Jan. 21, 2010 Dunes of sand-sized materials have been trapped on
the floors of many Martian craters. This view shows dunes inside
a crater in Noachis Terra, west of the giant Hellas impact basin
in Mars' southern hemisphere. The High Resolution Imaging
Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance
Orbiter captured this view on Dec. 28, 2009. The orbiter resumed
making observations in mid-December following a three-month
hiatus. A set of new images from the HiRISE camera is on the
camera team's site, at http://hirise.lpl.arizona.edu/nea.php.
The dunes here are linear, thought to be due to shifting wind
directions. In places, each dune is remarkably similar to
adjacent dunes, including a reddish (or dust-colored) band on
northeast-facing slopes. Large angular boulders litter the floor
between dunes. The most extensive linear dune fields known in
the solar system are on Saturn's large moon Titan. Titan has a
very different environment and composition, so at meter-scale
resolution they probably