January, 2008: Thorium Map
This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma rays from the element thorium. Thorium, with the chemical symbol Th, is a naturally radioactive element that exists in rocks and soils in extremely small amounts. Regions high in thorium content appear red and yellow; regions low in thorium appear violet and dark blue. The distribution of elements such as thorium and potassium provide insight into processes that have formed and altered the rocks found on the martian surface. The lower values for thorium shown at the polar regions of the map are probably due to dilution of the soil by large amounts of water ice. The locations of the five successful lander missions are marked: The locations of the five successful lander missions are marked: Viking 1 (VL1), Viking 2 (VL2), Pathfinder (PF), Spirit at Gusev (G), and Opportunity at Meridiani (M). More information about this map can be found in the recent article by Boynton, W. V., et al. (2007), Concentration of H, Si, Cl, K, Fe, and Th in the low- and mid-latitude regions of Mars . You may obtain full resolution versions of this and other elemental maps at http://grs.lpl.arizona.edu/specials/.