Triton, the largest moon of Neptune, does not have any cracks that are visible to the naked eye. However, images taken by the Voyager 2 spacecraft in 1989 show evidence of extensive faulting and cratering on the surface of Triton. The most likely explanation for this is that Triton was once a much larger body that underwent significant internal heating early in its history. This heat caused the interior of Triton to differentiate into layers, with a denser core surrounded by lighter material. As Triton cooled, it shrank slightly and the outer layers cracked due to the stresses imposed by the changing volume.