Adsorption of water on olivine and the origin of Earth's water

L. Vattuone 1,2, M. Smerieri 2, L. Savio 2, A.M. Asaduzzaman 3, K. Muralidharan 4, M. Rocca 1,2 1 DIFI Università di Genova, Italy 2 IMEM-CNR Genova, Italy 3 School of Science, Engineering and Technology Pennsylvania State University, USA 4 Department of Materials Sciences and Engineering; Lunar and Planetary Laboratory, University of Arizona, USA Earth's water is usually believed to be delivered by comets or wet asteroids after the Earth formed: however wet asteroids and comets have elemental and isotopic properties that are inconsistent with those of the Earth. It was thus proposed that water was introduced by adsorption onto grains in the accretion disc prior to planetary growth, with bonding energies so high as to be stable under high temperature conditions. We investigated adsorption of H2O on olivine both by laboratory experiments under UHV conditions and by numerical simulations. We found [1] that water adsorbs dissociatively on the olivine {100} surface at the temperature (approx. 500–1500 K) and water pressure (approx. 10−8 bar) expected for the accretion disc, leaving an OH adlayer that is stable at least up to 900 K. If an effective mechanism able to produce water from hydroxyl exists, many Earth oceans could form. Such mechanism would be effective in all disc environments around young stars leading to conclude that water should be prevalent on terrestrial planets in the habitable zone also around other stars. [1] Vattuone L et al. 2013, Phil Trans R Soc A