Tracing Saturn’s Watery Past: JWST Detects Heavy Water on Saturn’s Moons

Using JWST, Brown et al. detected deuterated water (heavy water) on Saturn’s icy moons, finding D/H ratios about 1.5 times higher than Earth’s oceans. This consistency across moons suggests they formed from the same cold, unprocessed ices, not from a hot gas disk. The results rule out earlier claims of extreme D/H on Phoebe and provide new insight into how Saturn’s satellites and solar system ices formed.