More than four years after Mars rover Spirit visited the Comanche outcrop in Gusev Crater's Columbia Hills, scientists armed with a new instrument calibration have discovered the rocks are rich in long-sought carbonate minerals. Comanche (left) and Comanche Spur (right) appear reddish-brown in this false-color image from Spirit's Pancam. (The bluish-wite rocks in the foreground belong to an unrelated outcrop.) Credit: NASA/JPL/Cornell University