This image shows dark sand dunes in Chasma Boreale. Chasma Boreale is a giant trough that cuts into the north polar ice cap for 570 kilometers (350 miles) forming a broad valley bordered by stacked layers of ice. A portion of the north polar ice cap is visible at the northern edge of the trough in the upper portion of the image.

Many dark toned sand dunes march down the trough under the winds’ direction. The sand dunes visible here are barchan dunes. Barchan dunes are also commonly found on Earth, and are crescent-shaped with a steep slip face bordered by horns oriented in the downwind direction. Barchan dunes form by uni-directional winds and thus are good indicators of the dominant wind direction. In this case, the dunes indicate that the direction of the strongest winds are parallel to the chasma walls, roughly east to west. The dark material composing the dunes could be volcanic ash or is possibly dark sand eroding out of the polar layered materials.


Written by: Maria Banks

All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible: Image: NASA/JPL/University of Arizona

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.