Necho crater detail: Boulders on hills but not in valleys

Necho crater detail: Boulders on hills but not in valleys
Necho crater detail: Boulders on hills but not in valleys Knobs on the floor of Necho crater are covered with boulders, but the flat areas between the knobs are relatively boulder-free. The image is 538 meters square. NASA / GSFC / ASU