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September 02, 2011

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Remnants of ancient Mars lake reported

Sept. 2, 2011
Courtesy of ESA
and World Science staff

A Eu­ro­pe­an Space Agen­cy space­craft has spot­ted what sci­en­tists call a rare case of a crat­er once filled by a lake, re­vealed by the pres­ence of a del­ta—an an­cient fan-shaped de­pos­it of dark sed­i­ments, laid down in wa­ter.

At the up­per right of the crat­er, me­an­der­ing chan­nels lead­ing in­to the struc­ture used to de­pos­it wa­ter in­to the crat­er, re­search­ers say. (Cred­its: ESA/DL­R/FU Ber­lin (G. Neu­kum) )
The del­ta is in the Eber­swalde crat­er, in the south­ern high­lands of Mars. The crat­er, 65 km (40 miles) wide, was formed more than 3.7 bil­lion years ago when an as­ter­oid hit the plan­et, re­search­ers say, though only half its rim is in­tact due to a lat­er im­pact.

But with­in the vis­i­ble part of Eber­swalde, the del­ta and small, me­an­der­ing feed­er chan­nels that would have filled it with wa­ter are clearly vis­i­ble, ac­cord­ing to sci­en­tists. Thought to be a re­minder of Mars’ past, wet­ter cli­mate, the pur­ported del­ta co­vers 115 square kilo­me­tres (44 square miles).

Af­ter del­ta sed­i­ments were de­pos­ited in the an­cient lake, re­search­ers be­lieve fresh­er sed­i­ments ac­cu­mu­lat­ed to cov­er up much of both the chan­nels and the del­ta. These sec­ond­ary sed­i­ments, pre­sumably de­pos­ited by the wind, were lat­er erod­ed in the del­ta ar­ea.

The struc­ture was first iden­ti­fied with NASA’s Mars Glob­al Sur­vey­or space­craft, though the Eu­ro­pe­an agen­cy’s Mars Ex­press craft was used to make the lat­est find­ings.

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A European Space Agency spacecraft has spotted what scientists call a rare case of a crater once filled by a lake, revealed by the presence of a delta—an ancient fan-shaped deposit of dark sediments, laid down in water. The delta is in the Eberswalde crater, in the southern highlands of Mars. The crater, 65 km (40 miles) wide, was formed more than 3.7 billion years ago when an asteroid hit the planet, researchers say, though only half its rim is intact due to a later impact. But within the visible part of Eberswalde, the delta and small, meandering feeder channels that would have filled it with water are clearly visible, according to scientists. Thought to be a reminder of Mars’ past, wetter climate, the delta covers an area of 115 square kilometres (44 square miles). After delta sediments were deposited in the ancient lake, researchers believe fresher sediments accumulated to cover up much of both the channels and the delta. These secondary sediments, presumably deposited by the wind, were later eroded in the delta area, exposing an upside-down relief of the delta structure. The structure was first identified with NASA’s Mars Global Surveyor spacecraft. Both Eberswalde crater and Holden crater on Mars were on a short list of four possible destinations for the next NASA Mars rover, to be launched late this year. The European agency’s Mars Express craft, used to make the latest findings, has been helping in the search for the best landing site. n