This image shows a small portion of the rim of the caldera at the top of the volcano Alba Patera.
This volcano has shallower slopes than most of the other large volcanoes on Mars. Unfortunately, this image is not able to help us understand what is unique about Alba Patera because of the thick dust cover.
Instead it shows that the dust has been carved into streamlined shapes by the wind, cut by small landslides. Interestingly, there are some isolated patches that appear smooth and undisturbed by the wind.
Written by: Laszlo Kestay (2 December 2009)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_001510_2195
Image: NASA/JPL/University of Arizona