This diagram depicts a vertical cross section through geological layers deposited by rivers, deltas and lakes. A delta builds where a river enters a body of still water, such as a lake, and the current decelerates abruptly so sediment delivered by the river settles to the floor.

In the pattern of deposits illustrated here, a series of deltas from southward-flowing rivers have been deposited successively farther southward as the accumulating sediments raise the floor level of the basin. The delta deposits build out higher and higher in elevation as they migrate southward (toward the center of the basin) over lake deposits.

During NASA's Mars Curiosity rover's approach to the base of Mount Sharp, the rover found sedimentary rocks fitting this pattern of successive delta deposits, with the ones farther south (toward the mountain) higher in elevation. This suggests that where the mountain stands now was formerly a lake or series of lakes.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover.

More information about Curiosity is online at http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/.