An Etymological Dictionary of Astronomy and Astrophysics

A unique feature of → Pluto’s large satellite → Charon. It appears as a dark reddish area about 475 km in diameter in Charon’s north polar region, as revealed in → New Horizons’ approach images. It has been proposed that the feature is due to gas from Pluto. A part of Pluto’s → atmosphere (→ methane molecules) is transiently cold-trapped and processed at Charon’s winter pole (W. M. Grundy et al., 2016, Nature, 14 September).

See also: Unofficial name.