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Article Dans Une Revue Icarus Année : 2009

First observation of CO at 345 GHz in the atmosphere of Saturn with the JCMT. New constaints on its origin

Résumé

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 modelling 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.
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Dates et versions

hal-00400419 , version 1 (30-06-2009)

Identifiants

Citer

T. Cavalié, F. Billebaud, M. Dobrijevic, T. Fouchet, E. Lellouch, et al.. First observation of CO at 345 GHz in the atmosphere of Saturn with the JCMT. New constaints on its origin. Icarus, 2009, 203 (2), pp.531-540. ⟨10.1016/j.icarus.2009.05.024⟩. ⟨hal-00400419⟩
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