Assessing the Interior Structure of Terrestrial Exoplanets with Implications for Habitability

TL;DR

This paper discusses methods to characterize the interior structures of terrestrial exoplanets, emphasizing their implications for habitability despite data limitations and model uncertainties.

Contribution

It introduces approaches to assess exoplanet interior structures and explores their connection to habitability, highlighting challenges in constraining interior dynamics.

Findings

Interior models can fit available data with diverse structures.

Thermal state has limited impact on interior structure models.

Habitability is unlikely for close-in super-Earths with high surface temperatures.

Abstract

Astrophysical observations reveal a large diversity of radii and masses of exoplanets. It is important to characterize the interiors of exoplanets to understand planetary diversity and further determine how unique, or not, Earth is. Assessing interior structure is challenging because there are few data and large uncertainties. Thus, for a given exoplanet a range of interior structure models can satisfy available data. Typically, interior models aim to constrain the radial structure and composition of the core and mantle, and additionally ice, ocean, and gas layer if appropriate. Constraining the parameters of these layers may also inform us about interior dynamics. However, it remains challenging to constrain interior dynamics using interior structure models because structure models are relatively insensitive to the thermal state of a planet. Nevertheless, elucidating interior dynamics remains a key goal in exoplanetology due to its role in determining surface conditions and hence habitability. Thus far, Earth-like habitability can be excluded for super-Earths that are in close proximity to their stars and therefore have high surface temperatures that promote local magma oceans.