Probing the interiors of the ice giants: Shock compression of water to 700 GPa and 3.8 g/ccm

TL;DR

This study provides precise shock compression data for water up to 700 GPa, revealing that current models overestimate its compressibility and supporting a first-principles equation of state for planetary interior simulations.

Contribution

It presents highly accurate shock compression measurements of water at extreme conditions, validating a first-principles equation of state for planetary modeling.

Findings

Current models overestimate water's compressibility at planetary interior conditions.

The behavior of water under these conditions aligns with a recent first-principles equation of state.

Results improve modeling of Neptune, Uranus, and exoplanets with water-rich interiors.

Abstract

Recently there has been tremendous increase in the number of identified extra-solar planetary systems. Our understanding of their formation is tied to exoplanet internal structure models, which rely upon equations of state of light elements and compounds like water. Here we present shock compression data for water with unprecedented accuracy that shows water equations of state commonly used in planetary modeling significantly overestimate the compressibility at conditions relevant to planetary interiors. Furthermore, we show its behavior at these conditions, including reflectivity and isentropic response, is well described by a recent first-principles based equation of state. These findings advocate this water model be used as the standard for modeling Neptune, Uranus, and "hot Neptune" exoplanets, and should improve our understanding of these types of planets.