NASA’s New Horizons spacecraft captured images in July 2015 that offer a sneak peek into the history of the largest of Pluto’s five moons, Charon.
The side of Charon captured showed what looked like a network of tectonic faults that have been “pulled apart” causing scarps, ridges, and valleys to form. Further analysis proved that the culprit of the multiple tears was Charon itself.
To explain the “hulk-like” occurrence, scientists noted that Charon’s outer layer is primarily water ice. At some point in the early days of Charon, this layer was kept warm by heat provided by two sources—decay of radioactive elements and internal heat of formation of Charon.
Scientists believe the heat from these two sources could have been warm enough to melt the water ice at levels far below the surface to form a subsurface ocean.
However, since both sources of heat were not sustainable. Charon inevitably cooled over time, causing the ocean below to freeze and expectedly expand—when water freeze, the ice that forms take up more space than the water it replaces.
It is this expansion that pushed up the outermost layers of the moon, essentially fracturing the surface as it stretched, like the Incredible Hulk character tearing his shirt when Bruce Banner transforms.
A pronounced feature caused by this phenomenon is an expansive equatorial belt of chasms on Charon’s surface. The system of chasms is currently the largest, pending any new discovery, in the solar system. It has a length of at least 1,100 miles (1,800 kilometers) and a depth of 4.5 miles (7.5 kilometers). The Grand Canyon, humongous on an earthly scale, does not come close at a comparatively meagre length of 277 miles (446 kilometers) and depth of a little over a mile (1.6 kilometers).
The Long-Range Reconnaissance Image (LORRI) on the New Horizon Spacecraft captured the image when it was at a range of approximately 48,900 miles (78,700 kilometers) from Charon on July 14, 2015.