New Dune Gullies
One of the many mysteries associated with martian geology is the origin of gullies found at latitudes poleward of 30Â°. Most of these gullies are found within craters or other depressions, and appear to be related to the bedrock. Several alternative hypotheses have been proposed for their origin, including groundwater seepage and melting at the base of a dust-mantled snowpack.
Some middle-latitude gullies are found on sand dunes. These gullies appear to be different from those found on the slopes of craters, but generally have been interpreted to form by similar processes. In the present martian environment, it is difficult to introduce water to the surface. The temperature and atmospheric pressure may permit water to exist, but the rate of heating of the ground and atmosphere, and the amount of energy available to warm the ground or melt snow, is not conducive to such processes.
As part of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission science investigation, the MOC team has an on-going effort to re-image locations known from previous observations to have gullies. The intent is to see if gully-forming processes are operating on Mars at the present time.
During the ~1.4 Mars years (nearly 3 Earth years) that elapsed between the time that the two pictures in this image were acquired, a couple of gullies formed on the dune slip face.