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L.M. Feaga (University of Maryland)
Io's molecular atmosphere has been studied and its global distribution mapped with 200 km spatial resolution via Lyman-\alpha data obtained with the \textit{Hubble Space Telescope}. Examination of the extensive data set reveals a daytime SO2 atmosphere which is temporally stable, with only small local changes. An anti-/sub-Jovian asymmetry in the SO2 distribution persists in all of the observations. The atmosphere is densest in the anti-Jovian equatorial regions, with a maximum column density of 5.0\times1016\,cm-2 at 140\arcdeg longitude. The SO2 atmosphere also has greater latitudinal extent on the anti-Jovian hemisphere as compared to the sub-Jovian. Theoretical sublimation atmosphere models can not reproduce the asymmetry alone and the distribution is not well correlated with surface frosts. The atmospheric distribution is best correlated with the location of known volcanic plumes.
Support for this work was provided by NASA through grant number HST-AR-10313.02-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.