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Gorgeous new images of Charon reveal a violent past for Pluto’s moon

October 1, 2015 at 1:27 p.m. EDT
The best ever image of Charon. Its red polar region is informally named Mordor Macula. (NASA/JHUAPL/SwRI)

Pluto's largest moon Charon is proving to be a magnificent world in its own right. The latest images from NASA's New Horizons flyby mission -- the highest resolution color images of Charon to date -- show a moon much more alive than our own.

“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,” Ross Beyer, an affiliate of the New Horizons Geology, Geophysics and Imaging (GGI) team from the SETI Institute and NASA Ames Research Center, said in a statement. “but I couldn't be more delighted with what we see."

The most notable feature is a canyon at least four times as long as the Grand Canyon, and as much as twice as deep. It stretches across the entire Pluto-facing side of Charon, which is more than 1,000 miles across. For all we know, it could continue even farther across the unseen side of the moon.

“It looks like the entire crust of Charon has been split open,” said John Spencer, deputy lead for GGI at the Southwest Research Institute. “With respect to its size relative to Charon, this feature is much like the vast Valles Marineris canyon system on Mars.”

We've known for some time that Charon was a very special moon: At half the size of Pluto, it's closer in size to its host planet than any other satellite in the solar system. In fact, one could make the argument that it's more of a binary (dwarf) planet than a moon. Instead of Charon orbiting Pluto in the usual way, the two worlds face each other and spin around a common point in between.

Despite its unusual qualities, researchers expected to find a moon that was old and battered, covered in nothing more intriguing than impact craters. Instead, in addition to its impressive canyon, Charon seems to show mountains and landslides, as well as extreme variations in color across its surface. The moon also has unusually smooth planes in some areas, suggesting that recent geological processes have smoothed out the many impact craters such an object should posses.

It's not yet clear what processes might have smoothed Charon out so recently. Mission scientists have suggested ice volcanoes as one possibility. If an ancient, internal ocean inside of Charon turned to ice, the pressure could have caused cracks that spewed water-based lavas.

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