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C. Dumas, R. J. Terrile (Jet Propulsion Laboratory, Caltech), B. A. Smith (University of Hawaii), G. Schneider (University of Arizona)
A complete compositional inventory of the small planetesimals of the outer solar system, relics of the early proto-planetary nebula, must not only include trans-Neptunian objects and Centaurs, but also the population of small satellites of the outer-planets. Due to their close proximity to the central planet (2-5 Rplanet), and their low brightness (Vmag~20-25), high-angular resolution imaging is required to carry-out a detailed spectrophotometric study of the surfaces of the inner moons of Uranus and Neptune. We have collected HST-NICMOS near-infrared images of the small inner satellites of Neptune Galatea, Despina, Larissa and Proteus. Their reddish color in the 0.5-1.9\mum range and low albedo (p1.9\mu m~8.5%) suggest the presence of dark and primitive material on the surface. Also, Proteus' albedo shows a depression beyond 1.6\mum that could be the first spectral evidence for the presence of C-H or C\equivN bearing material on the surface of this satellite. Comparison with similar NICMOS data obtained for the Uranian satellite Puck will be made. \\
This work was performed at the Jet Propulsion Laboratory, Caltech, under contract with the National Aeronautics and Space Administration, and is supported by NASA grant NAG5-3042.
The author(s) of this abstract have provided an email address for comments about the abstract: Christophe.Dumas@jpl.nasa.gov