{"id":14313,"date":"2017-09-27T20:32:46","date_gmt":"2017-09-27T12:32:46","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/scientists-celebrate-10th-anniversary-of-dawn-missions-launch\/"},"modified":"2017-09-27T20:32:46","modified_gmt":"2017-09-27T12:32:46","slug":"scientists-celebrate-10th-anniversary-of-dawn-missions-launch","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/scientists-celebrate-10th-anniversary-of-dawn-missions-launch\/","title":{"rendered":"Scientists celebrate 10th anniversary of Dawn mission\u2019s launch"},"content":{"rendered":"<figure id=\"attachment_16590\" aria-describedby=\"caption-attachment-16590\" style=\"width: 676px\" class=\"wp-caption alignnone\"><img fetchpriority=\"high\" decoding=\"async\" class=\" wp-image-16590\" src=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard.jpg\" alt=\"\" width=\"676\" height=\"507\" srcset=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard.jpg 1600w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-300x225.jpg 300w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-768x576.jpg 768w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-1024x768.jpg 1024w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-678x509.jpg 678w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-326x245.jpg 326w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/07\/dawnjournal_standard-80x60.jpg 80w\" sizes=\"(max-width: 676px) 100vw, 676px\"><figcaption id=\"caption-attachment-16590\" class=\"wp-caption-text\">Artist\u2019s concept of the Dawn spacecraft with imagery of Ceres (left) and Vesta (right) captured during the mission. Credit: NASA\/JPL-Caltech<\/figcaption><\/figure>\n<p>In the ten years since its launch from Cape Canaveral, NASA\u2019s Dawn spacecraft has orbited the two largest worlds in the asteroid belt and overcome defective components that threatened to derail the mission on its 4 billion-mile voyage, discovering unexpectedly&nbsp;rich geologic tapestries suggesting both destinations have a watery past.<\/p>\n<p>The roughly $500 million project has made history, becoming the first spacecraft to orbit two different objects other than the Earth and the moon, and making the first up-close surveys of the dwarf planet Ceres and the giant asteroid Vesta, which rank No. 1 and No. 2 among the biggest objects in the asteroid belt, a region between the orbits of Mars and Jupiter.<\/p>\n<p>\u201cDawn has exceeded everybody\u2019s expectations, and certainly mine,\u201d said Carol Raymond, Dawn\u2019s deputy principal investigator from the Jet Propulsion Laboratory in Pasadena, California. \u201cI think it\u2019s been an exceptional mission from so many different perspectives. Certainly, the fact that we flew to and orbited two objects in the main asteroid belt, the two most massive objects in the main belt, is a feat in and of itself.\u201d<\/p>\n<hr>\n<h6>Spaceflight Now members can read a transcript of Carol Raymond\u2019s interview.<\/h6>\n<hr>\n<h5><\/h5>\n<p>The mission almost never made it to the launch pad.<\/p>\n<p>Cost overruns and difficulties with Dawn\u2019s electric propulsion system \u2014 a set of three ion engines using electricity and xenon gas to produce thrust \u2014 prompted NASA to cancel the mission in March 2006. The space agency reinstated the mission less than a month later after an appeal from managers at JPL.<\/p>\n<p>NASA selected the Dawn mission in 2001 from a list of proposals submitted by scientists. Then slated for launch in 2006, Dawn joined NASA\u2019s Discovery line of cost-capped missions exploring the solar system, a program that has included the Mars Pathfinder rover mission and the Messenger orbiter sent to Mercury.<\/p>\n<p>Built by Orbital Sciences Corp. \u2014 now known as Orbital ATK \u2014 the solar-powered spacecraft was finally readied for a June 2007 launch aboard a United Launch Alliance Delta 2 rocket. But problems with a crane needed to help assemble the rocket and an aircraft needed to receive telemetry from the launcher after liftoff forced a delay until September.