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Ethane's 12C/13C Ratio in Titan: Implications for Methane ReplenishmentAs the .main destination of carbon in the destruction of methane in the atmosphere of Titan, ethane provides information about the carbon isotopic composition of the reservoir from which methane is replenished. If the amount of methane entering the atmosphere is presently equal to the amount converted to ethane, the 12C/13C ratio in ethane should be close to the ratio in the reservoir. We have measured the 12C/13C ratio in ethane both with Cassini CIRS(exp 1) and from the ground and find that it is very close to the telluric standard and outer planet values (89), consistent with a primordial origin for the methane reservoir. The lower 12C/13C ratio measured for methane by Huygens GCMS (82.3) can be explained if the conversion of CH4 to CH3 (and C2H6) favors 12C over 13C with a carbon kinetic isotope effect of 1.08. The time required for the atmospheric methane to reach equilibrium, i.e., for replenishment to equal destruction, is approximately 5 methane atmospheric lifetimes.
Document ID
Acquisition Source
Goddard Space Flight Center
Document Type
Jennings, Donald E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nixon, C. A.
(Maryland Univ. United States)
Romani, P. N.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Bjoraker, G. L.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Sada, P. V.
(Universidad de Monterrey Monterrey, Mexico)
Lunsford, A. W.
(Catholic Univ. of America Washington, DC, United States)
Boyle, R. J.
(Dickinson Coll. Carlisle, PA, United States)
Hesman, B. E.
(National Radio Astronomy Observatory United States)
McCabe, G. H.
(CMA Consulting Services United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2009
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
Meeting Information
Meeting: 41st Annual Meeting of the AAS Division for Planetary Sciences
Location: Fajardo
Country: Puerto Rico
Start Date: October 4, 2009
End Date: October 9, 2009
Sponsors: American Astronomical Society
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