Study Suggests It Rained on Ancient Mars

[n2doc]

By SPACE.com Staff
posted: 24 September 2008 03:33 pm ET

Scientists studying the Martian landscape said yes, a river ran through it — and not just one. The ancient red planet also seems to have experienced rain, they say.

The rivers may have cut the deep valleys in the Martian highlands near the equator, and also left calling cards elsewhere. Three Mars spacecraft spotted signs of fan-shaped river deltas inside ancient craters which some valleys clearly flow into.

"We can see layered sediments where these valleys open into impact craters," said Ernst Hauber, a geologist at the DLR (German space agency) Institute of Planetary Research in Berlin-Adlershof. "The shape of certain sediments is typical for deltas formed in standing water."

Rivers carry sediment downstream until the currents become too weak and let the material fall to the river bottom. The flow almost drops to zero at places where rivers empty into a larger body of water, such as a lake-filled crater.

Hauber and other researchers focused on possible ancient river valleys crisscrossing the Xanthe Terra highland region. They examined crater images taken by the European Mars Express, NASA's Mars Global Surveyor, and NASA's Mars Reconnaissance Orbiter.

more:
http://www.livescience.com/space/080924-mars-rain.html


The picture shows a topographic map of a crater in the Xanthe highlands, which held a lake 3.8 to 4 billion years ago. Sediments were deposited in the lake, forming a distinctly shaped delta. The lake was fed by a river that flowed through the Nanedi valley and into the crater from the south. Credit: ESA/DLR (E. Hauber)