Mars. Coloured Viking 2 image of a crescent Mars superimposed on a starfield. North is at top. The two dark dots at upper right are the volcanoes Ascraeus Mons (right) and Pavonis Mons (left). These volcanoes are on a raised area known as the Tharsis Ridge. Below these volcanoes is part of the vast Valles Marineris valley system (dark, centre right). Further south are the dark cratered highlands of Noachis Terra and the snow-filled impact crater Argyre Planitia (white, lower centre). This image was taken in 1975, when it was the Martian summer in the northern hemisphere.