.</p>
<p>Once the spacecraft exhausts the small supply of conventional rocket propellant it squirts through thrusters to control its orientation in the zero-gravity, frictionless conditions of spaceflight, it will no longer be able to point its solar arrays at the sun, its antenna at Earth, its sensors at Ceres or its ion engines in the direction needed to travel elsewhere. But the ship will remain in orbit around Ceres as surely as the moon remains in orbit around Earth and Earth remains in orbit around the sun. Its legacy in the history of our efforts to reach out from our humble home to touch the stars is secure. Dawn will become an inert celestial monument to humankind’s creativity, ingenuity, and passion for exploring the cosmos.</p>
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<span class="caption">This part of Ceres, near the south pole, has such long shadows because, from the perspective of this location, the sun is near the horizon. At the time When Dawn took this image on December 10, the sun was 4 degrees north of the equator. If you were standing this close to Ceres’ south pole, the sun would never get high in the sky during the course of a nine-hour Cerean day.</span>
<span class="attribution"><a class="source" href="http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20188">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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</figure><img src="https://counter.theconversation.com/content/49274/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marc D Rayman receives funding from NASA through Caltech for the Dawn mission at JPL. </span></em></p>Dawn’s mission director and chief engineer describes his ‘dream come true’ job – and how the new data coming back from Ceres could unlock some of the secrets of the earliest days of our solar system.Marc D Rayman, Dawn Chief Engineer and Mission Director at JPL, NASALicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/441582015-07-15T05:22:46Z2015-07-15T05:22:46ZFrom comets to planets near and far, space probes reveal the universe<figure><img src="https://images.theconversation.com/files/88370/original/image-20150714-21701-xe0wt3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="http://solarviews.com/cap/vss/VSS00041.htm">NASA/JHUAPL/SwRI</a></span></figcaption></figure><p>If space is humankind’s ultimate challenge, then the first step starts close to home – we have still to explore much of our solar system that spans across enormous distances, never mind those galaxies and stars more distant still. </p>
<p>To learn more we must get closer, dispatching spacecraft such as New Horizons – which has <a href="http://www.bbc.co.uk/news/science-environment-33524589">just returned our first ever close-up images of Pluto</a> after a nine year journey. Here are my top five missions that are chipping away at what we don’t know and building up a better sense of universe around us.</p>
<h2>1. New Horizons</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88373/original/image-20150714-21719-1dnittw.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"></a>
<figcaption>
<span class="caption">Time for your close-up, Pluto.</span>
<span class="attribution"><a class="source" href="http://pluto.jhuapl.edu/Multimedia/Science-Photos/image.php?gallery_id=2&image_id=222">NASA/JHU APL/SwRI</a></span>
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</figure>
<p>Rocketing past at 14km/s, the New Horizons spacecraft has provided our first close view of Pluto which will enormously improve our understanding of this distant body. Our facts regarding this icy dwarf are sketchy at best. Just knowing what Pluto looks like makes it much more real.</p>
<p>The probe’s brief two-hour visit captured images of parts of Pluto and its largest moon Charon at high resolution, improving our understanding of planet formation. This is an amazing feat, considering the signals take more than 4.5 hours to reach Earth and that the sun is so weak at this extreme distance that solar power is not an option. </p>
<p>But the mission doesn’t end here: in 2019 New Horizons will visit a small object in the Kuiper belt, a region of space filled with small rocky planetoids, giving us a chance to examine the make-up of these remnants of the early solar system. And by 2026, it will reach the outer edges of the solar system. </p>
<h2>2. Rosetta</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=534&fit=crop&dpr=1 600w, https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=534&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=534&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=671&fit=crop&dpr=1 754w, https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=671&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/87345/original/image-20150703-20478-13i4cyi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=671&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Comet 67P/Churyumov-Gerasimenko, as seen from Rosetta 20km above.</span>
