Density of FeS up to the Martian core condition using the X-ray absorption method with laser-heated diamond anvil cell: implication to the Martian core structure

A relationship between density of solid FeS and that of coexisting liquid Fe–S is crucial for understanding the Martian core structure. In the sulfur-rich Martian core (S > 25 wt%), FeS could be a liquidus phase. In this study, the density of FeS V phase was measured using the X-ray absorption method combined with a laser-heated DAC up to 26 GPa and 1950K. The density from the X-ray absorption method is consistent with that from X-ray diffraction (0.04–2.82% in difference). The density of FeS is found to be lower than that of the liquid Fe–30wt%S at the Martian core pressures. Therefore, solid FeS could float in the liquid Fe–S core. The solid FeS outer core may influence the weak Martian magnetic field. If Mars has a solid inner core, FeS is excluded from the liquidus phases in the core, indicating that the sulfur content in the core is constrained to be <25 wt%.