Techniques developed for the reduction and analysis of terrestrial satellite magnetic field data are used to better understand the magnetic field observations made by Mars Global Surveyor. A global distribution of radial (Br) magnetic field observations and associated uncertainties is inverted for an equivalent source magnetization distribution and then used to generate an altitude-normalized map of Br at 200 km. The observations are well-represented by a potential function of crustal origin, consistent with a remanent origin for the Martian magnetic features. The correlation between the 40546 Br observations and Br calculated from the magnetization solution at observation locations is 0.978. For a magnetization distribution confined to a 50 km layer, calculated magnetizations range from -22 to +17 A/m. We see correlations with tectonics that were only hinted at in earlier maps. Magnetic features appear to be truncated against Valles Marineris and Ganges Chasma, suggestive of a major change in crustal properties associated with faulting. ¿ 2000 American Geophysical Union