Mars volcanoes, artwork. Volcanic features occur over large areas of the Martian surface. At lower centre are the peaks of the three large Tharsis Ridge volcanoes (top to bottom): Ascraeus Mons, Pavonis Mons and Arsia Mons. On the left is Olympus Mons, the largest volcano in the solar system. Lower right is the vast system of canyons known as Valles Marineris. At top centre the edge of the ice cap covering the north pole can be seen.