Nili Fossae

The two linear depressions in this VIS image are part of the Nili Fossae fracture system. Nili Fossae is the name of a collection of curved faults and down-dropped blocks of crust between the faults {called graben}. The grabens lie northeast of the large volcano Syrtis Major and northwest of the ancient impact basin Isidis. The grabens make concentric curves that follow the outline of Isidis Planitia. The faults likely formed as the crust sagged under the weight of lava flows filling Isidis.