<span class="attribution"><a class="source" href="http://www.esa.int/spaceinimages/Images/2014/12/Comet_on_10_December_2014_NavCam">ESA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Conceived decades ago, Rosetta flew alone through space for years before it reached the tiny comet that was its target and swung into orbit around it. Given the comet’s highly irregular shape this is an outstanding feat by itself.</p>
<p>The lander Philae managed to touch down and collect surface data of the comet, and while it was forced to shut down from lack of sunlight falling on its solar panels, it has now awoken and is transmitting data again. The Rosetta orbiter mission has also been extended to 2016 when it will also attempt to land on the comet.</p>
<p>The missions have improved our understanding of comets which contain <a href="http://blogs.esa.int/rosetta/2015/06/24/exposed-water-ice-detected-on-comets-surface/">frozen, icy rocks</a>, and have measured the <a href="http://blogs.esa.int/rosetta/2015/06/02/ultraviolet-study-reveals-surprises-in-comet-coma">gas composition of jets streaming off the comet</a> before they are altered by solar radiation.</p>
<p>But more than just hard numbers, this mission has been capturing images that speak for themselves, showing an ambitious mission conceived by many nations working together. Images such as Rosetta’s pictures of Philae descending resonates with us more than just hard facts and figures.</p>
<h2>3. Dawn</h2>
<p>Dawn is another mission expanding our knowledge of dwarf planets, in this case Ceres. It is now orbiting this interesting object having spent 2011 conducting similar work around nearby Vesta. Both Vesta and Ceres in the asteroid belt are protoplanets but of quite different composition.</p>
<p>Dawn has illustrated how powerful imagery can be. The most intriguing image is a crater that contains a <a href="http://dawn.jpl.nasa.gov/news/news-detail.html?id=4633">handful of bright white spots</a> on a surface otherwise darker than coal – unexpected, unexplored, challenging terrain.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/87351/original/image-20150703-20462-1tdeqzs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">What is the bright spot on the surface of Ceres? Dawn will find out.</span>
<span class="attribution"><a class="source" href="http://dawn.jpl.nasa.gov/news/news-detail.html?id=4619">NASA</a></span>
</figcaption>
</figure>
<h2>4. Messenger</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88366/original/image-20150714-21701-nnpb7n.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">Incredibly detailed images from Messenger’s visit to Mercury.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PIA19419-Mercury-Messenger-MASCS-20150416.jpg">NASA/JHU APL/Carnegie Institution of Washington</a></span>
</figcaption>
</figure>
<p>Messenger is still in my list of impressive space probes even though the mission ended with its controlled crash on Mercury’s surface this April. Sent to explore a planet of which we had barely any imagery of its surface, in four years Messenger managed to not only give us high-resolution maps of the innermost planet, it <a href="http://www.space.com/29281-messenger-spacecraft-mercury-crash.html">discovered water in its dark polar craters</a>. On a planet baked by the sun this could only arrive from comets and water-rich asteroids – objects currently under investigation by Rosetta and New Horizons.</p>
<h2>5. Curiosity</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88368/original/image-20150714-21701-bgp637.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">Curiosity Rover’s famous off-world self-portrait from Mars.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:PIA16239_High-Resolution_Self-Portrait_by_Curiosity_Rover_Arm_Camera_square.jpg">NASA/JPL-Caltech/Malin Space Science Systems</a></span>
</figcaption>
</figure>
<p>The last is the Curiosity rover. For me it sums up the efforts to explore our neighbour, Mars. These missions went in search of life and traces of water, carrying a complex laboratory, drills, laser and high resolution cameras.</p>
<p>Curiosity particularly illustrates the challenges we are capable of mastering to land a probe on Mars – described by NASA themselves as “seven minutes of terror”.</p>
<p>These rovers have achieved an outstanding feat, where now those exploring beyond Earth are not astronomers but geologists, the rovers’ equipment replacing the hammer and microscope used during fieldwork. The missions have added Mars to the “territory” that humans have access to. It’s even on <a href="http://www.google.co.uk/mars/">Google Maps</a> – imagery so good that we can see its surface as if we were there and can <a href="http://www.huffingtonpost.com/2014/09/02/11-rocks-on-mars-illusions_n_5697695.html">look at rocks in such detail</a> as if we were picking up pebbles at the beach.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ki_Af_o9Q9s?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>It’s out there waiting for us</h2>
