Temperature dependence of the water-ice spectrum between 1 and 4 microns - Application to Europa, Ganymede and Saturn's rings

Reflection spectra of water ice from 1 to 4 microns are presented as a function of temperature. It is found that a feature at 6056 reciprocal cm changes its intensity sufficiently so that it can be used as a spectroscopic measurement of the ice temperature. A temperature calibration curve of this feature down to 55 K is developed and used to determine ice temperatures for the Galilean satellites Europa (95 + or -10 K), Ganymede (103 + or -10 K), and the rings of Saturn (80 + or -5 K). The ice temperatures for the Galilean satellites are lower than their measured brightness temperatures, which can be explained by a higher albedo of the ice-covered regions relative to the rest of the satellite and possibly a concentration of the ice near the polar caps.