This spectrum, taken by the Mars Exploration Rover Spirit's Moessbauer spectrometer, shows the presence of an iron-bearing mineral called goethite in a rock called "Clovis" in the "Columbia Hills" of Mars. Goethite contains water in the form of hydroxyl as a part of its structure. By identifying this mineral, the examination of Clovis produced strong evidence for past water activity in the area that Spirit is exploring.