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…. [More at link]
More CRISM images.