3D modelling of the impact of stellar activity on tidally locked terrestrial exoplanets: atmospheric composition and habitability

TL;DR

This study models how stellar flares and coronal mass ejections from M dwarf stars affect the atmospheres of tidally locked terrestrial exoplanets, revealing significant atmospheric composition changes that influence habitability.

Contribution

It introduces a coupled climate-chemistry model to simulate atmospheric responses to stellar activity, highlighting the impact on ozone and potential biosignatures.

Findings

Stellar flares increase atmospheric ozone by 20 times.

Coronal mass ejections produce detectable bio-signatures like N₂O.

Atmospheric changes reduce ultraviolet radiation reaching the surface.

Abstract

Stellar flares present challenges to the potential habitability of terrestrial planets orbiting M dwarf stars through inducing changes in the atmospheric composition and irradiating the planet's surface in large amounts of ultraviolet light. To examine their impact, we have coupled a general circulation model with a photochemical kinetics scheme to examine the response and changes of an Earth-like atmosphere to stellar flares and coronal mass ejections. We find that stellar flares increase the amount of ozone in the atmosphere by a factor of 20 compared to a quiescent star. We find that coronal mass ejections abiotically generate significant levels of potential bio-signatures such as N$_2$O. The changes in atmospheric composition cause a moderate decrease in the amount of ultraviolet light that reaches the planets surface, suggesting that while flares are potentially harmful to life, the changes in the atmosphere due to a stellar flare act to reduce the impact of the next stellar flare.