Pluto and its large satellite, Charon, have not been visited by spacecraft (although they may be the target of a proposed mission in the early twenty-first century). This 3-D view of Pluto and Charon was created at the Lunar and Planetary Institute using a map of Pluto’s surface created by Marc Buie and Alan Stern from Hubble Space Telescope (HST) images. Pluto is 2300 kilometers across, and Charon is 1200 kilometers across. The smallest features detectable on the Pluto map are roughly 200 kilometers across. In this view, the Pluto-Charon system is shown from the side, with the north pole of each object pointing toward the right. This view is similar to that of HST in 1994, when the image map was obtained. Charon, represented by a gray sphere, is in front of Pluto and orbits from top to bottom across the scene. Latitude and longitude lines have been added to aid in viewing the stereo effect.
Pluto and Charon are probably composed of roughly 50% rock and 50% ice. The bright and dark spots may be deposits of nitrogen, methane, carbon monoxide, or carbon dioxide frosts and ices. Water ice has also been detected. The frost patterns may be seasonal deposits formed by Pluto's thin atmosphere. Whether impact craters or volcanos exist on the surface is not known.