The de­plet­ing at­mos­phere

All About Space - - Mars Express -

Mars was once a planet with wa­ter flow­ing across the sur­face and had a suit­able at­mos­phere that kept it rel­a­tively warm, which could have sup­ported life. To­day, Mars is a cold, dry planet with an at­mos­phere 150-times lower in pres­sure than on Earth, so Mars Ex­press set out to find out what hap­pened dur­ing its evo­lu­tion to trans­form the planet.

Mars Ex­press’ Anal­yser of Space Plasma and En­er­getic Atoms (ASPERA) in­stru­ment took valu­able data about the in­ter­ac­tion be­tween the so­lar wind and the up­per at­mos­phere and iono­sphere. Data showed that in just a few min­utes the up­per at­mos­phere can al­ter and open a path for the so­lar wind to pen­e­trate deeper into the at­mos­phere, in­ter­act­ing with wa­ter ions and caus­ing them to es­cape into space.

How­ever, this ion es­cape rate de­pends on vary­ing so­lar winds and can­not fully ac­count for the dras­tic de­ple­tion over the last 3.5 bil­lion years. This means an­other mech­a­nism must have been at work, pos­si­bly re­mov­ing neu­tral atoms in the up­per at­mos­phere. A re­cent the­ory even sug­gests that dust storms play a part in kick­ing up atoms to higher al­ti­tudes where they then es­cape Mars.

The in­tense so­lar winds strip away the at­mos­phere of Mars

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