NASA Mars Picture of the Day: Dark Barchan Dunes

Mars Global Surveyor Mars Orbiter Camera

MGS MOC Release No. MOC2-725, 13 May 2004

NASA/JPL/Malin Space Science Systems

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)
image shows north polar sand dunes in the summertime. During
winter and early spring, north polar dunes are covered with
bright frost. When the frost sublimes away, the dunes appear
darker than their surroundings. To a geologist, sand
has a very specific meaning. A sand grain is defined independently
of its composition; it is a particle with a size between
62.5 and 2000 microns. Two thousand microns equals 2 millimeters.
The dunes are dark because they are composed of sand grains
made of dark minerals and/or rock fragments. Usually, dark grains
indicate the presence of unoxidized iron, for example,
the dark volcanic rocks of Hawaii, Iceland, and elsewhere.
This dune field is located
near 71.7°N, 51.3°W. Dune slip faces indicate
winds that blow from the upper left toward lower right.
This picture covers an area approximately 3 km (1.9 mi) across
and is illuminated by sunlight from the lower left.

Malin Space Science Systems and the California Institute of Technology
built the MOC using spare hardware from the Mars Observer mission.
MSSS operates the camera from its facilities in San Diego, California.
The Jet Propulsion Laboratory’s Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena,
California and Denver, Colorado.