paper

A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations

arXiv:2604.15304 · doi:10.1093/mnras/stag1076

Abstract

The increasing precision of planetary mass and radius observations is bringing major questions about the structure and formation of planets--such as the nature of the radius valley and origin of super-Mercuries--within reach, demanding the development of interior structure models with more physics to more accurately determine planetary radii for a given composition. Here, we present a new model that includes state-of-the-art equations of state following the latest experimental and computational results, a physically-motivated mineralogy allowing multiple species to coexist within planetary layers, a non-adiabatic temperature profile, melting, and other features. This model replicates Earth's radius and moment of inertia coefficient to within , Mars and the Moon's to within , and Mercury, Venus, and Europa's to within or 3. We use this model to calculate mass-radius relationships for H/He-enveloped, water-rich, Earth-like, and iron-rich bodies with masses between --. We calculate mass-radius tables and fit piece-wise power-laws to them for planets, finding that the exponent in increases with mass and core mass fraction. We find radii generally smaller than in literature mass-radius relations at low instellations and larger at high instellations, with our improvement on the literature comparable to observational uncertainties. State-of-the-art interior structure models are thus required to interpret observational data. Our mass-radius curves comprising 32,975 model planets are publicly available.

41 pages, 19 figures, 6 tables. Second revision, accepted by reviewer but awaiting formal acceptance from journal

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