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Light-Toned Bedrock Along Cracks as Evidence of Fluid
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Light-Toned Bedrock Along Cracks as Evidence of Fluid Alteration

March 22, 2007
This enhanced-color image from the High Resolution Imaging Science Experiment Camera on NASA's Mars Reconnaissance Orbiter shows a landscape of sand dunes and buttes among a background of light-toned (tan-colored) bands and dark-toned (blue-colored) bands in the Candor Chasma region of Mars' Valles Marineris canyon system.

The scene includes examples of thin dark lines bordered by light-toned bedrock. The dark lines are interpreted as fractures, called joints, that were formerly underground but have been exposed at the surface by erosion of overlying material. The light-toned material along the joints is interpreted as features called halos, resulting from mineral alteration (bleaching, cementation or both) of the walls of the fractures by fluid moving through the fractures.

The image was acquired on Sept. 30, 2006, during winter in Mars' southern hemisphere, at a local Mars time of 3:29 p.m. It combines separate band passes taken by the High Resolution Imaging Science Experiment in blue-green light, red light and near-infrared light.

The scene is illuminated from the west (left) with a solar incidence angle of 58.5 degrees. The image scale is 26 centimeters (10 inches) per pixel, the scale of the red bandpass image. The other bandpasses were acquired with two-by-two pixel binning to 52 centimeters (20 inches) per pixel.

The image, in the camera's catalogue as TRA_000836_1740, is centered at 5.7 degrees south latitude, 284.6 degrees east longitude.


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