New thermodynamic constraints on internal, thermal and magnetic states of terrestrial-like Super-Earths

TL;DR

This paper investigates the internal thermophysical and magnetic properties of super-Earths, revealing how high-pressure mineral physics influences their thermal states and magnetic dynamo activity, with implications for planetary classification.

Contribution

It provides new constraints on super-Earth internal structures and magnetic evolution based on high-pressure mineral physics experiments and modeling.

Findings

Deep basal magma oceans possible in planets >4 ME

Iron cores likely frozen in planets >4 ME

Dynamo action suppressed in planets >2.5 ME

Abstract

Ascertaining rocky exoplanets dynamic evolution requires better understanding of key internal thermophysical processes that shaped their geological surfaces, heat fluxes, volatiles and atmospheric content. New high-pressure experiments on iron and silicates compressible, melting and transport properties are providing new constraints that demand reassessments of super-Earths thermal and magnetic evolution models. We examine the interior structure, temperature distribution, thermal states and dynamo action of these planets with masses ranging from 1-10 ME. We show that the shallow adiabaticity of iron-alloys and perovskite or stishovite silicates compared to their liquidus at high pressure would allow for deep basal magma oceans, and frozen iron cores in planets larger than 4 ME. The presence and partitioning of MgO may alter this scenario. For the more massive planets, the dramatic reduction in liquid silicates viscosity should ensure a vigorous convection in the lower mantle, while the rise of iron thermal conductivity under high pressures, is shown to keep the internal cores of planets more massive than 2.5 ME subadiabatic and non-convicting. This will preclude the dynamo action in the more massive super-Earths (SE). Our results could allow a new mineral physics centered classification of terrestrial-like superEarths.