<\/p>\n<p><iframe loading=\"lazy\" width=\"678\" height=\"509\" src=\"https:\/\/www.youtube.com\/embed\/jo3BDzI82wc?feature=oembed\" frameborder=\"0\" allowfullscreen=\"\"><\/iframe><\/p>\n<p>Dawn finally blasted off from Florida\u2019s Space Coast just after sunrise Sept. 27, 2007, getting an interplanetary kick toward Mars for a swingby in February 2009 that reshaped the probe\u2019s trajectory to take aim on Vesta, where it arrived in July 2011.<\/p>\n<p>But Dawn lost the first of its four reaction wheels on the trip to Vesta in 2010, and a second wheel failed in 2012 as the spacecraft prepared to depart the approximately 330-mile-wide&nbsp;(530-kilometer) asteroid.<\/p>\n<p>The spinning reaction wheels used momentum to control Dawn\u2019s orientation without expending precious chemical propellant, helping aim its antenna toward Earth and point its camera and scientific sensors toward their targets.<\/p>\n<p>With two of the wheels lost, ground controllers at JPL and Orbital ATK devised a hybrid control method to point the spacecraft using a blend of its hydrazine thrusters and reaction wheels, minimizing fuel consumption on the solar-powered probe.<\/p>\n<p>\u201cThere were a couple of dramatic points,\u201d Raymond said in an interview with Spaceflight Now. \u201cThe first was right before launch when we learned that we were launching with defective reaction wheels, and there was nothing we could do about it. We went into a mode where we were trying to preserve wheel lifetime.\u201d<\/p>\n<p>Dawn\u2019s time at Vesta yielded several big surprises, chiefly with the discovery of evidence that liquid water may have once flowed on the asteroid, Raymond said.<\/p>\n<p>Scientists already have some samples from Vesta in laboratories on Earth.<\/p>\n<p>Before Dawn\u2019s mission, researchers suspected a special class of rock samples called&nbsp;Howardite\u2013Eucrite\u2013Diogenite, or HED, meteorites that fell to Earth from space were chunks knocked off Vesta by an ancient interplanetary collision.<\/p>\n<p>Dawn confirmed that hypothesis, and found Vesta likely once had global tectonic activity, something scientists did not expect on such a small world.<\/p>\n<p>The Dawn spacecraft\u2019s German-built camera suite found pits in the bottom of several relatively fresh craters on Vesta, suggesting volumes of gas \u2014 perhaps water vapor \u2014 were released by violent impacts with other asteroids.<\/p>\n<p>\u201cIn the same young craters where we saw the pitted terrains, Marcia Crater and Cornelia Crater, there are gullies which are grooves carved into the slopes of the crater in a dendritic pattern, which can\u2019t be explained, or are hard to explain, without invoking a liquid flowing on the surface, and the most obvious volatile would be water,\u201d Raymond said. \u201cSo there is a hypothesis that water was delivered by an impactor, the ice was buried in the subsurface and the ejecta, and then a subsequent impact would melt that ice, it would briefly flow and sublimate and leave behind these telltale gullies.\u201d<\/p>\n<figure id=\"attachment_27516\" aria-describedby=\"caption-attachment-27516\" style=\"width: 676px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-27516\" src=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2017\/09\/PIA19170_hires.jpg\" alt=\"\" width=\"676\" height=\"409\" srcset=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2017\/09\/PIA19170_hires.jpg 1692w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2017\/09\/PIA19170_hires-300x182.jpg 300w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2017\/09\/PIA19170_hires-768x465.jpg 768w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2017\/09\/PIA19170_hires-678x410.jpg 678w\" sizes=\"(max-width: 676px) 100vw, 676px\"><figcaption id=\"caption-attachment-27516\" class=\"wp-caption-text\">This image shows Cornelia Crater on the large asteroid Vesta. The crater is about 4 to 5 million years old. On the right is an inset image showing an example of curved gullies, indicated by the short white arrows, and a fan-shaped deposit, indicated by long white arrows. The inset image is about 0.62 miles (1 kilometer) wide. Credit: NASA\/JPL-Caltech\/UCLA\/MPS\/DLR\/IDA<\/figcaption><\/figure>\n<p>Many scientists believe an extraterrestrial impactor \u2014 a comet or an asteroid \u2014 brought water to Earth soon after it formed.