The Habitability of Proxima Centauri b: Environmental States and Observational Discriminants

Abstract Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planetsorbiting M dwarfs. Although Proxima Cen b orbits within its star's habitablezone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions. We show that these modeled environments can be habitableor uninhabitable at Proxima Cen b's position in the habitablezone. We use radiative transfer models to generate synthetic spectra and thermal phase curvesfor these simulated environments, and use instrument models to explore our ability to discriminate between possible planetary states. These results are applicable not only to Proxima Cen b but to other terrestrial planetsorbiting M dwarfs. Thermal...