Two dark rimless pits are located to the Northwest of Ascraeus Mons. These pits are approximately 180 meters and 310 meters in diameter, respectively, and are situated in the midst of a large, wispy dark boomerang-shaped deposit.
These pits are aligned with what appears to be larger, degraded depressions. The wispy deposit may consist of dark material that has been either blown out of the pits or from some other source and scattered about by the local winds.
Subimage (A) and (B) are close-ups of both pits. These images have been highly processed to reveal the surface details within each pit. The Eastern most and smaller of the two pits (A) contains boulders and sediment along its walls and brighter aeolian dune sediments on its floor. The larger, Western most pit (B) contains sediment and boulders with faint dune-like patterns visible on the deepest part of the floor. Both pits have steep Eastern walls and more gently sloped Western walls that transition gradually into the pit floor. Steep resistant ledges containing boulders that overhang and obscure the pit floors form the Eastern walls.
Careful study of the walls and floors of the pits as well as of the surrounding terrains will help unravel the complicated series of processes that must have been responsible for their formation and subsequent modification.
Written by: Ginny Gulick (1 December 2010)
This is a stereo pair with PSP_003317_1975 .
More info and image formats at http://hirise.lpl.arizona.edu/ESP_019997_1975
Image: NASA/JPL/University of Arizona