31st Annual Meeting of the DPS, October 1999
Session 69. Outer Planet Chemistry
Contributed Oral Parallel Session, Friday, October 15, 1999, 10:30-12:00noon, Sala Kursaal

## [69.02] The Origin of Carbon Monoxide on Jupiter

B. B\'ezard (Obs.\ Paris), D. Strobel (JHU), J.-P. Maillard (IAP), P. Drossart, E. Lellouch (Obs.\ Paris)

On October 10--11 1998 UT, we recorded 5--\mum spectra of hot spots in the NEB of Jupiter, using the Fourier Transform Spectrometer (FTS) at the Canada-France-Hawaii telescope (CFHT). We observed the 2080--2175 cm-1 interval at a resolution of 0.038 cm-1. About 12 lines of CO, relatively free of other atmospheric absorption (NH3, PH3, CH3D, GeH4), are clearly seen. The very high spectral resolution of these observations allows us to resolve the line profiles and provides constraints on the CO vertical profile. We find that a constant mixing ratio profile yields CO lines broader than observed, and we conclude that the mean mixing ratio above (in height) ~200 mbar is larger than that at 4-5 bars. Observed CO lines can be reproduced with a mixing ratio of about 0.75\times10-9 below the 200-mbar level and 5\times10-9 above, although the solution is not unique. These results imply that at least part of the Jovian CO has an external origin, as suggested by Beer and Taylor (1978) and Noll {\em et al.\/} (1997). However the stratosphere/troposphere abundance ratio we infer (5:0.75) is much less pronounced than indicated by Noll {\em et al.\/} (100:1.3). Implications of the results in terms of eddy mixing and magnitude of the CO source(s) will be discussed.