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A new astrobiological model of the atmosphere of Titan

Willacy, K. and Allen, M. and Yung, Y. (2016) A new astrobiological model of the atmosphere of Titan. Astrophysical Journal, 829 (2). Art. No. 79. ISSN 0004-637X.

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We present results of an investigation into the formation of nitrogen-bearing molecules in the atmosphere of Titan. We extend a previous model to cover the region below the tropopause, so the new model treats the atmosphere from Titan's surface to an altitude of 1500 km. We consider the effects of condensation and sublimation using a continuous, numerically stable method. This is coupled with parameterized treatments of the sedimentation of the aerosols and their condensates, and the formation of haze particles. These processes affect the abundances of heavier species such as the nitrogen-bearing molecules, but have less effect on the abundances of lighter molecules. Removal of molecules to form aerosols also plays a role in determining the mixing ratios, particularly of HNC, HC_3N, and HCN. We find good agreement with the recently detected mixing ratios of C_2H_5CN, with condensation playing an important role in determining the abundance of this molecule below 500 km. Of particular interest is the chemistry of acrylonitrile (C_2H_3CN) which has been suggested by Stevenson et al. as a molecule that could form biological membranes in an oxygen-deficient environment. With the inclusion of haze formation, we find good agreement of our model predictions of acrylonitrile with the available observations.

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Additional Information:© 2016 American Astronomical Society. Received 2016 May 3; revised 2016 July 11; accepted 2016 July 15; published 2016 September 23. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. Support was provided by the NASA Astrobiology Institute/Titan as a Prebiotic Chemical System. Y.L.Y. was supported in part by the Cassini UVIS program via NASA grant JPL.1459109 to the California Institute of Technology. The authors thank Dr. Run-Lie Shia for his assistance with the KINETICS code and Dr. Panyotis Lavvas for providing the aerosol data used in these models. Software: KINETICS (Allen et al. 1981).
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Subject Keywords:planets and satellites: atmospheres; planets and satellites: composition; planets and satellites: individual (Titan)
Record Number:CaltechAUTHORS:20160928-154658017
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Official Citation:K. Willacy et al 2016 ApJ 829 79
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70649
Deposited By: Ruth Sustaita
Deposited On:29 Sep 2016 15:08
Last Modified:29 Sep 2016 15:08

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