July, 2004: Global Map of Martian Hydrogen
This gamma ray spectrometer map of the planet Mars is based on gamma rays from the element hydrogen. Regions of high hydrogen content at the north and south pole, shown in dark blue and violet, are believed to consist of very high concentrations of mostly buried water ice. In these regions, the soil is well over 50 volume percent ice, which is more like dirty ice than icy dirt. The equatorial regions of Mars are significantly drier, shown in red and yellow, than the polar regions, although two regions of moderate hydrogen concentration, shown in light blue, are centered around Arabia Terra (center of map) and around and to the east of Apollineris (left and right center of map). This hydrogen may be in the form of hydrated minerals or buried ice deposits, but the former is more likely. 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).