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New Horizons opens new window on icy Charon, Pluto's largest moon

As New Horizons closes in on Pluto, Charon, the largest moon in the dwarf planet's system, is now emerging as its own world, NASA officials say.

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    New Horizons was about 3.7 million miles from Pluto and Charon when it snapped this portrait late on July 8.
    NASA/JHUAPL/SWRI
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Everyone has heard of Pluto, the dwarf planet formerly known as the solar system's 9th planet. But few details are known about Pluto’s satellite Charon, the dwarf planet’s largest moon. Now, detailed photographs captured by NASA are revealing new information about the icy orb.

“They’re a fascinating pair: Two icy worlds, spinning around their common center of gravity like a pair of figure skaters clasping hands,” noted NASA’s website.

An unmanned New Horizons spacecraft is currently closing in on Pluto’s system after a journey that has taken more than nine-years. On July 14 it will speed past Pluto while seven science instruments gather data about the dwarf planet and its surroundings. New Horizons has already managed to send photographs back to NASA that offers the closest look at the dwarf planet to date.

Meanwhile, scientists are noting that, while revolving in proximity for billions of years, Pluto and Charon have some very notable differences. The two have similarly cold climates, but while Pluto is believed to be covered by exotic ices composed of frozen nitrogen, methane, and carbon monoxide, frozen water exists on Charon’s surface.

Furthermore, some researchers have speculated that Charon may be more of a planetary companion than a moon. Charon and Pluto orbit a center of mass that falls between them, while in the case of most planet-moon systems the center of mass lies within the interior of the planet.

 “Charon is now emerging as its own world. Its personality is beginning to really reveal itself,” John Spencer, Geophysics and Imaging deputy team leader of the Southwest Research Institute in Boulder, Colo., told NASA.  

Pluto has five known moons: Nix, Hydra, Kerberos, Styx, and Charon. Charon was discovered in 1978 and is almost half the size of Pluto.

“After observing Pluto for more than 80 years, researchers have assembled the outlines of a story for the Pluto-Charon system,” the Monitor’s Pete Spotts noted in April.

“Given the sizes, masses, and densities of the two, Charon most likely formed from a high-speed collision between Pluto and another Kuiper Belt object. This also provides the simplest pathways for forming the other four moons.”

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