Areas showing LTD on Mars

Global map of Mars indicating areas that show LTD.

An analysis of data and images from Mars Express suggests that several Light Toned Deposits, or LTD, some of the least understood structures on Mars, were formed when large amounts of groundwater burst on to the surface. Scientists propose that groundwater had a greater role in shaping the martian surface than previously believed, and may have sheltered primitive life forms as the planet started drying up.

These deposits occur on a large scale in the Arabia Terra, Chaotic Terrain and Valles Marineris, close to the Tharsis volcanic bulge, on Mars.