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First observation of CO at 345 GHz in the atmosphere of Saturn with the JCMT: New constraints on its origin |
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| Authors: | T Cavalié F Billebaud M Dobrijevic T Fouchet T Encrenaz GH Moriarty-Schieven P Hartogh |
| Institution: | a Max Planck Institute for Solar System Research, 37191 Katlenburg-Lindau, Germany b Université de Bordeaux, Laboratoire d’Astrophysique de Bordeaux (LAB), France c CNRS/INSU, UMR 5804, 33271 Floirac cedex, France d LESIA, Observatoire de Paris, 92195 Meudon, France e National Research Council, Herzberg Institute of Astrophysics, Victoria, BC, Canada V9E 2E7 f Joint Astronomy Center, Hilo, HI 96720, USA |
| Abstract: | We have performed the first observation of the CO(3-2) spectral line in the atmosphere of Saturn with the James Clerk Maxwell Telescope. We have used a transport model of the atmosphere of Saturn to constrain the origin of the observed CO. The CO line is best-fit when the CO is located at pressures less than (15±2) mbar with a mixing ratio of (2.5±0.6)×10-8 implying an external origin. By modeling the transport in Saturn’s atmosphere, we find that a cometary impact origin with an impact 200-350 years ago is more likely than continuous deposition by interplanetary dust particles (IDP) or local sources (rings/satellites). This result would confirm that comet impacts are relatively frequent and efficient providers of CO to the atmospheres of the outer planets. However, a diffuse and/or local source cannot be rejected, because we did not account for photochemistry of oxygen compounds. Finally, we have derived an upper limit of ∼1×10-9 on the tropospheric CO mixing ratio. |
| Keywords: | Saturn Atmosphere Spectroscopy |
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