Mysterious Pluto and Charon
Pluto is the only planet in our Solar System remaining unphotographed by a passing spacecraft. Distant Pluto and its moon Charon therefore remain somewhat mysterious. In addition to direct imaging by the Hubble Space Telescope , careful tracking of brightness changes that occur as each object eclipses the other have allowed astronomers to build up the above black & white surface maps . These maps depict the face of Pluto (left) that always faces Charon, and the face of Charon that always faces away from Pluto . The rectangular pixels are an artifact of the mapping software. The Pluto-Kuiper Express mission is tentatively planned for launch in 2004 and might encounter Pluto as early as 2012.