Frosted Dunes in the Depths of Winter

Usually, HiRISE takes pictures of well-illuminated terrain where there is plenty of light to produce clear images. Sometimes though, we would like to know what's going on in the dim wintertime areas.

This picture was taken far north of the equator just two days after the winter solstice when the Sun was just a few degrees above the horizon. Sand dunes are moving across this landscape from top left to bottom right. Winter frost covers the colder, north-facing half of each dune (but not the warmer south-facing half). The frost here is a mixture of carbon dioxide ice and water ice and will disappear in a few months when spring arrives.

The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. (The original image scale is 62.1 centimeters [24.4 inches] per pixel [with 2 x 2 binning]; objects on the order of 186 centimeters [73.2 inches] across are resolved.) North is up.

The University of Arizona, in Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., in Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.