Ethyl cyanide on Titan: Spectroscopic detection and mapping using ALMA

M. A. Cordiner; M. Y. Palmer; C. A. Nixon; P. G. J. Irwin; N. A. Teanby; S. B. Charnley; M. J. Mumma; Z. Kisiel; J. Serigano; Y. -J. Kuan; Y. -L. Chuang; K. -S. Wang

doi:10.1088/2041-8205/800/1/L14

paper

Ethyl cyanide on Titan: Spectroscopic detection and mapping using ALMA

arXiv:1410.5325 · doi:10.1088/2041-8205/800/1/L14

Abstract

We report the first spectroscopic detection of ethyl cyanide (C $_{2}$ H $_{5}$ 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 $_{2}$ H $_{5}$ CN in Titan's ionosphere was previously inferred from Cassini ion mass spectrometry measurements of C $_{2}$ H $_{5}$ CNH $^{+}$ . Here we report the detection of 27 rotational lines from C $_{2}$ H $_{5}$ CN (in 19 separate emission features detected at $> 3 σ$ confidence), in the frequency range 222-241 GHz. Simultaneous detections of multiple emission lines from HC $_{3}$ N, CH $_{3}$ CN and CH $_{3}$ CCH were also obtained. In contrast to HC $_{3}$ N, CH $_{3}$ CN and CH $_{3}$ CCH, which peak in Titan's northern (spring) hemisphere, the emission from C $_{2}$ H $_{5}$ 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 $_{2}$ H $_{5}$ CN. Radiative transfer models show that most of the C $_{2}$ H $_{5}$ CN is concentrated at altitudes 300-600 km, suggesting production predominantly in the mesosphere and above. Vertical column densities are found to be in the range (2-5) $\times 1 0^{14}$ cm $^{- 2}$ .

Published in 2015, ApJL, 800, L14

Ethyl cyanide on Titan: Spectroscopic detection and mapping using ALMA

Abstract

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