Pluto’s Big Moon Charon Reveals a Colorful and Violent History

NASA | OCTOBER 4, 2015

NASA’s New Horizons spacecraft has returned the best color and the highest resolution images yet of Pluto’s largest moon, Charon – and these pictures show a surprisingly complex and violent history.

Charon in Enhanced Color NASA's New Horizons captured this high-resolution enhanced color view of Charon just before closest approach on July 14, 2015. Credits: NASA/JHUAPL/SwRI

At half the diameter of Pluto, Charon is the largest satellite relative to its planet in the solar system. Many New Horizons scientists expected Charon to be a monotonous, crater-battered world; instead, they’re finding a landscape covered with mountains, canyons, landslides, surface-color variations and more.

High-resolution images of the Pluto-facing hemisphere of Charon, reveal details of a belt of fractures and canyons just north of the moon’s equator. This great canyon system stretches more than 1,000 miles (1,600 kilometers) across the entire face of Charon and likely around onto Charon’s far side. Four times as long as the Grand Canyon, and twice as deep in places, these faults and canyons indicate a titanic geological upheaval in Charon’s past.

The plains south of the Charon’s canyon -- informally referred to as Vulcan Planum -- have fewer large craters than the regions to the north, indicating that they are noticeably younger. The smoothness of the plains, as well as their grooves and faint ridges, are clear signs of wide-scale resurfacing.

One possibility for the smooth surface is a kind of cold volcanic activity, called cryovolcanism. An internal water ocean could have frozen long ago, and the resulting volume change could have led to Charon cracking open, allowing water-based lavas to reach the surface at that time.

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