Constraining the Thermochemical Structure of Mars Through Joint Inversion of Multidisciplinary Geophysical Data

Abstract Understanding Mars' deep interior is essential to reconstruct its geological history, thermal evolution, and present‐day dynamics. To this end, the NASA InSight mission has provided unprecedented seismic observations. However, strong trade‐offs between temperature and composition in seismic interpretations continue to limit our ability to resolve interior models. To address this challenge, we account for electromagnetic induction data from Mars Global Surveyor as an additional, independent constraint. We develop a joint probabilistic inversion framework that simultaneously fits seismic body wave arrival times, electrical conductivity, the Love number, and the moment of inertia. A key feature of our approach is the integration of Mars' long‐term thermal evolution within the forward model, along with mineral physics and petrology data, to better constrain geodynamical parameters. We explore three different mantle compositions (Sanloup et al., 1999, https://doi.org/10.1016/s0031‐9201(98)00175‐7 ; Taylor, 2013, https://doi.org/10.1016/j.chemer.2013.09.006 ; Yoshizaki & McDonough, 2020, https://doi.org/10.1016/j.gca.2020.01.011 ) and consider both radially homogeneous and heterogeneous (with a basal molten layer (Samuel et al., 2023, https://doi.org/10.1038/s41586‐023‐06601‐8 )) mantle scenarios. For homogeneous mantle models, two families of solutions emerge regardless of the bulk composition: one with low Mg content and high potential temperature, which better reproduces electrical conductivity data due to a thicker lithosphere, and another with high Mg content and lower potential temperature. Models with a heterogeneous mantle reproduce electrical conductivity data less accurately, due to thinner lithospheres, and the mantle composition of Yoshizaki and McDonough (2020, https://doi.org/10.1016/j.gca.2020.01.011 ) appears to be less consistent with the full data set. To further refine models of Mars' interior, future efforts should focus on acquiring electromagnetic data with reduced uncertainties and seismically constraining more precisely the depth of mantle discontinuities associated with mineral phase transitions.