Water condensation zones around main sequence stars

Vol. 679
10. Planets and planetary systems

Water condensation zones around main sequence stars

As a primary prerequisite for the development of life, the conditions that allow rocky planets to have liquid water on their surface are of extreme interest. Numerical climate investigations into this topic have concentrated on the conditions needed to maintain existing water bodies but have seldom addressed those needed to form them in the first place. Turbet et al. use a numerical global climate model to investigate the conditions needed to form an early water ocean through condensation of the primordial water reservoir at the end of the magma ocean phase. They find that stellar irradiation must be drastically lower to allow the condensation of an ocean than to merely not evaporate a preexisting one, because water clouds change from low-altitude dayside convective clouds to high-altitude nightside stratospheric clouds. The water condensation limit, which they introduce, is therefore significantly outward of the inner limit of the traditional habitable zone, defined by the survival of existing water bodies.