The Wet Past of Mars

From AFP

A new detailed map of Mars shows what was likely a vast ocean in the north and valleys around the equator, suggesting that the planet once had a humid, rainy climate, according to research published Monday.

The computer-generated map, based on topographic data from NASA satellites, also shows that the network of valleys on the red planet is at least twice as extensive as previously estimated.

"The relatively high values over extended regions indicate the valleys originated by means of precipitation-fed runoff erosion -- the same process that is responsible for formation of the bulk of valleys on our planet," said Wei Luo, geography professor at Northern Illinois University who co-authored the report.

"A single ocean in the northern hemisphere would explain why there is a southern limit to the presence of valley networks," Luo said.

"The southernmost regions of Mars, located farthest from the water reservoir, would get little rainfall and would develop no valleys. This would also explain why the valleys become shallower as you go from north to south, which is the case."

Rain, said Luo, "would be mostly restricted to the area over the ocean and to the land surfaces in the immediate vicinity, which correlates with the belt-like pattern of valley dissection seen in our new map."

The report appears in the Journal of Geophysical Research.

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