The Pluto-Charon system - The escape of Charon's primordial atmosphere

Although Charon seems to have lost its atmosphere and surface volatiles, a lack of heating that would be sufficient to generate melting and consequent separation of the lighter and heavier nonvolatiles has probably resulted in the outer layers' retention of the primordial mix of nonvolatiles. Spectroscopically-determined relative abundances for the Charon surface should accordingly be representative of its entire mass, and thereby constitutes the basis of an understanding of Charon's origin. The study of Charon's exposed nonvolatile ices may ascertain whether the Pluto-Charon system condensed out of the solar nebula directly or from a protoplanetary nebula.