Detection of an Atmosphere on a Rocky Exoplanet

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.

22 pages, 12 figures, accepted for publication in Astronomical Journal

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• Understanding planetary context to enable life detection on exoplanets and test the Copernican principle
• A Catalogue of Exoplanet Atmospheric Retrieval Codes
• TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
• A transmission spectrum of the sub-Earth planet L98-59~b in 1.1-1.7 $\mu$m
• Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD235088 b (TOI-1430 b) with CARMENES
• Hubble WFC3 Spectroscopy of the Rocky Planet L 98-59 b: No Evidence for a Cloud-Free Primordial Atmosphere
• Sporadic Spin-Orbit Variations in Compact Multi-planet Systems and their Influence on Exoplanet Climate
• Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere
• Narrow loophole for H2-dominated atmospheres on habitable rocky planets around M dwarfs
• Impact of M-dwarf Stellar Wind and Photoevaporation on the Atmospheric Evolution of Small Planets
• The Tianlin Mission: a 6m UV/Opt/IR space telescope to explore the habitable worlds and the universe
• On the Utility of Transmission Color Analysis I: Differentiating Super-Earths and Sub-Neptunes
• HyDRo: Atmospheric Retrieval of Rocky Exoplanets in Thermal Emission
• Effect of clouds on emission spectra for Super Venus