An improved model of metal/silicate differentiation during Earth's accretion

TL;DR

This paper enhances a model of Earth's chemical differentiation during accretion by integrating SPH simulation data to better predict the bulk silicate Earth's composition, including challenging elements like W and Mo.

Contribution

The authors improved the differentiation model by removing free parameters and incorporating SPH simulation data, leading to more accurate predictions of Earth's chemical composition.

Findings

Model reproduces bulk silicate Earth's composition more accurately.

Successful models also match W and Mo abundances.

Not all dynamical simulations yield satisfactory results.

Abstract

We improved the algorithm presented in Rubie et al. (2015) to model the chemical evolution of Earth driven by iron/silicate differentiation during the planet's accretion. The pressure at which the equilibration occurs during a giant impact is no longer a free parameter but is determined by the smooth particle hydrodynamic (SPH) simulations of Nakajima et al. (2021). Moreover, impacting planetesimals are now assumed to be too small to cause melting and differentiation and thus their materials are stored in the crystalline upper mantle of the growing planet until a hydrostatically relaxed global magma ocean forms in the aftermath of a giant impact, whose depth is also estimated from Nakajima et al. (2021). With these changes, not all dynamical simulations lead to a satisfactory reproduction of the chemical composition of the bulk silicate Earth (BSE). Thus, the latter becomes diagnostic of the success of dynamical models. In the successful cases also the BSE abundances of W and Mo can be reproduced, that were previously hard to fit (Jennings et al., 2021).