Satellite gravity-rate observations to uncover Martian plume-lithosphere dynamics

Several orbiters and landers at Mars have allowed to unravel valuable knowledge about its surface and interior. Tracking of the satellites MGS, MRO, and Odyssey have provided us with detailed knowledge about the gravitational field of Mars, revealing the presence of subsurface structures in crust and mantle. With the InSight mission, seismic waves have indicated the presence of more frequent Marsquakes than assumed before the mission. This raises questions regarding the planet's formation and why Mars is more geologically active than was expected. Another important milestone in studying the interior of Mars is not only the recovery of static gravity field models but addition the seasonal variations, providing information on the periodic behavior of the polar ice caps. With the longer time-period of gravity variation could the secular time varying gravity field be linked to the solid deformation of the planet?

In this study, we focus on a new method for estimating the secular variations of Mars' gravity field using available Deep Space Network (DSN) tracking data with an open-source orbit estimation tool called TUDAT (TU Delft Astrodynamics Toolbox). We have constructed an orbit simulation, including realistic environmental models like the Mars-DTM atmosphere model, that has an orbital accuracy within 2 meters of SPICE kernels.

With this orbital simulator, we conduct sensitivity analyses to study the decoupling of secular gravity variations from other disturbing acceleration signals. These analyses incorporate all relevant dynamic forces acting on the satellite. We perform covariance analysis for various estimation parameters, including the satellite's initial state, atmospheric drag, static, periodic, as well as global versus arc-wise secular gravity coefficients.

By evaluating the formal errors of the estimated parameters and the correlations between them, we aim to identify scenarios where we can effectively separate the atmospheric signal from the gravitational changes of solid Mars. This investigation will contribute to addressing the unresolved question of Martian interior activity.