Did Pluto’s moon Charon once have an ocean?

Image: Charon
This close-up of Charon’s canyons was taken by NASA’s New Horizons probe during last July’s flyby. The color-coded picture shows elevation data. Serenity Chasma’s depth can exceed 4 miles in places. In comparison, the Grand Canyon’s maximum depth is a mile. (Credit: NASA / JHUAPL / SwRI)

Scientists say the patterns of ice in canyons on Charon, Pluto’s largest moon, look as if some the frozen water was once liquid. And that suggests Charon had a subsurface ocean in ancient times.

The evidence comes from close analysis of images and elevation data collected last July when NASA’s New Horizons probe zoomed past Pluto and its moons. Even before the flyby, scientists speculated that Charon may have harbored liquid water, and that some water may still flow beneath its icy surface. The stereo measurements from New Horizons’ Long Range Reconnaissance Orbiter, or LORRI, are consistent with that hypothesis.

The clues come in the form of stretch marks in the ice around Serenity Chasma, a canyon that’s 4.5 miles deep in some places.

“Charon’s tectonic landscape shows that, somehow, the moon expanded in its past, and – like Bruce Banner tearing his shirt as he becomes the Incredible Hulk – Charon’s surface fractured as it stretched,” the science team said in an image advisory on Thursday.

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By Alan Boyle

Mastermind of Cosmic Log, contributor to GeekWire and Universe Today, author of "The Case for Pluto: How a Little Planet Made a Big Difference," past president of the Council for the Advancement of Science Writing.

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