Detection of an Atmosphere on a Rocky Exoplanet

TL;DR

This study reports the first detection of an atmosphere on a rocky exoplanet, GJ 1132 b, using Hubble measurements, revealing spectral signatures indicative of a low molecular weight atmosphere potentially formed by outgassing.

Contribution

It provides the first observational evidence of an atmosphere on a rocky exoplanet and models its possible origin through magma outgassing, offering insights into terrestrial planet atmospheres.

Findings

Detected atmospheric spectral signatures including aerosol scattering, HCN, and CH4.

Concluded the atmosphere was likely reestablished after atmospheric loss.

Suggested outgassing from ultrareduced magma as a plausible source.

Abstract

We report the detection of an atmosphere on a rocky exoplanet, GJ 1132 b, which is similar to Earth in terms of size and density. The atmospheric transmission spectrum was detected using Hubble WFC3 measurements and shows spectral signatures of aerosol scattering, HCN, and CH$_{4}$ in a low mean molecular weight atmosphere. We model the atmospheric loss process and conclude that GJ 1132 b likely lost the original H/He envelope, suggesting that the atmosphere that we detect has been reestablished. We explore the possibility of H$_{2}$ mantle degassing, previously identified as a possibility for this planet by theoretical studies, and find that outgassing from ultrareduced magma could produce the observed atmosphere. In this way we use the observed exoplanet transmission spectrum to gain insights into magma composition for a terrestrial planet. The detection of an atmosphere on this rocky planet raises the possibility that the numerous powerfully irradiated Super-Earth planets, believed to be the evaporated cores of Sub-Neptunes, may, under favorable circumstances, host detectable atmospheres.