Spectral Geometric Albedo of the Galilean Satellites, 0.3 to 2.5 Microns
Abstract
The spectral geometric albedos for the Galilean satellites of Jupiter were determined over the spectral range 0.9-2.5 ,s with a spectral resolution of 0.05 . These observations were combined wfth albedos for the 0.3-I.1- spectral region taken from earlier ork. The spectral albedo curves confirm the decrease in albedo beyond 1.0 for J II and J III. Jupiter I and J IV have relatively constant albedos from 1.0 to 2.5 . The curve for J III appears to show a relative minimum near 1.6 j , as suggested by other observers. No spectral absorption feature is identifiable in the curve of J III near 2.0 . The infrared spectral albedos for J II and J III are similar to the spectra of frosts and not to those of common silicates. Considering only the infrared reflection spectrum, the most likely possibilities for surface composition are water frost or hydrated ammonia frost. The lack of features in the infrared spectra of J I and J IV does not preclude the possibility of frosts on their surfaces. The visible reflectivities of the satellites (0.3-1.0 ) do not resemble the reflectivities of pure frosts or of common silicates. Contaminent chromophors such as polysulfide compounds or ice radiation damage may produce this coloring at visible wavelengths.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1971
- DOI:
- 10.1086/151177
- Bibcode:
- 1971ApJ...169..589J