| Close-up image of Mars' satellite Deimos from Viking 2 showing craters and associated streaks. The streaks run from upper right to lower left, and may have been formed by the base surge "wind" of an impacting meteoroid. |
Viking 2 view of the Martian satellite Deimos taken from 500 km distance. Deimos is about 8 km across at its widest part. Note the smoother appearance of the craters, caused by partial burial in dusty regolith. |
This Viking 2 image shows the surface of Deimos from a distance of 30 km. Features as small as 3 meters across can be seen. Note many of the craters are covered over by a layer of dust estimated to be about 50 meters thick. Large blocks, 10 to 30 meters across, are also visible. |
Deimos is the smaller of the two Martian moons and is less irregular in shape. The largest crater on Deimos is approximately 2.3 km in diameter, 1/5 the size of the largest crater on Phobos. Although both moons are heavily cratered, Deimos has a smoother appearance caused by the partial filling of some of its craters. When impacted, dust and debris will leave the surface of the moon because it doesn't have enough gravitational pull to retain the ejecta. However, the gravity from Mars will keep a ring of this debris around the planet in approximately the same region that the moon orbits. As the moon revolves, the debris is redeposited as a dusty layer on its surface. 
