Infrared spectra of the Galilean satellites of Jupiter

Spectra of the four Galilean satellites from 1 to 4 microns were obtained with a Michelson interferometer. The spectra show that the albedo of Io is very nearly constant with wavelength; no absorptions are found in the region observed. Europa and Ganymede have large amounts of water ice on their surface. Callisto shows some faint ice absorptions. Upper limits of 0.5 cm-atm (STP) corresponding to 6 x 10 to the minus 8th power atm partial surface pressure were set for CH4 and NH3 on all four satellites.