Seeing Rocks' Internal Composition
Detections of minerals in Mars rocks by spectrometers that analyze reflected light can be foiled by coatings on the rocks. The mineral-mapping spectrometers on Mars orbiters see the surface of rocks but not the bulk composition. The Mars Exploration Rovers Spirit and Opportunity are each equipped with a rock abrasion tool (RAT) to remove the dust and weathered surface material of rocks, exposing the interior for analysis.
Image Credit: NASA/JPL-Caltech