Runoff from orographic precipitation -- moisture carried part of the way up a mountain by prevailing winds and deposited as snow on the slopes -- appears to have shaped valley networks branching across the martian surface, researchers at Brown University reported Tuesday.
The new findings are the most convincing evidence yet of an orographic effect on ancient Mars and could shed new light on the planet's early climate and atmosphere, they said.
The scientists ran computer simulations which suggested precipitation would have been heaviest at the heads of the densest valley networks.
"Their drainage density varies in the way you would expect from the complex response of precipitation to topography," research leader Kat Scanlon, a geological sciences graduate student, said.
"That's what immediately came to mind in trying to figure out if these valleys on Mars are precipitation related," she said.
"We were able to confirm that in a pretty solid way."
The study's suggestion of precipitation as important in carving the valleys means the findings could provide important insight into the climate on Mars billions of years ago, the researchers said.