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Title: Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA

Abstract

Vinyl cyanide (C{sub 2}H{sub 3}CN) is theorized to form in Titan’s atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C{sub 2}H{sub 3}CN on Titan by Palmer et al. with the detection of three new C{sub 2}H{sub 3}CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C{sub 2}H{sub 3}CN on Titan. We present simultaneous observations of C{sub 2}H{sub 5}CN, HC{sub 3}N, and CH{sub 3}CN emission, and obtain the first (tentative) detection of C{sub 3}H{sub 8} (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC{sub 3}N and C{sub 2}H{sub 5}CN, which are theorized to be short-lived in Titan’s atmosphere, C{sub 2}H{sub 3}CN is most abundant over the southern (winter) pole, whereas the longer-lived CH{sub 3}CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan’s atmosphericmore » circulation system following the recent transition from northern to southern winter. We confirm that C{sub 2}H{sub 3}CN and C{sub 2}H{sub 5}CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C{sub 2}H{sub 3}CN is found to be 3.03 ± 0.29 ppb, with a C{sub 2}H{sub 5}CN/C{sub 2}H{sub 3}CN abundance ratio of 2.43 ± 0.26. Our HC{sub 3}N and CH{sub 3}CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 ± 0.16 and 1.63 ± 0.02, respectively.« less

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [3];  [4]
  1. NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)
  2. School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol, BS8 1RJ (United Kingdom)
  3. Institute of Physics, Polish Academy of Sciences, Al. Lotnikøw 32/46, 02-668 Warszawa (Poland)
  4. Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU (United Kingdom)
Publication Date:
OSTI Identifier:
22663118
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 154; Journal Issue: 5; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTROSCOPY; ACETONITRILE; ACRYLONITRILE; ADVECTION; ALTITUDE; ASTRONOMY; ATMOSPHERIC CIRCULATION; DETECTION; MAPPING; METHANE; PHOTOCHEMISTRY; PLANETS; PROPANE; SATELLITE ATMOSPHERES; SATELLITES; SCALE HEIGHT; TROPOPAUSE; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Lai, J. C.-Y., Cordiner, M. A., Nixon, C. A., Achterberg, R. K., Molter, E. M., Palmer, M. Y., Charnley, S. B., Lindberg, J. E., Mumma, M. J., Teanby, N. A., Kisiel, Z., and Irwin, P. G. J., E-mail: martin.cordiner@nasa.gov. Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA8EEF.
Lai, J. C.-Y., Cordiner, M. A., Nixon, C. A., Achterberg, R. K., Molter, E. M., Palmer, M. Y., Charnley, S. B., Lindberg, J. E., Mumma, M. J., Teanby, N. A., Kisiel, Z., & Irwin, P. G. J., E-mail: martin.cordiner@nasa.gov. Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA. United States. doi:10.3847/1538-3881/AA8EEF.
Lai, J. C.-Y., Cordiner, M. A., Nixon, C. A., Achterberg, R. K., Molter, E. M., Palmer, M. Y., Charnley, S. B., Lindberg, J. E., Mumma, M. J., Teanby, N. A., Kisiel, Z., and Irwin, P. G. J., E-mail: martin.cordiner@nasa.gov. Wed . "Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA". United States. doi:10.3847/1538-3881/AA8EEF.
@article{osti_22663118,
title = {Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA},
author = {Lai, J. C.-Y. and Cordiner, M. A. and Nixon, C. A. and Achterberg, R. K. and Molter, E. M. and Palmer, M. Y. and Charnley, S. B. and Lindberg, J. E. and Mumma, M. J. and Teanby, N. A. and Kisiel, Z. and Irwin, P. G. J., E-mail: martin.cordiner@nasa.gov},
abstractNote = {Vinyl cyanide (C{sub 2}H{sub 3}CN) is theorized to form in Titan’s atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C{sub 2}H{sub 3}CN on Titan by Palmer et al. with the detection of three new C{sub 2}H{sub 3}CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C{sub 2}H{sub 3}CN on Titan. We present simultaneous observations of C{sub 2}H{sub 5}CN, HC{sub 3}N, and CH{sub 3}CN emission, and obtain the first (tentative) detection of C{sub 3}H{sub 8} (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC{sub 3}N and C{sub 2}H{sub 5}CN, which are theorized to be short-lived in Titan’s atmosphere, C{sub 2}H{sub 3}CN is most abundant over the southern (winter) pole, whereas the longer-lived CH{sub 3}CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan’s atmospheric circulation system following the recent transition from northern to southern winter. We confirm that C{sub 2}H{sub 3}CN and C{sub 2}H{sub 5}CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C{sub 2}H{sub 3}CN is found to be 3.03 ± 0.29 ppb, with a C{sub 2}H{sub 5}CN/C{sub 2}H{sub 3}CN abundance ratio of 2.43 ± 0.26. Our HC{sub 3}N and CH{sub 3}CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 ± 0.16 and 1.63 ± 0.02, respectively.},
doi = {10.3847/1538-3881/AA8EEF},
journal = {Astronomical Journal (Online)},
number = 5,
volume = 154,
place = {United States},
year = {Wed Nov 01 00:00:00 EDT 2017},
month = {Wed Nov 01 00:00:00 EDT 2017}
}