Seminar by Mélanie Drilleau (IPGP) – « Inferring Mars’ Internal Structure from a Probabilistic Inversion of Complementary Geophysical Data »

The present-day structure of terrestrial planets encodes their long-term thermochemical evolution and provides key constraints on their formation and thermal history. Mars, particularly in the wake of the InSight mission, offers unprecedented seismic and geodetic observations, enabling robust estimates of core size, mantle thermal structure, and crustal layering, as well as indications of complexity near the core–mantle boundary.

However, most models of the Martian interior rely on independent inversions of seismic, geodetic, gravity, or electromagnetic datasets, which can lead to inconsistencies due to their differing sensitivities to depth, temperature, and composition. Fully integrated approaches remain scarce, and a unified thermochemical model of Mars, from crust to core, remains elusive. Moreover, such models are inherently non-unique, given observational uncertainties and their uneven spatial and temporal coverage.

A central challenge lies in the trade-off between temperature and composition, as distinct mantle compositions can produce similar seismic signatures. Electrical conductivity provides a powerful complementary constraint, owing to its strong sensitivity to temperature and iron content, although its application to Mars has been limited by environmental uncertainties and sparse data coverage.

In this seminar, I will present a probabilistic framework that jointly inverts seismic, geodetic, and electrical conductivity data to derive a self-consistent model of the Martian interior. This approach allows us to assess the extent to which electromagnetic constraints help disentangle thermal and compositional effects. Such approaches are directly applicable to upcoming lunar missions, including the Farside Seismic Suite (FSS) and the South Pole Seismic Suite (SPSS).