Layered Sediments in Valles Marineris

Layered sedimentary rocks are key to understanding the geologic history of a planet, recording the sequence of deposition and the changes over time in the materials that were deposited.

These layered sediments are on the floor of eastern Coprates Chasma in Valles Marineris, the grandest canyon on Mars. They are erosional remnants of a formerly much more extensive sedimentary deposit that once filled the floor of the canyon but is nowadays reduced to isolated mesas.

The origin of the deposits is not yet known. Various theories attribute the sediments to wind blown dust and sand, or to volcanic materials, or accumulations of debris from avalanches originating from the canyon walls, or even to lakebed sediments laid down when the canyons were filled with liquid water. Some sediments are devoid of boulders or blocks larger than the limit of resolution (about 0.5 meters), so avalanche debris is unlikely. We see fine laminations with a horizontal spacing of about 2 meters and a vertical separation less than 2 meters. No previous orbital observations were capable of resolving such fine scale layering.

The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. (The original image scale is 26.9 centimeters [10.6 inches] per pixel [with 1 x 1 binning]; objects on the order of 81 centimeters [31.9 inches] across are resolved.) North is up.

The University of Arizona, in Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.