The 8 to 13 µm Spectrum of Jupiter

Abstract

THE spectrum of Jupiter in the wavelength range 8 to 13 µm is dominated by planetary thermal radiation and can give information on the thermal structure of the atmosphere. Spectra in this wavelength range have been published by Low¹ and by Gillet, Low and Stein². The latter, with resolution Δλ/λ∼0.02, gives a hint of the absorption structure of the ν₂ band of NH₃, and the high brightness temperature observed in the region 7.8 to 8.4 µm has been interpreted as due to CH₄ emission from a temperature inversion in the atmosphere of Jupiter. Encrenaz³ has computed the expected Jovian infrared spectrum for a number of model atmospheres, with and without temperature inversion. Here we present observations with resolution Δλ/λ = 0.007 in which details of the ν₂ band of NH₃ are seen in absorption, resembling the model atmosphere of Encrenaz with monotonically decreasing temperature.