Gravimetry And Internal Structure Of Terrestrial Planets

Several present day numerical tools provide thermal convection models in 3D spherical shells, taking into account the large viscosity gradients due to temperature variations. In addition, spectral methods allow the computation of dynamic topography and geoid for a medium with such a variable viscosity. In the present study, we combine both simulation tools in order to better understand the relationship between internal dynamics and surface gravimetry of terrestrial planets. The pressure gradient and temperature fields obtained from a 3D convection model (cubed sphere gridding technique, multigrid flow solver) are used as inputs for the calculation of dynamic topography and gravity anomalies. As a start, we will show the gravimetric and topographic signatures of synthetic models for several convective regimes depending on the viscosity law (isoviscous case, stagnant lid), heating conditions (from below, from within) and Rayleigh number (number of plumes, time-dependency). A comparison between Mars Global Surveyor data and these simple synthetic results will be proposed in order to reinterpret some of the large scale gravity potential and topographic features. In the future, more complex simulations will be performed (e.g., taking into account a more realistic rheology).