The New Horizons spacecraft has returned the best color and the highest resolution images yet of Pluto’s largest moon, Charon.
At half the diameter of Pluto, Charon is the largest satellite relative to its planet in the solar system. Many New Horizons scientists expected Charon to be a monotonous, crater-battered world; instead, they’re finding a landscape covered with mountains, canyons, landslides, surface-color variations, and more.
“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,” said Ross Beyer, an affiliate of the New Horizons Geology, Geophysics and Imaging (GGI) team from the SETI Institute and NASA Ames Research Center in Mountain View, California, “but I couldn’t be more delighted with what we see.”
High-resolution images of the Pluto-facing hemisphere of Charon, taken by New Horizons as the spacecraft sped through the Pluto system on July 14 and transmitted to Earth on September 21, reveal details of a belt of fractures and canyons just north of the moon’s equator. This great canyon system stretches more than 1,000 miles (1,600 kilometers) across the entire face of Charon and likely around onto Charon’s far side. 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.
“It looks like the entire crust of Charon has been split open,” said John Spencer from the Southwest Research Institute in Boulder, Colorado. “With respect to its size relative to Charon, this feature is much like the vast Valles Marineris canyon system on Mars.”
The team has also discovered that the plains south of Charon’s canyon — informally referred to as Vulcan Planum — have fewer large craters than the regions to the north, indicating that they are noticeably younger. The smoothness of the plains, as well as their grooves and faint ridges, are clear signs of wide-scale resurfacing.
One possibility for the smooth surface is a kind of cold volcanic activity called cryovolcanism. “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 from the Lunar and Planetary Institute in Houston.
Even higher-resolution Charon images and composition data are still to come as New Horizons transmits data, stored on its digital recorders, over the next year. As that happens, “I predict Charon’s story will become even more amazing!” said Hal Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.
The New Horizons spacecraft is currently 3.1 billion miles (5 billion km) from Earth, with all systems healthy and operating normally.
Images from NASA's New Horizons spacecraft were used to create this flyover video of Pluto's largest moon, Charon. The “flight” starts with the informally named Mordor (dark) region near Charon’s north pole. The camera then moves south to a vast chasm, descending from 1,100 miles (1,800 kilometers) to just 40 miles (60km) above the surface to fly through the canyon system. From there, it’s a turn to the south to view the plains and "moat mountain," informally named Kubrick Mons, a prominent peak surrounded by a topographic depression. New Horizons Long-Range Reconnaissance Imager (LORRI) photographs showing details at up to 400 meters per pixel were used to create the base map for this animation. Those images, along with pictures taken from a slightly different vantage point by the spacecraft’s Ralph/ Multispectral Visible Imaging Camera (MVIC) were used to create a preliminary digital terrain (elevation) model. The images and model were combined and super-sampled to create this animation. // NASA/JHUAPL/SwRI/Stuart Robbins
