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.

The “demoted” dwarf planet Pluto and its largest moon Charon make an unusual pair, and for decades, scientists have been discussing how the binary system—in which each mutually orbits the other—came to be.

"We were definitely surprised by the 'kiss' part of kiss-and-capture. There hasn't really been a kind of impact before where the two bodies only temporarily merge before re-separating!"