(2) Acheron Fossae horsts and grabens (black/white)

Image 2 of 6. These images were taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express are of the Acheron Fossae region, an area of intensive tectonic (continental ‘plate’) activity in the past.
Acheron Fossae marks the northern edge of the Tharsis plateau. It is part of a network of extensional fractures that radiates outward from their central focus in the Tharsis ‘bulge’, a huge area of regional uplift where intensive volcanic activity occurred.

These curved ‘faults’ were caused in the process of this uplift: cracks in the crust formed when the hot material rising from deep in the mantle of Mars pushed the overlying ‘elastic’ lithosphere (surface layers of rock) upward. When the distorting tensions became too strong, the brittle crust on top of the lithosphere broke along zones of weakness.

Images 1-3, from orbit 37, are dominated by these curved features, showing a highly fractured, faulted and deformed area in the central part of the Acheron Fossae.

The feature is situated at approximately 35º-40º North and 220º-230º East, about 1000 kilometres north of the large Olympus Mons volcano.

For practical use on the internet, the images have been reduced in their resolution – the data originally obtained from orbit at an altitude of 765 kilometres (orbit 37) and 1240 kilometres (orbit 143) have a resolution of 30 metres and 50 metres per pixel respectively.