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Night Falls on Pluto's Largest Moon Charon

Pluto's largest moon, Charon, is cloaked in darkness, with just a tiny sliver lit up by the distant sun, in a newly released photo.

Pluto's largest moon, Charon, is cloaked in darkness, with just a tiny sliver lit up by the distant sun, in a newly released photo.

NASA's New Horizons spacecraft captured the image on July 17, 2015, three days after the probe's historic flyby of Pluto. That close encounter brought New Horizons within just 7,800 miles (12,550 kilometers) of Pluto's surface; the night-side view of Charon, on the other hand, was taken from a distance of 1.9 million miles (3.1 million km), NASA officials said.

PHOTO: Pluto's Moon Charon is Battered, Bruised and Beautiful

"Charon's nighttime landscapes are still faintly visible by light softly reflected off Pluto, just as 'Earthshine' lights up a new moon each month," agency officials wrote in a description of the image, which was released Friday (Jan. 22).

"Scientists on the New Horizons team are using this and similar images to map portions of Charon otherwise not visible during the flyby," the officials added. "This includes Charon's south pole - toward the top of this image - which entered polar night in 1989 and will not see sunlight again until 2107. Charon's polar temperatures drop to near absolute zero during this long winter."

At 753 miles (1,207 km) in diameter, Charon is more than half as wide as Pluto itself. The dwarf planet's other four moons - Nix, Hydra, Kerberos and Styx - are all tiny by comparison. For example, Nix and Hydra measure just 33 miles (54 km) and 27 miles (43 km), respectively, in their longest directions, while Styx and Kerberos are even smaller.

NEWS: Ammonia 'Splat' on Charon Could be a Fresh Impact

The $720 million New Horizons mission launched a decade ago, in January 2006. The probe is currently zooming toward a potential January 2019 flyby of a small object called 2014 MU69, which lies about 1 billion miles (1.6 billion km) beyond Pluto.

New Horizons will study 2014 MU69 up close, if NASA approves and funds a proposed extended mission. The spacecraft is also still beaming home the data and images it collected during the July 2015 flyby; this relay work should be done by this coming autumn, mission team members have said.

More from SPACE.com:

Photos of Pluto and Its Moons How NASA's New Horizons Mission to Pluto Works (Infographic)

Pluto Quiz: How Well Do You Know the Dwarf Planet?

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NASA's New Horizons spacecraft captured this image of the night side of Pluto's largest moon, Charon, on July 17, 2015.

Newly returned pictures taken by NASA’s New Horizons spacecraft are giving scientists -- and the rest of us -- the most detailed views of Pluto’s stunningly diverse landscape. “We continue to be amazed by what we see,” NASA chief scientist John Grunsfeld said in a statement. The latest images form a strip 50 miles wide and were taken when New Horizons was about 15 minutes away from its closest approach to Pluto on July 14.

PHOTOS: New Pluto Pics Show Beautiful, Complex World

As NASA’s New Horizons spacecraft raced toward a July 14 close encounter with Pluto, the probe’s telescopic long-range camera got to work on a sequence of pictures that revealed features smaller than half of a city block. Pluto’s surface turned out to be unexpectedly diverse, evidence of a complicated and rich geology. The mosaic pictured here starts about 500 miles northwest of Pluto's smooth Sputnik Planum region and covers the rugged al-Idrisi mountains, the shoreline of Sputnik Planum and its icy plains.

This image has been scaled and rotated, for the full, high-resolution view,

check out the mission website

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which includes a video

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PHOTO: New Horizons Returns Photos of Hazy 'Arctic' Pluto

Scientists aren’t sure yet how some of Pluto’s craters came to contain layers, such as the one picture here in the upper right. “Layers in geology usually mean an important change in composition or event, but at the moment New Horizons team members don’t know if they are seeing local, regional or global layering,” NASA said. New Horizons’ Long Range Reconnaissance Imager (LORRI) took a series of images about 15 minutes before the spacecraft’s July 14 close encounter with Pluto. The dark crater at the center of the image is apparently younger than the others because material thrown out by the impact is still visible. Most of the craters are within a 155-mile wide region known as Burney Basin, the outer rim of which appears as a line of hills at the bottom of this image.

VIDEO: Fly With New Horizons During Stunning Pluto Encounter

New Horizons gathered a 50-mile-wide view of Pluto’s rugged northern hemisphere, including a 1.2-mile high cliff, seen here from the left to the upper right, during a series of pictures taken by the spacecraft’s telescopic Long Range Reconnaissance Imager (LORRI) on July 14. The cliff is part of a canyon system that stretches for hundreds of miles across Pluto’s northern hemisphere. Scientists believe the mountains in the middle are comprised of water ice that has been changed by the motion of nitrogen or other exotic ice glaciers over the eons. At the bottom of the image, which was taken when New Horizons was about 10,000 miles from Pluto, the badlands meet the giant icy plains of Sputnik Planum.

PHOTO: Weird Woodworm-like Pits on Pluto Reveal Icy Puzzle

Blocks of ice, upper left, appeared to be jammed together in an area the New Horizon scientists are calling the al-Idrisi mountains. Some of the mountains seem to be coated with a dark material, while others are bright. Scientists think material crushed between the mountains may be from the ice blocks jostling back and forth. The mountains end at the shoreline of a region named Sputnik Planum, which is marked by soft, nitrogen-rich ices that form a nearly flat surface. New Horizon’s Long Range Reconnaissance Imager (LORRI) took a series of images in the span of about one minute at 11:36 Universal Time on July 14, about 15 minutes before the spacecraft’s closest approach.

ANALYSIS: Pluto Mystery Tour: A Weird 'Snakeskin' Landscape?