The Shock Physics of Giant Impacts: Key Requirements for the Equations of State

Abstract

We discuss major challenges in modeling giant impacts between planetary bodies, focusing on the equations of state (EOS). During the giant impact stage of planet formation, rocky planets are melted and partially vaporized. However, most EOS models fail to reproduce experimental constraints on the thermodynamic properties of the major minerals over the required phase space. Here, we present an updated version of the widely-used ANEOS model that includes a user-defined heat capacity limit in the thermal free energy term. Our revised model for forsterite (Mg${}_2$SiO${}_4$), a common proxy for the mantles of rocky planets, provides a better fit to material data over most of the phase space of giant impacts. We discuss the limitations of this model and the Tillotson equation of state, a commonly used alternative model.

M-ANEOS source code public release (https://github.com/isale-code/M-ANEOS); forsterite EOS public release (https://github.com/ststewart/aneos-forsterite-2019); manuscript accepted (no changes): Stewart, S., et al. (accepted). In J. Lane, T. Germann, and M. Armstrong (Eds.), 21st Biennial APS Conference on Shock Compression of Condensed Matter (SCCM19). AIP Publishing

References in corpus (2)

• The structure of terrestrial bodies: Impact heating, corotation limits and synestias
• Silicate Melting and Vaporization during Rocky Planet Formation

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