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

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 Fe0.75S0.25 liquid under Martian core conditions was thoroughly in a magnetic state without existing spin crossover. The Fe0.75S0.25 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 (Stahler et al., 2021, ) and ab initio calculated properties of the Fe0.75S0.25 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. The knowledge of the density and thermoelastic properties of the Martian core is very limited. The thermoelastic properties of Fe0.75S0.25 liquid under Martian core conditions were calculated by ab initio molecular dynamics, and the thermal evolution of the Martian core was modeled by the thermoelastic properties and the reported Insight data (Stahler et al., 2021, ). The Fe0.75S0.25 liquid under the Martian core condition is magnetic and its thermal conductivity is 21-23 W/m/K. If the temperature at the core-mantle boundary is higher than the core's melting temperature, the Martian core is entirely liquid with simple cooling. If the temperature is lower than the melting temperature, there exists iron snow at the top of the Martian core at present. The parameter uncertainty on the effect of the iron snow evolution of the Martian core was explored. The thermoelastic properties were calculated by the polynomial fitted equation of state The Fe0.75S0.25 liquid under the Martian core condition was thoroughly in the magnetic state The Fe0.75S0.25 liquid in magnetic calculation had a low thermal conductivity (21-23 W/m/K)