Highlights - 19 February 2010 (vol. 510)

In section 10. Planets and planetary systems

“A cometary origin for CO in the stratosphere of Saturn?”, by T. Cavalié, P. Hartogh, F. Billebaud, M. Dobrijevic, T. Fouchet, E. Lellouch, T. Encrenaz, J. Brillet, and G.H. Moriarty-Schieven, A&A 510, A88

In the stratospheres of Jupiter, Saturn, Neptune, and probably Uranus, CO is present as a chemical species in disequilibrium with its environment. This implies that it has to be either transported to the stratosphere from the hot interior of the planet where it is present or delivered from external sources (most probably from cometary impacts). In both Jupiter and Neptune, observations and their analysis have led to the conclusion that CO was provided mostly by large-comet impacts similar to the Shoemaker-Levy 9 impact on Jupiter's atmosphere in 1994. The authors analyze submillimeter observations of CO(3-2) and CO(6-5) that probe FOR the presence of CO at different levels in the atmosphere of Saturn. Using a one-dimensional model for the mixing of this species, they show that the CO that is observed was most likely delivered by a cometary impact that occurred about 200 years ago.