CRATER DENSITY AS AN AID TO MAPPING THE CRATERED SURFACE AT GALE CRATER, MARS
In Gale, some of these mapping results can be examined using data from the Mastcam and ChemCam instruments. For instance, ChemCam data show that rocks interpreted to be part of the CS have higher concentrations of Al, Na, and K than the SH and RU units, although how these elemental differences translate to specific mineralogies and lithologies is not yet understood. Potential CS targets analyzed by ChemCam near the Shaler outcrop showed no signs of chemical alteration. This is consistent with CS material being well-cemented and impermeable to water that was present post-deposition. Mastcam images show that the CS is comprised of material that is much darker in color than any other unit in the landing ellipse. The images also show that the CS weathers into boulders of various sizes, which is a much different weathering pattern than other units. All of these characteristics suggest the CS is harder and more resistant to erosion than the SH and RU units. Crater densities enable us to more confidently link the physical characteristics seen in satellite images to the relative pattern of erosional resistance and rock types present on Mars.