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Astron. Astrophys. 355, L13-L17 (2000)


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Letter to the Editor

Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of [FORMULA] and [FORMULA], detection of [FORMULA]

T. Fouchet 1, E. Lellouch 1, B. Bézard 1, H. Feuchtgruber 2, P. Drossart 1 and T. Encrenaz 1

1 DESPA, Observatoire de Paris, 5 Place Jules Janssen, 92195 Meudon Cedex, France (thierry.fouchet@obspm.fr)
2 Max-Planck-Institut für Extraterrestrische Physik, 85748 Garching, Germany

Received 3 January 2000 / Accepted 9 February 2000

Abstract

We have analysed the ISO-SWS spectrum of Jupiter in the 12-16 [FORMULA] range, where several hydrocarbons exhibit rovibrational bands. Using temperature information from the methane and hydrogen emissions, we derive the mixing ratios (q) of acetylene and ethane at two independent pressure levels. For acetylene, we find [FORMULA] at 0.3 mbar and [FORMULA] at 4 mbar, giving a slope [FORMULA], while for ethane [FORMULA] at 1 mbar and [FORMULA] at 10 mbar, giving [FORMULA]. The ethane slope is consistent with the predictions of Gladstone et al. (1996), but that predicted for acetylene is larger than we observe. This disagreement is best explained by an overestimation of the acetylene production rate compared to that of ethane in the Gladstone et al. (1996) model.

At 15.8 [FORMULA], methylacetylene is detected for the first time at low jovian latitudes, and a stratospheric column density of [FORMULA] molecule cm-2 is inferred. We also derive an upper limit for the diacetylene column density of [FORMULA] molecule cm-2.

Key words: planets and satellites: individual: – infrared: solar system

Send offprint requests to: T. Fouchet

© European Southern Observatory (ESO) 2000

Online publication: March 17, 2000

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