Pluto likely acquired large moon Charon in a “kiss and capture” collision billions of years ago. It may have created a subsurface ocean on the icy dwarf planet.

Researchers accounted for the previously overlooked structures of the dwarf planet and moon in computer simulations of a celestial collision

Using simulations that took into account parameters like the size and composition of the bodies, along with the strength at which they collided, researchers reported that in the early stages of formation Charon and Pluto came together and orbited as one,

The reason that Pluto and Charon are so interesting is because Charon is 50% the size of Pluto,” said Adeene Denton, a planetary scientist at the University of Arizona who led the paper. “The only comparable system is Earth and its moon.