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T. Fouchet, E. Lellouch (DESPA), J.-P. Maillard (IAP), B. Bezard (DESPA), C. Cottaz, I. Kleiner (LPPM)
In december 1995, the Galileo Probe fell into Jupiter's atmosphere. From the analysis of its radio signal, Folkner et al (1998) determined a Jovian N/H ratio equal to 4 times solar. This measurement has shaken the commonly accepted value of a solar N/H ratio. Since the N/H ratio plays an important role in the formation scenarios of Jupiter, we wanted to confirm or infirm the Galileo findings.
To do so, we observed Jupiter in the 5-\mum hot spots, that gave an opportunity to probe deep in the jovian atmosphere (7~bar). We used the Fourier Transform Spectrometer (FTS) mounted on the Canada-France-Hawaii Telescope (CFHT), providing high spectral resolution \Delta\nu=0.1 cm-1. Between 25-28 September 1999, we observed 3 different hot spots between 1800 and 2200 cm-1. The terrestrial gaseous absorptions were removed by fitting a synthetic spectrum to the observed spectrum, and then dividing the observations by the synthetic spectrum.
To analyse the jovian spectrum we used the NH3 line positions and intensities newly predicted by Cottaz et al (2000). The wavenumber range covered by the FTS allowed us to determine three points on the ammonia vertical distribution at approximately 2, 4 and 7 bar. We found that the NH3 mixing ratio strongly increases between 2 and 4 bar, and moderatly increases between 4 and 7 bar, as was found by the Galileo Probe. At 7 bar, our prefered N/H value lies between 3 and 5 times solar.
The author(s) of this abstract have provided an email address for comments about the abstract: Thierry.Fouchet@obspm.fr