<\/p>\n<p>\u201cThis idea that wet asteroids, more volatile-rich asteroids, could deliver water to the Earth was lent some credence by the fact that we could see the evidence of that volatile delivery to a body like Vesta,\u201d Raymond said. \u201cI think those kinds of results made very clear that going to Vesta and investigating it up close really had a big payoff above and beyond the fact that we already knew so much about Vesta from those samples we had in hand.\u201d<\/p>\n<p>Dawn switched on its ion drive again in 2012 for the journey to Ceres, moving farther out into the solar system and adjusting the tilt of the probe\u2019s orbit around the sun to from 7 to nearly 11 degrees. The maneuvers put Dawn on course to be captured by Ceres\u2019s gravity field in March 2015.<\/p>\n<p>Before Dawn\u2019s arrival, the best imagery of Ceres from the Hubble Space Telescope gave scientists a glimpse of the mysterious mini-planet\u2019s appearance. Scientists knew its size and shape, and they believed Ceres might contain a sub-glacial ocean.<\/p>\n<p>Ceres astonished Dawn\u2019s team almost as soon as the spacecraft moved within visual range.<\/p>\n<p>\u201cThe big surprise during the early approach phase was that there is an area of high reflectivity near Occator (Crater),\u201d said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research in Gottingen, Germany. \u201cIt was so bright in the first images that we saturated all the chips (in the camera) because we didn\u2019t expect such a bright feature on a dark surface.\u201d<\/p>\n<p>The bright spots in Occator Crater immediately triggered speculation that they might be icy patches, or perhaps an erupting volcano spewing water into space. Scientists initially favored the ice explanation, but a closer examination by Dawn\u2019s science instruments revealed them to be deposits of sodium carbonate, a type of salt.<\/p>\n<figure id=\"attachment_13820\" aria-describedby=\"caption-attachment-13820\" style=\"width: 675px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-13820\" src=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/03\/PIA20355.jpg\" alt=\"\" width=\"675\" height=\"344\" srcset=\"https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/03\/PIA20355.jpg 1704w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/03\/PIA20355-300x153.jpg 300w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/03\/PIA20355-768x391.jpg 768w, https:\/\/spaceflightnow.com\/wp-content\/uploads\/2016\/03\/PIA20355-1024x522.jpg 1024w\" sizes=\"auto, (max-width: 675px) 100vw, 675px\"><figcaption id=\"caption-attachment-13820\" class=\"wp-caption-text\">The bright central spots near the center of Occator Crater are shown in enhanced color in this view from NASA\u2019s Dawn spacecraft. Such views can be used to highlight subtle color differences on Ceres\u2019 surface. This image combines high-resolution black-and-white imagery from February 2016 with lower-resolution color data collected by Dawn in September 2015. NASA\/JPL-Caltech\/UCLA\/MPS\/DLR\/IDA\/PSI\/LPI<\/figcaption><\/figure>\n<p>The presence of salts inside the 57-mile-wide (92-kilometer) Occator crater has left experts trying to learn how the deposits got there.<\/p>\n<p>Ralf Jaumann, a planetary scientist and Dawn co-investigator from Germany\u2019s DLR space agency, said one leading theory are that the impactor that excavated Occator created a pool of melted rock and water, an impact-driven hydrothermal system that separated different chemicals in the aftermath of the cosmic smash, leaving behind the salt slabs at the surface.<\/p>\n<p>\u201cAnother idea is that we have (watery) material beneath the surface, which has been released by the impact itself,\u201d Jaumann said. \u201cSo the impact triggered cryovolcanic activity. There\u2019s an open debate about this. It\u2019s not clear how this works.