Pluto's ices may snow down on its nearby moon

During its historic flyby, the New Horizons spacecraft has not forgotten about Pluto’s giant, airless moon Charon, which is 20 times closer to Pluto than the moon is to Earth. Charon is dark gray and rich in water ice, because it is not massive enough to hold onto the brighter methane and nitrogen ices seen on Pluto—except, maybe, at Charon’s pole. Today, the New Horizons team released a false color image of the duo (pictured above), which shows the different materials that blanket each body. The team also offered an intriguing theory for Charon’s reddish polar cap. Although it lacks an atmosphere of its own, Charon orbits through and picks up gas molecules of ices that sublimate from Pluto’s surface and then escape from its atmosphere. Some of these stray molecules may bounce around Charon until they end up at a place cold enough to freeze out and stay put: the pole. The reddish regions on both Charon and Pluto thus offer an intriguing hint of a material connection between the two bodies.
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