Superhabitable Planets Around Mid-Type K Dwarf Stars Enhance Simulated JWST Observability and Surface Habitability

Abstract: In our search for life beyond the Solar System, certain planetary bodies may be more conducive to life than Earth. However, the observability of these `superhabitable' planets in the habitable zones around K dwarf stars has not been fully modeled. This study addresses this gap by modeling the atmospheres of superhabitable exoplanets. We employed the 1D model $\texttt{Atmos}$ to define the superhabitable parameter space, $\texttt{POSEIDON}$ to calculate synthetic transmission spectra, and $\texttt{PandExo}$ to simulate $\text{JWST}$ observations. Our results indicate that planets orbiting mid-type K dwarfs, receiving $80\%$ of Earth's solar flux, are optimal for life. These planets sustain temperate surfaces with moderate $CO_2$ levels, unlike those receiving $60\%$ flux, where necessarily higher $CO_2$ levels could hinder biosphere development. Moreover, they are easier to observe, requiring significantly fewer transits for biosignature detection compared to Earth-like planets around Sun-like stars. For instance, detecting biosignature pairs like oxygen and methane from $30$ parsecs would require $150$ transits ($43$ years) for a superhabitable planet, versus over $1700$ transits ($\sim 1700$ years) for Earth-like planets. While such observation times lie outside of $\text{JWST}$ mission timescales, our study underscores the necessity of next-generation telescopes and provides valuable targets for future observations with, for example, the $\text{ELT}$.