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, both characteristic of H2O ice. We have successfully modeled the surface of Phoebe with an intimate (granular) mix of H2O ice (3% by weight, grain size 500 mu m) mixed with fine grains of H2O ice (0.25%) with amorphous carbon (grain size 900 mu m) as the dominant component. This model reproduces the shape of the measured spectrum and the observed albedo of 0.10 for Phoebe, but it is not unique. The presence of ice establishes Phoebe as an original member of the outer Solar System rather than a renegade asteroid. (C) 1999 Academic Press.