Terrestrial Accretion from the Solar Wind

Abstract

THE new observations reported by Gringauz and Bridge appear to confirm each other and, if they are correct, the resulting hydrogen accretion-rate will certainly be too small to account for the bulk of terrestrial hydrogen. Moreover, it is now certain that terrestrial deuterium is definitely not due to a slow accretion of solar deuterium. The previously proposed rate of deuterium production at the solar surface (3.3 × 10¹¹ atoms cm.⁻² sec.⁻¹) through neutron capture by hydrogen would imply a flux of 2.2-MeV. gamma radiation of 3.5 × 10⁶ photons cm.⁻² sec.⁻¹ at the orbit of the Earth, whereas Northrop and Hostetler¹ have set an upper limit of only 0.5 photon cm.⁻² sec.⁻¹ for this flux. It seems inescapable that terrestrial deuterium was produced in situ by neutron irradiation of terrestrial hydrogen at an early stage in the evolution of the solar system, as proposed by Fowler et al.². In view of these considerations, and the difficulties raised by oxygen supplies, the suggestion I made earlier concerning the origin of the oceans has lost all plausibility and I wish to withdraw it.