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Title: ETHYL CYANIDE ON TITAN: SPECTROSCOPIC DETECTION AND MAPPING USING ALMA

We report the first spectroscopic detection of ethyl cyanide (C{sub 2}H{sub 5}CN) in Titan’s atmosphere, obtained using spectrally and spatially resolved observations of multiple emission lines with the Atacama Large Millimeter/submillimeter Array (ALMA). The presence of C{sub 2}H{sub 5}CN in Titan’s ionosphere was previously inferred from Cassini ion mass spectrometry measurements of C{sub 2}H{sub 5}CNH{sup +}. Here we report the detection of 27 rotational lines from C{sub 2}H{sub 5}CN (in 19 separate emission features detected at >3σ confidence) in the frequency range 222–241 GHz. Simultaneous detections of multiple emission lines from HC{sub 3}N, CH{sub 3}CN, and CH{sub 3}CCH were also obtained. In contrast to HC{sub 3}N, CH{sub 3}CN, and CH{sub 3}CCH, which peak in Titan’s northern (spring) hemisphere, the emission from C{sub 2}H{sub 5}CN is found to be concentrated in the southern (autumn) hemisphere, suggesting a distinctly different chemistry for this species, consistent with a relatively short chemical lifetime for C{sub 2}H{sub 5}CN. Radiative transfer models show that C{sub 2}H{sub 5}CN is most concentrated at altitudes ≳200 km, suggesting production predominantly in the stratosphere and above. Vertical column densities are found to be in the range (1–5) × 10{sup 14} cm{sup −2}.
Authors:
; ; ; ; ;  [1] ;  [2] ;  [3] ;  [4] ; ;  [5] ;  [6]
  1. NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)
  2. Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU (United Kingdom)
  3. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ (United Kingdom)
  4. Institute of Physics, Polish Academy of Sciences, Al. Lotnikøw 32/46, 02-668 Warszawa (Poland)
  5. National Taiwan Normal University, Taipei 116, Taiwan (China)
  6. Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan (China)
Publication Date:
OSTI Identifier:
22364182
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 800; 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; ACETONITRILE; ALTITUDE; ASTROPHYSICS; COSMOCHEMISTRY; CYANIDES; DENSITY; DETECTION; GHZ RANGE; MAPPING; MASS SPECTROSCOPY; PLANETS; RADIANT HEAT TRANSFER; SATELLITE ATMOSPHERES; SATELLITES; STRATOSPHERE