Neptune moon could be only intact survivor from ancient collision

Key Points:

• New research using James Webb Space Telescope data suggests that Nereid, Neptune’s third-largest moon, may be the only intact survivor of an original set of moons destroyed by the capture of Triton over 4 billion years ago.
• Unlike Triton, which likely originated from the Kuiper Belt and disrupted Neptune’s primordial satellites, Nereid’s composition—rich in water and CO2—differs significantly from Kuiper Belt objects and resembles regular moons of Uranus, challenging previous assumptions about its origin.
• Computer simulations indicate that when Triton was captured, some moons like Nereid could have survived on distant, eccentric orbits, supporting the idea that Nereid is a remnant of Neptune’s original satellite system rather than a captured object.
• The study highlights the unique and chaotic nature of Neptune’s moon system compared to other outer planets, with Nereid’s survival offering new insights into the formation and evolution of satellites around ice giants.
• Experts praise the findings as a compelling explanation for Neptune’s moon system and emphasize the potential for future James Webb observations and a dedicated Neptune mission to further unravel Nereid’s history and composition.