Figure: Potassium map

This gamma ray spectrometer map of the mid-latitude region of Mars is based on gamma-rays from the element potassium. Potassium, having the chemical symbol K, is a naturally radioactive element and is a minor constituent of rocks on the surface of both Mars and Earth. The region of highest potassium content, shown in red, is concentrated in the northern part of Acidalia Planitia (centered near 55 degrees N, -30 degrees). Several areas of low potassium content, shown in blue, are distributed across the mid-latitudes, with two significant low concentrations, one associated with the Hellas Basin (centered near 35 degrees S, 70 degrees) and the other lying southeast of Elysium Mons (centered near 10 degrees N, 160 degrees). Contours of constant surface elevation are also shown. The long continuous line running from east to west marks the approximate separation of the younger lowlands in the north from the older highlands in the south.

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 potassium shown at the polar regions of the map are most probably due to dilution of the soil by large amounts of water ice.

Credit: NASA/JPL/University of Arizona

http://photojournal.jpl.nasa.gov/catalog/PIA04255