NH3, H2S, and the radio brightness temperature spectra of the giant planets

Abstract

Recent radio interferometer observations of Neptune enable comparisons of the radio brightness temperature (TB) spectra of all four giant planets. This comparison reveals evidence for fundamental differences in the compositions of Uranus’ and Neptune’s upper tropospheres, particularly in their ammonia (NH3) and hydrogen sulfide (H2S) mixing ratios, despite those planets’ outward similarities. The tropospheric abundances of these constituents yield information about their deep abundances, and ultimately about the formation of the planets from the presolar nebula (Atreya et al., 1995).