Olympus Mons the -diameter Pangboche crater (). The craters are notable for being two of several suspected source areas for shergottites, the most abundant class of Martian meteorites. As a shield volcano, Olympus Mons resembles the shape of the large volcanoes making up the Hawaiian Islands. The edifice is about wide. Because the mountain is so large, with complex structure at its edges, allocating a height to it is difficult. Olympus Mons stands above the Mars global datum, and its local relief, from the foot of the cliffs which form its northwest margin to its peak, is nearly (a little over twice
Ascraeus Mons zone of knobby terrain outlined by a semicircular zone of concentric ridges. Similar deposits are also found at the northwestern edges of the other two Tharsis Montes, Pavonis Mons and Arsia Mons, as well as on Olympus Mons. The FSD at Ascraeus Mons is the smallest of those on the Tharsis Montes, covering an area of 14,000 km and extending outward from the volcano's base for about 100 km. The origin of these deposits has been debated for decades. However, recent geologic evidence suggests that FSDs are deposits left by glaciers, which covered portions of the volcanoes during a recent