CRISM: Hydrated minerals near Nili Fossae

This image shows a site near Nili Fossae, a group of long, narrow tectonic depressions called graben. Mars’ crust is mostly made up of igneous rock and mafic materials, shown here with red denoting olivine. There are also aqueously-altered minerals in this scene, meaning minerals that have been changed by water. They are shown by the cyan and blue colors and most likely reflect the presence of iron/magnesium-containing phyllosilicates. Phyllosilicates, also known as sheet silicates, are comprised of microscopic crystal forms stacked in very thin layers…. [More at link]