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C-12/C-13 Ratio in Ethane on Titan and Implications for Methane's ReplenishmentThe C-12/C-13 abundance ratio in ethane in the atmosphere of Titan has been measured at 822 cm(sup -1) from high spectral resolution ground-based observations. The value 89(8), coincides with the telluric standard and also agrees with the ratio seen in the outer planets. It is almost identical to the result for ethane on Titan found by the composite infrared spectrometer (CIRS) on Cassini. The C-12/C-13 ratio for ethane is higher than the ratio measured in atmospheric methane by Cassini/Huygens GCMS, 82.3(l), representing an enrichment of C-12 in the ethane that might be explained by a kinetic isotope effect of approximately 1.1 in the formation of methyl radicals. If methane is being continuously resupplied to balance photochemical destruction, then we expect the isotopic composition in the ethane product to equilibrate at close to the same C-12/C-13 ratio as that in the supply. The telluric value of the ratio in ethane then implies that the methane reservoir is primordial.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Jennings, Donald E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Romani, Paul N.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Bjoraker, Gordon L.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Sada, Pedro V.
(Universidad de Monterrey San Pedro Garza Garcia, Mexico)
Nixon, Conor A.
(Maryland Univ. College Park, MD, United States)
Lunsford, Allen W.
(Catholic Univ. of America Washington, DC, United States)
Boyle, Robert J.
(Dickinson Coll. Carlisle, PA, United States)
Hesman, Brigette E.
(National Radio Astronomy Observatory Socorro, NM, United States)
McCabe, George H.
(CMA Consulting Services Latham, NY, United States)
Date Acquired
August 25, 2013
Publication Date
June 24, 2009
Publication Information
Publication: Journal of Physical Chemistry A: Chemistry: Titan Atmosphere
Volume: 113
Issue: 42
Subject Category
Inorganic, Organic And Physical Chemistry
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