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

Kurzfassung

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.