<\/p>\n<p>There still may be water underneath the bright salty features in Occator, which have been named Cerealia Facula and Vinalia Faculae. The central deposit has a fractured salt dome.<\/p>\n<p>\u201cI\u2019m pretty sure that there\u2019s also water in Occator in the subsurface,\u201d Jaumann said. \u201cThe problem we have is all of our instruments are not able to penetrate the surface. We just get the first millimeters of the surface in our data.\u201d<\/p>\n<p>A mountain on another part of Ceres, named Ahuna Mons, is an example of a more recent cryovolcano. The peak, towering more than 15,000 feet (5 kilometers) above nearby terrain, is no longer erupting, but scientists believe it only went dormant in a relatively recent era of geologic history, perhaps as little as a few hundred million years ago.<\/p>\n<p>Ahuna Mons likely spewed out a mixture of water, salt and mud that flowed down its slopes.<\/p>\n<p>\u201cWe\u2019re seeing that there are features on the surface which indicate mobility,\u201d Raymond said. \u201cThere are cryomagmas that have erupted at the Ahuna Mons volcanic construct, as well as the bright spots inside of Occator crater and other craters. So we do think that there are residual pockets of briny liquids in the subsurface today, and the real challenge that we\u2019re working on is by what process are they getting to the surface.\u201d<\/p>\n<p>The briny stuff could be water saturated with salts, lowering its freezing point and allowing it to remain liquid at depths of up to 30 miles (50 kilometers).<\/p>\n<p>Although the buried ocean is gone today, Ceres likely had one earlier in its history, drawing comparisons to Europa and Enceladus, icy moons of Jupiter and Saturn with subsurface seas that have become hotspots in the search for alien microbial life.<\/p>\n<p>But Ceres is much closer to the sun than Europa or Enceladus, and those moons have their insides tugged at by the strong gravity of Jupiter and Saturn, generating internal heat that keeps their oceans liquid to the present day.<\/p>\n<p>\u201cThere is an affinity between some of the icy moons and Ceres, and certainly they do bear resemblances,\u201d Raymond said. \u201cBut since Ceres now lives in such a warm environment relative to those objects, it looks very different. Its ocean froze out. It doesn\u2019t have any tidal heat. So it\u2019s ocean is frozen, and its surface is baking relative to the icy moons. The way it formed, what it formed of, appears to be similar, but the evolutionary paths are quite different.\u201d<\/p>\n<p>Dawn\u2019s gamma ray and neutron detector has sensed hydrogen in Ceres\u2019s crust, suggesting ice embedded in the dwarf planet rocks.<\/p>\n<p>\u201cLiquid water had to be in the interior of Ceres in order for us to see the mineralology that\u2019s on the surface \u2014 the phyllosilicates (clay minerals) \u2014 and also the concentration of the hydrogen that we see in the equator that\u2019s presumed to be ice-free,\u201d said Thomas Prettyman, lead scientist on Dawn\u2019s Gamma Ray and Neutron Detector, or GRAND, instrument from the Planetary Science Institute in Tucson, Arizona.<\/p>\n<p>\u201cSo Ceres\u2019s surface, the fact that it\u2019s ice-rich, and that there are alteration products on the surface, means that at some point in time there was liquid water,\u201d Prettyman said in a press conference last year.<\/p>\n<p>Ceres formed from a collection of pebbles and dust in the proto-solar system around 4.5 billion years ago, likely farther from the sun thats its current location, giving it a heritage closer to the moons of the outer solar system than most asteroids.<\/p>\n<p>\u201cThe material in Occator, the supposed cryovolcanic deposits at Ahuna and the craters, are dominated by sodium carbonate and ammonium salts, and that composition is only found in certain deposits on the Earth that are created in briny lakes, and coming out of the interior of Enceladus in the plumes,\u201d Raymond said. \u201cThis is a very fundamental connection between what\u2019s coming out of Enceladus and what we\u2019re seeing on the surface of Ceres. It doesn\u2019t seem to very common in the solar system.