Pluto has a massive moon, Charon, orbiting it at a distance of 8 times the dwarf planet's diameter. To explain the configuration, illustrated in a montage of images taken in 2015 by the New Horizons probe, astronomers had used a hydrodynamic model that in 2001 helped describe the collision between the Moon and Earth, likening them to fluids with no cohesive force. An American team led by Robert Melikyan (University of Arizona, Tucson) has proposed new simulations taking into account the solidity of the two bodies in the January 6 edition of Nature Geoscience.

They put forward a scenario dubbed "Kiss and Capture," in which the two stars would originally have been 85% rock and 15% ice. The proto-Charon would have had twice the mass it has today and would have collided with Pluto at an angle of 45 degrees, at around 1 kilometer per second. It would have taken just a few dozen hours for the future moon, stripped of part of its mass, to start rotating around the dwarf planet, before moving away towards its current circular orbit. In this scenario, Charon would have remained relatively intact, retaining its core and most of its mantle, and would be as old as Pluto, whose radius (1,200 kilometers) is twice as large. The impact would have produced debris that could have contributed to the formation of Pluto's four other moons.