2007/09/13 by Hidenori Genda, Masahiro Ikoma · 141 citations
Environmental Science · Physics and Astronomy · #Astro and Planetary Science #Astrobiology #Astronomy #Atmosphere (unit) #Atmospheric sciences #Atomic physics #Chondrite #Deuterium #Early Earth #Earth (classical element) #Formation and evolution of the Solar System #Geology #Hydrogen #Isotope Analysis in Ecology #Meteorite #Meteorology #Nebula #Physics #Planetary Science and Exploration #Solar System #Stars #Water vapor #astro-ph #physics.ao-ph
paper · pdf · doi:10.1016/j.icarus.2007.09.007
published in Icarus 194(1), 42-52 (Elsevier BV) · Accepted to Icarus
arxiv created 2007/09/13 · openalex publication_date 2007/10/04 · arxiv updated 2014/11/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The origin of the Earth's ocean has been discussed on the basis of deuterium/hydrogen ratios (D/H) of several sources of water in the solar system. The average D/H of carbonaceous chondrites (CC's) is known to be close to the current D/H of the Earth's ocean, while those of comets and the solar nebula are larger by about a factor of two and smaller by about a factor of seven, respectively, than that of the Earth's ocean. Thus, the main source of the Earth's ocean has been thought to be CC's or adequate mixing of comets and the solar nebula. However, those conclusions are correct only if D/H of water on the Earth has remained unchanged for the past 4.5 Gyr. In this paper, we investigate evolution of D/H in the ocean in the case that the early Earth had a hydrogen-rich atmosphere, the existence of which is predicted by recent theories of planet formation no matter whether the nebula remains or not. Then we show that D/H in the ocean increases by a factor of 2-9, which is caused by the mass fractionation during atmospheric hydrogen loss, followed by deuterium exchange between hydrogen gas and water vapor during ocean formation. This result suggests that the apparent similarity in D/H of water between CC's and the current Earth's ocean does not necessarily support the CC's origin of water and that the apparent discrepancy in D/H is not a good reason for excluding the nebular origin of water.