{"id":16351,"date":"2015-04-30T19:58:17","date_gmt":"2015-04-30T11:58:17","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/messenger-mission-ends-with-plunge-into-mercury\/"},"modified":"2015-04-30T19:58:17","modified_gmt":"2015-04-30T11:58:17","slug":"messenger-mission-ends-with-plunge-into-mercury","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/messenger-mission-ends-with-plunge-into-mercury\/","title":{"rendered":"Messenger mission ends with plunge into Mercury"},"content":{"rendered":"
\"Artist's
Artist\u2019s concept of the Messenger spacecraft flying over Mercury\u2019s surface displayed in enhanced color. The crater ringed by bright orange is Calvino crater. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington<\/figcaption><\/figure>\n

NASA\u2019s Messenger spacecraft closed out a successful four-year tour in Mercury\u2019s orbit Thursday with a cataclysmic crash into the scorching planet after consuming its last gasps of fuel.<\/p>\n

The $446 million robotic science mission was the first probe to ever enter orbit around the closest planet to the sun, where it mapped Mercury\u2019s tortured landscape, confirmed the existence of water ice buried inside permanently dark polar craters, and found a world far more dynamic than researchers predicted.<\/p>\n

The orbiter launched from Cape Canaveral aboard a Delta 2 rocket in August 2004 and returned to Earth a year later to reshape its trajectory toward Mercury. Two fleeting flybys of Venus and three encounters with Mercury set up for Messenger\u2019s final approach to the innermost planet in March 2011.<\/p>\n

Messenger was fitted with a sunshield to weather temperatures up to 600 degrees Fahrenheit during the trek toward the sun.<\/p>\n

Designed for a one-year mission, Messenger lasted four years and spent the last 12 months gathering unprecedented data on Mercury from lower altitudes than any mission before it.<\/p>\n

Messenger ran out of hydrazine fuel April 6, and it used leftover helium pressurant in a last-ditch effort to counteract the pull of gravity and extend the mission a few extra weeks.<\/p>\n

Ground controllers at the Johns Hopkins University Applied Physics Laboratory in Maryland tracked Messenger\u2019s final days, predicting the space probe would strike Mercury around 3:26 p.m. EDT (1926 GMT) Thursday.<\/p>\n

Mission managers expected Messenger to impact Mercury at a velocity of 8,750 mph on the planet\u2019s northern hemisphere, out of view of Earth. Messenger\u2019s operations team confirmed the probe\u2019s crash a few minutes later when they did not receive a signal from the spacecraft at the time it would have emerged back in range of ground-based communications antennas.<\/p>\n

\"Messenger
Messenger was predicted to impact near the center of this region on Mercury, located at 54.4 degrees north latitude and 210.1 degrees east longitude near the \u201cShakespeare\u201d impact basin. This image includes data from Messenger\u2019s dual imaging system and laser altimeter, with red colors representing higher elevations. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington<\/figcaption><\/figure>\n

Scientists said the high-speed impact would carve fresh crater 50 feet wide on Mercury\u2019s surface, and the BepiColombo spacecraft built in Europe and Japan will look for Messenger\u2019s impact scar after its scheduled arrival at Mercury in 2024.<\/p>\n

Messenger collected science data up to its last day, with the final downlink of stored observations and images streaming back to Earth on Thursday morning.<\/p>\n

\u201cGoing out with a bang as it impacts the surface of Mercury, we are celebrating Messenger as more than a successful mission,\u201d said John Grunsfeld, head of NASA\u2019s science directorate. \u201cThe Messenger mission will continue to provide scientists with a bonanza of new results as we begin the next phase of this mission \u2014 analyzing the exciting data already in the archives, and unravelling the mysteries of Mercury.\u201d<\/p>\n

Messenger\u2019s suite of science instruments gathered 10 terabytes of data on Mercury over its four-year mission, completing 4,105 laps of the planet.<\/p>\n

\u201cThe spacecraft and the instruments have worked virtually flawlessly over those four years,\u201d said Jim Green, director of NASA\u2019s planetary science division. \u201cThe data is on Earth, and we have it now. We\u2019re going to continue to make wonderful discoveries with it.\u201d<\/p>\n

Before Messenger\u2019s mission, less than half of Mercury was mapped from images during flybys in the 1970s by NASA\u2019s Mariner 10 spacecraft.<\/p>\n

\u201cI think it\u2019s good to put this into perspective,\u201d said Nancy Chabot, lead scientist for Messenger\u2019s dual camera system at the Applied Physics Laboratory. \u201cBefore this mission, we had seen 45 percent of the planet. I had a globe, and more than half of it was blank. It\u2019s just been huge, changing our understanding of the planet as a whole.\u201d<\/p>\n

Images of fault scarps on Mercury taken by Messenger indicate the planet is contracting \u2014 a sign that its internal core is still cooling \u2014 and measurements show Mercury\u2019s magnetic field is surprisingly offset from the planet\u2019s center, said Sean Solomon, Messenger\u2019s principal investigator from Columbia University\u2019s Lamont-Doherty Earth Observatory.<\/p>\n

\"Sean
Sean Solomon, Messenger\u2019s principal investigator, speaks at a celebration of the mission in April. Credit: NASA\/Aubrey Gemignani<\/figcaption><\/figure>\n

Messenger also revealed a tenuous atmosphere around Mercury extending into a comet-like tail behind the planet as molecules are blasted away by intense solar radiation. The mission monitored seasonal changes in the atmosphere as Mercury sped around the sun in its 88-day orbit.<\/p>\n

