Upper Limits for Condensed O2 on Saturn's Icy Satellites and Rings

J. R. Spencer

Icarus 136, 349-352.

Preprint available in postscript form, including figures from here, or if that doesn't work, try anonymous ftp to ftp.lowell.edu, pub/spencer, and get file satsato2.ps. File size is 270 kbytes


New 4800-7200 A spectra of Saturn's rings, and the icy Saturnian satellites Enceladus, Tethys, Dione, Rhea, and Iapetus, do not show the weak 5773 and 6275 A absorption bands due to high-density condensed O2, that are seen, with a maximum depth of 1.8%, on Ganymede's trailing side. The 5773 A band depth must be < 0.6% (and very probably < 0.3%) on the rings, Tethys, Dione, Rhea, and the trailing side of Iapetus, and < 1.2% on the trailing side of Enceladus. The lack of detectable absorption does not rule out abundant O2 molecules that are too well-separated to produce these absorption bands. The observations show that the presence of O3, recently detected on Rhea and Dione (Noll et al. 1997b) , does not require the presence of detectable quantities of high-density O2. I discuss the implications of the new observations for models of O2 formation on Ganymede.

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