August 18, 2019

Charon takes center stage in new batch of New Horizons images


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This enhanced color view of Charon comes from New Horizons' Ralph color camera. The colors highlight the subtle variations in the composition of Charon's crust, with the reddish region near the north pole -- informally named Mordor Macular -- standing out most prominently. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
This enhanced color view of Charon comes from New Horizons’ Ralph color camera. The colors highlight the subtle variations in the composition of Charon’s crust, with the reddish region near the north pole — informally named Mordor Macular — standing out most prominently. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

With a meandering canyon system four times as long, and twice as deep, as the Grand Canyon in the American Southwest, the crust of Pluto’s moon Charon may have been shaped by violent eruptions and complicated geology once thought improbable for such a small body in the far depths of the solar system, scientists said Thursday.

Two-and-a-half months on from its historic first-ever encounter with Pluto on July 14, NASA’s New Horizons spacecraft is beaming home bits of data and imagery a little at a time, its radio link with Earth strained by the probe’s location 3.1 billion miles away.

The latest pictures released Thursday illustrate Charon as a complex world covered in ridges, canyons, mountains and different colors, with a noticeable change in terrain between the moon’s northern and southern hemispheres.

Said Ross Beyer, an affiliate of the New Horizons geology team from the SETI Institute and NASA’s Ames Research Center: “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!”

Sharper than the view above, this image combines high-resolution imagery from New Horizons' telescopic LORRI black and white camera with color data from the Ralph instrument. Features as small as a half-mile (0.8 kilometers) are resolved here. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Sharper than the view above, this image combines high-resolution imagery from New Horizons’ telescopic LORRI black and white camera with color data from the Ralph instrument. Features as small as a half-mile (0.8 kilometers) are resolved here. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Although Charon is relatively modest in size — just slightly bigger than Ceres, the largest object in the asteroid belt — it has more than half the diameter of its companion Pluto. The similar sizes make Pluto and Charon a binary planet, where they move around each other in a wobbly 6.4-day orbit centered on a point in space just outside Pluto.

Many scientists expected Charon to be dull, gray and pockmarked with craters like the moon, but the story is changing.

Images released Thursday by NASA are the best views yet of Charon — even sharper views are still to come — and show a network of canyons and crevasses just north of the moon’s equator. Scientists say the chasms stretch more than 1,000 miles across the face of Charon observed by New Horizons during its July flyby, and apparently wraps around to the unseen far side of the frozen world.

“Four times as long as the Grand Canyon, and twice as deep in places, these faults and canyons indicate a titanic geological upheaval in Charon’s past,” NASA said in a press release.

The New Horizons spacecraft downlinked the pictures showing the canyon system Sept. 21. The images were captured just before the probe’s closest approach to Charon.

“It looks like the entire crust of Charon has been split open,” said John Spencer, deputy lead for the mission’s geology, geophysics and imaging team at the Southwest Research Institute in Boulder, Colorado. “In respect to its size relative to Charon, this feature is much like the vast Valles Marineris canyon system on Mars.”

This composite image of Pluto and Charon with enhanced colors shows a direct comparison of the brightness and terrain types, highlighting the similarity between Charon's reddish north pole and red colors on Pluto. The separation between the two worlds is not to scale. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
This composite image of Pluto and Charon with enhanced colors shows a direct comparison of the brightness and terrain types, highlighting the similarity between Charon’s reddish north pole and red colors on Pluto. The separation between the two worlds is not to scale. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Farther to the south, the rugged canyon lands give way to a smooth plain informally dubbed Vulcan Planum. Geologists say the region appears to be younger than the terrain to the north, a sign that something resurfaced that part of Charon more recently.

“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,” said Paul Schenk, a New Horizons team member from the Lunar and Planetary Institute in Houston.

The eruptions could have spewed material across Charon’s landscapes, refreezing to cover up ancient craters and other features now more prevalent in the northern hemisphere.

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Follow Stephen Clark on Twitter: @StephenClark1.


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