skip to main content

Title: DETECTION OF PROPENE IN TITAN'S STRATOSPHERE

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 (C{sub 3}H{sub 8}) and propyne (CH{sub 3}C{sub 2}H), while the intermediate-sized C{sub 3}H {sub x} hydrocarbon (C{sub 3}H{sub 6}) was curiously absent. Using spectra from the Composite Infrared Spectrometer on Cassini, we show the first positive detection of propene (C{sub 3}H{sub 6}) in Titan's stratosphere (5σ 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 C{sub 3}H{sub 6} is less than both C{sub 3}H{sub 8} and CH{sub 3}C{sub 2}H, and we remark on an emerging paradigm in Titan's hydrocarbon abundances whereby alkanes > alkynes > alkenes within the C{sub 2}H {sub x} and C{sub 3}H {sub x} 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.
Authors:
;  [1] ;  [2] ; ; ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  2. Detector Systems Branch, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  3. LESIA, Observatoire de Paris, CNRS, 5 Place Jules Janssen, F-92195 Meudon Cedex (France)
  4. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ (United Kingdom)
  5. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, CA 91109 (United States)
  6. Department of Space Science, Cornell University, Ithaca, NY 14853 (United States)
  7. Atmospheric, Oceanic and Planetary Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom)
  8. IACS, Catholic University of America, Washington, DC 20064 (United States)
  9. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
Publication Date:
OSTI Identifier:
22224067
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 776; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ALTITUDE; DETECTION; INFRARED SPECTROMETERS; INTERFEROMETERS; MOLECULES; PHOTOLYSIS; PLANETS; PROPANE; PROPYLENE; PROPYNE; SATELLITE ATMOSPHERES; SATELLITES; STRATOSPHERE; VOYAGER SPACE PROBES