DETECTION OF PROPENE IN TITAN'S STRATOSPHERE

C. A. Nixon*, D. E. Jennings, B. Bezard, S. Vinatier, N. A. Teanby, K. Sung, T. M. Ansty, P. G. J. Irwin, N. Gorius, V. Cottini, A. Coustenis, F. M. Flasar

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

The Voyager 1 flyby of Titan in 1980 gave a first glimpse of the chemical complexity of Titan's atmosphere, detecting many new molecules with the infrared interferometer spectrometer (IRIS). These included propane (C3H8) and propyne (CH3C2H), while the intermediate-sized C3Hx hydrocarbon (C3H6) was curiously absent. Using spectra from the Composite Infrared Spectrometer on Cassini, we show the first positive detection of propene (C3H6) in Titan's stratosphere (5 sigma significance), finally filling the three-decade gap in the chemical sequence. We retrieve a vertical abundance profile from 100-250 km, that varies slowly with altitude from 2.0 +/- 0.8 ppbv at 125 km, to 4.6 +/- 1.5 ppbv at 200 km. The abundance of C3H6 is less than both C3H8 and CH3C2H, and we remark on an emerging paradigm in Titan's hydrocarbon abundances whereby alkanes > alkynes > alkenes within the C2Hx and C3Hx chemical families in the lower stratosphere. More generally, there appears to be much greater ubiquity and relative abundance of triple-bonded species than double-bonded, likely due to the greater resistance of triple bonds to photolysis and chemical attack.

Original languageEnglish
Article number14
Number of pages6
JournalAstrophysical Journal Letters
Volume776
Issue number1
Early online date30 Sep 2013
DOIs
Publication statusPublished - 10 Oct 2013

Keywords

  • planets and satellites: atmospheres
  • planets and satellites: composition
  • planets and satellites: individual (Titan)
  • FAR-INFRARED SPECTRA
  • MOLECULAR SPECTROSCOPIC DATABASE
  • CASSINI CIRS
  • COUPLING PHOTOCHEMISTRY
  • UPPER-ATMOSPHERE
  • HAZE FORMATION
  • WATER-VAPOR
  • MODEL
  • HC3N
  • HYDROCARBONS

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