Drilleau, Melanie ; Verhoeven, Olivier ; Samuel, Henri ; Rivoldini, Attilio ; Garcia, Raphael ; Tarits, Pascal ; Lognonné, Philippe

Poster presented at AGU Fall Meeting 2024, Washington, USA on 2024-12-12

Abstract: Inferring the internal structure of Mars from geophysical observations is one of the fundamental goals of Mars exploration. In particular, it is the physical state (temperature, composition, fluid content, etc.) of the deep mantle rocks that drives processes such as volcanism, seismic activity, and tectonics. The NASA InSight mission, which operated for 1440 Martian days, marked a turning point in the exploration of the Red Planet. Thanks to its seismometer, the mission has significantly increased our knowledge about the crust, mantle, and core. Despite such improvements, the use of separate types of data that have different sensitivities to the planet’s structure makes it difficult to compare the models among different studies. In particular, there exists a well-known trade-off between temperature and composition for seismic wave speed. To minimize this trade-off, the use of electromagnetic induction data from Mars Global Surveyor can provide additional constraints. We address the following main questions: Which 1D interior structure models of Mars are compatible with different and complementary geophysical observables? What can we deduce about the evolution of Mars’ interior? We adopt a synergetic strategy in which we simultaneously invert for multiple types of geophysical data (body wave arrival time, electrical conductivity, Love number, moment of inertia) using a probabilistic approach. This offers the advantage of reducing the uncertainties associated with modeling a single type of observable, and distinguishing between temperature and/or composition variations at different depths, because observables have different sensitivities to temperature/composition and surface/deep anomalies. Our inversion scheme fully integrates the thermal history of Mars directly in the forward problem, allowing to constrain geodynamical parameters (e.g., mantle rheology, initial thermal state and composition), and includes a priori information relying on laboratory mineral-physics and petrology experiments (bulk modulus, shear modulus, and electrical conductivity of mantle assemblages). Our results show a clear potential for joint inversion of multiple types of geophysical observables, to better constrain the 1D interior structure of Mars.

Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT