2024/05/30 by Cooke, G. J., Marsh, D. R., Walsh, C. +1
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2405.20167
Ozone (\textrmO3) is important for the survival of life on Earth because it shields the surface from ionising ultraviolet (UV) radiation. However, the existence of \textrmO3 in Earth's atmosphere is not always beneficial. Resulting from anthropogenic activity, \textrmO3 exists as a biologically harmful pollutant at the surface when it forms in the presence of sunlight and other pollutants. As a strong oxidiser, \textrmO3 can be lethal to several different organisms; thus, when assessing the potential habitability of an exoplanet, a key part is determining whether toxic gases could be present at its surface. Using the Whole Atmosphere Community Climate Model version 6 (WACCM6; a three-dimensional chemistry-climate model), twelve atmospheric simulations of the terrestrial exoplanet TRAPPIST-1 e are performed with a variety of \textrmO2 concentrations and assuming two different stellar spectra proposed in the literature. Four atmospheric simulations of the exoplanet Proxima Centauri b are also included. Some scenarios for both exoplanets exhibit time-averaged surface \textrmO3 mixing ratios exceeding harmful levels of 40 ppbv, with 2200 ppbv the maximum concentration found in the cases simulated. These concentrations are toxic and can be fatal to most life on Earth. In other scenarios \textrmO3 remains under harmful limits over a significant fraction of the surface, despite there being present regions which may prove inhospitable. In the case that \textrmO3 is detected in a terrestrial exoplanet's atmosphere, determining the surface concentration is an important step when evaluating a planet's habitability.