The Pressure and Temperature Limits of Likely Rocky Exoplanets

Abstract

The interior composition of exoplanets is not observable, limiting our direct knowledge of their structure, composition, and dynamics. Recently described observational trends suggest that rocky exoplanets, that is, planets without significant volatile envelopes, are likely limited to $<$1.5 Earth radii. We show that given this likely upper limit in the radii of purely-rocky super-Earth exoplanets, the maximum expected core-mantle boundary pressure and adiabatic temperature is relatively moderate, 630 GPa and 5000 K, while the maximum central core pressure varies between 1.5 and 2.5 TPa. We further find that for planets with radii less than 1.5 Earth radii, core-mantle boundary pressure and adiabatic temperature are mostly a function of planet radius and insensitive to planet structure. The pressures and temperatures of rocky exoplanet interiors, then, are less than those explored in recent shock-compression experiments, ab-initio calculations, and planetary dynamical studies. We further show that the extrapolation of relevant equations of state does not introduce significant uncertainties in the structural models of these planets. Mass-radius models are more sensitive to bulk composition than any uncertainty in the equation of state, even when extrapolated to TPa pressures.

arXiv comment27 Pages, 8 Figures, Accepted to JGR Planets

References in corpus (25)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Mass-Radius Relationships for Solid Exoplanets
• Most 1.6 Earth-Radius Planets are not Rocky
• The Mass-Radius Relation for 65 Exoplanets Smaller than 4 Earth Radii
• Internal Structure of Massive Terrestrial Planets
• Mass-Radius Relation for Rocky Planets based on PREM
• Terrestrial Planet Occurrence Rates for the Kepler GK Dwarf Sample
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• The nature of the TRAPPIST-1 exoplanets
• Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog
• Solar System Abundances of the Elements
• A Detailed Model Grid for Solid Planets from 0.1 through 100 Earth Masses
• A Plateau in the Planet Population Below Twice the Size of Earth
• Geodynamics and Rate of Volcanism on Massive Earth-like Planets
• A Study of the Accuracy of Mass-Radius Relationships for Silicate-Rich and Ice-Rich Planets up to 100 Earth Masses
• Observable Consequences of Planet Formation Models in Systems with Close-in Terrestrial Planets
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• Scaling the Earth: A Sensitivity Analysis of Terrestrial Exoplanetary Interior Models
• Outgassing on stagnant-lid super-Earths
• An Earth-sized exoplanet with a Mercury-like composition
• Coreless Terrestrial Exoplanets
• The Star-Planet Connection I: Using Stellar Composition to Observationally Constrain Planetary Mineralogy for the Ten Closest Stars
• Phase transitions in MgSiO3 post-perovskite in super-Earth mantles
• A Universal Break in the Planet-to-Star Mass-Ratio Function of Kepler MKG stars
• A Simple Analytical Model for Rocky Planet Interiors

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• Machine learning inference of the interior structure of low-mass exoplanets
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• Hunting for exoplanets via magnetic star-planet interactions: geometrical considerations for radio emission
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• The GALAH Survey: Using Galactic Archaeology to Refine our Knowledge of TESS Target Stars
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• A Geologically Robust Procedure For Observing Rocky Exoplanets to Ensure that Detection of Atmospheric Oxygen is an Earth-Like Biosignature
• Implications of an improved water equation of state for water-rich planets
• Chemical composition of planetary hosts: C, N, and $\alpha$-element abundances
• Volatile-rich evolution of molten super-Earth L 98-59 d
• Geoastronomy: Rocky planets as the Lavosier-Lomonosov Bridge from the non-living to the living world
• A Validated Low-to-Intermediate Mass Planetary Interior Structure Model and New Mass-Radius Relations
• NaZnF3 as a low-pressure analogue of MgSiO3
• The effect of a biosphere on the habitable timespan of stagnant-lid planets and implications for the atmospheric spectrum
• Mantle Degassing Lifetimes through Galactic Time and the Maximum Age Stagnant-lid Rocky Exoplanets can Support Temperate Climates
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