DPS 2001 meeting, November 2001
Session 17. Io, Tori, and Satellite Atmospheres Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Wednesday, November 28, 2001, 10:30am-12:30pm, French Market Exhibit Hall

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[17.06] The Abundance of Atomic Sulfur in the Atmosphere of Io

L.M. Feaga (JHU), M.A. McGrath (STScI), P.D. Feldman (JHU)

Observations with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope have been used to constrain the atomic sulfur column density in Io's atmosphere. The \ion{S}{1} \lambda1479 dipole allowed and forbidden transition multiplets have been resolved for the first time at Io, enabling the study of both optically thick and thin transitions from a single atomic species. The allowed transitions contribute 62 ± 8% and the forbidden transitions 38 ± 8%, on average, to the total signal of the \ion{S}{1} \lambda1479 multiplets. Using the optically thick and thin transitions of \ion{S}{1} \lambda1479 and \ion{S}{1} \lambda1814, we derive an atmospheric sulfur column abundance of 2.8\times1012\,cm-2\,<\,{\cal N}s\,<\,\,1.3\times1013\,cm-2, which is independent of electron temperature and density. A low density SO2 atmosphere, {\cal N}so_2~\,\,5-10\times1015\,cm-2, consistent with that inferred from other recent observations, is most consistent with these bounds.

Support for this work was provided by NASA through grant number HST-AR-09211.01-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

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