In this perspective view of Tithonium Chasma, the surrounding areas are covered by a thin layer of dark sand (shown bluish in these contrast-enhanced images), which also forms imposing dark dunes in the central part of Tithonium Chasma (seen in plan view). Due to the proximity of the Tharsis volcanic region to the west, many of the rocks present in this area consist of layers of lava flows and volcanic ash that have been eroded and are the source of the black-grey sands that make up the dunes. Mineralogical studies of the dune material confirmed their volcanic origin.