Surface composition in "Endurance Crater" is mapped with color-coded interpretation of data from the miniature thermal emission spectrometer on NASA's Mars Exploration Rover Opportunity. The information has been overlaid onto a view of the crater from Opportunity's panoramic camera. Green, such as on some slopes, indicates material rich in the mineral hematite. Blue and purple, such as on some cliffs of exposed rock, indicate the presence of basalt. Basaltic material is volcanic in origin, but the basalt may have been broken down into sand by weathering, then re-deposited by wind or water. Red indicates areas covered by martian dust.