<p>Probes have witnessed solar eclipses and comet fly-bys that provide an entirely different view than is possible from Earth – something that adds a feel of awe and wonder, like looking back on Earth from the moon.</p>
<p>The sort of incredible images provided by these probes connects us with the solar system, bringing it closer to home. Famous images of Earth from space, such as the <a href="http://visibleearth.nasa.gov/view_cat.php?categoryID=1484">Blue Marble</a> and the <a href="https://www.youtube.com/watch?v=p86BPM1GV8M">Pale Blue Dot</a> catalysed our ecological conscience, reminding us of the fragility of our world in comparison to the vast, cold emptiness of outer space. </p>
<p>Such images lead us on to explore the universe and ourselves, and the findings of these remarkable spacecraft that have travelled millions, sometimes billions of miles through space over many years remind us that it’s out there to be discovered. The challenge and rewards await, as J F Kennedy said: we choose to go to space not because it is easy, but because it is hard.</p><img src="https://counter.theconversation.com/content/44158/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Brown 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>Everything in space is so far away, but probes bring us closer.Daniel Brown, Lecturer in Astronomy, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/404132015-04-17T16:15:53Z2015-04-17T16:15:53ZFirst colour images of Ceres revealed as Dawn approaches<figure><img src="https://images.theconversation.com/files/78412/original/image-20150417-3249-19285wg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cratered surface of Ceres in colour.</span> <span class="attribution"><span class="source">NASA/JPL-Caltec/UCLA</span></span></figcaption></figure><p>Astronomers and planetary scientists have been waiting with bated breath for the first detailed close-up images of Ceres, the solar system’s largest asteroid. Now, with NASA’s <a href="http://www.nasa.gov/mission_pages/dawn/main/index.html">Dawn spacecraft</a> approaching closer each day, tantalising new colour imagery has revealed new details of the geological processes that formed Ceres.</p>
<p>Orbiting the sun between Mars and Jupiter, Ceres is also given the somewhat controversial classification “<a href="https://theconversation.com/nasa-missions-may-re-elevate-pluto-and-ceres-from-dwarf-planets-to-full-on-planet-status-36081">dwarf planet</a>”. The Dawn spacecraft <a href="https://theconversation.com/dawn-breaks-over-distant-ceres-and-perhaps-reveals-signs-of-habitability-38967">eased into orbit around Ceres</a> a few weeks ago, and has since then been slowly circling across the dark, night-side of Ceres away from the sun. As the spacecraft begins to creep within sight of the day-side of Ceres, we wait for more detailed images of the <a href="https://theconversation.com/dawn-breaks-over-distant-ceres-and-perhaps-reveals-signs-of-habitability-38967">“white spots” and other intriguing features</a> seen during the spacecraft’s initial approach.</p>
<figure><a href="http://www.nasa.gov/jpl/dawn-glimpses-ceres-north-pole/index.html"><img src="http://www.jpl.nasa.gov/images/dawn/20150416/pia19317-16.gif"></a><figcaption>Ceres, seen from 21,000km. Source: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</figcaption></figure>
<h2>Gravity, ice and the white spots</h2>
<p>Ceres measures nearly 1,000km across its equator, massive enough for it to have been pulled into a rough sphere by the force of its own gravity. This is made somewhat easier by roughly a quarter of its outer portion comprising of ice, whereas its interior is rocky. Is Ceres’ icy shell solid all the way down to the rock, or have lower layers of the ice melted to produce the sort of internal ocean known to exist within some of the icy satellites of Jupiter (<a href="https://theconversation.com/the-moon-was-a-first-step-mars-will-test-our-capabilities-but-europa-is-the-prize-37253">Europa</a>) and Saturn (<a href="https://theconversation.com/icy-plumes-bursting-from-saturns-moon-enceladus-suggest-it-could-harbour-life-38673">Enceladus</a>)? If there is an internal ocean, this could account for plumes of water vapour seen <a href="http://www.nasa.gov/jpl/herschel/ceres-20140122/">venting from Ceres</a> last year by the Herschel space telescope – not to mention those mysterious white spots seen on the Ceres’ surface.</p>
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<figcaption>
<span class="caption">A Ceres of images taken by Dawn during its approach. White spots, possibly water vapour plumes, can be glimpsed in the 2nd and 3rd images.</span>
<span class="attribution"><span class="source">NASA/JPL-Caltech/UCLA/MPS/DLR/IDA</span></span>
</figcaption>
</figure>
