Ev­i­dence of Mar­tian life?

Ac­cord­ing to a new study, if there was ever life on Mars, Gale Crater could have hosted mi­crobes.

The Star Malaysia - Star2 - - Science - By AMINA KHAN

SCI­EN­TISTS with NASA’s Mars Cu­rios­ity rover mis­sion have found that Gale Crater had the right phys­i­cal and chem­i­cal con­di­tions for life for 700 mil­lion years – and for part of that his­tory, held a lake that could have hosted a wide va­ri­ety of mi­cro­bial life.

The find­ings, pub­lished re­cently in the jour­nal Science, doc­u­ment a long-last­ing Mar­tian en­vi­ron­ment that had the po­ten­tial to host a wide va­ri­ety of liv­ing things.

“It helps to broaden our un­der­stand­ing of what it meant to be a hab­it­able en­vi­ron­ment on Mars, three bil­lion years ago,” said lead au­thor Joel Hurowitz, a geo­chemist at Stony Brook Uni­ver­sity.

Since land­ing in Gale Crater in 2012, Cu­rios­ity has drilled, x-rayed and laser-blasted a va­ri­ety of rocks in the quest to un­der­stand whether the Red Planet – a world that be­gan much like our own – could ever have been hos­pitable to life.

Us­ing its state-of-the-art in­stru­ments, Cu­rios­ity’s mis­sion was to drive to Mount Sharp, the 4.8km-high mound in the mid­dle of the crater. There, it would climb its slopes, read­ing each sed­i­men­tary layer of rock like a chap­ter in the ge­o­logic his­tory of Mars.

On its jour­ney, Cu­rios­ity dis­cov­ered ev­i­dence of past wa­ter and the right chem­i­cal in­gre­di­ents for life; re­cent stud­ies have found that Gale Crater was once filled with a se­ries of lakes that may have risen and fallen over time.

But what was that an­cient body of wa­ter like? In this new study, sci­en­tists have now put to­gether the ev­i­dence from sev­eral spots along the jour­ney to and up Mount Sharp, in­clud­ing six drilled rock sam­ples pulled from very dif­fer­ent an­cient en­vi­ron­ments.

The re­sults re­vealed a wealth of the in­gre­di­ents needed for life as we know it, in­clud­ing or­ganic car­bon com­pounds, ni­tro­gen, and phos­phate min­er­als, as well as iron and sul­phur min­er­als in dif­fer­ent re­dox states.

“Our anal­y­sis of those rocks in­di­cates that gra­di­ents in lake wa­ter ox­i­da­tion state were present in the pri­mary la­cus­trine en­vi­ron­ment,” the study au­thors wrote. “Taken to­gether, these re­sults pro­vide com­pelling ev­i­dence that the phys­i­cal, chem­i­cal and en­er­getic con­di­tions nec­es­sary to es­tab­lish a hab­it­able en­vi­ron­ment were present on Mars be­tween 3.8 and 3.1 (bil­lion years ago).”

The sci­en­tists also no­ticed a strange pat­tern in a stretch of lay­ered rock. There were re­gions where lots of coarse sed­i­ment had been rapidly dumped – mark­ing the shal­lows where wa­ter flow­ing into the lake from a stream or river would have dropped much of its heavy ma­te­rial.

There were also ar­eas where much finer-grained sed­i­ment had been lay­ered on more grad­u­ally – closer to the mid­dle of the lake, and far­ther away from the river mouth.

Here was the odd bit: Chem­i­cally speak­ing, the min­er­als in the shal­lower parts of the lake ap­pear to have been ex­posed to more oxy­gen, while the min­er­als in the deeper ar­eas had not.

It seems that the wa­ters of Gale’s lake had, for at least a por­tion of its his­tory, dif­fer­en­ti­ated into an oxy­gen-rich layer near the sur­face, and an oxy­gen-poor layer in its depths.

That’s a lot like lakes on Earth, which also dif­fer­en­ti­ate in the same way.

“It’s that re­la­tion­ship be­tween the min­er­al­ogy and the thick­ness of the sed­i­ment lay­ers that al­lows us to con­nect the dots,” said study co-au­thor Ash­win Vasavada, the mis­sion’s project sci­en­tist at Jet Propul­sion Lab­o­ra­tory.

This com­plex lake could have lasted any­where from hun­dreds of thou­sands of years to 10 mil­lion years, Hurowitz said.

Like the lakes on Earth, the one in Gale Crater could have hosted a va­ri­ety of micro­organ­isms, in­clud­ing some that pre­ferred the oxy­genated wa­ters near the sur­face, oth­ers who pre­ferred the anoxic wa­ters deeper down, and those who liked to hang out at the in­ter­face be­tween the two.

Over this pe­riod, the sci­en­tists also found that Mars seemed to progress from a colder, drier en­vi­ron­ment to a warmer, wet­ter one.

On top of that, its lay­ers of sed­i­men­tary record were mod­i­fied by what ap­pears to be briny liq­uid.

Study­ing these rocks could help sci­en­tists un­der­stand the ul­ti­mate dry­ing of Mars as its wa­ter es­caped to space, leav­ing the salts be­hind.

For now, there’s no way to know whether life ever did emerge on the Red Planet; Cu­rios­ity is only de­signed to de­ter­mine whether en­vi­ron­ments are hab­it­able, not in­hab­ited.

That ques­tion will have to wait for fu­ture mis­sions, in­clud­ing the Mars 2020 rover, which will col­lect and cache promis­ing rock sam­ples for later space­craft to come re­trieve. – Los An­ge­les Times/ Tri­bune News Ser­vice

NASA’s Cu­rios­ity rover landed on the Mar­tian crater known as Gale Crater. Sci­en­tists say the crater had the right phys­i­cal and chem­i­cal con­di­tions for life for 700 mil­lion years. — TNS.

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