The Distribution of Sulfur Dioxide and Other Infrared Adsorbers on the Surface of Io from Galileo NIMS
R.W. Carlson, W.D. Smythe, R.M.C. Lopes-Gautier, A.G. Davies, L.W. Kamp, J.A. Mosher (JPL-Caltech), L.A. Soderblom (USGS-Flagstaff), F.E. Leader, R. Mehlman (UCLA), R.N. Clark (USGS-Denver)
The Galileo Near Infrared Mapping Spectrometer (NIMS) was used to
investigate the distribution and relative particle size variations
of sulfur dioxide over one hemisphere of Io, centered at 210 W.
Using bands of differing strength, we find that large SO grains
(diameter of order 500 m) are prevalent in the equatorial region
of Colchis Regio and that smaller-sized particles occur almost
everywhere, but with spatially variable concentrations. The exception
is volcanic hot spots, where high surface temperatures promote rapid
vaporization and produce SO -free areas. The high-latitude
abundance of total sulfur dioxide exceeds that found in equatorial
regions. A feature at 3.15 m, perhaps due to an O-H stretch
transition, is equatorially distributed and similiarly absent in hot
spots. A broad adsorption in the 1 m region, which may be
produced by iron-containing silicates, shows a concentration at Io's
southern polar region, with an absence in the Pele plume deposition
ring.