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Valleys may be Mars climate clue

November 25, 2009 Edition 1

WASHINGTON: A network of valleys discovered on Mars indicates that the red planet was once covered by a vast ocean which fed a humid, rainy climate, according to research published this week.

Debate has raged over whether Martian valleys resulted from water erosion caused by humidity and rainfall or through groundwater-sapping erosion, which happens in cold, dry conditions. The comparative lack of river networks on the planet's surface supported theories that rain was unlikely, but mapping based on topographic data from Nasa satellites has found the valley network is more extensive than previously estimated. - Sapa-AFP

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