These striking features on Mars were caused by the planet’s crust stretching apart in response to ancient volcanic activity.
The fractures in the Sirenum Fossae region in the southern hemisphere were imaged by ESA’s Mars Express in March. They extend for thousands of kilometres in length, far beyond the boundaries of this image.
The fractures divide the crust into blocks: the movement along a pair of faults causes the centre section to drop down into ‘graben’ several kilometres wide and a few hundred metres deep. Elevated blocks of crust remain between the graben when there is a parallel series of fault, as seen in this scene.
The Sirenum Fossae are part of a larger radial fracture pattern around the Arsia Mons volcano in the Tharsis region, which is situated some 1800 km to the northeast. [More at link]