Mars Express image of a region close to Ma’adim Vallis, one of the largest canyons on Mars. After Valles Marineris, Ma’adim Vallis is one of the largest canyons on Mars. The imaged region lies south-east of Ma’adim Vallis; the pictures are centred at about 29°S and 182°E and have a ground resolution of 15 m/pixel.
Ma’adim Vallis is located between the volcanic region of Tharsis, which harbours four volcanoes, including the largest in the Solar System, and the Hellas Planitia impact basin. The canyon, 20 km wide and 2 km deep, originates in the southern highlands close to the ‘dichotomy boundary’ and ends in Gusev crater. The dichotomy boundary is a narrow region separating the cratered highlands, located mostly in the southern hemisphere of Mars, from the northern hemisphere's lowland plains.
The images cover 138 x 70 km, roughly the size of Cyprus. A sharp boundary is visible in the centre, dividing dark material to the west and light material to the east. Scientists suspect that this feature is most likely the edge of a basaltic lava flow.