Who Run the World? (Flares) – how M-Dwarf flares impact atmospheric O2 and O3 production on early steam atmospheres

The majority of planets that we have observed within a system’s habitable zone have an M-type host star, which are long-lived, smaller, and cooler stars compared to our Sun. Most terrestrial planets suitable for atmospheric characterization orbit M stars due to their high signal to noise ratios, short orbital periods and high occurrence rates. However, M-type stars are notorious for their frequent stellar flares, during which the star can brighten by more than 10,000 times its usual total brightness, with even greater enhancements in the FUV wavelengths that cause heating in planetary atmospheres. In addition to such flaring events, terrestrial planets residing within the habitable zones of these stars are also likely to experience an early runaway greenhouse phase, which can lead to loss of hydrogen from water vapor due to heightened XUV fluxes during the star’s youth before it reaches its main sequence. While the detection of atmospheric O2 is a key item of interest in the search for life, these steam atmospheres could lead to O2 atmospheres containing up to 300 bars, although magma oceans or solid crustal layers could bring O2 levels down to a few bars. Previous models have considered the effects of M-type flares on Earth-like atmospheres. However, the effects of these flares on early steam atmospheres have not yet been considered, including their effect on O2 and O3 production in a terrestrial planet’s atmosphere around these stars. Here, we present preliminary results from a photochemical model which considers the production and evolution of O2 and O3 over time, during- and post-flare event. The authors acknowledge funding support from the Research Corporation for Science Advancement Scialog and the Heising-Simons Foundation.