Image PSP_001481_2410 shows a region of approximately 7 x 7 km (4.4-by-4.4 miles) located in Vastitas Borealis, part of the Northern Plains.

The surface imaged is relatively young, as indicated by the lack of recent impact craters. Eolian and periglacial activity seem to be the dominant geological processes at work, as shown by numerous crisscrossing dust devil tracks and ubiquitous polygonal features, respectively.

Dust devils form when the sun warms up the air near a flat, dry surface. Warm air then rises quickly through the cooler air above and starts spinning, causing a forward motion. The spinning, forward-moving cell may pick up dust and sand as it advances, thus leaving behind a "clean" track. We infer from this image that a thin veneer of light-colored particles of dust and/or fine-grained sand cover relatively darker materials, apparent in the dust devil tracks.

The tracks pictured in this image are in many cases more than 30 meters (27 yards) wide and over 4 km (2.5 miles) long, surpassing the dimensions of average terrestrial dust devil tracks.

The polygons shown in this image's subset, which covers approximately 400 x 250 m (350 x 225 yards), are in the order of 10 m (0.9 yards) across; in some cases they are delimited by aligned rocks. Similar features in both shape and scale are found in terrestrial periglacial regions such as Antarctica, where ice is present at or near the surface.

Antarctica's polygons and rock alignments are produced by repeated expansion and contraction of the soil-ice mixture due to seasonal temperature oscillations; dry soil falling into the cracks form sand wedges and amplify this effect. This results in polygonal networks of stress fractures and in the resurfacing and sorting of rocks along these fractures.

(Thin diagonal lines are artifacts in the image).
Written by: Sara Martinez-Alonso

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.