Higher water loss on Earth-like exoplanets in eccentric orbits

Many rocky exoplanets have higher eccentricities than those in the Solar system, and about 18 per cent of planets with masses 0.1. Underexplored are the implications of such high eccentricities on the atmosphere, climate, and potential habitability on such planets.

We use WACCM6, a state-of-the-art fully coupled Earth-system model, to simulate the climates of two Earth-like planets: one in a circular orbit (e = 0), and one in an eccentric orbit (e = 0.4) with the same mean insolation. We quantify the effects of eccentricity on the atmospheric water abundance and loss given the importance of liquid water for habitability. The asymmetric temperature response in the eccentric orbit results in a water vapour mixing ratio in the stratosphere ( >20 ppmv) that is approximately five times greater than that for circular orbit (similar to 4 ppmv).