Images taken by the Long-Range Reconnaissance Imager (LORRI) instrument on board NASA’s New Horizons spacecraft suggest that Charon once had an underground water ocean that has long since frozen and expanded, pushing out on the moon’s surface and causing it to stretch and fracture on a massive scale.
A close-up of the canyons on Charon, taken by New Horizons’ LORRI instrument during the spacecraft’s close approach to the Pluto system on July 14, 2015. When New Horizons took this image, a distance of 48,900 miles (78,700 km) separated the spacecraft and Charon. The image measures 240 miles (386 km) long and 110 miles (175 km) wide. Multiple views taken by the spacecraft as it passed by the Pluto’s largest moon allow stereo measurements of topography, shown in the color-coded version of the image. The scale bar indicates relative elevation. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
The side of Charon viewed by NASA’s passing New Horizons in July 2015 is characterized by a system of ‘pull apart’ tectonic faults, which are expressed as ridges, scarps and valleys.
Charon’s tectonic landscape shows that, somehow, the moon expanded in its past, and the surface fractured as it stretched.
According to members of the New Horizons science team, the moon’s outer layer is primarily water ice.
When Charon was young this layer was warmed by the decay of radioactive elements, as well as its own internal heat of formation.
New Horizons planetary researchers said that Charon could have been warm enough to cause the water ice to melt deep down, creating a subsurface ocean.
But as the moon cooled over time, this ocean would have frozen and expanded, lifting the outermost layers of the moon and producing the massive chasms we see today.
The top segment of this image shows a section of Serenity Chasma, part of a vast equatorial belt of chasms on Charon.
In fact, this system of chasms is one of the longest seen anywhere in the Solar System, running at least 1,100 miles (1,800 km) long and reaching 4.5 miles (7.5 km) deep.
The lower portion of the image shows color-coded topography of the same scene.
Measurements of the shape of this feature tell the New Horizons team that Charon’s water-ice layer may have been at least partially liquid in its early history, and has since refrozen.
New Horizons is currently 3.3 billion miles (5.31 billion km) from Earth and 162.7 million miles (261.8 million km) beyond Pluto, with all systems healthy and operating normally.
The spacecraft is on course for a close flyby of a small Kuiper Belt object, 2014 MU69, in January 2019.
