Olympus Mon from Mariner 9, on 27 November 1971, as the spacecraft orbited Mars. Olympus Mons is the largest volcano in the solar system. Here, most of the Martian surface is obscured by a dust storm, but the summit of Olympus Mons, at an altitude of 24 kilometres, rises above the dust storms in the lower atmosphere. The multiple summit calderas (centre left) cover an area some 64 kilometres across. Mariner 9 reached Mars on 13 November 1971, becoming the first spacecraft to orbit another planet. Previous Mars missions had only flown past the planet. It used television cameras to return pictures of the Martian surface to Earth, and studied the composition of the planet's atmosphere and surface.