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Floor of Baldet Crater
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Floor of Baldet Crater

October 8, 2009
This THEMIS visible image shows a remarkable array of dunes on the floor of a large impact crater named Baldet. Many of the dunes in this region are isolated features, with large, sand-free "interdune" surfaces between the individual dunes. These isolated dunes typically occur in regions where there is a limited supply of sand. Any sand that is present moves rapidly across the interdune surfaces, which in many cases are hardened surfaces over which the sand can easily bounce, or "saltate". When this loose sand lands on a dune it cannot travel as quickly and is trapped within the dune. In some areas within this sand mass the dunes have grown together to form crescent dunes and dune ridges. The dunes in this image are likely active today, slowly migrating across the crater floor. THEMIS will re-image this and other dunes throughout the Mars Odyssey mission to search for any evidence of dune motion over time. Based on the asymmetrical shape of the dunes, the wind direction over much of the dune field appears to be from the right (west) or upper right (northwest). However, the topography of the crater floor apparently produces complex wind patterns within the dune field, as can be seen by the different orientations of the dunes. For example the dunes in the lower portion of the image appear to be somewhat symmetrical and aligned east-west, suggesting that the wind in this region blows from both the north (top) and south (bottom).