The formation of Charon’s red poles from seasonally cold-trapped volatiles

摘要: A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on surface have been attributed to tholin-like organic macromolecules produced by energetic radiation processing hydrocarbons. The location implicates the temperature extremes that result from Charon's high obliquity and long seasons in production this material. escape atmosphere provides a potential feedstock for complex chemistry. Gas Pluto transiently cold-trapped processed at winter pole was proposed as an explanation coloration basis image hemisphere, but not modelled quantitatively. Here we report images southern hemisphere illuminated Pluto-shine also taken during approach phase show cap over range longitudes. We model thermal environment supply temporary cold-trapping material escaping Pluto, well photolytic into more less volatile molecules while cold-trapped. results are consistent with mechanism producing observed colour pattern Charon.