The carbon dioxide ice – more commonly known as dry ice – appears to be a thin layer covering a subsurface mostly made up of water ice. The carbon dioxide was likely stored beneath the surface of the moon until it was exposed by impact events, while the hydrogen peroxide could be formed by radiation breaking up the water ice.
Charon has been extensively studied since its discovery in 1978, but previous spectral data were limited to wavelengths below two point five micrometers, leaving gaps in our understanding of its surface composition.
The presence of water ice, ammonia-bearing species, and organic compounds has previously been noted, but the spectral range used was insufficient to detect other compounds. Understanding these compounds is important for studying the origin of icy bodies in the Kuiper Belt, home to Pluto and other dwarf planets.
