This image is of the rim of a crater . The sun is low in the sky (only 15 degrees above the horizon) and shining full on this crater wall (you can see that the area beyond the rim has got long shadows).
The sun is beautifully illuminating a series of layers exposed in the crater wall which have a variety of different colors.
Note: the subimage is non map-projected, so approximate North is down.
Written by: Ross A. Beyer (4 April 2012)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_026061_1435
Image: NASA/JPL/University of Arizona