During the 1980s, Earth crossed the orbital plane of Charon so that, from our vantage point, Charon and Pluto alternately passed in front of each other. These eclipses enabled the size of the two objects and other valuable data on the Pluto-Charon system to be collected. Albedo measurements suggest that Charon is covered mainly with water-ice, while Pluto has a coating of frozen nitrogen. Also Charon's density (about 1.2 g/cm3) is significantly lower than that of Pluto (about 2.0 g/cm3) suggesting that the moon has very little rock and adding to the controversy of how Charon formed. Set against the favored view that Charon stemmed from the collision between Pluto and another large object in the early days of the Solar System, is the suggestion that Pluto and Charon formed independently.
The likely presence of water-ice, together with the possibility that Charon is subject to significant tidal heating as a result of Pluto's gravity, has led to the hypothesis that there may be a sub-ice liquid ocean of water on the moon which could harbor microbial life. Charon is due to be observed at close range by the New Horizons probe in 2015.
MythologyIn Greek mythology, Charon was the son of Erebus and Nyx. It was his duty to ferry over the Rivers Styx and Acheron the souls of the dead who had received the rites of burial. His payment for this was a coin, which was placed in the mouth of the corpse. If this rite was neglected, Charon refused to convey the soul across, and it was doomed to wander restlessly along the shores of Acheron.
Archived newsPluto's moon created by cosmic hit-and-run (Jan 29, 2005)
Related category PLANETS AND MOONS
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