Images taken by New Horizons show Pluto’s moon Charon is riddled with huge stretch marks and fractures. Astronomers believe those signs of stress indicate the moon once may have had a subsurface ocean.

Images taken by NASA's New Horizons show Pluto’s moon Charon is riddled with huge stretch marks and fractures. 
Astronomers believe those signs of stress indicate the moon once may have had a subsurface ocean. 
NASA notes, "Scientists say Charon could have been warm enough to cause the water ice to melt deep down, creating a subsurface ocean. But as Charon cooled over time, this ocean would have frozen and expanded (as happens when water freezes), lifting the outer