Water loss, abiotic oxygen and atmospheric collapse on rocky exoplanets

With the explosion of exoplanet discoveries and atmospheric characterization over the last decade, there is now the hope that in the near future, it will be possible to study the atmospheres of low mass, possibly Earth-like exoplanets. Interpreting these observations will be a grand challenge, because the diversity of rocky planet climates is likely to be enormous. Here I discuss the role that theory and idealized modeling can play in advancing our understanding of the possibilities. I present results on two key problems in exoplanet climate evolution: the loss of a planet’s water to space and the circulation (and possible nightside collapse) of atmospheres on tidally locked planets. I show that in both cases, scaling analysis allows the fundamentals of the problem to be understood in a robust and general way. I discuss the implications of these results for exoplanet habitability and the future search for biosignatures by ground- and space-based telescopes.