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

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 N2O. 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.

Automated summary

Stellar flares and coronal mass ejections from M dwarf stars have significant impacts on the habitability and atmospheric composition of terrestrial planets. This study used a general circulation model coupled with a photochemical kinetics scheme to examine the response of an Earth-like atmosphere to these events. The research found that stellar flares increase ozone levels in the atmosphere and coronal mass ejections generate potential bio-signatures. However, the changes in atmospheric composition also reduce the amount of harmful ultraviolet light reaching the planetary surface.