New research using the James Webb Space Telescope (JWST) suggests that Pluto’s midsize moons, Nix and Hydra, might be made up of material from Pluto’s largest moon, Charon. Studies indicate that these moons resemble Charon’s insides rather than other objects in the Kuiper Belt, hinting they could contain remnants of Charon’s interior that were ejected during a past collision.
Previously, it was believed that Pluto and Charon formed through a “kiss-and-capture” process, where a collision stripped the outer layers of Charon, creating a disk of debris. This debris eventually became small moons, including Nix and Hydra.
Using JWST, researchers explored the colors of trans-Neptunian objects (TNOs) in the outer solar system. They found that Nix and Hydra don’t match any other Kuiper Belt objects. Brian Holler, a planetary scientist, pointed out that the moons have a reddish surface, likely due to carbon-containing materials, making them stand out in their region.
Interestingly, Nix and Hydra may be dumping materials back onto Charon. When small meteorites hit these moons, debris could be flung into space, captured by Charon’s gravity, and then landed back on its surface. Holler suggested this might represent the original materials of proto-Charon, forming a thick layer of dust over time.
JWST’s observations of Nix and Hydra weren’t just limited to their surfaces; they also offered a chance to compare these moons with others in the outer solar system. Holler noted that while New Horizons provided initial insights in 2015, JWST allows for more detailed comparisons of their composition.
According to Holler, Nix and Hydra have likely remained unchanged since their formation. They’re too small to have significant geological activity, so any changes are mainly due to impacts and space weather. Holler expressed optimism to further study these moons with JWST to understand their surface materials better, particularly the ammonia found on them. This substance is fragile, often deteriorating due to solar radiation, suggesting there may be a process that replenishes it on Nix.
Further studies might draw insights from other TNOs created through similar collisions. This knowledge could deepen our understanding of the nature and formation of Pluto’s intriguing moons.
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