Dunes in West Arabia Terra Crater
Dunes in West Arabia Terra Crater
PSP_006952_1870  Science Theme: Aeolian Processes
This image shows dunes in an unnamed crater in the west Arabia Terra region. The rim of the crater lies to the south of the image and a dark, toned field of barchan sand dunes rests on the crater floor in the northern portion of the observation.

Barchan dunes are commonly found on Earth, and are generally crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction (see the subimage). Barchan dunes form by unidirectional winds and are good indicators of the dominant wind direction. In this case, the strongest winds blew approximately north to south.

These dunes are most likely composed of basaltic sand that has collected on the bottom of the crater. Superimposed on their surface are smaller secondary dunes which are commonly seen on terrestrial dunes of this size (see the sub image). Many smaller and brighter bed forms—most likely small dunes or granule ripples—also cover the substrate between the larger dark dunes. The dark dunes overlie the small bright bed forms indicating that the darker dunes formed more recently.

Written by: Maria Banks  (20 February 2008)
Acquisition date
20 January 2008

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
276.9 km (172.1 miles)

Original image scale range
27.7 cm/pixel (with 1 x 1 binning) so objects ~83 cm across are resolved

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25 cm/pixel and North is up

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Solar incidence angle
39°, with the Sun about 51° above the horizon

Solar longitude
20.1°, Northern Spring

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North azimuth:  97°
Sub-solar azimuth:  9.9°
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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. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.