Recent studies suggest that Pluto's moon Charon may have played a significant role in the formation of Pluto's two outermost moons, Styx and Hydra. This is based on a new theory called the "kiss-and-capture" collision model, which challenges the traditional view of how Pluto's moons formed.
The Traditional View vs. "Kiss-and-Capture"
The prevailing theory for how Pluto's moons, including Charon, formed is similar to the model for Earth's moon. This model suggests that a large object collided with a young Pluto, and the ejected debris from the collision formed a disk around the dwarf planet. Over time, this debris accreted to form Charon and the other moons.
However, a new study using advanced computer simulations proposes an alternative. Instead of a messy, destructive collision that sends material flying everywhere, the "kiss-and-capture" model suggests a more gentle, yet intense, encounter. In this scenario, two protoplanetary bodies, one of which was proto-Pluto and the other proto-Charon, came into contact with each other. This wasn't a head-on crash, but more of a brief, glancing blow. The two bodies would have joined up and rotated together for about 30 hours, with each body remaining largely intact.
Charon's Role in Moon Formation
The "kiss-and-capture" model suggests that this brief, intimate contact between proto-Pluto and proto-Charon generated enough heat to create a debris disk around them. This debris, which may have included material from the mantles and cores of both bodies, then coalesced to form the smaller, more distant moons of Pluto, including Styx and Hydra. This model helps explain the unusual characteristics of Pluto's moon system, such as their nearly circular orbits and their orbital resonances.
The findings also have implications for other binary systems in the Kuiper Belt, like Eris and its moon Dysnomia, suggesting that similar "kiss-and-capture" collisions may have been a common way for these systems to form in the early solar system.