Webb Finds Ancient Hydrated Clay on Neptune’s Inner Moons, Hinting at a Lost Satellite System

NASA’s JWST detected magnesium-rich phyllosilicates on Neptune’s tiny inner moons Larissa and Galatea and on its rings, a hydrated mineral signature formed by liquid water. The small, cold moons could not have heated enough to create these minerals, implying they inherited them from much larger, differentiated icy satellites that were shattered when Neptune captured Triton. Fragments from that primordial system likely remain as the current inner moons and rings, with Nereid possibly a surviving member; the researchers note alternate scenarios and call for more simulations and spectra to confirm the history.