Unveiling the Interior Structure and Thermal Evolution of Super-Earth GJ 486b

TL;DR

This paper models the interior structure and thermal evolution of super-Earth GJ 486b, revealing its core size, cooling timeline, and atmospheric development, to better understand such exoplanets' unobservable interiors.

Contribution

It introduces SERPINT, a new 1-D coupled interior and evolution model, applied to GJ 486b, providing detailed insights into its interior and atmospheric evolution.

Findings

Core is 1.34 times larger than Earth's

Mantle cools and solidifies in about 0.93 million years

Water and oxygen-rich atmospheres form during cooling

Abstract

Recent ground- and space-based surveys have shown that planets between Earth and Neptune in size, known as "super-Earths," are among the most frequently found planets in the Galaxy. Although the JWST era has provided high-quality atmospheric data on several such super-Earths, modeling tools are crucial for understanding their unobservable interiors. Consequently, interior studies represent the next essential step in gaining a comprehensive understanding of this class of exoplanets. This study investigates the interior structure, thermal evolution, and atmospheric dynamics of the super-Earth GJ 486b using SERPINT, a 1-D self-consistent coupled interior structure and evolution model, aiming to understand the planet's thermal evolution based on an Earth-like structure. Our results indicate that GJ 486b's core is approximately 1.34 times larger than Earth's, with a core pressure of about 1171 GPa. The thermal evolution model predicts that the planet's mantle cools and solidifies over approximately 0.93 million years. As the magma ocean cools, water is released from the melt, forming a water-rich atmosphere during early solidification. Photolysis of water vapor and subsequent hydrogen escape lead to oxygen accumulation, forming a water- and oxygen-rich secondary atmosphere. Future high-sensitivity JWST observations, with improved wavelength coverage and the detection of additional trace gases, will enable a detailed analysis of the planet's atmospheric composition, providing crucial insights into the interior, surface, and subsurface properties of GJ 486b.