Quantifying Exoplanet Habitable Lifetime for a Diverse Range of Orbital Configurations

The climate and habitable potential of a planet is controlled in part by its orbital configuration, including its obliquity, eccentricity, rotation period, and separation from the host star. Recent studies have suggested the exoplanets with higher eccentricity or obliquity than Earth might be able to produce larger biospheres, potentially leading to "super-habitable" worlds. However, high-obliquity and high-eccentricity planets have also been shown to be susceptible to increased water loss, which would decrease the habitable lifetime.

I use ExoPlaSim, a 3D General Climate Model, to investigate the habitable lifetimes of a diverse range of possible orbital configurations by varying the planetary obliquity (0-90^o), eccentricity (0-0.4), rotation period (6-96 hr), and stellar constant (1350-1650 W/m²). I study each orbital parameter independently while also co-varying obliquity with eccentricity and rotation period for the entire range of stellar constants. I find that stellar constant is the primary control on atmospheric water vapor, but also that the planetary obliquity, eccentricity and rotation period can determine the escape regime. Increasing the obliquity or eccentricity can push the climate into the significant escape regime at lower stellar constants relative to low-obliquity or low-eccentricity planets. Increasing the rotation period at high obliquities maximizes the habitable lifetime of an exoplanet.