Re-Evaluation of the Inner Edge of Habitable Zone

Existence of liquid water on the planetary surface is thought to be an important condition for the origin and evolution of life. Planets with oceans (or lakes) are classified in two types: Earth-like `aqua planets' and less water `land planets'. The latter shows stronger resistance than the former to the runaway greenhouse caused by the increase of stellar luminosity. We examined the possibility of evolution from an aqua planet to a land planet by water loss. We showed that an aqua planet with less than about 0.1 present Earth's ocean mass can evolve to a land planet without having experience of the runaway greenhouse, and maintains liquid water on its surface for about 2Gyrs longer than planets with larger amount of water. Our results mean that the initial amount of water is important for their evolution paths and habitability.