Formation and Survival of Water Vapor in the Terrestrial Planet–Forming Region

Abstract

Watery Worlds Water vapor has been detected in the protoplanetary disks of a variety of stars. Explaining its origin is important because it bears on our understanding of planet formation. Bethell and Bergin (p. 1675 ) propose that this water originates in photochemistry occurring in the upper layers of the disks. In these regions, the rate at which water is produced exceeds the rate at which water is destroyed by ultraviolet radiation. Water forming in the upper layers of the disks then shields water vapor within the disks' interiors, allowing that vapor to interact with planet-forming materials and possibly be incorporated into young planets.