ISO-SWS Observations of Uranus: the Stratospheric Distribution of C tex2html_wrap_inline13 H tex2html_wrap_inline13

Th. Encrenaz, B. Bézard (Obs. Paris), H.Feuchtgruber (MPI Garching), E. Lellouch (Obs. Paris), Th. de Graauw (SRON, Groningen), M. F. Kessler (ISO SOC, Villafranca), M. J. Griffin (QMWC, London), S. K. Atreya (U. Michigan)

The infrared spectrum of Uranus has been recorded between 7 and 16.5 tex2html_wrap_inline17 m with the grating mode of the Short-Wavelength Spectrometer of the Infrared Space Observatory, with a resolving power of 1500. The spectrum shows no signal except in the C tex2html_wrap_inline13 H tex2html_wrap_inline13 band centered at 13.7 tex2html_wrap_inline17 m. From the absence of emission in the region of the CH tex2html_wrap_inline25 tex2html_wrap_inline27 band at 7.7 tex2html_wrap_inline17 m, where the flux is lower than 0.5 Jy, an upper limit of 10 tex2html_wrap_inline31 can be estimated for the stratospheric mixing ratio of methane. The C tex2html_wrap_inline13 H tex2html_wrap_inline13 band can be fitted with a stratospheric mixing ratio of 3 10 tex2html_wrap_inline37 . The CH tex2html_wrap_inline25 and C tex2html_wrap_inline13 H tex2html_wrap_inline13 estimates mostly refer to the 1 - 100 tex2html_wrap_inline17 bar region. Our calculations assume a thermal profile based upon Voyager UVS and radio data (Atreya et al, in "Uranus", U. Arizona, 1991). It should be noted that these results are very preliminary, and strongly depend upon the stratospheric thermal profile.