Photos taken by a NASA spacecraft in July 2015 suggest that Pluto's biggest moon, Charon, once had a subsurface ocean.
Its outer layer could have been warm enough to cause the ice to melt deep down, creating a subsurface ocean.
But as the moon cooled over time, the ocean would have frozen and expanded, producing the chasms.
The side viewed by the probe has a system of tectonic faults, including ridges more than 6.5 km deep.