A Compound Model for the Origin of Earth's Water

Abstract

One of the most important subjects of debate in the formation of the solar system is the origin of Earth's water. Comets have long been considered as the most likely source of the delivery of water to Earth. However, elemental and isotopic arguments suggest a very small contribution from these objects. Other sourceshave also been proposed, among which, local adsorption of water vapor onto dustgrains in the primordial nebula and delivery through planetesimals and planetaryembryos have become more prominent. However, no sole source of water providesa satisfactory explanation for Earth's water as a whole. In view of that, usingnumerical simulations, we have developed a compound model incorporatingboth the principal endogenous and exogenous theories, and investigating theirimplications for terrestrial planet formation and water-delivery. Comets are alsoconsidered in the final analysis, as it is likely that at least some of Earth's waterhas cometary origin. We analyze our results comparing two different water dis-tribution models, and complement our study using D/H ratio, finding possiblerelative contributions from each source, focusing on planets formed in the habitable zone. We find that the compound model play an important role by showing more advantage in the amount and time of water-delivery in Earth-like planets. (AU)