Peneus Patera Crater
This image, near the southeast rim of Peneus Patera crater, is marked by depressions in the mantle with scalloped edges. Several of the depressions have apparently coalesced together.
These features are most commonly found at approximately 55 degrees north and south latitude. Their presence has led to hypotheses of the removal of subsurface material, possibly interstitial ice by sublimation (evaporation).
Steep scarps consistently face the south pole while more gentle slopes face in the direction of the equator. This is most likely due to differences in solar heating.
A polygonal pattern of fractures, commonly associated with "scalloped terrain," can be found on the surface surrounding and within the depressions. The fractures indicate that the surface has undergone stress that may have been caused by subsidence, desiccation, or thermal contraction.
Scallop formation is believed to be an ongoing process at the present time.
Image PSP_002296_1215 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 22-Jan-2007. The complete image is centered at -58.0 degrees latitude, 53.7 degrees East longitude. The range to the target site was 250.7 km (156.7 miles). At this distance the image scale is 50.2 cm/pixel (with 2 x 2 binning) so objects ~150 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel and north is up.
The image was taken at a local Mars time of 04:01 PM and the scene is illuminated from the west with a solar incidence angle of 78 degrees, thus the sun was about 12 degrees above the horizon. At a solar longitude of 170.9 degrees, the season on Mars is Northern Summer.