<p>Dawn has also taken colour images, now released, of Ceres as it approached. The colour images are formed by combining data recorded through three different colour filters in Dawn’s camera: blue, green, and near-infrared. These three channels, displayed as blue, green and red and amplified a little, look much like what human eyes would see if we were able to see a little beyond the red end of the spectrum. A <a href="http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19063">colour map made</a> of Ceres has been created by stitching together a series of images taken as Ceres rotated underneath the spacecraft, as seen in the main image above. The colours are different to the <a href="http://www.nasa.gov/jpl/dawns-ceres-color-map-reveals-surface-diversity/">image released by NASA</a> as the channels have been rearranged to match natural RGB more closely.</p>
<p>The detail and colour from the images reveal many variations across the surface of Ceres. What is probably relatively pure or clean ice appears blue, whereas areas contaminated by rocky or carbonaceous material appear relatively red, as in this image of Europa.</p>
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<a href="https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=461&fit=crop&dpr=1 600w, https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=461&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=461&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=580&fit=crop&dpr=1 754w, https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=580&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/78416/original/image-20150417-3261-z0yekp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=580&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Jupiter’s moon Europa, showing relatively pure ice in blue and rocky or contaminated ice in red.</span>
<span class="attribution"><span class="source">NASA/JPL/University of Arizona</span></span>
</figcaption>
</figure>
<p>Within weeks Dawn will reach its final orbit distance of around 250km from the surface, and we’ll start seeing Ceres, bathed in the light, in much greater detail.</p><img src="https://counter.theconversation.com/content/40413/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Rothery 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>Approaching Ceres, the Dawn spacecraft reveals the dwarf planet in colour for the first time.David Rothery, Professor of Planetary Geosciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/389672015-03-18T12:44:38Z2015-03-18T12:44:38ZDawn breaks over distant Ceres … and perhaps reveals signs of habitability<figure><img src="https://images.theconversation.com/files/75137/original/image-20150317-2175-1q3yp4o.jpg?ixlib=rb-1.1.0&rect=0%2C115%2C1150%2C845&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What is the bright spot of Ceres? Not long till we find out.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:PIA18920-Ceres-DwarfPlanet-20150219.jpg">NASA</a></span></figcaption></figure><p>NASA’s <a href="http://dawn.jpl.nasa.gov/mission/">Dawn spacecraft</a> is about to start its investigation of the largest member of the asteroid belt, <a href="http://space-facts.com/ceres/">1 Ceres</a>. It will take detailed images of the dwarf planet, and produce a geological map of its entire surface. But even before the spacecraft has reached its optimum orbit, the preliminary results just released are already surprising and delighting planetary scientists.</p>
<p>Up until February 2015, the best images taken of Ceres were from the <a href="http://hubblesite.org/newscenter/archive/releases/2005/27/image/e">Hubble space telescope</a>, showing a near-spherical body with one area that was much brighter than the rest of the surface. As Dawn approached Ceres, its camera acquired some remarkable images, at about three times the resolution of those from Hubble. The pictures verified that there was indeed a brighter region. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=376&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=376&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75133/original/image-20150317-2165-y1j1mt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=376&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Exploded map of Ceres showing ‘bright spot’.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Even better, close examination of the images showed that the area varied in brightness over the course of Ceres’ day (which is only about nine hours long), growing dimmer as the dwarf planet moved into darkness. It is interpretation of this variability that has planetary scientists buzzing.</p>
<p>As if that were not enough, a further series of pictures appear to show a plume emanating from the surface. Is Ceres active? Does it have a layer of water or ice below a thin crust of rock? Could it be a ball of mud, overlain by a muddy ocean, on top of which is another thin muddy crust? The exact structure of Ceres is not yet known, although it is clear that it’s not rocky all the way through – its density is too low, so there must be at least some water or ice present.
