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On the discovery of CO nighttime emissions on Titan by Cassini/VIMS : Derived stratospheric abundances and geological implications

Show simple item record Bainesa, Kevin H. Drossart, Pierre Lopez-Valverde, Miguel A. Atreya, Sushil K. Sotin, Christophe Momary, Thomas W. Brown, Robert H. Buratti, Bonnie J. Clark, Roger N. Nicholson, Philip D. 2008-07-14T16:45:19Z 2008-07-14T16:45:19Z 2006-12
dc.identifier.citation Planetary and Space Science 54 (2006) 1552–1562, doi:10.1016/j.pss.2006.06.020 en_US
dc.identifier.clearanceno 05-3546
dc.description.abstract We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147]. in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 mu m. For CH3D, the prominent Q branch of the nu(2) fundamental band of CH3D near 4.55 mu m is apparent. CO2 emissions from the strong nu(3) vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32 +/- 15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 kin altitude. The corresponding total atmospheric content of CO in Titan is similar to 2.9 +/- 1.5 x 10(14) kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (similar to 0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6 +/- 3 x 105 kg yr(-1). Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8 +/- 0.9 X 10(-4), based on an average methane surface emission rate over the past 0.5Gyr of 1.3 x 10(-13) gm cm(-2) s(-1) as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. en_US
dc.description.sponsorship NASA/JPL en_US
dc.language.iso en_US en_US
dc.publisher Pergamon-Elsevier Science Ltd en_US
dc.subject astrochemistry en_US
dc.subject astronomical spectra en_US
dc.subject carbon compounds en_US
dc.subject organic compounds en_US
dc.subject planetary atmospheres en_US
dc.subject planetary satellites en_US
dc.subject Titan
dc.title On the discovery of CO nighttime emissions on Titan by Cassini/VIMS : Derived stratospheric abundances and geological implications en_US
dc.type Article en_US

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