Thermoelastic Properties of Liquid Fe-Rich Alloys Under Martian Core Conditions

Seismic measurements made on Mars indicate that the liquid iron-nickel core is rich in light elements; however, the effects of these light components on the elasticity of Mars' core remain poorly constrained. Here, we calculate elastic properties of various liquid Fe-X (X = Ni, S, C, O and H) mixtures using ab initio molecular dynamics simulations. We find that, at martian core conditions, the addition of S and O most effectively decreases the density of liquid iron, followed by C and H, while Ni has a minimal effect. As for compressional sound velocity (Vp), C increases Vp of liquid Fe throughout Mars' core, while both S and O reduce Vp, the intensity of which diminishes with increasing pressure. Assuming a martian core made of a binary mixture, the seismically-inferred density would require the presence of at least 30 wt% S.

Automated summary

Seismic measurements on Mars reveal that the liquid core is rich in light elements, but the effect of these elements on core elasticity is not well understood. Through molecular dynamics simulations, we calculate the elastic properties of different liquid Fe-X (X = Ni, S, C, O, and H) mixtures. Our findings show that the addition of S and O significantly decreases the density of liquid iron in the Martian core, while Ni has minimal effect. Additionally, C increases the compressional sound velocity throughout the core, while both S and O decrease it with diminishing intensity at higher pressures. Assuming a binary mixture for the Martian core, the seismic density measurements suggest the presence of at least 30 wt% S.