Suggestions at the 46th <a href="http://www.hou.usra.edu/meetings/lpsc2015">Lunar and Planetary Science Conference</a> in Houston, Texas, of icy volcanism on Ceres have led to speculation that the dwarf planet could potentially be habitable. Although Ceres does not have an atmosphere, life might exist in a subsurface ocean, as has been suggested for <a href="https://theconversation.com/the-moon-was-a-first-step-mars-will-test-our-capabilities-but-europa-is-the-prize-37253">Europa</a> or <a href="https://theconversation.com/icy-plumes-bursting-from-saturns-moon-enceladus-suggest-it-could-harbour-life-38673">Enceladus</a>, moons orbiting Jupiter and Saturn respectively. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=482&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=482&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=482&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=605&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=605&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75138/original/image-20150317-2172-7petmp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=605&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Is Ceres more slush than solid inside?</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Ceres_Cutaway.jpg">NASA</a></span>
</figcaption>
</figure>
<p><a href="http://link.springer.com/article/10.1007%2FBF00613296#page-1">Cryovolcanism</a> – the presence of ice volcanoes – is not the only mechanism that can produce a plume of dust and ice from a planetary surface. The Rosetta mission has delivered amazing images of plumes coming from comet <a href="http://www.esa.int/spaceinimages/Images/2015/03/Comet_on_9_March_2015_NavCam">P/67 Churyumov-Gerasimenko</a>, caused by sublimation of ice that releases dust and gas trapped inside the ice. Could the bright spot be an icy plume caused by the vaporisation of Ceres’ surface as it turns towards the sun’s heat, and then dropping away as night falls? Corridor talk at the conference speculates that Ceres might be closer to a comet than the asteroid it is usually regarded as.</p>
<p>Fortunately, we won’t have to wait much longer before we get some more definitive answers to questions of Ceres’ physical structure and heritage. By the beginning of April, the Dawn spacecraft will be much closer and will start its imaging campaign in earnest, at which point we will start seeing craters and other surface features at better resolution.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1053&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1053&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1053&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1323&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1323&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75134/original/image-20150317-2147-q2t4d3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1323&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 not the Ceres you are looking for.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Ceres_statue.jpg">Borghese Collection, Louvre</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In preparation for descriptions of such features, and bearing in mind that Ceres was the Roman goddess of the harvest, the International Astronomical Union has <a href="http://astrogeology.usgs.gov/news/nomenclature/two-themes-approved-for-ceres">ruled</a> that craters on Ceres should be named after international deities of agriculture and vegetation, while other features will be named after agricultural festivals of the world. </p>
<p>I’m not sure just how many of these there are, or how memorable their names will turn out to be. But as the Dawn mission’s principal investigator Chris Russell pointed out, there is one Mayan deity named Yum (<a href="http://www.godchecker.com/pantheon/mayan-mythology.php?deity=YUM-KAAX">Yum Kaax</a>, god of agriculture and the jungle), who should readily be remembered. One can only hope the mission scientists find a suitably delicious feature on Ceres to give that name.</p><img src="https://counter.theconversation.com/content/38967/count.gif" alt="The Conversation" width="1" height="1" />
NASA’s Dawn spacecraft hasn’t reached optimum orbit around Ceres but the data it’s returning has already got scientists excited.Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/385022015-03-06T17:53:01Z2015-03-06T17:53:01ZDawn of a new era: the revolutionary ion engine that took spacecraft to Ceres<figure><img src="https://images.theconversation.com/files/74087/original/image-20150306-13559-6iw76i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">I've seen the future, and the future's blue.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>The NASA spacecraft Dawn has spent more than seven years travelling across the Solar System to intercept the asteroid Vesta and the dwarf planet Ceres. Now <a href="http://dawn.jpl.nasa.gov/feature_stories/Dawn_First_Orbit_Dwarf_Planet.asp">in orbit around Ceres</a>, the probe has returned the first images and data from these distant objects. But inside Dawn itself is another first – the spacecraft is the first exploratory space mission to use an electrically-powered ion engine rather than conventional rockets.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74084/original/image-20150306-13576-1h6u568.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">The mysterious bright spot of Ceres seen as Dawn approaches.</span>
