20 May 2004
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the wall on one of the calderae at the summit of the large volcano, Ascraeus Mons. A caldera is a large depression formed by collapse after magma in a volcano is erupted from or withdrawn to a greater depth. After collapse, the wall of this caldera was further modified by downslope movement of debris and it was pelted by small meteors to form a scattering of small craters. This image is located near 11.6°N, 104.6°W, and covers an area about 3 km (1.9 mi) across. The picture is illuminated by sunlight from the lower left.