Albedo maps of Pluto and Charon: Initial mutual event results

Abstract

We present single-scattering albedo maps of the surfaces of Pluto and Charon based primarily on mutual event observations. The dataset contains 3374 photometric observations that cover 15 different satellite transit events, 14 satellite eclipse events, and other out-of-eclipse photometry spanning 1954 to 1986. The maps consist of a 59 × 29 grid of tiles for each body. We applied the technique of maximum entropy image reconstruction to invert the lightcurves, thus revealing surface maps of single-scattering albedo. The surface of Pluto is seen to have albedo features similar to our previous spot model maps (Buie and Tholen 1989). In particular, a south polar cap is evident in the map of Pluto. The north polar region is brighter than the equatorial regions but is not as bright as the south pole. Single-scattering albedos range from 0.98 in the south polar cap to a low near 0.2 at longitudes corresponding to the lightcurve minimum. The map of Charon is somewhat darker with single-scattering albedos as low as 0.03.