An altitude-normalized magnetic map of Mars and its interpretation

Techniques developed for the reduction and analysis of terrestrial satellit e magnetic field data are used to better understand the magnetic field obse rvations made by Mars Global Surveyor. A global distribution of radial (B-r ) magnetic field observations and associated uncertainties is inverted for an equivalent source magnetization distribution and then used to generate a n altitude- normalized map of B-r at 200 km. The observations are well-repr esented by a potential function of crustal origin, consistent with a remane nt origin for the Martian magnetic features. The correlation between the 40 546 B-r observations and B-r calculated from the magnetization solution at observation locations is 0.978. For a magnetization distribution confined t o a 50 km layer, calculated magnetizations range from -22 to +17 A/m. We se e correlations with tectonics that were only hinted at in earlier maps. Mag netic features appear to be truncated against Valles Marineris and Ganges C hasma, suggestive of a major change in crustal properties associated with f aulting.