Big Fans

March 6, 2018

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Shown in this image from NASA's Mars Reconnaissance Orbiter (MRO) are alluvial fans, fan-shaped deposits emerging from regions of steep topography. Alluvial fans on Mars are thought to be ancient and record past episodes of flowing water. This image shows part of one of those fans, which has been eroded.

The old stream channels now stand above the rest of the fan as ridges, mostly in the southern (bottom) part of the image. This can occur because the channel materials are more resistant to erosion; perhaps they had larger grains (gravel) or because minerals deposited from the water cemented together.

The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. [The original image scale is 52.4 centimeters (20.6 inches) per pixel (with 2 x 2 binning); objects on the order of 157 centimeters (61.8 inches) across are resolved.] North is up.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., 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.

Credit

NASA/JPL-Caltech/Univ. of Arizona

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