Structure and Thermal Evolution of Exoplanetary Cores

Abstract

We investigate the evolution of the cores of rocky planets with masses 0.8-2 M Earth and variable bulk and mantle iron contents • The content and distribution of iron in a planetary body significantly influence core evolution and magnetic field lifetimes • The cores of iron-rich planets tend to become fully solid, shutting off any pre-existing magnetic field and shortening the dynamo lifetime

Energetic Requirements for Dynamos in the Metallic Cores of Super‐Earth and Super‐Venus Exoplanets

“…Relative to Earth and/or Venus, massive cores may take much longer to solidify (e.g., Boujibar et al., 2020). Thermal evolution models are required to quantify these important time scales (e.g., Bonati et al., 2021).…”

Synergies Between Venus & Exoplanetary Observations

“…Driscoll and Olson 2011) and, depending on their bulk composition, are still expected to grow solid inner cores that provide a strong power source for a dynamo (e.g. Boujibar et al 2020;Bonati et al 2021;van Summeren et al 2013). Simple scaling laws predict that the actual cooling rate of the core would increase with planetary mass faster than the critical value required to drive convection (Blaske and O'Rourke 2021).…”

Thermal Properties of Liquid Iron at Conditions of Planetary Cores

“…The adiabatic slope $${(dT/dP)}_{s}\equiv \frac{\alpha T}{\rho {C}_{p}}$$, with α thermal expansivity, ρ density, C p isobaric heat capacity, determines the core's temperature profile (Boujibar et al., 2020; Grant et al., 2021). Thermal properties of iron are also vital to understand the evolution of the core and the dynamo responsible for the planet's magnetic field (Bonati et al., 2021; Gaidos et al., 2010). Even though iron cannot be the sole element in planetary cores, using pure iron to model the cores provides a primary framework from which more realistic models can be constructed.…”