Extensive layered deposits are found in both polar regions of Mars, and are thought to contain evidence of recent climate changes like ice ages on Earth.
Radar observations suggest that the polar layered deposits are composed mostly of water ice, but many layered exposures, including this one, appear to be covered by a layer of dust that protects the underlying water ice from further erosion. The south polar layered deposits are more extensive than the northern deposits, and have generally been less active recently.
The greater age of the surface of the south polar layered deposits is indicated by the higher density of craters on its surface; a cluster of small craters is visible above center in this image. Also visible are widespread polygonal fractures, evidence of water ice expansion/contraction below the surface.
Written by: Ken Herkenhoff (21 October 2009)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_004650_0975
Image: NASA/JPL/University of Arizona