Seminar Rémy Pierru

Mars likely experienced a global magma ocean during its early evolution, strongly influencing the planet’s cooling history, crystallization processes, and mantle differentiation. Recent seismic observations from NASA’s InSight mission suggest the possible presence of a molten or partially molten silicate layer at the core–mantle boundary (CMB), raising the question of whether this basal melt layer could represent a long-lived remnant of the primordial magma ocean. Addressing this issue requires direct constraints on the physical properties of Fe-rich Martian melts, including viscosity, density, and seismic velocities, as well as on the melting relations and phase equilibria governing deep-mantle behaviour.

To investigate these processes, we conducted high-pressure and high-temperature experiments combining ex situ measurements at the Bayerisches Geoinstitut with in situ experiments at SPring-8 and DESY. Our results show that deep Martian melts are highly FeO-rich, exhibit low viscosities, and can significantly reduce seismic velocities even at very small melt fractions. Complementary melting experiments at ~19 GPa further constrain melting behaviour, melt chemistry, and phase relations expected near the Martian CMB.

Together, these measurements provide an experimental framework to evaluate the formation, stability, and seismic detectability of a basal melt layer, and to link the dynamics of Mars’ early magma ocean to the present-day structure of its interior.