A deeper and hotter Martian core-mantle differentiation inferred from FeO partitioning.

Abstract

The core-mantle differentiation process plays a pivotal role in redistributing material on a massive scale, shaping the long-term evolution of rocky planets. Understanding this process is crucial for gaining insights into the accretion and evolution of planets like Mars. However, the details of Mars's core-mantle differentiation remain poorly understood due to limited compositional data for its core and mantle. In this study, we aim to constrain the Martian core-mantle differentiation by examining FeO partitioning between core and mantle materials, incorporating improved Martian compositional data from the InSight mission. Using ab initio thermodynamic techniques, we calculated the FeO partition coefficient between liquid iron and silicate melt. Our results align with previous studies while also clarifying the factors affecting partitioning behavior. Based on these findings and estimates of oxygen concentration in the core, we infer that Mars's core and mantle likely differentiated at temperatures above 2440 K and pressures ranging from 14 to 22 GPa. Although these estimates are higher than previously reported, they are consistent with observed abundances of moderately siderophile elements and Mars's accretion models.