The James Webb Space Telescope (JWST) has detected clay minerals on Neptune’s inner moons that only form in the presence of liquid water. For the researchers, it is a strong hint: the small moons are likely the wreckage of much larger, long-destroyed icy worlds.
The find
A Caltech team led by astronomer Ryleigh Davis used the JWST to study Neptune’s moons Larissa, Galatea and Proteus, as well as the planet’s rings. The result: magnesium-rich phyllosilicates – clay minerals that only form on contact with liquid water. Surprisingly, no water ice is detectable on the moons themselves. And such minerals had never before been found in the outer solar system beyond Jupiter.
The theory
The material likely comes from the interior of once much larger icy moons. When Neptune captured the moon Triton – an object drawn in from the Kuiper Belt – it destroyed the planet’s original moon system. Today’s small inner moons formed from the debris. The study was published on 29 July 2026 in the journal Science Advances.
Sources: Caltech, ScienceDaily.
