Sensitivity of rocky planet structures to the equation of state

TL;DR

This study investigates how different equations of state influence the modeled internal structures of rocky planets and moons, highlighting the effectiveness of linear Grueneisen equations in reproducing observed moments of inertia.

Contribution

It demonstrates that simpler linear Grueneisen equations of state can better match observed planetary moments of inertia than more complex models with phase transitions.

Findings

Linear Grueneisen equations fit observed data better.

Choice of equation of state significantly affects structure models.

Simpler models are effective for impact simulations.

Abstract

Structures were calculated for Mercury, Venus, Earth, the Moon, and Mars, using a core-mantle model and adjusting the core radius to reproduce the observed mass and diameter of each body. Structures were calculated using Fe and basalt equations of state of different degrees of sophistication for the core and mantle. The choice of equation of state had a significant effect on the inferred structure. For each structure, the moment of inertia ratio was calculated and compared with observed values. Linear Grueneisen equations of state fitted to limited portions of shock data reproduced the observed moments of inertia significantly better than did more detailed equations of state incorporating phase transitions, presumably reflecting the actual compositions of the bodies. The linear Grueneisen equations of state and corresponding structures seem however to be a reasonable starting point for comparative simulations of large-scale astrophysical impacts.