Mars valleys formed by episodic floods?

SANTA CRUZ, Calif., Sept. 10 (UPI) -- A U.S. study suggests ancient Martian surface features called valley networks were formed during a long period of episodic flooding.

Researchers said they determined the valley networks were created during a time when the Martian climate might have been similar to that of some of Earth's arid or semiarid regions.

"Our results argue for liquid water being stable at the surface of Mars for prolonged periods in the past," said University of California-Santa Cruz graduate student Charles Barnhart. He led the study as a Graduate Student Research Program scholar at the National Aeronautics and Space Administration's Ames Research Center, working with NASA planetary scientist Jeffrey Moore and Alan Howard of the University of Virginia.

Barnhart said the valley networks formed on Mars during a period of tens of thousands to hundreds of thousands of years. During that time he said episodic flooding alternated with long dry periods when water could evaporate or soak into the ground.

"Precipitation on Mars lasted a long time -- it wasn't a brief interval of massive deluges," he said.

A paper describing the study has been accepted for publication in the Journal of Geophysical Research-Planets and is currently available online.