Wednesday, January 5, 2011

Small Valleys and Colorful Bedrock in Terra Cimmeria

This image shows a network of small valleys in the Terra Cimmeria region of the Martian southern highlands. This location is approximately 1,000 kilometers (600 miles) south of Gusev Crater, the landing site of the Mars Exploration Rover Spirit.

The valleys in this image are carved into light-toned bedrock exhibiting a range of colors, which likely reflect a range of mineralogical compositions. The bedrock is pervasively fractured, and some of the fractures appear to be filled with material of a different color, possibly composed of minerals that crystallized or were cemented together when fluids (perhaps water) circulated through the fractures.

On the right side of the subimage is a valley filled with dark material and a central, bright ridge. If the valley was carved by liquid water, then this ridge may mark a former stream channel where coarse-grained sediment was deposited, which has survived erosion more effectively than the finer-grained sediment in the valley outside the channel.

Similar “inverted channel” deposits are visible elsewhere on Mars, and some examples in the southern highlands have been inferred to contain chloride salts (similar to table salt). The color and texture of the possible inverted channels in this image are similar to those inferred to contain chlorides, which may have been deposited when salty water evaporated.

Considered together, the features in this image attest to a history of water-related activity at this location on Mars.

Photo credit: NASA/JPL/University of Arizona

Note: This image is located about halfway between Ariadnes Colles and the source of Ma'adim Vallis.

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