Mercury\u2019s reputation as a hellish world is well-deserved \u2014 temperatures can get up to 800 degrees Fahrenheit during daytime \u2014 but isolated pockets of the planet never see the sun.<\/p>\n

Such regions at the bottoms of Mercury\u2019s polar craters are cold enough to support deposits of water ice, and Messenger\u2019s science team verified the ice\u2019s presence at or just below Mercury\u2019s surface after scanning the material with cameras, a laser altimeter and a neutron spectrometer.<\/p>\n

Earth-based radars hinted at the ice on Mercury, but evidence from Mercury gave researchers confidence the ice slabs are there.<\/p>\n

\u201cPerhaps the most interesting discovery might be the polar deposits,\u201d Solomon said.<\/p>\n

The last leg of Messenger\u2019s mission at low altitude gave scientists a chance to see into the shaded bottoms of the craters in more detail, according to Chabot.<\/p>\n

\u201cWe\u2019re actually seeing into these regions where the sun never shines on Mercury in higher resolution than has ever been possible before,\u201d Chabot said in March.<\/p>\n

Snapping long exposures and using sunlight scattered off crater walls, high-contrast images from Messenger\u2019s two-eyed camera exposed sharp features that appear to be soils laid on top of ice.<\/p>\n

\u201cMost of these deposits don\u2019t consist of water ice directly at the surface, but rather water ice covered by a dark layer which we think is 20 to 30 centimeters (8 to 12 inches) thick,\u201d Solomon said. \u201cAnd that dark layer is darker than anything else on Mercury.\u201d<\/p>\n

\"A
A view inside the permanent shadow of Fuller crater, where ice is thought to reside. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington<\/figcaption><\/figure>\n

The stuff preserved on Mercury\u2019s hidden crater floors could the same type of mixture of water and organic compounds that ripened into life on Earth.<\/p>\n

\u201cThe team has put forward the hypothesis that this dark material is, in fact, organic carbonaceous material delivered to Mercury by the same objects that brought the water ice stored in these deep freezes at the north and south poles, giving us a record in these poles of the delivery process from the outer solar system not only of water ice, but of what \u2014 on our planet \u2014 were once the building blocks of organic chemistry and life,\u201d Solomon said.<\/p>\n

Mercury has a larger iron core relative to its overall size than any other planet in the solar system, so scientists assumed its other elements would be blown away by intense heat from the sun.<\/p>\n

Messenger found a world rich in lighter elements like sodium, sulfur, potassium and chlorine. Despite Mercury\u2019s iron interior, scientists say Messenger saw relatively little of the element in the planet\u2019s crust.<\/p>\n

\u201cSo the ideas for how the inner planets got assembled, and how the building blocks of planetary materials were delivered to the inner solar system and survived the process of plaentary accretion, are all being changed by Messenger\u2019s results,\u201d Solomon said.<\/p>\n

Larry Nittler, the No. 2 scientist working on the Messenger mission, said the probe\u2019s data archive will be tapped to help refine models on how the solar system\u2019s rocky planets formed.<\/p>\n

\u201cOne of the big science questions that Messenger set out to answer was why Mercury has this large core and this thin silicate shell, and I would argue we still don\u2019t know the answer to that question a whole lot better than we knew before we went into orbit,\u201d Nittler said. \u201cPart of this is not due to a lack of data, but a lack of quantitative understanding of the different possibilities that could lead to this.<\/p>\n

\u201cFor example, a very popular model for a long time was the idea that Mercury might have formed much larger and had a giant impact that stripped off much of its pre-existing mantle and crust,\u201d Nittler said. \u201cThen it formed a new crust on its small remaining mantle.<\/p>\n

\"Messenger
Messenger obtained this global view of Mercury during a flyby encounter in 2008. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington<\/figcaption><\/figure>\n

\u201cI think a lot of the questions that were raised \u2014 and are still raised \u2014 are possibly still answerable with the data we obtained,\u201d Nittler said. \u201cThat\u2019s the big one that I really hope we eventually answer.\u201d<\/p>\n

Solomon singled out Mercury\u2019s ice deposits as the most interesting discovery by Messenger\u2019s mission, noting the finding\u2019s implications for life.<\/p>\n

\u201cI don\u2019t think anybody would count Mercury as habitable in the sense that there\u2019s no part of the surface or the near-subsurface where water can be stable in a liquid form,\u201d Solomon said.<\/p>\n

But Mercury has a story to tell in the pursuit of life\u2019s origins, he added, because like Earth, it was bombarded by organic-rich asteroids and comets that left behind water and the chemical constituents of organisms.<\/p>\n

\u201cEven a planet that is not in the nominal habitable zone of our own star is a witness to the delivery of the ingredients of habitability from the outer solar system to the inner solar system, including the ice and including the organic building blocks that are capable \u2014 on other bodies \u2014 of leading to pre-biotic organic chemistry,\u201d Solomon said.<\/p>\n

\u201cIn terms of understanding what leads to habitability, Mercury has to be included.\u201d<\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/i><\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

Artist\u2019s concept of the Messenger spacecraft flying over Mercury\u2019s surface displayed in enhanced color. The crater ringed by bright orange is Calvino crater. Credit: NASA\/Johns Hopkins University Applied Physics Laboratory\/Carnegie Institution of Washington NASA\u2019s Messenger spacecraft closed out a successful four-year tour in Mercury\u2019s orbit Thursday with a cataclysmic crash into the scorching planet after […]<\/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":[1861,2040,4070],"class_list":["post-16351","post","type-post","status-publish","format-standard","hentry","category-news","tag-jhuapl","tag-mercury","tag-messenger"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/16351"}],"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=16351"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/16351\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=16351"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=16351"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=16351"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}