This image shows an apparent valley north of a 37-kilometer long pit called Ophir Cavus.This valley is just west of another 155-km long valley system called Allegheny Vallis that also emanates from the pit.
The association of valleys with the pit suggests that water was released when the pit formed, perhaps when volcanic eruptions melted ice in the surface or subsurface. The HiRISE image reveals light-toned units along portions of the plains and these could be minerals deposited by the flowing water or alteration of the plains by the water that once flowed here.
Written by: Cathy (12 August 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_009011_1705
Image: NASA/JPL/University of Arizona