Dust Devil Tracks and Barchan Dunes in Terra Cimmeria
NASA/JPL/University of Arizona

Dust Devil Tracks and Barchan Dunes in Terra Cimmeria
PSP_006248_1235  Science Theme: Aeolian Processes



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This image shows a set of dark sand dunes within the northern part of an unnamed crater in the Terra Cimmeria region.

The dunes have a distinctive shape, with two horns on one end and a rounded edge on the other. The side of the dunes with the horns has a steeper slope and the rounded side a more shallow slope. These types of dunes are called “barchans” and, by analogy with similar dunes on Earth, form in areas with limited sand supply.

The horns of the barchans point in the downwind direction, thereby indicating that the predominant surface winds in this region blew from the east (right side of image). Further evidence of this wind regime is apparent when one zooms into the image. “Wind tails” are visible on the western (left) side of many rocks (many of these rocks may be ejecta from the degraded crater in the northern part of the image). Wind tails are formed by the accumulation of dust and sand in the lee of rocks, which act as wind shadows. Very small light ripples at a scale of a few meters (yards) are also apparent.

The dark, sinuous forms in the image are tracks left by dust devils, which lift bright dust off the surface, revealing the darker surface. Where dust devils cross the dunes, the fine texture on the dunes is undisturbed, indicating that the particles making up the dunes are coarse and fairly immobile.Written by: Nathan Bridges   (13 January 2008)



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Acquisition date:26 November 2007 Local Mars time: 2:34 PM
Latitude (centered):-56.034° Longitude (East):157.496°
Range to target site:251.1 km (156.9 miles)Original image scale range:25.1 cm/pixel (with 1 x 1 binning) so objects ~75 cm across are resolved
Map projected scale:25 cm/pixel and North is upMap projection:Equirectangular
Emission angle:0.3° Phase angle:61.7°
Solar incidence angle:62°, with the Sun about 28° above the horizon Solar longitude:353.2°, Northern Winter
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North azimuth:97° Sub-solar azimuth:50.6°
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North azimuth:270°Sub solar azimuth:223.9°

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For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.