This image spans the floor and two walls of a pit in Noctis Labyrinthus, a system of deep, steep-walled valleys on the western edge of Valles Marineris.

The valleys themselves are tectonic features known as graben - trench-like features that form in response to extension (or stretching) of the crust. In the case of Noctis Labyrinthus, volcanic activity in the Tharsis region may have formed a bulge, which then stretched and fractured the crust above it.

The subimage focuses on one of the pit walls, where numerous boulder tracks criss-cross each other in a large patch of smooth, dust-covered terrain. Boulders leave linear patterns in the dust as they tumble down the steep slopes.

Written by: Nicole Baugh