Methane on Jupiter

Since its identification on Jupiter and the other giant planets (Wildt, 1932), from spectra recorded in the first part of this century, methane has proved to be a fundamental compound to analyze their atmospheres.
With an abundance of the order of 2 per thousand, methane is the most active infrared radiator in Jupiter's upper atmosphere. Its infrared radiation largely controls the stratospheric thermal profile. Thus, enhanced emissions are associated with upper atmospheric heating, like in the auroral regions, or during the collision of the fragments of comet Shoemaker Levy 9 with Jupiter. Methane can also be used as a tracer of the upper clouds variations, as a thermometer for retrieving the thermal profile, and, more recently, as an indicator of the turbulence in the upper stratosphere, from the detection of fluorescence in methane bands at 3 micrometer with ISO. Recent improvements in laboratory measurements of CH4 infrared bands continue to give to methane a key role in the understanding of the atmospheric structure of Jupiter and of the other giant planets.