Tempe Fossae

Today's VIS image is shows a portion of Tempe Fossae. The fossae are graben comprised of paired, parallel fractures with a down-dropped block of material between the fracture set. This morphology is created by extensional tectonic stresses. When large amounts of pressure or tension are applied to rocks on timescales that are fast enough that the rock cannot respond by deforming, the rock breaks along faults. In the case of a graben, two parallel faults are formed by extension of the crust and the rock in between the faults drops downward into the space created by the extension. Numerous sets of graben are visible in this THEMIS image, trending from north-northeast to south-southwest. Because the faults defining the graben are formed perpendicular to the direction of the applied stress, we know that extensional forces were pulling the crust apart in the north-northwest/south-southeast direction.

This fossae system is located in Tempe Terra, a complexly fractured region between Tharsis and Acidalia Planitia. The complete fossae system in almost 2000 km (1242 miles) long.