Drifting into habitability

Following on from the work of Vinson and Hansen, we investigate simple models of thermal balance on terrestrial planets in the habitable zone of low mass main sequence stars. For planets in or near mean motion pairs, the mutual planetary perturbations can maintain asynchronous spins, even in the regime where tidal forces are strong.

The resulting planetary spins are still almost synchronous, but not quite, and the so the pattern of stellar illumination drifts slowly over the planetary surface. We examine the implications of this kind of irradiation pattern for the thermal balance of simple planetary atmosphere models and how this might influence the concept of habitability. We include in this a discussion of how climate is affected when the orbital dynamics of the multiplanet system is chaotic in nature.