Perspective view of the Melas Chasma
Thursday 2 December 2010
Instrument: HRSC: High-Resolution Stereo Camera
Melas Chasma is part of the huge Valles Marineris rift valley, which stretches for more than 4000 km across the surface of Mars. Around Melas Chasma, there is abundant evidence for water having flowed across Mars in the past. As well as ancient water-cut channels, there are lighter-coloured deposits of sulphate components that were probably deposited in a former lake. On the high plateau at the top of the cliff, a few ancient valleys have been preserved. The orientation of the largest one is parallel to the edge of the cliff, which may indicate that the valley originally followed an old fault line. Remaining faults are probably the main reason for the instability of the flanks, which have frequently collapsed forming huge landslides. The valley sides show evidence of multiple large landslides that have created vast fan shapes of material. This debris appears rough and jumbled, contrasting with the underlying smoother surface visible further into the basin. The rocks display flow textures indicating that they were once deposited by liquid water, water ice or mud. Levees of sediment can also been seen here.