Mars mys­tery: What is pro­duc­ing meth­ane gas?

The Buffalo News - - NATIONAL NEWS - By Ken­neth Chang

Meth­ane gas pe­ri­od­i­cally wafts into the at­mos­phere of Mars; that no­tion, once con­sid­ered im­plau­si­ble and perplexing, is now widely ac­cepted by planetary sci­en­tists.

Why the meth­ane is there is still a be­wil­der­ing mys­tery. It might even point to present-day Mar­tian mi­crobes liv­ing in the rocks below the sur­face.

In Na­ture Geo­science on Mon­day, sci­en­tists work­ing with the Euro­pean Space Agency’s Mars Ex­press or­biter re­ported that in the sum­mer of 2013, the space­craft de­tected meth­ane within Gale Crater, a 96-mile-wide de­pres­sion near the Mar­tian equa­tor.

That is note­wor­thy, be­cause NASA’s Cu­rios­ity rover has been ex­plor­ing that re­gion since 2011, and in the sum­mer of 2013 it, too, mea­sured a marked rise of meth­ane in the air that lasted at least two months.

“Our find­ing con­sti­tutes the first in­de­pen­dent con­fir­ma­tion of a meth­ane de­tec­tion,” said Marco Gi­u­ranna, a sci­en­tist at the Na­tional In­sti­tute for Astro­physics in Italy, in an email. Gi­u­ranna is prin­ci­pal in­ves­ti­ga­tor for the Mars Ex­press in­stru­ment that made the mea­sure­ments.

The pres­ence of meth­ane is sig­nif­i­cant be­cause the gas de­cays quickly. Cal­cu­la­tions in­di­cate that sun­light and chem­i­cal re­ac­tions in the thin Mar­tian at­mos­phere would break up the mol­e­cules within a few hun­dred years, so any meth­ane de­tected must have been cre­ated re­cently.

It might have been cre­ated by a ge­o­log­i­cal process known as ser­pen­tiniza­tion, which re­quires both heat and liq­uid wa­ter. Or it could be a prod­uct of life – specif­i­cally methanogens, mi­crobes that re­lease meth­ane as a waste prod­uct. Methanogens thrive in places lack­ing oxy­gen, such as rocks deep un­der­ground and the di­ges­tive tracts of an­i­mals.

Even if the source of the meth­ane turns out to be ge­o­log­i­cal, the hy­dro­ther­mal sys­tems that pro­duce the emis­sions would still be prime lo­ca­tions to search for signs of life.

A decade and a half ago, three teams of sci­en­tists re­ported that they had de­tected meth­ane in the Mar­tian at­mos­phere.

Two used ob­ser­va­tions from Earth, and the third used data from Mars Ex­press. All of the mea­sure­ments were at the edge of the in­stru­ments’ ca­pa­bil­i­ties,

Two years later, the meth­ane seemed to have dis­ap­peared. If that find­ing was ac­cu­rate, it sug­gested that not only was some­thing cre­at­ing meth­ane on Mars, but that some­thing else was quickly de­stroy­ing it.

The Cu­rios­ity mis­sion ini­tially cast more doubt on the meth­ane claims, as it de­tected very lit­tle of the gas, about 0.7 parts per bil­lion.

Then in 2013, the lev­els jumped by a fac­tor of 10. The fol­low­ing Jan­uary, lev­els fell back to less than 1 part per bil­lion.

The meth­ane dis­ap­peared so quickly, and the usual lev­els are so low, that sci­en­tists are now try­ing to ex­plain how meth­ane could have been de­stroyed so quickly.

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