<span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/File:Ceres_RC2_Bright_Spot.jpg">NASA</a></span>
</figcaption>
</figure>
<p>The ion engine will propel the next generation of spacecraft. Electric power is used to create charged particles of the fuel, usually the gas xenon, and accelerate them to extremely high velocities. The exhaust velocity of conventional rockets is limited by the chemical energy stored in the fuel’s molecular bonds, which limits the thrust to about 5km/s. Ion engines are in principle limited only by the electrical power available on the spacecraft, but typically the exhaust speed of the charged particles range from 15km/s to 35km/s. </p>
<p>What this means in practice is that electrically powered thrusters are much more fuel efficient than chemical ones, so an enormous amount of mass can be saved through the need for less fuel onboard. With the cost to launch a single kilogramme of mass into Earth orbit of around US$20,000, this can make spacecraft significantly cheaper.</p>
<p>This can be of great benefit to commercial manufacturers of geostationary satellites, where electric propulsion can allow them to manoeuvre adding new capabilities to the satellite during its mission. However, for scientific missions such as interplanetary travel to the outer regions of the Solar System, electric propulsion is the only means to carry useful scientific payload quickly across the enormous distances involved.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74086/original/image-20150306-13543-5n966m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Inside an ion engine.</span>
<span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/File:Ion_engine.svg">NASA</a></span>
</figcaption>
</figure>
<h2>Electric space power</h2>
<p>There are three broad types of electric propulsion, depending on the method used to accelerate the fuel. </p>
<p>Electrothermal engines use electric power to heat the propellant either by passing a current through a heating element, a configuration known as a <a href="http://www.lr.tudelft.nl/?id=26232&L=1">resistojets</a>, or by passing a current through the hot ionized gas or plasma itself, an <a href="http://www.lr.tudelft.nl/en/organisation/departments/space-engineering/space-systems-engineering/expertise-areas/space-propulsion/propulsion-options/thermal-rockets/arcjets/">arcjet</a>. </p>
<p>Electromagnetic engines ionise the propellant by turning it into an electrically conductive plasma, which is accelerated via the interaction of a high electrical current and a magnetic field. Known as <a href="http://www.nasa.gov/centers/glenn/about/fs23grc.html">pulsed plasma thrusters</a>, this technique is in fact quite similar to how an electric motor works.</p>
<p>Electrostatic engines use an electric field generated by applying a high voltage to two grids perforated with many tiny holes to accelerate the propellant, called a <a href="http://www.nasa.gov/centers/glenn/technology/Ion_Propulsion1.html">gridded ion engine</a>, which is what powers Dawn. Another electrostatic design is the <a href="http://www.aps.org/units/dfd/meetings/upload/Gallimore_APSDFD08.pdf">Hall effect thruster</a>, which operates in a similar fashion but instead of high voltage grids generates an electric field at the thruster’s exit plane by trapping electrons in a magnetic field. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0Kl-vromzaQ?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>Half a century in the making</h2>
<p>The concept of electric propulsion has been around for 50 years or more, but was deemed too experimental to commit to major projects. Only now is it beginning to find real applications. For example, keeping geostationary satellites in their correct orbit, to counteract the aerodynamic drag from the very tenuous atmosphere 200km above the Earth. Or interplanetary missions such as <a href="http://www.jpl.nasa.gov/missions/deep-space-1-ds1/">Deep Space 1</a> – the first experimental mission to use ion engines, it was originally intended as a technology demonstrator but performed a successful fly-past of the <a href="http://neo.jpl.nasa.gov/images/braille.html">asteroid 9969 Braille</a> and the <a href="http://science.nasa.gov/science-news/science-at-nasa/2001/ast25sep_1/">comet Borrelly</a> 15 years ago. </p>
