Methance escape from Titan's atmosphere

R. V. Yelle; J. Cui; I. C.F. Müller-Wodarg

doi:10.1029/2007JE003031

Methance escape from Titan's atmosphere

R. V. Yelle, J. Cui, I. C.F. Müller-Wodarg

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112 Scopus citations

Abstract

Measurements of the mole fractions of CH₄ and ⁴⁰Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH₄. Analysis of the ⁴⁰Ar data indicates an eddy mixing rate of 2-5 × 107 cm² s^-1, an order of magnitude smaller than previously determined from analysis of the CH₄ distribution. The eddy profile determined from the ⁴⁰Ar data implies that CH₄ distribution is best explained by postulating that it is escaping the atmosphere at the diffusion limited rate of 2.5-3.0 × 10⁹ cm^-2 S^-1, referred to the surface. This represents a significant loss of atmospheric CH₄, smaller than but comparable to the photochemical destruction rate. The escape rate is much larger than predicted by the Jeans escape formula and vigorous nonthermal mechanisms are not apparent.

Original language	English (US)
Article number	E10003
Journal	Journal of Geophysical Research: Planets
Volume	113
Issue number	10
DOIs	https://doi.org/10.1029/2007JE003031
State	Published - Oct 20 2008

ASJC Scopus subject areas

Geochemistry and Petrology
Geophysics
Earth and Planetary Sciences (miscellaneous)
Space and Planetary Science

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title = "Methance escape from Titan's atmosphere",

abstract = "Measurements of the mole fractions of CH4 and 40Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH4. Analysis of the 40Ar data indicates an eddy mixing rate of 2-5 × 107 cm2 s-1, an order of magnitude smaller than previously determined from analysis of the CH4 distribution. The eddy profile determined from the 40Ar data implies that CH4 distribution is best explained by postulating that it is escaping the atmosphere at the diffusion limited rate of 2.5-3.0 × 109 cm-2 S-1, referred to the surface. This represents a significant loss of atmospheric CH4, smaller than but comparable to the photochemical destruction rate. The escape rate is much larger than predicted by the Jeans escape formula and vigorous nonthermal mechanisms are not apparent.",

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T1 - Methance escape from Titan's atmosphere

AU - Yelle, R. V.

AU - Cui, J.

AU - Müller-Wodarg, I. C.F.

PY - 2008/10/20

Y1 - 2008/10/20

N2 - Measurements of the mole fractions of CH4 and 40Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH4. Analysis of the 40Ar data indicates an eddy mixing rate of 2-5 × 107 cm2 s-1, an order of magnitude smaller than previously determined from analysis of the CH4 distribution. The eddy profile determined from the 40Ar data implies that CH4 distribution is best explained by postulating that it is escaping the atmosphere at the diffusion limited rate of 2.5-3.0 × 109 cm-2 S-1, referred to the surface. This represents a significant loss of atmospheric CH4, smaller than but comparable to the photochemical destruction rate. The escape rate is much larger than predicted by the Jeans escape formula and vigorous nonthermal mechanisms are not apparent.

AB - Measurements of the mole fractions of CH4 and 40Ar by the Ion Neutral Mass Spectrometer on the Cassini orbiter are analyzed to determine the rate of vertical mixing in Titan's atmosphere and the escape flux of CH4. Analysis of the 40Ar data indicates an eddy mixing rate of 2-5 × 107 cm2 s-1, an order of magnitude smaller than previously determined from analysis of the CH4 distribution. The eddy profile determined from the 40Ar data implies that CH4 distribution is best explained by postulating that it is escaping the atmosphere at the diffusion limited rate of 2.5-3.0 × 109 cm-2 S-1, referred to the surface. This represents a significant loss of atmospheric CH4, smaller than but comparable to the photochemical destruction rate. The escape rate is much larger than predicted by the Jeans escape formula and vigorous nonthermal mechanisms are not apparent.

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Methance escape from Titan's atmosphere

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