Pluto and its moon Charon may have once been briefly locked in a unique gravitational embrace before it released and recaptured Charon into its orbit. This intriguing dynamic has sparked renewed interest among astronomers regarding the formation of Charon, the largest of Pluto’s five moons, which boasts a radius exceeding half that of Pluto.
Historically, one of the leading theories posited that Charon formed from debris resulting from a colossal impact on Pluto, akin to the theory behind Earth’s moon. However, Charon’s significant size and close orbit—approximately eight times the diameter of Pluto—render this scenario less straightforward.
Recent research led by scientists at the University of Arizona suggests an alternative, less cataclysmic origin dubbed the “kiss and capture” theory. Traditionally, simulations have treated Pluto and Charon as fluid-like bodies, a method effective for larger celestial collisions. However, current findings indicate that the material strength of smaller objects like Pluto and Charon plays a crucial role in their interactions. “Pluto and Charon are quite small, so the assumption that they are fluid bodies probably no longer applies,” notes one leading researcher.
In their simulations, the researchers considered the rocky and icy compositions of Pluto and Charon, ultimately revealing a scenario where the two bodies gently adhered before separating. The model indicates that a proto-Charon may have penetrated Pluto’s icy shell, leading them to spin together for roughly 10 hours. Eventually, this spinning motion would have cast Charon out, allowing it to settle into its current orbit around Pluto.
While the kiss-and-capture hypothesis presents an exciting perspective, it faces the challenge of explaining the intricate geological features observed on both Pluto and Charon. Prominent features, including heavily cratered surfaces and instances of icy volcanism, require further exploration to enhance this emerging theory.
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