  The closest stars that harbor potentially habitable planets are cool M-stars.
Upcoming ground- and space-based telescopes will be able to search the
atmosphere of such planets for a range of chemicals. To facilitate this search
and to inform upcoming observations, we model the high-resolution reflection
spectra of two of the closest potentially habitable exoplanets for a range of
terrestrial atmospheres and surface pressures for active and inactive phases of
their host stars for both oxic and anoxic conditions: Proxima b, the closest
potentially habitable exoplanet, and Trappist-1e, one of 3 Earth-size planets
orbiting in the Habitable Zone of Trappist-1. We find that atmospheric spectral
features, including biosignatures like O2 in combination with a reduced gas
like CH4 for oxic atmospheres, as well as climate indicators like CO2 and H2O
for all atmospheres, show absorption features in the spectra of Proxima b and
Trappist-1e models. However for some features like oxygen, high-resolution
observations will be critical to identify them in a planet's reflected flux.
Thus these two planets will be among the best targets for upcoming observations
of potential Earth-like planets in reflected light with planned Extremely Large
Telescopes.
