The news from Mars

Dust storms, or­ganic chem­istry and liq­uid wa­ter on the Red Planet.

Cosmos - - Digest -

It’s been a big few months for Mars watchers. First, in late June, a small dust storm grew and grew, com­bin­ing with other storms un­til it fi­nally kicked up a dust cloud so big it en­veloped al­most the en­tire planet.

Dust storms the size of con­ti­nents are com­mon on Mars, but global dust storms only oc­cur roughly once ev­ery three years (that’s once ev­ery five or six Earth years), usu­ally dur­ing sum­mer in the Red Planet’s south­ern hemi­sphere. The storms are self-lim­it­ing, as the dusty haze blocks the sun­light that de­liv­ers the heat to power them. In this case, by late July, a month or so af­ter it be­gan, the dust was slowly set­tling back to the ground.

The sun-block­ing tem­pest was good news for storm-watchers but bad news for NASA’S so­lar-pow­ered ‘Op­por­tu­nity’ rover, which has yet to re­sume op­er­a­tions.

Sec­ond, three dis­cov­er­ies boosted the prospects of past and present life on Mars. The ‘Cu­rios­ity’ rover (it’s nu­clear-pow­ered so it sur­vived the dust storm) de­tected de­posits of or­ganic mol­e­cules in 3.5 bil­lion year old rock sam­ples. Back in 2014, Cu­rios­ity’s on-board lab iden­ti­fied or­ganic mol­e­cules in the mud­stone of Gale crater, an an­cient lakebed. This June, Cu­rios­ity’s in­stru­ments de­tected de­posits 100 times richer in sam­ples drilled from the slopes of 5 km high Mt Sharp which sits in the cen­tre of Gale crater. Af­ter bak­ing the sam­ples to re­lease the mol­e­cules, it de­tected a rich ar­ray of or­ganic com­pounds such as thio­phene, ben­zene and propane. Coal or shale sam­ples on Earth, baked the same way, re­lease sim­i­lar mol­e­cules.

The next thrill was that Cu­rios­ity de­tected lev­els of methane ris­ing over the sum­mer – 2.5 fold higher than in win­ter. It could mean the gas is be­ing vented from thaw­ing or­ganic ma­te­ri­als, as hap­pens on Earth. Nev­er­the­less while Earth’s methane is mostly of bi­o­log­i­cal ori­gin, Mar­tian methane could just as eas­ily be pro­duced by non-bi­o­log­i­cal means. Both of Cu­rios­ity’s dis­cov­er­ies were re­ported in Science in June.

Per­haps the most dra­matic boost to the search for Mar­tian life came in late July, when an­other Science pa­per re­ported a lake ly­ing 1.5 km be­neath the south­ern po­lar ice cap. Dis­cov­ered us­ing the radar probe on the Euro­pean Space Agency’s Mars Ex­press satel­lite, the lake is some 20 km wide and at least a me­tre deep. While the wa­ter would un­doubt­edly be cold and salty, the lake is per­haps the least in­hos­pitable lo­ca­tion for life on Mars.

But lest we get out hopes up too high, it turns out we are un­likely to be able to ter­raform Mars. One pro­posal is that by re­leas­ing frozen CO locked in the po­lar ice­caps, the green­house gas might both warm the planet and pro­vide for plant growth. Alas, a re­port in Na­ture Astron­omy finds there’s just not enough CO .

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