Meet Serenity Chasma, a stunning rut on Pluto’s largest moon, Charon. It’s part of a natural geological network four times as long and four-and-a-half times as deep as the Grand Canyon. The planet’s surface area, for comparison’s sake, is less than one percent of Earth’s.
“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,” says NASA’s news release. Scientists speculate that Charon may have at one time had a subsurface ocean, kept liquid from the heat of radioactive decay and the moon’s own formation. Later, the ocean cooled and froze, pushing and expanding outward with the formation of the ice.
Pluto’s radius is about two-thirds that of Earth’s moon, and Charon’s radius is about half of Pluto’s. Yes, we’re talking about tiny proportions, but because Charon is relatively large compared its host dwarf planet, it exerts much more gravitational pull.
Instead of Charon orbiting around Pluto, the planets orbit together around a point in space — picture an uncle grabbing his niece’s arms to swing her around in circles, leaning back and pivoting around his feet to compensate for her weight pulling against him.
Pluto has four other known moons — Styx, Nix, Kerberos, and Hydra — and the largest of them is no more than about 25 miles across. That’s pretty impressive for a rock that doesn’t even meet the definition of a proper planet.