Bouguer gravity profiles across the highland-lowland escarpment on Mars

Selected Bouguer gravity profiles crossing the highland-lowland boundary of Mars are calculated. Density-depth models are presented for two areas. All profiles show an isostatic behaviour of the ancient highlands and the adjacent lowlands. Especially isostasy must be implied for the area of the escarpment. It is found that the whole Elysium dome is also nearly in isostatic equilibrium. These geophysical results and additional geological investigations imply a combination of subcrustal and minor surface erosion associated with relatively small vertical isostatic movements of the crust (sinking) in former highland areas. These processes caused a retreat of the highland escarpment of at least several hundred kilometers.