Germane in the atmosphere of Jupiter

Germane, GeH4, is a tetrahedral molecule like methane. The nu 3 fundamental mode of GeH4 falls in the middle of the 5-micrometer Jupiter window. Jupiter observations were made in December 1975 during three flights with the 0.9-m telescope of the Kuiper Airborne Observatory. The spectrometer is a rapid-scanning Michelson interferometer having InSb detectors at each of the two outputs. The germane identification procedure is based on a comparison of the obtained Jupiter spectrum with that of laboratory germane. It appears that the detection of GeH4 in Jupiter's atmosphere with a mixing ratio of 0.6 ppb is the smallest concentration of a trace constituent yet detected in a nonterrestrial planetary atmosphere. It is pointed out that a strict interpretation of thermochemical equilibrium predictions for the spectral line forming regions of Jupiter's atmosphere does not explain the observation of GeH4.