<p>Another very successful mission using ion engines was the ESA Gravity field and steady-state Ocean Circulation Explorer (<a href="http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/GOCE_completes_its_mission">GOCE</a>) satellite which for four years until 2013 was able to map in unprecedented detail the Earth’s gravity field. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=279&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=279&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=279&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=350&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=350&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74088/original/image-20150306-13585-138gpx4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=350&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 Dawn spacecraft, equipped with large solar panels to power its electrical engine.</span>
<span class="attribution"><a class="source" href="http://sec353ext.jpl.nasa.gov/ep/multimedia.html">NASA</a></span>
</figcaption>
</figure>
<h2>Future designs</h2>
<p>Now that electric spacecraft engines have entered mainstream use, they look set to reduce the cost of deploying satellites. With compact ion engines onboard, satellites can raise themselves from low Earth orbit to their final geostationary orbit under their own power. This will save enormous amounts of fuel required to lift the satellite through conventional chemical rockets, and allow the use of much smaller launch vehicles which will save a lot of money. Boeing was the first off the blocks in 2012 with an all-electric version of their <a href="http://www.boeing.com/boeing/defense-space/space/bss/factsheets/702/702SP.page">702 platform satellite</a> fitted with xenon-powered gridded ion engines, and other satellite manufacturers are following suit.</p>
<p>Currently all electric power designs use xenon gas as the propellant, but the search is on for alternative propellants since xenon is enormously expensive and in limited supply. But electrical power is here to stay, and over the longer term, space tugs and even <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a429836.pdf">manned missions to Mars</a> based on nuclear electric propulsion will be the next on the drawing board.</p><img src="https://counter.theconversation.com/content/38502/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steve Gabriel receives funding from ESA.</span></em></p>It’s no TIE fighter, but the Dawn probe is driven by the future of spacecraft propulsion: ion engines.Steve Gabriel, Professor of Aeronautics and Astronautics, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/358632015-01-05T13:34:03Z2015-01-05T13:34:03ZSpace exploration promises to be spectacular in 2015<figure><img src="https://images.theconversation.com/files/68188/original/image-20150105-13830-1j57955.jpg?ixlib=rb-1.1.0&rect=0%2C1164%2C2700%2C1232&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hey Jupiter and Io, I'm on my way to Pluto.</span> <span class="attribution"><a class="source" href="http://www.nasa.gov/multimedia/imagegallery/image_feature_2107.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>There is no doubt that 2014 was a fantastic year for planetary sciences – the high points were the <a href="https://theconversation.com/scientists-at-work-from-rosetta-mission-control-as-philae-lands-34152">successful landing of Philae on comet 67P</a>, the <a href="https://theconversation.com/curiosity-catches-a-whiff-of-methane-on-mars-and-a-possibility-of-past-life-35595">discovery of methane by the Curiosity rover on Mars</a> and a doubling in the number of known <a href="https://theconversation.com/explainer-how-do-you-find-exoplanets-24153">exoplanets</a>.</p>
<p>As well as scientific advances, there were important technology developments – the <a href="https://theconversation.com/billion-people-hold-their-breath-as-india-becomes-the-first-asian-country-to-reach-mars-32071">arrival of the Mangalyaan spacecraft</a> at Mars signalled that India had become a significant member of the space-faring club of nations. And China continued its <a href="https://theconversation.com/chinas-success-means-october-wasnt-all-bad-news-for-space-exploration-33803">inexorable progress in lunar exploration</a> with the successful launch and return of a robotic mission to the moon. </p>
<p>Despite setbacks in human space exploration, most notably the <a href="https://theconversation.com/pilots-of-virgin-galactic-spaceshiptwo-deserve-our-admiration-and-honour-33710">explosion of Virgin Galactic’s SpaceShip Two</a> and the tragic death of its pilot, there were encouraging steps forward, including a <a href="https://theconversation.com/orion-to-boldly-go-so-long-as-the-wind-blows-fair-and-the-weather-holds-34170">successful test flight of NASA’s Orion</a> exploration vehicle.</p>
