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.

Simulations suggest Pluto and its largest moon may have gently stuck together for a few hours before Charon settled into a stable orbit around the dwarf planet