The largest moon of Pluto may have become quite huge for its own skin. Pictures from NASA's New Horizons mission have suggested that once Charon used to have a subsurface ocean that was frozen and extended, pushing out on the surface of the moon and forcing it to stretch and fracture on a big scale.

In July 2015, passing New Horizons spacecraft had a look over the side of Charon, and was characterized by a system of ‘pull apart’ tectonic faults, described as ridges, scarps and valleys, the latter at times spanning over four miles deep.

The tectonic landscape of Charon shows that in some way, the moon extended in its past, and the surface of Charon fractured when it stretched.

The outer layer of Charon is mainly water ice. At young age, the moon’s layer became warm due to the decay of radioactive elements and its internal heat of formation.

According to scientists, Charon could have been sufficiently hot to result into water ice to melt deep down, forming a subsurface ocean. However, with the passage of time, as Charon cooled down, this ocean would have frozen and extended, forcing the surface outward and creating huge chasms visible today.

The focus of the picture is on a part of the feature informally dubbed Serenity Chasma, belonged to a huge equatorial belt of chasms on Charon. Actually, the system of chasms is among the longest detected anywhere in the solar system. It runs at least 1,100 miles long and is 4.5 miles deep. In comparison, the Grand Canyon is 277 miles long and only more than a mile deep.

The image’s lower parts showed color-coded topography of the same scene. From the measurements of the shape of this feature, scientists came to know that the water-ice layer of Charon was liquid state during its distant past.