The aim of this paper is to propose a Mars Quantum Gravity Mission (MaQuIs). The mission is targeted at improving the data on the gravitational field of Mars, enabling studies on planetary dynamics, seasonal changes, and subsurface water reservoirs. MaQuIs follows well known mission scenarios, currently deployed for Earth, and includes state-of-the-art quantum technologies to enhance the gained scientific signal.

Mars hosts the largest volcano in our solar system, Mons Olympus. Up until now, flexural isostasy has commonly been used to understand the relationship between observed topography, crustal structure, and gravity. NASA’s InSight mission has brought new information about the Martian lithosphere, which warrants a re-analysis of the support of the large volcanic complex. After conducting spectral analysis on the topographic and gravity results from the flexural models, the gravitational signal of Martian topography with thin shell compensation fits well with the observed free-air anomaly for degrees, n≥2. The Martian lithosphere can be modelled by a thin shell model using the following parameters: crustal thickness of 60 ±10 km, crustal density of 3050 ±50 kg/m3, mantle density of 3550 ±100 kg/m3, and the best-fit elastic thickness (Te) is found to be 80 ±5 km. The remaining short scale gravity residuals give insight in Martian crustal density distributions. There appear to be buried mass anomalies in the subsurface of the northern polar plains, suggesting an older history of the northern hemisphere of Mars. A mismatch between modeled and observed gravity field for the long-wavelengths (between n=2-6 degrees) exists. The location of the residual anomaly correlates with the Tharsis Rise. which suggests active large-scale dynamic support of the volcanic region. A substantial negative mass anomaly in the mantle underneath the Tharsis Region can explain the gravity residual. Could mantle convection is still be active in Mars, explaining the relatively young geologic surface volcanism on Mars.

The long-wavelength negative gravity anomaly over Hudson Bay coincides with the area depressed by the Laurentide ice sheet during the Last Glacial Maximum, suggesting that it is, at least partly, caused by Glacial Isostatic Adjustment (GIA). Additional contributions to the static gravity field stem from dynamic topography and density anomalies in the subsurface. Previous estimates of the contribution of GIA to the gravity anomaly range from 25 percent to more than 80 percent. However, these estimates did not include uncertainties in all components that contribute to the gravity field. In this study, we develop a forward model for the gravity anomaly. We combine density anomalies, isostatic balance, and non-isostatic contributions from GIA and dynamic topography. The largest uncertainty in the predicted gravity anomaly is due to the lower mantle viscosity; uncertainties in the ice history, the crustal model, the lithosphere-asthenosphere boundary and the conversion from seismic velocities to density are found to have a smaller effect. A preference for lower mantle viscosities >10^22 Pa s is found, in which case at least 60 percent of the observed long-wavelength gravity anomaly can be attributed to GIA. This lower bound on the lower mantle viscosity has implications for models employing a viscosity profile in the mantle, such as models for mantle convection and GIA, and inferences based on these models.