Defrosting Barchan Dunes
NASA/JPL/University of Arizona
Defrosting Barchan Dunes
ESP_025118_2570  Science Theme: Seasonal Processes
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This HiRISE image shows sand dunes near the eastern part of North Polar erg.

The dunes imaged here are similar to barchan dunes, commonly found in desert regions on Earth. Barchan dunes are generally crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction. Barchan dunes form by winds blowing mainly in one direction and thus are good indicators of the dominant wind direction when the dunes formed.

The dunes and surrounding surface appear bright because they are covered with seasonal frost left over from the Northern hemisphere winter. Sunlight is now falling on the North Polar region, and carbon dioxide frost that accumulated during winter is sublimating (going directly from solid to gas) and the surface beneath the frost is being revealed.

Composed primarily of basaltic sand, the dunes will appear dark during the Northern hemisphere summer. The dark spots are areas where some of this frost has begun to sublime away, and/or where wind has exposed the underlying dark sand.

Written by: Maria Banks   (11 January 2012)

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Acquisition date
05 December 2011

Local Mars time:
13:58

Latitude (centered)
76.586°

Longitude (East)
104.117°

Range to target site
317.7 km (198.6 miles)

Original image scale range
31.8 cm/pixel (with 1 x 1 binning) so objects ~95 cm across are resolved

Map projected scale
25 cm/pixel

Map projection
Polarstereographic

Emission angle:
0.8°

Phase angle:
63.5°

Solar incidence angle
63°, with the Sun about 27° above the horizon

Solar longitude
39.2°, Northern Spring

North azimuth:
103°

Sub-solar azimuth:
314.0°
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NASA/JPL/University of Arizona



Postscript
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.