Charon’s chasms suggest it once had a subsurface ocean
A belt of chasms running along the equator of Pluto’s largest moon, Charon, suggests it once harbored a subsurface ocean that eventually froze and expanded outward.
That process would have stretched the large moon’s surface, creating the massive fractures and chasms seen and imaged by NASA’s New Horizons spacecraft.
Images of Charon’s encounter side taken by the spacecraft’s Long Range Reconnaissance Imager (LORRI) show ridges, scarps, and valleys up to four miles (6.5 km) deep, sometimes referred to as “pull apart” tectonic faults that were likely created when the ancient underground ocean froze, pushing outward against the surface
In its early days, Charon had internal heat produced by its formation process and by the radioactive decay of elements. That heat source could have been warm enough to melt underground water ice, producing a subsurface ocean.
Eventually, that heat mechanism stopped, resulting in the water ice re-freezing. Water expands outwards when it freezes, and in Charon’s case, this lifted up the moon’s outermost layers, also composed of water ice.
The New Horizons team have released two blown-up cut-out images of Serenity Chasma, one in black and white, and the other in color, showing the elevations of the various regions.
The LORRI images of a large equatorial canyon dubbed Serenity Chasma, taken from a distance of 48,900 miles (78,700 km) approximately an hour and 40 minutes before closest approach to Charon, show close-ups of the faults and fractures that run at minimum 1,100 miles (approximately 1,800 km) along the center right of the large moon’s encounter hemisphere.
These images are illuminated from the top left, with north at the top. They cover a 240-mile (386-km) long, 110-mile (175-km) wide section of the canyon at a resolution of approximately 1,290 feet (394 meters) per pixel. Images of Earth taken at this resolution would show individual buildings.
Charon’s deepest chasms are estimated to have a depth of 4.5 miles (7.5 km). In contrast, the Grand Canyon on Earth is slightly over one mile (1.6 km) deep and is 277 miles (446 km) long.
Areas marked in yellow are about 3.5 miles high while those in pink reach an incredible height of seven LORRI took multiple images of the area to obtain stereo measurements of its topography.
By measuring the shapes and sizes of features like Serenity Chasma, scientists can trace the area’s geologic history and determine that surface water ice had once been liquid only to have subsequently refrozen.
The images of Charon’s chasms were released as the world marked the 86th anniversary of Pluto’s discovery on February 18, 1930.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.