Several characteristics of crater wall gullies are visible in this image that provide possible insight into the formation mechanisms of gullies on Mars.

Gullies near the top (north) end of the image are deeper and originate in alcoves near the rim of the crater. Gullies near the middle of the image are shallow and contain a more complex array of small channels. These smaller gullies initiate from a uniform elevation within the crater wall rather than at the crater rim. This suggests that the materials which flow down the crater slopes to form the gullies originates at a specific layer exposed in the crater wall.

The undulating pattern of ridges on the crater floor ( left side of the image ) appear similar to features interpreted as elsewhere on Mars that involve ice-rich materials.
Written by: Kelly Kolb   (28 July 2008)

More info and image formats at http://hirise.lpl.arizona.edu/PSP_007143_1370

Image: NASA/JPL/University of Arizona