An altitude-normalized magnetic map of Mars and its interpretation

Techniques developed for the reduction and analysisofterrestrialsatellitemagneticelddataareusedto better understand the magnetic eld observations made by Mars Global Surveyor. A global distribution of radial (Br) magnetic eld observations and associated uncertainties is invertedfor an equivalentsource 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 rema- nent origin for the Martian magnetic features. The correla- tion between the 40546 Br observations andBr calculated from the magnetization solution at observation locations is 0.978. For a magnetization distribution connedto a 50 km layer,calculatedmagnetizationsrangefrom-22to+17A/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 fault- ing.