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Title:
From the Interstellar Medium to Earth's Oceans via Comets—An Isotopic Study of HDO/H 2O
Authors:
Laufer, D.; Notesco, G.; Bar-Nun, A.; Owen, T.
Affiliation:
AA(Department of Geophysics and Planetary Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel ; ), AB(Department of Geophysics and Planetary Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel ; ), AC(Department of Geophysics and Planetary Sciences, Tel-Aviv University, Tel-Aviv, 69978, Israel ; ), AD(Institute for Astronomy, University of Hawaii, Honolulu, Hawaii)
Publication:
Icarus, Volume 140, Issue 2, pp. 446-450 (1999). (Icarus Homepage)
Publication Date:
08/1999
Origin:
AP; ELSEVIER
Keywords:
, atmospheres
Abstract Copyright:
(c) 1999 Academic Press
DOI:
10.1006/icar.1999.6140
Bibliographic Code:
1999Icar..140..446L

Abstract

The isotopic enrichment of HDO over H2O when water vapor freezes into ice at 60-170 K was studied experimentally. No such enrichment was detected (1.003-1.007 in the 95% confidence interval). Thus HDO cannot be enriched when ice is formed by freezing of water vapor. The very similar D/H ratio in the water of Comets Halley, Hyakutake, and Hale-Bopp (∼3 × 10-4) is 10-20 times larger then the D/H ratio in the solar nebula. Therefore the cometary water had to originate in a giant molecular cloud, where the HDO is enriched by ion-molecule reactions. We cannot determine whether the ice grains which agglomerated into these comets were formed in a ∼50 K warm clump in the giant molecular cloud and settled intact to the solar nebula or sublimated and refroze in the ∼50 K Uranus-Neptune region. The HDO/H2O ratio in Earth's oceans suggests that the water was delivered by both comets and rocky material formed in Earth's region of the solar nebula.
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