IUE's detection of tenuous SO₂ frost on Ganymede and its rapid time variability

International Ultraviolet Explorer (IUE) observations of Ganymded demonstrate decade length or less temporal variations at a few discreet trailing side longitude regions. The temporal changes are seen in comparisons of IUE spectra from 1984–1986 with new IUE observations from 1996. Variations are observed on the trailing side associated with the new detection of SO₂ frost. A distinctive SO₂ frost spectral signature at 0.32 µm is detected in the 1984–1986 spectra of trailing side regions from 225° to 285° which are absent in corresponding 1996 measurements.