"Long before it's in the papers"
January 27, 2015


Comet lander said to find dusty ice, organic molecules

Nov. 18, 2014
World Science staff

A lan­der that spent two days on a com­et be­fore los­ing pow­er has sent da­ta sug­gest­ing the sur­face be­neath was of dusty ice, mis­sion sci­en­tists said Tues­day.

An in­ves­ti­ga­tor for the Eu­ro­pe­an Space Agen­cy mis­sion, called Ro­set­ta, al­so told Brit­ish me­dia that the lan­der had de­tected or­gan­ic molecules, but did not say which ones.

The lighter shaded area in the diagram focuses on the MUPUS instrument aboard the Philae lander. (Credits: ESA/ATG medialab)

Some pre­lim­i­nar­y find­ings come from an in­stru­ment pack­age called Mu­pus, for Mul­ti­-Purpose Sen­sors for Sur­face and Subsur­face Sci­ence, aboard the Phi­lae lan­der. Mu­pus is de­signed to test out the tem­per­a­ture, com­pact­ness and hard­ness of the sur­face.

At Phi­lae’s fi­nal land­ing spot, Mu­pus in­i­tially rec­orded a tem­per­a­ture of –153 de­grees Cel­si­us (–243 de­grees F) next to the lan­der, mis­sion sci­en­tists said, an­nounc­ing pre­lim­i­nar­y re­sults on the agen­cy’s Ro­set­ta Blog. 

These tem­per­a­tures are si­m­i­lar to what a ther­mom­e­ter would rec­ord on the shad­ed side of the In­terna­t­ional Space Sta­t­ion above Earth, al­though the com­et is cur­rently about three times fur­ther from the Sun than that.

The cold­est tem­per­a­ture the­o­ret­ic­ally pos­si­ble, called ab­so­lute ze­ro, is only around one or two hun­dred de­grees low­er (for Cel­si­us or Fahr­en­heit, re­spec­tive­ly).

Af­ter taking the in­i­tial read­ing, Mu­pus sen­sors cooled by about 10 de­grees Cel­si­us over about half an hour, pos­sibly be­cause the in­stru­ment ra­di­at­ed away heat or “the probe had been pushed in­to a cold dust pile,” said Jörg Knol­len­berg, in­stru­ment sci­ent­ist for Mu­pus at Ger­man­y’s DLR aer­o­space cen­ter.

The in­stru­ment then started to ham­mer it­self in­to the ground but could­n’t get fur­ther than a few mil­lime­ters, hav­ing hit “a hard sur­face with strength com­pa­ra­ble to that of sol­id ice,” added Tilman Spohn, Mu­pus prin­ci­pal in­ves­ti­ga­tor.

At great­er depths in­side the com­et, the ice likely is likely more po­rous, as in­stru­ments on Ro­set­ta it­self sug­gest the in­te­ri­or is not very com­pact, ac­cord­ing to the Ro­set­ta Blog.

Sci­en­tists orig­i­nally hoped to get re­peat­ed mea­sure­ments out of Mu­pus to ob­serve any changes as the com­et cir­cled around the Sun. As it turned out, they said, the Phi­lae lan­der lost pow­er on Nov. 15 be­cause—af­ter two un­in­tend­ed bounces off an initial landing spot—it wound up in a place in too poorly lit for the so­lar pan­els to re­charge a sec­ond­ary bat­tery. Scientists still have no more than a rough idea of the lander’s location on the comet, called 67P/Chur­yu­mov-Ge­ras­i­men­ko.

“Mu­pus could be used again if we get enough pow­er” as the com­et ap­proaches the sun, when sci­entists hope to re­awak­en the land­er, Spohn said.

Sep­a­rate­ly, a sci­ent­ist work­ing with the lan­der’s Cosac in­stru­ment (COm­et­ary SAm­pling and Com­po­si­tion) told the BBC News on Tues­day that its sen­sors had de­tected or­gan­ic mo­le­cules in the gas­es sur­round­ing the com­et. How­ev­er, the sci­ent­ist, in­stru­ment Prin­ci­pal In­ves­ti­ga­tor Fred Goess­mann, did not of­fer de­tails pend­ing fur­ther stu­dy. NASA’s Deep Im­pact com­et mis­sion in 2005 al­so de­tected a va­ri­e­ty of or­gan­ic mo­le­cules af­ter it sent a probe, Deep Im­pact, to hit com­et Tempel 1.

Since or­gan­ic, or carbon-containing, mo­le­cules are the ba­sis of life, some the­o­ries hold that com­ets have been one way that life spreads through­out the uni­verse.

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A lander that spent two days on a comet before losing power has sent data suggesting the surface beneath was of dusty ice, mission scientists said Tuesday. An investigator for the European Space Agency mission, called Rosetta, also told British media that the lander had detected organic molecules, but did not say which ones. Some preliminary findings come from an instrument package called Mupus, for Multi-Purpose Sensors for Surface and Subsurface Science, aboard the Philae lander. Mupus is designed to test out the temperature, compactness and hardness of the surface. At Philae’s final landing spot, Mupus initially recorded a temperature of –153 degrees Celsius (–243 degrees F) next to the lander, mission scientists said, announcing preliminary results on the agency’s Rosetta Blog. These temperatures are similar to what a thermometer would record on the shaded side of the International Space Station above Earth, although the comet is currently about three times further from the Sun than that. The coldest temperature theoretically possible, called absolute zero, is only around one or two hundred degrees lower (for Celsius or Fahrenheit, respectively). After the initial reading, Mupus sensors at the tip of the instrument cooled by about 10 degrees Celsius over about half an hour, possibly because the instrument radiated away heat or “the probe had been pushed into a cold dust pile,” said Jörg Knollenberg, instrument scientist for Mupus at Germany’s DLR aeronautics center. The instrument then started to hammer itself into the ground but couldn’t get further than a few millimeters, having hit “a hard surface with strength comparable to that of solid ice,” added Tilman Spohn, Mupus principal investigator. At greater depths inside the comet, the ice likely is likely more porous, as instruments on Rosetta itself suggest the interior is not very compact, according to the Rosetta Blog. Scientists originally hoped to get repeated measurements out of Mupus to observe any changes as the comet circled around the Sun. As it turned out, they said, the Philae lander lost power on Nov. 15 because, after two unintended bounces, it landed in a spot too poorly lit for the solar panels to recharge a secondary battery. “Mupus could be used again if we get enough power” as the comet approaches the sun, Spohn said. Separately, a scientist working with the lander’s Cosac instrument (COmetary SAmpling and Composition) told the BBC News on Tuesday that its sensors had detected organic molecules in the gases surrounding the comet. However, the scientist, instrument Principal Investigator Fred Goessmann, did not offer details pending further study. NASA’s Deep Impact comet mission in 2005 also detected a variety of organic molecules after it sent a probe, Deep Impact, to hit a comet. Since organic, or carbon-containing, molecules are the basis of life, some theories hold that comets have been one way that life spreads throughout the universe.