This image shows part of the floor of a large crater in Terra Tyrrhena. Here, dark mesas contrast with light-colored, topographically lower outcrops.

The mesas have sharp cliffs, indicating the dark materials are not loose, but rather consolidated; layering is also visible along the cliffs. The underlying light materials are also layered and profusely fractured. Their superposition relationship indicates that the light materials are older than the dark, mesa-forming materials.

The image also shows a number of crest-like features criss-crossing the landscape. The fact that their relief is so prominent indicates they are more resistent to erosion (harder) than their surroundings. These crests could be indurated fractures (fractures cemented by fluids) or dikes. Dikes are tabular intrusions of rock formed when underground magma is injected along fractures.

The lowest regions in the image are covered by dark-colored dunes (see for instance the NW or upper left section of the image). These are possibly accumulations of fine-grained materials eroded-out from the mesas. Written by: Kelly Kolb   (15 November 2007)

This is a stereo pair with ESP_011485_1555 .

More info and image formats at http://hirise.lpl.arizona.edu/PSP_005710_1555

Image: NASA/JPL/University of Arizona