Alma measurements of the HNC and HC3N distributions in Titan's atmosphere

M. A. Cordiner, C. A. Nixon, N. A. Teanby, P. G.J. Irwin, J. Serigano, S. B. Charnley, S. N. Milam, M. J. Mumma, D. C. Lis, G. Villanueva, L. Paganini, Y. J. Kuan, A. J. Remijan

Research output: Contribution to journalArticle

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Abstract

We present spectrally and spatially resolved maps of HNC and HC3N emission from Titan's atmosphere, obtained using the Atacama Large Millimeter/submillimeter Array on 2013 November 17. These maps show anisotropic spatial distributions for both molecules, with resolved emission peaks in Titan's northern and southern hemispheres. The HC3N maps indicate enhanced concentrations of this molecule over the poles, consistent with previous studies of Titan's photochemistry and atmospheric circulation. Differences between the spectrally integrated flux distributions of HNC and HC3N show that these species are not co-spatial. The observed spectral line shapes are consistent with HNC being concentrated predominantly in the mesosphere and above (at altitudes z ≳ 400 km), whereas HC3N is abundant at a broader range of altitudes (z ≈ 70-600 km). From spatial variations in the HC3N line profile, the locations of the HC3N emission peaks are shown to be variable as a function of altitude. The peaks in the integrated emission from HNC and the line core (upper atmosphere) component of HC3N (at z ≳ 300 km) are found to be asymmetric with respect to Titan's polar axis, indicating that the mesosphere may be more longitudinally variable than previously thought. The spatially integrated HNC and HC3N spectra are modeled using the NEMESIS planetary atmosphere code and the resulting best-fitting disk-averaged vertical mixing ratio profiles are found to be in reasonable agreement with previous measurements for these species. Vertical column densities of the best-fitting gradient models for HNC and HC3N are 1.9 × 1013 cm-2 and 2.3 × 1014 cm-2, respectively.

Original languageEnglish
Article numberL30
JournalAstrophysical Journal Letters
Volume795
Issue number2
DOIs
Publication statusPublished - 2014 Nov 10

Fingerprint

Titan atmosphere
Titan
atmosphere
mesosphere
atmospheric circulation
planetary atmosphere
planetary atmospheres
upper atmosphere
photochemistry
Southern Hemisphere
Northern Hemisphere
vertical mixing
mixing ratios
profiles
mixing ratio
photochemical reactions
line spectra
line shape
molecules
spatial distribution

Keywords

  • planets and satellites: atmospheres
  • planets and satellites: individual (Titan)
  • techniques: imaging spectroscopy
  • techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Cordiner, M. A., Nixon, C. A., Teanby, N. A., Irwin, P. G. J., Serigano, J., Charnley, S. B., ... Remijan, A. J. (2014). Alma measurements of the HNC and HC3N distributions in Titan's atmosphere. Astrophysical Journal Letters, 795(2), [L30]. https://doi.org/10.1088/2041-8205/795/2/L30

Alma measurements of the HNC and HC3N distributions in Titan's atmosphere. / Cordiner, M. A.; Nixon, C. A.; Teanby, N. A.; Irwin, P. G.J.; Serigano, J.; Charnley, S. B.; Milam, S. N.; Mumma, M. J.; Lis, D. C.; Villanueva, G.; Paganini, L.; Kuan, Y. J.; Remijan, A. J.

In: Astrophysical Journal Letters, Vol. 795, No. 2, L30, 10.11.2014.

Research output: Contribution to journalArticle

Cordiner, MA, Nixon, CA, Teanby, NA, Irwin, PGJ, Serigano, J, Charnley, SB, Milam, SN, Mumma, MJ, Lis, DC, Villanueva, G, Paganini, L, Kuan, YJ & Remijan, AJ 2014, 'Alma measurements of the HNC and HC3N distributions in Titan's atmosphere', Astrophysical Journal Letters, vol. 795, no. 2, L30. https://doi.org/10.1088/2041-8205/795/2/L30
Cordiner MA, Nixon CA, Teanby NA, Irwin PGJ, Serigano J, Charnley SB et al. Alma measurements of the HNC and HC3N distributions in Titan's atmosphere. Astrophysical Journal Letters. 2014 Nov 10;795(2). L30. https://doi.org/10.1088/2041-8205/795/2/L30
Cordiner, M. A. ; Nixon, C. A. ; Teanby, N. A. ; Irwin, P. G.J. ; Serigano, J. ; Charnley, S. B. ; Milam, S. N. ; Mumma, M. J. ; Lis, D. C. ; Villanueva, G. ; Paganini, L. ; Kuan, Y. J. ; Remijan, A. J. / Alma measurements of the HNC and HC3N distributions in Titan's atmosphere. In: Astrophysical Journal Letters. 2014 ; Vol. 795, No. 2.
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AU - Cordiner, M. A.

AU - Nixon, C. A.

AU - Teanby, N. A.

AU - Irwin, P. G.J.

AU - Serigano, J.

AU - Charnley, S. B.

AU - Milam, S. N.

AU - Mumma, M. J.

AU - Lis, D. C.

AU - Villanueva, G.

AU - Paganini, L.

AU - Kuan, Y. J.

AU - Remijan, A. J.

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AB - We present spectrally and spatially resolved maps of HNC and HC3N emission from Titan's atmosphere, obtained using the Atacama Large Millimeter/submillimeter Array on 2013 November 17. These maps show anisotropic spatial distributions for both molecules, with resolved emission peaks in Titan's northern and southern hemispheres. The HC3N maps indicate enhanced concentrations of this molecule over the poles, consistent with previous studies of Titan's photochemistry and atmospheric circulation. Differences between the spectrally integrated flux distributions of HNC and HC3N show that these species are not co-spatial. The observed spectral line shapes are consistent with HNC being concentrated predominantly in the mesosphere and above (at altitudes z ≳ 400 km), whereas HC3N is abundant at a broader range of altitudes (z ≈ 70-600 km). From spatial variations in the HC3N line profile, the locations of the HC3N emission peaks are shown to be variable as a function of altitude. The peaks in the integrated emission from HNC and the line core (upper atmosphere) component of HC3N (at z ≳ 300 km) are found to be asymmetric with respect to Titan's polar axis, indicating that the mesosphere may be more longitudinally variable than previously thought. The spatially integrated HNC and HC3N spectra are modeled using the NEMESIS planetary atmosphere code and the resulting best-fitting disk-averaged vertical mixing ratio profiles are found to be in reasonable agreement with previous measurements for these species. Vertical column densities of the best-fitting gradient models for HNC and HC3N are 1.9 × 1013 cm-2 and 2.3 × 1014 cm-2, respectively.

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