<h2>How can 2015 follow these achievements?</h2>
<p>Early in the new year, NASA’s Dawn mission will approach the largest body in the asteroid belt, <a href="https://solarsystem.nasa.gov/planets/profile.cfm?Object=Dwa_Ceres">Ceres</a>. This stony object is about 1,000 km across and is thought to be almost completely unchanged since its formation some 4.6 billion years ago.</p>
<p>The <a href="http://pluto.jhuapl.edu/">New Horizons mission</a> will take increasingly detailed images of Pluto and its moons, leading up to closest approach in July. This mission was launched back in 2006 – when Pluto was still considered a planet. Now Pluto is classified as a Kuiper Belt object (KBO), demoted by the International Astronomical Union a few years ago. The Kuiper Belt, a swarm of many thousands of rocky and icy objects which orbit the sun beyond Neptune, is also presumed to be the location from which many short-period comets originate.</p>
<p>Comets, or at least one comet, 67P Churyumov-Gerasimenko, will continue to hog science headlines, as the Rosetta spacecraft <a href="https://theconversation.com/video-the-amazing-rosetta-spacecraft-and-philae-lander-34116">accompanies the comet</a> on its approach towards the sun. By late spring, it is hoped that the Philae lander will have warmed sufficiently for its solar-powered batteries to charge up, allowing the probe to continue its analysis of the cometary nucleus. Even if that does not happen, there will be spectacular images from Rosetta of changes to the comet’s surface. Perihelion (closest approach to the sun) is in August, by which time the comet’s tail should be well developed.</p>
<h2>The space twins experiment</h2>
<p>The Human Space Exploration programme will remain centred on the operation of the International Space Station – especially from March when the NASA astronaut Scott Kelly and the Russian cosmonaut Mikhail Kornienko are due to commence a <a href="http://www.nasa.gov/content/one-year-crew/index.html#.VKRBJdKsWSq">one-year mission</a>. They will be closely monitored for the effects of lengthy space habitation in preparation for future space travel to Mars. Scott Kelly’s twin brother Mark, who is also an astronaut, <a href="http://time.com/meet-the-twins-unlocking-the-secrets-of-space/?pcd=hp-magmod">will remain on Earth</a> and will be monitored as a terrestrial “control” for the mission. There will be a roster of astronauts joining Kelly and Kornienko, including Tim Peake, the UK’s first astronaut to visit the ISS. He will join the crew in November 2015. </p>
<p>Depending on when the launch takes place, Kelly and Kornienko might have a prime view of the total eclipse of the sun, which is due to take place on March 20. The eclipse track is across the northern hemisphere, but only crosses the land masses of <a href="http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2015Mar20Tgoogle.html">Svalbard and the Faroe Isles</a>. </p>
<p>A week before the eclipse, NASA plans to launch the <a href="http://mms.gsfc.nasa.gov/">Magnetosphere MultiScale</a> (MMS) mission into Earth orbit. This is a flotilla of four probes which, broadly speaking, will measure interactions between the solar wind and the Earth’s magnetic field. The observations will not only help us to understand (and possibly predict the effects of) <a href="https://theconversation.com/why-were-preparing-weather-forecasts-in-space-32638">space weather</a>, but will also cast light on behaviour of turbulent plasmas in other environments, such as close to black holes. </p>
<p>So 2015 promises many exciting events – and these are only the ones which are planned. The excitement of planetary sciences is that we don’t know what else might be in store. A new, bright comet <a href="https://theconversation.com/attention-all-martian-satellites-and-rovers-a-comet-is-coming-33159">might swim into view</a>, an Earth-sized exoplanet with an oxygen-rich atmosphere might be discovered, or a <a href="https://theconversation.com/secrets-revealed-of-dash-cam-meteorite-that-rocked-russia-19923">meteorite might hit the Earth</a>, bringing fresh information about our origins. </p>
<p>No-one knows what is in store – but I wish that whatever your field all your systems will be nominal.</p><img src="https://counter.theconversation.com/content/35863/count.gif" alt="The Conversation" width="1" height="1" />
There is no doubt that 2014 was a fantastic year for planetary sciences – the high points were the successful landing of Philae on comet 67P, the discovery of methane by the Curiosity rover on Mars and…Monica Grady, Professor of Planetary and Space Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.