Opportunity's Mini-Thermal Emission Spectrometer (Mini-TES) detected the presence of grey hematite at the robot's Meridiani Planum landing site. This finding will help unlock the truth about Mars' past, specifically the role that water may have played in the area. The yellow line represents the spectrum, or light signature, of the martian soil, while the red line shows the spectrum of pure hematite. Credit: NASA/JPL/Arizona State University
