The global magnetic field of Mars and implications for crustal evolution

The Mars Global Surveyor spacecraft obtained globally-distributed vector ma gnetic field measurements approximately 400 km above the surface of Mars. T hese have been compiled to produce the first complete global magnetic field maps of Mars. Crustal magnetization appears dichotomized, with intense mag netization mainly confined to the ancient, heavily cratered highlands in th e south. The global distribution of sources is consistent with a reversing dynamo that halted early in Mars evolution. Intense crustal magnetization r equires an increased oxidation state relative to mantle-derived rock, consi stent with assimilation of an aqueous component at crustal depths.