Constraints on the maximum crustal density from gravity-topography modeling: Applications to the southern highlands of Mars

Gravimetric methods commonly used to constrain crustal parameters such as the mean crustal thickness and density are ambiguous with a noted trade-off between these parameters. However, combining two different methods, the geoid-topography ratio and Bouguer inversion, in regions that are homogeneous with respect to lateral density variations and compensation state can help to constrain a maximum density of the crust. For the Martian Noachian southern highlands a combination of these methods gives us a maximum crustal density of 3020 ± 70 kg m− 3, assuming a single-layer crustal structure. We also test various two-layer crustal structures to check how they influence the results. We find a possibility to fit the observed data with a crust having a dense uniformly thick lower crust, but in these models the upper crustal density was also limited to ~ 3000 kg m− 3. The obtained results together with the findings on crustal densities (and composition) of other regions on Mars are consistent with various scenarios of crustal evolution: a temporal increase in the crustal density or a large scale density variation that has been already manifested in the early evolution during the formation of the crustal dichotomy.