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[40.03] Atomic Chlorine in the Atmosphere of Io

L.M. Feaga (JHU/STScI), M.A. McGrath (STScI)

We report on atomic chlorine emissions detected in the atmosphere of Io via Hubble Space Telescope (HST) observations using the Goddard High Resolution Spectrograph (GHRS). The \ion{Cl}{1} \lambda1349 dipole allowed and \ion{Cl}{1}] \lambda1386 forbidden transition multiplets are detected at a signal to noise ratio of ~,5 in a combined spectrum of GHRS data acquired between 1994--1996.

We present theoretical and observational constraints on the atmospheric chlorine column density and atmospheric mixing ratios at Io. These results are compared to an independent study of atmospheric chlorine by Retherford (2002) using data from the Space Telescope Imaging Spectrograph (STIS). Implications of our analysis regarding the Io plasma torus chlorine abundances (Küppers & Schneider, 2000; Schneider, Park & Küppers, 2000; Feldman et al., 2001) are also discussed.

Support for this work was provided by 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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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.