\u201d<\/p>\n<p>NASA granted Dawn a one-year extension in mid-2016, and Raymond said mission managers are waiting for the agency to determine what the spacecraft will do next.<\/p>\n<p>Dawn lost its third reaction wheel earlier this year, leaving it fully reliant on rocket thrusters.<\/p>\n<p>\u201cThe spacecraft is still operating,\u201d Raymond said. \u201cIt\u2019s in excellent health. The instruments are all operating. I think that\u2019s pretty remarkable after 10 years, that everything is working as well as it is, other than the doomed wheels, which were a problem from the start.\u201d<\/p>\n<p>Dawn is currently orbiting in a 30-day elliptical loop&nbsp;ranging from less than 3,200 miles (5,100 kilometers) up to 23,800 miles (38,300 kilometers) from Ceres. The spacecraft is collecting data on cosmic rays in a bid to improve measurements of Dawn\u2019s surface composition, Raymond said.<\/p>\n<p>\u201cThe status of our extended mission proposal is that what Dawn is going to be doing is still under evaluation,\u201d Raymond said. \u201cIt\u2019s really unfortunate that we don\u2019t have answer because obviously a lot of people are going to be looking at Dawn because it\u2019s the 10th anniversary of the launch. It would be nice to have an answer, but we don\u2019t.\u201d<\/p>\n<p>Jim Green, director of NASA\u2019s planetary science division, said last month that senior managers want to ensure Dawn gets al the data it can at Ceres before running out of fuel.&nbsp;That push is being balanced with the desires of some scientists to send Dawn toward another object in the asteroid belt for a flyby.<\/p>\n<p>NASA nixed a proposal last year to send Dawn on a low-speed flyby of asteroid Adeona in favor of continued observations at Ceres, but Raymond said there are still options to redirect the spacecraft to another object with its xenon-fueled ion engines.<\/p>\n<p>\u201cWe will have fuel to operate for at least another year at Ceres,\u201d assuming Dawn remains at relatively high altitudes, Raymond said. \u201cIt\u2019s just a matter of what we\u2019ll be doing, not necessarily whether we\u2019ll be doing something.\u201d<\/p>\n<p>Perturbations from Ceres\u2019s gravity at distances within a few hundred miles of the frozen world would tax Dawn\u2019s dwindling fuel reserve to maintain pointing.<\/p>\n<p>\u201cIf we go back down low, like into a low-altitude orbit that we were in, we wouldn\u2019t last a month,\u201d Raymond said.<\/p>\n<p>\u201cWe\u2019re actually doing a lot of study right now of how we could get the best new data at Ceres,\u201d she said. \u201cWe\u2019ve collected so much data that the challenge is, with the same flight system and the same instruments, how do you get new science data. We\u2019re looking hard at that.\u201d<\/p>\n<p><b><i>Email the author.<\/i><\/b><\/p>\n<p><em><strong>Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Artist\u2019s concept of the Dawn spacecraft with imagery of Ceres (left) and Vesta (right) captured during the mission. Credit: NASA\/JPL-Caltech In the ten years since its launch from Cape Canaveral, NASA\u2019s Dawn spacecraft has orbited the two largest worlds in the asteroid belt and overcome defective components that threatened to derail the mission on its [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1519,3175,2838,2839,2840,1183,2899,1561],"class_list":["post-14313","post","type-post","status-publish","format-standard","hentry","category-news","tag-asteroids","tag-carol-raymond","tag-ceres","tag-dawn","tag-dwarf-planets","tag-jet-propulsion-laboratory","tag-orbital-atk","tag-planetary-science"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/14313"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=14313"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/14313\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=14313"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=14313"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=14313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}