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Detection of atomic deuterium in the upper atmosphere of MarsHigh-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O left and right arrow HDO + H2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere.
Document ID
20040172666
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Krasnopolsky, V. A.
(Catholic University of America Washington, DC 20064, United States)
Mumma, M. J.
Gladstone, G. R.
Date Acquired
August 22, 2013
Publication Date
June 5, 1998
Publication Information
Publication: Science
Volume: 280
Issue: 5369
ISSN: 0036-8075
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Other
Keywords
Flight Experiment
long duration
Hubble Telescope Project
unmanned

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