Spring Sandfall in North Polar Erg
Spring Sandfall in North Polar Erg
ESP_025042_2650  Science Theme: Seasonal Processes
In the winter a portion of Mars’ carbon dioxide atmosphere condenses onto the surface forming seasonal polar caps. In the spring as the sun gets higher in the sky this ice sublimates (goes directly from solid to gas).

We see many seasonal phenomena associated with the sublimation of the carbon dioxide ice (dry ice). In this observation, we are looking at barchan dunes, made of dark basaltic sand (like in Hawaii) mostly still covered with ice.

Where there are cracks in the ice the dark sand can be seen escaping. Some cracks are at the crests of the dunes, and the sand is freed to slide down the slipface of the dunes. The cracks in the ice develop as a result of gas from sublimation being trapped under the ice - when the pressure gets high enough it cracks the ice.

Written by: Candy Hansen  (31 January 2012)

Acquisition date
29 November 2011

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
320.3 km (199.1 miles)

Original image scale range
64.1 cm/pixel (with 2 x 2 binning) so objects ~192 cm across are resolved

Map projected scale
50 cm/pixel

Map projection

Emission angle

Phase angle

Solar incidence angle
70°, with the Sun about 20° above the horizon

Solar longitude
36.5°, Northern Spring

For non-map projected images
North azimuth:  120°
Sub-solar azimuth:  311.0°
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Black & white is 5 km across; enhanced color about 1 km
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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:

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.