Neptune’s tiny moons may be the wreckage of shattered ancient worlds

JWST has uncovered surprising clues that Neptune’s strange inner moons may be the wreckage of an ancient cosmic catastrophe. Researchers detected clay-like minerals on Larissa, Galatea, and Neptune’s rings that form in the presence of liquid water—yet the moons themselves show no obvious water ice. The material likely came from deep inside much larger icy moons that were shattered when Triton was captured by Neptune, destroying much of the planet’s original satellite system.

This image of the Neptune system, captured by the Near-Infrared Camera (NIRCam) on NASA's James Webb Space Telescope in 2022, reveals stunning views of the planet's rings—which have not been seen with this clarity in more than three decades—along with the planet's inner moons. Credit: NASA, ESA, CSA, STScI; Image Processing: Joseph DePasquale (STScI), Naomi Rowe-Gurney (NASA-GSFC)
In 1989, Voyager 2 discovered six previously unknown moons around Neptune. Five of them are tiny satellites that travel just beyond the planet's main rings. Their small size and distant location have made them extremely difficult to investigate from Earth.

Now, NASA's James Webb Space Telescope (JWST) has given scientists a much closer look. A Caltech led team used Webb to study Neptune's rings along with three of its inner moons, Larissa, Galatea, and Proteus. The observations revealed a chemical makeup unlike anything previously identified among bodies in the outer solar system.