Near-Infrared Spectral Geometric Albedos of Charon and Pluto: Constraints on Charon's Surface Composition

Abstract The spectral geometric albedos of Charon and Pluto are derived at near-infrared wavelengths (1.4–2.5 μm) from measurements obtained in 1987. Comparisons of these to theoretical calculations are used to place constraints on the identity and relative abundances of surface ices on Charon. These comparisons suggest that widespread regions of pure CH 4 ice do not occur on Charon and that if CH 4 is abundant on Charon then it is large grained (≈5 mm) and is likely mixed at the granular level with H 2 O ice, and possibly CO 2 ice.