A Martian River Bed . ... Credit Copyright: MGS Project , JPL , NASA Explanation: This canyon on the surface of Mars appears to have been carved by flowing water. ... But the lack of smaller surface channels and other features argue that the valley was formed by a surface collapse. Further images of Martian valley systems will help distinguish the degree to which these processes affected the Martian surface. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...