A cometary origin for CO in the stratosphere of Saturn?
Hartogh, P.; Lellouch, E.; Encrenaz, T.; Fouchet, T.; Cavalié, T.; Dobrijevic, M.; Billebaud, F.; Moriarty-Schieven, G. H.; Brillet, J.
Germany, France, Canada
Abstract
Context. The CO(3-2) line has been observed in the atmosphere of Saturn. The CO(3-2) observation proves that an external source of CO exists in the stratosphere of the planet.
Aims: We attempt to constrain the type and magnitude of the external source of CO in the atmosphere of Saturn, by observing the emission core of the CO(6-5) line.
Methods: We observed the CO(6-5) line at the limbs of Saturn. We analysed the observations by means of a 1-D transport model of the atmosphere of Saturn, coupled with a radiative transfer model.
Results: We obtained a high signal-to-noise ratio spectrum that confirms the existence of an external source of CO in the stratosphere of Saturn. We demonstrated that a cometary origin of CO is the most probable, an impact occurring 220±30 years ago and depositing (2.1±0.4)×1015 g of CO above 0.1 mbar. However, we cannot totally reject the possibility of CO originating (at least partially) in a steady source.
Conclusions: Complete photochemical modelling of the oxygen compounds is required to determine realistic error bars of the inferred quantities and to conclude on the origin of CO.