Detection of water ice on Saturn's satellite Phoebe

The near-infrared reflectance spectrum of Saturn's satellite Phoebe shows a broad absorption band at 2.0 mu m and absorption at lambda > 2.2 mu m, bot h characteristic of H2O ice. We have successfully modeled the surface of Ph oebe with an intimate (granular) mix of H2O ice (3% by weight, grain size 5 00 mu m) mixed with fine grains of H2O ice (0.25%) with amorphous carbon (g rain size 900 mu m) as the dominant component. This model reproduces the sh ape of the measured spectrum and the observed albedo of 0.10 for Phoebe, bu t it is not unique. The presence of ice establishes Phoebe as an original m ember of the outer Solar System rather than a renegade asteroid. (C) 1999 A cademic Press.