BOULDER, Colo., Oct. 1 (UPI) -- New imagery from NASA's New Horizons probe reveals Pluto's moon Charon in remarkable detail.
As seen in the high-resolution images, Charon hosts a diverse range of topographical features -- a surprise to many scientists who expected to see mostly craters.
"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, but I couldn't be more delighted with what we see," geologist Ross Beyer said in a press release.
Beyer is a researcher at the SETI Institute and NASA Ames Research Center who is currently working on New Horizons' imaging team.
Instead of a planet peppered with small holes, the imagery reveals a surface marked by ridges and valleys, mountains and canyons -- and, of course, impact craters.
One of the most interesting features revealed by the new photos is a massive rift just above Charon's equator. The canyon extends the entirety of the side of Charon facing Pluto, some 1,000 miles, and likely continues across the moon's backside.
Measurements show the canyon system to be four times longer than the Grand Canyon and, in some places, double its depth.
"It looks like the entire crust of Charon has been split open," said John Spencer, lead scientist on the imaging team and a researcher 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."
Plains to the south of the moon's canyon, called the Vulcan Planum, are smoother and marked by fewer craters than regions to the north, which suggests the plains are younger. The southern region's resurfacing may be the result of cryovolcanism -- like regular volcanism but with ice and liquid water, ammonia or methane.
"The team is discussing the possibility that 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," explained Paul Schenk, a New Horizons scientist and researcher at Houston's Lunar and Planetary Institute.
New Horizons is between Charon and Pluto, passing within 17,000 miles of the moon, in June. It will continue to send back new and more detailed images of Charon and its features through the end of the year.
Charon is an especially expansive moon relative to Pluto's size -- the largest satellite-to-host ratio in the solar system.