FOL­LOW THE WA­TER

Cosmos - - Holodeck -

In Septem­ber 2015, NASA’S Mars Re­con­nais­sance Or­biter had a bet­ter rea­son to grab head­lines: it found ev­i­dence of flow­ing wa­ter. MRO’S spec­trom­e­ter showed that dark streaks on the slopes of some craters and canyons were com­posed of salts left by evap­o­rat­ing wa­ter. It also iden­ti­fied clay sed­i­ments on a canyon floor in the Nili Fos­sae re­gion (far left), a can­di­date site for a fu­ture land­ing mis­sion. Two older or­biters, the 2001 Mars Odyssey and Mars Global Sur­veyor, iden­ti­fied an­cient lakes and snowmelt-fed streams in the Ara­bia Terra re­gion (left: white rep­re­sents low­est el­e­va­tion, yel­low high­est). Based on the num­ber of craters, sci­en­tists es­ti­mate they held wa­ter un­til 2-3 bil­lion years ago – a bil­lion years later than pre­vi­ously thought.

CREDIT: ( LEFT) NASA / JPL- CAL­TECH / UNIV. OF ARI­ZONA ( RIGHT) NASA / JPL- CAL­TECH / ASU

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