NASA Mars HiRise: Proctor Crater Dunes

An extract from a detailed NASA HiRise image of Mars.

The full image, a stereo pair of images and many more images of Mars can be found on the NASA HiRise website.

NASA MARS: Sand Dunes of Proctor Crater

Large sand dunes on the floor of Proctor Crater on Mars.

The above picture was taken by HiRISE camera on board the Mars Reconnaissance Orbiter (MRO), a robot spacecraft currently in orbit around Mars.

The dark rippled dunes likely formed more recently than the lighter rock forms they appear to cover, and are thought to slowly shift in response to pervasive winds.

The dunes arise from a complex relationship between the sandy surface and high winds on Mars. Similar dunes were first seen in Proctor Crater by Mariner 9 more than 35 years ago.

NASA Mars: HiRise Image - Proctor Crater, Mars

This view from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter is of the Proctor Crater.

The relatively bright, small ridges are ripples. From their study on Earth, and close-up examination by the MER rovers (roving elsewhere on Mars), scientists surmise that the ripples are composed of fine sand (less than 200 microns in diameter) or fine sand coated with coarser sand and granules.

The larger, darker bedforms are dunes composed of sand, most likely of fine size. Ripples tend to move slower than dunes. Because of this, over time, ripples get covered with dust, possibly explaining the bright tone visible here. The dunes are dark probably because they are composed of basaltic sand (derived from dark, volcanic rock) that is blown by the wind enough that dust does not sufficiently accumulate to change their color.

This area in Proctor Crater is being monitored by HiRISE to document any changes over time.

This image is a portion of the HiRISE observation taken on Feb. 9, 2009.

Image Credit: NASA/JPL-Caltech/University of Arizona