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

Sarah T. Stewart; Erik J. Davies; Megan S. Duncan; Simon J. Lock; Seth Root; Joshua P. Townsend; Richard G. Kraus; Razvan Caracas; Stein B. Jacobsen

doi:10.1063/12.0000946

arXiv · 1910.04687

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

Sarah T. Stewart·Erik J. Davies·Megan S. Duncan·Simon J. Lock·Seth Root·Joshua P. Townsend·Richard G. Kraus·Razvan Caracas·Stein B. Jacobsen

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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.

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Sarah T. Stewart, Erik J. Davies, Megan S. Duncan, Simon J. Lock, Seth Root, Joshua P. Townsend, Richard G. Kraus, Razvan Caracas, Stein B. Jacobsen. 2019-10-10. The Shock Physics of Giant Impacts: Key Requirements for the Equations of State. https://doi.org/10.1063/12.0000946

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