Detection of an Atmosphere on a Rocky Exoplanet (2103.05657v1)

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.

• The paper presents the first detection of a thin, evolving atmosphere on rocky exoplanet GJ 1132 b using transmission spectroscopy with Hubble WFC3.
• It employs multifaceted retrieval models to associate specific spectral features with aerosol scattering, hydrogen cyanide, and methane signatures.
• The findings suggest significant atmospheric evolution via photo-evaporation and volcanic outgassing, broadening the understanding of super-Earth atmospheric dynamics.

Detection of an Atmosphere on a Rocky Exoplanet

The paper "Detection of an Atmosphere on a Rocky Exoplanet" presents significant findings from the paper of GJ 1132 b, a rocky exoplanet. Through the utilization of transmission spectroscopy using the Hubble Wide Field Camera 3 (WFC3), the researchers detected the presence of an atmosphere with specific spectral features, including aerosol scattering, hydrogen cyanide (HCN), and methane (CH$_{4}$).

The atmosphere of GJ 1132 b appears to be thin with low molecular weight and exhibits signs of having undergone significant evolution, likely losing its initial hydrogen-helium (H/He) envelope. This premise correlates with the atmospheric loss models that suggest heavily irradiated planets could lose substantial primordial atmospheres within the first hundred million years post-formation. The atmospheric loss is typically attributed to photo-evaporation driven by high levels of stellar insolation.

Notably, the presence of HCN and CH$_{4}$ provides potentially important insights into chemical processes occurring in the atmosphere, suggesting that photochemistry might play a role alongside primary atmospheric processes. The research further posits that the current atmosphere might owe its existence to volcanic outgassing, specifically via hydrogen-release processes. This aligns with theoretical studies that previously suggested the potential for hydrogen-containing mantle degassing as a mechanism for rebuilding atmospheres post-envelope loss.

These findings have broader implications for the paper of super-Earths and sub-Neptunes, particularly those subjected to intense stellar radiation, which can alter atmospheric compositions significantly. The discovery of an atmosphere on GJ 1132 b challenges previously held assumptions about atmospheric presence in such planets and opens up further avenues for detailed studies of their surface and subsurface geological activities.

From a methodological perspective, this research advances the understanding of transit spectroscopy and its capacity to characterize exoplanetary atmospheres. The use of multifaceted retrieval models has proven effective in associating specific molecules with observed spectral features, which is pivotal in atmospheric characterization.

The implications of detecting a secondary atmosphere on GJ 1132 b underscore the potential for numerous similarly irradiated exoplanets to harbor detectable atmospheres, thereby broadening the horizon for future investigations in exoplanet science. The paper suggests that with adequate observations from instruments such as the James Webb Space Telescope, it may be possible to confirm or refute hypotheses about volcanic outgassing and other atmospheric rejuvenation processes, drawing a comprehensive picture of extraterrestrial planetary evolution and atmospheric chemistry. This research sets a precedent for the exploration of atmospheres on rocky exoplanets and challenges current understanding, paving the way for future theoretical and observational advancements in the field.