Accretion disc origin of the Earth's water

Abstract

Earth's water is conventionally believed to be delivered by comets or wet asteroids after the Earth formed. However, their elemental and isotopic properties 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. Here, we show both by laboratory experiments and numerical simulations 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. This may result in the formation of many Earth oceans, provided that a viable mechanism to produce water from hydroxyl exists. This adsorption process must occur in all disc environments around young stars. The inevitable conclusion is that water should be prevalent on terrestrial planets in the habitable zone around other stars.

Incorporation of water into olivine during nebular condensation: Insights from density functional theory and thermodynamics, and implications for phyllosilicate formation and terrestrial water inventory

“…These results are consistent with the experimental investigation of water adsorption on olivine surfaces (Vattuone et al. ), where it was shown that even at partial pressures as low as 10 −8 bars, a hydrated olivine surface was stable at temperatures at least up to 900 K.…”

“…) as well as experimental investigations (Vattuone et al. ) that have considered this possibility have shown that water molecules could dissociate and adsorb strongly on to mineral surfaces and the resulting hydroxylated surfaces remain stable at temperatures at least up to 1200 °C at the nebular pressures. Further, temperature programmed desorption experiments demonstrated that even at low partial pressures (10 −8 bars), the olivine surface could be hydroxylated (via water dissociation) and the surface retained its water content even at high temperatures (~500–900 K) (Vattuone et al.…”

“…Further, temperature programmed desorption experiments demonstrated that even at low partial pressures (10 −8 bars), the olivine surface could be hydroxylated (via water dissociation) and the surface retained its water content even at high temperatures (~500–900 K) (Vattuone et al. ).…”

A computational investigation of adsorption of organics on mineral surfaces: Implications for organics delivery in the early solar system

“…The construction and size of the supercell of different adsorbents is discussed in the respective sections below. We note that a similar computational methodology was used to successfully characterize the adsorption of water molecules onto mineral surfaces and thereby provide new knowledge on the accretion-disk origin of planetary water (Asaduzzaman et al, 2012aAsaduzzaman and Muralidharan, 2012;de Leeuw et al, 2010;Muralidharan et al, 2008;Prigiobbe et al, 2013;Stimpfl et al, 2006;Vattuone et al, 2013). Further, to the best of our knowledge, this is the first study which deals with quantification of organics that can be delivered to the early Earth via adsorption.…”

Mineral Surface Rearrangement at High Temperatures: Implications for Extraterrestrial Mineral Grain Reactivity

“…3,4 However, recent computational and experimental studies have repeatedly demonstrated that gas adsorption onto mineral dust grains in the solar nebula could also be a source of volatiles. 5−8 This is supported by new D/H isotopic data from a potential primordial reservoir retained in terrestrial lavas, which indicate a nebula origin of water delivered via adsorption to dust grains. 9 In all of these mechanisms, at least part of the water delivered was most likely adhered to the mineral matrix of the delivering body, whether comets, asteroids, or interplanetary dust particles.…”