Pluto may have captured its moon Charon with a brief kiss

Pluto and its moon Charon may have been temporarily locked together in a cosmic “kiss” before the dwarf planet released the smaller object and recaptured it in orbit.

Charon is the largest of Pluto’s five moons, with a radius more than half that of Pluto itself, but the question of how it got into orbit around Pluto has puzzled astronomers.

One leading theory suggests that Charon formed after a giant object collided with Pluto and ejected its debris into space, similar to the way scientists think Earth’s moon formed. The same is true. But Charon’s large size and close orbit, eight times the width of Pluto itself, makes this scenario difficult to explain.

Now, Adine Denton and colleagues at the University of Arizona have proposed that Charon may have a less destructive origin story, which they describe as a “kiss and capture.”

Previous simulations treated Pluto and Charon as fluids. This is an assumption that comes into play when modeling collisions between larger objects. However, recent studies have shown that for objects with masses less than Earth’s moon, the material strength of their composition influences the results. “Pluto and Charon are so small that the assumption that they are fluid bodies probably no longer holds true,” Denton says.

The researchers ran simulations that took into account the rock and ice compositions of Pluto and Charon and found that a scenario where they gently stick together and break apart is more likely.

Their model showed that proto-Charon may have penetrated proto-Pluto’s icy shell, causing the two objects to rotate rapidly for about 10 hours. Eventually, the rotation knocked Charon off and brought it into Pluto’s orbit.

“We always thought that collisions between planets hundreds of kilometers in diameter would destroy the smaller object if it was caught,” said David Rothery of Britain’s Open University.

The kiss-and-catch scenario is interesting, Rosalie said, but it also explains complex geological features found on both Pluto and Charon that are currently unexplained, such as the cratered surface and icy volcanism. It is said that it is necessary.