Thermoelastic Properties and Thermal Evolution of the Martian Core From Ab Initio Calculated Magnetic Fe-S Liquid

Abstract

Accurate thermoelastic properties and thermal conductivity are crucial for understanding the thermal evolution of the Martian core. A fitting method based on ab initio calculated pressure-volume-temperature data was proposed for the formulation of the equation of state with high accuracy, by which the pressure and temperature dependent thermoelastic properties can be directly calculated by definitions. Ab initio results showed that Fe_0.75S_0.25 liquid under Martian core conditions was thoroughly in a magnetic state without existing spin crossover. The Fe_0.75S_0.25 liquid in magnetic calculations had a low thermal conductivity (21–23 W/m/K) when compared with non-magnetic calculations at the same state. Based on Insight's estimated Martian core properties (Stähler et al., 2021, https://doi.org/10.1126/science.abi7730) and ab initio calculated properties of the Fe_0.75S_0.25 liquid, the scenario for the thermal evolution of the Martian core is the iron-snow model crystallization regime. The parameter uncertainty effect on the cessation time of the dynamo and zone of iron snow was systematically analyzed.