Isotopic ratios of carbon and oxygen in Titan's CO using ALMA

Joseph Serigano, C. A. Nixon, M. A. Cordiner, P. G J Irwin, Nicholas A Teanby, S. B. Charnley, J. E. Lindberg

Research output: Contribution to journalArticle (Academic Journal)peer-review

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We report interferometric observations of carbon monoxide (CO) and its isotopologues in Titan's atmosphere using the Atacama Large Millimeter/submillimeter Array (ALMA). The following transitions were detected: CO (J = 1-0, 2-1, 3-2, 6-5), 13CO (J = 2-1, 3-2, 6-5), C18O (J = 2-1, 3-2), and C17O (J = 3-2). Molecular abundances and the vertical atmospheric temperature profile were derived by modeling the observed emission line profiles using NEMESIS, a line-by-line radiative transfer code. We present the first spectroscopic detection of 17O in the outer solar system with C17O detected at >8σ confidence. The abundance of CO was determined to be 49.6 ± 1.8 ppm, assumed to be constant with altitude, with isotopic ratios 12C/13C = 89.9 ± 3.4, 16O/18O = 486 ± 22, and 16O/17O = 2917 ± 359. The measurements of 12C/13C and 16O/18O ratios are the most precise values obtained in Titan's atmospheric CO to date. Our results are in good agreement with previous studies and suggest no significant deviations from standard terrestrial isotopic ratios.

Original languageEnglish
Article numberL8
Number of pages6
JournalAstrophysical Journal Letters
Issue number1
Early online date7 Apr 2016
Publication statusPublished - 10 Apr 2016


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

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