The polar layered deposits on Mars are thought contain a record of global climate changes, similar to ice ages on Earth. This image shows that the geologic history of the north polar layered deposits (NPLD) has been complex enough to form angular unconformities.
An angular unconformity represents a gap in the geologic record, where erosion has removed material followed by deposition of more material on the eroded surface. In this image, the angular unconformities are recognized by the truncation, or cutting off of layers, for example right of center and at bottom center.
Also visible in this image are numerous streaks, perhaps caused by recent redistribution of frost by winds.
Written by: Ken Herkenhoff (2 September 2008)
More info and image formats at http://hirise.lpl.arizona.edu/PSP_009293_2645
Image: NASA/JPL/University of Arizona