Pluto’s moon Charon shows fractured surface, signs of recent activity

The latest photos to come beaming down from New Horizons aren't focused on Pluto; instead, they target the dwarf planet's largest moon, Charon. Charon is the largest moon relative to its planet in the entire Solar System, but that still means it's quite small, at about 1,200 kilometers across. So it's even less likely than Pluto to have retained enough heat to be geologically active.

And that's not just Ars saying that. Ross Beyer of NASA Ames Research Center was quoted in a statement as saying, “We thought the probability of seeing such interesting features on this satellite of a world at the far edge of our Solar System was low.”

NASA/JHUAPL/SwRI

Enhanced color images of Pluto and Charon show that the bodies are quite distinctive despite their proximity.

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But Charon had a number of significant surprises in store. Chief among them: a canyon/fracture system that stretches across the entire face of the moon and presumably extends to the far side. That means it's easily in excess of 1,200km long. NASA says that makes the system over four times as long as the Grand Canyon, and it's twice as deep in spots. "It looks like the entire crust of Charon has been split open,” said John Spencer of the Southwest Research Institute.