Possible favored Great Oxidation Event scenario on exoplanets around M-Stars with the example of TRAPPIST-1e

TL;DR

This study models the atmospheric evolution of the exoplanet TRAPPIST-1e, suggesting that its ozone layer could form more efficiently and earlier than Earth's, potentially enabling quicker development of oxygen-dependent life, detectable by future telescopes.

Contribution

It introduces a 1D coupled photochemical-climate model to explore GOE timing on M-dwarf exoplanets, highlighting faster ozone formation and detection prospects.

Findings

Ozone forms more efficiently on TRAPPIST-1e due to stellar energy distribution.

GOE could occur up to 1 billion years earlier than on Earth.

Fewer transits are needed to detect ozone signatures than previously predicted.

Abstract

The Great Oxidation Event (GOE), which marked the transition from an anoxic to an oxygenated atmosphere, occurred 2.4 billion years ago on Earth, several hundreds of millions of years after the emergence of oxygenic photosynthesis. This long delay implies that specific conditions in terms of biomass productivity and burial were necessary to trigger the GOE. It could be a limiting factor for the development of oxygenated atmospheres on inhabited exoplanets. In this study, we explore the specificities of a terrestrial planet in the habitable zone of an M dwarf for a GOE. Using a 1D coupled photochemical-climate model, we simulate the atmospheric evolution of TRAPPIST-1 e, an Earth-like exoplanet, exploring the effect of oxygen sources (biotic or abiotic). Our results show that the stellar energy distribution promotes O3 production at lower O2 concentrations compared to Earth, and the ozone layer on TRAPPIST-1 e forms more efficiently. This lowers the threshold for atmospheric oxidation, suggesting that the GOE on TRAPPIST-1 e would occur quickly after the rise of oxygenic photosynthesis, up to 1Gyrs earlier than on Earth, and would reach O2 enabling oxygenic respiration and thus the development of animals. We may question whether this is a general behavior around several M-stars. Furthermore, we discuss how the overproduction of ozone could make O3 detection possible using the James Webb Space Telescope, providing a potential method to observe oxygenation signatures on exoplanets in the near future. Previous studies predicted that for an Earth-like atmosphere O3 would require over 150 transits for detection, but our results show that significantly fewer transits could be needed.