Melas Dorsa reveals a complex geological history on Mars

ESA's Mars Express has imaged an area to the south of the famed Valles Marineris canyon on the Red Planet, showing a wide range of tectonic and impact features. On 17 April, the orbiter pointed its high-resolution stereo camera at the Melas Dorsa region of Mars. This area sits in the volcanic highlands of Mars between Sinai and Thaumasia Plana, 250 km south of Melas Chasma. Melas Chasma itself is part of the Valles Marineris rift system. The image captures wrinkle ridges, some unusual intersecting faults and an elliptical crater surrounded by ejecta in the shape of a butterfly and with a strange 'fluid-like' appearance. Elliptical craters like this 16 km-wide example are formed when asteroids or comets strike the surface of the planet at a shallow angle. Scientists have suggested that a fluidised ejecta pattern indicates the presence of subsurface ice which melted during the impact.