NASA's Mars
Reconnaissance Orbiter depicts a traverse across the North Polar erg, a vast
sea of sand that surrounds the martian polar cap.
Speculation
suggests the eroding north polar
layered deposits may have provided the dunes with a source. Wind blowing on this
mixture of sand, dust, and ice has sculpted several dune types on top of bright
megaripples and polygons. Beyond the dunes lies a dark mantle of sand.
In the center
of the field, transverse dunes are seen with the dominant wind direction coming
from the northwest-west. The outer edges of the dune field gradually change into
star dunes (with multiple arms) and barchanoid dunes (having a crescent-like
shape). The star dunes indicate multidirectional winds, or a change in wind
direction over the dune field's evolution. The dunes appear somewhat confined
to their location, possibly having taken hundreds of years to form.
The image was acquired on July 28, 2008.
— NASA/JPL/University of Arizona and SPACE.com
Staff
Credit: NASA/JPL/University of Arizona
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