The valley networks on Mars are terrains eroded by flowing water billions of years ago.

In places where the bedrock is well exposed, we often see a variety of colors due to altered minerals and polygonal patterns perhaps due to wet, clay-rich deposits.

Written by: Alfred McEwen (audio: Tre Gibbs)   (18 May 2016)

More info and image formats at http://hirise.lpl.arizona.edu/ESP_045299_1545

Image: NASA/JPL/University of Arizona