Figure 9.
Geochemical classification diagram for volcanic rocks on Mars, showing the compositions of martian meteorites, Gusev and Gale crater rocks analyzed by the Spirit and Curiosity rovers, respectively, and orbital analyses by the Mars Odyssey gamma-ray spectrometer (colored rectangles labeled GRS). GRS does not measure sodium, so its abundance was estimated from Na/K ratios in Gusev rocks or martian (SNC) meteorites. Gusev rocks were either brushed or ground (RAT) by the Rock Abrasion Tool before analysis. Adapted from McSween et al. (2009), with additional data.