The detection of phosphine, PH₃, was reported in the atmospheres of Jupiter and Saturn in 1976 and 1980, respectively. The identifications were made using infrared spectra collected with the McMath Solar Telescope at Kitt Peak and by the Kuiper Airborne Observatory. Subsequent IR studies, such as the work by Kunde et al. based upon Voyager 1 IRIS data, confirmed the detection for Jupiter, as did the microwave work by Lellouch et al. However, phospine fell below the detection limit in ultraviolet spectra taken with the HST Faint Object Spectrograph by Edgington et al.. Confirming results for Saturn include work by de Graauw et al. with the Infrared Space Telescope.

Phosphine (phosphorous hydride) is the second-row analog of ammonia, though it is a much weaker base. It is used in semiconductor manufacture and as a food fumigant.