H2O ON IO - IR-SPECTRA OF SO2 H2O MIXED ICES IN THE 5000-450CM(-1) REGION/

Laboratory transmission IR spectra of relatively thick films (up to si milar to 500 mu m) of mixed H2O and SO2 ices were measured at several temperatures between 10 and 130 K in the range 5000-450 cm(-1). In add ition to the strong features due to crystalline SO2 the spectra reveal bands at similar to 3668 cm(-1), 3634 cm(-1) (with some structure) an d 3300 cm(-1) which are identified with H2O in SO2 environment. Also, there is no overlap between any of the H2O bands with the 3584 cm(-1) band of SO2 at any temperature in the above range. The implication of this result is that H2O, if present on Io, must be far less than 1 par t in 10(5) SO2.