Outer Limits of Hability in High CO2 ExoAtmospheres Modeled Based on Kepler ExoPlanets

The outer limit of the life supporting zone of exoplanets having CO2-rich atmospheres: Virtual exoplanets and Kepler planetary candidates

Authors:

1. David Neubauer (a, b)
2. Johannes J. Leitner (a, c)
3. Maria Gertrude Firneis (a, c)
4. Regina Hitzenberger (a,b)

Affiliations:

a. Research Platform: ExoLife, University of Vienna, Vienna, Austria

b. Faculty of Physics, University of Vienna, Vienna, Austria

c. Institute for Astrophysics, University of Vienna, Vienna, Austria

Abstract:

CO2 rich atmospheres have been considered for the outer limit of the classic water habitable zone. Here we provide a database for the outer limit of the life supporting zone consisting of a sulfuric acid, a water and a water/ammonia mixture (15 wt% ammonia) habitable zone for virtual exoplanets having CO2-rich atmospheres and orbiting G-, K-, or M-dwarf stars. We used recent CO2 line and continuum absorption data for CO2 pressures up to 100 bar for our simulations. Scenarios for different stellar spectra, stellar fluxes, planetary surface albedos, atmospheric pressures and planetary masses are explored. One notable result is that the surface temperature does not strongly increase if CO2 pressure is larger than approximately 25 bar, due to increased Rayleigh scattering or CO2 condensation at the surface and a thereby reduced greenhouse effect in these cases. The database is created for virtual exoplanets and applied to Kepler planetary candidates. All of the considered planetary candidates likely lie within the outer limit of the life supporting zone.