JWST detects semi-heavy water on hot Jupiter WASP-39b, opening new window for planetary formation

JWST detected semi-heavy water (HDO) on the hot Jupiter WASP-39b. The elevated D/H ratio hints at formation beyond the snow line or atmospheric escape. While not a habitability breakthrough itself, the method provides a new tool for tracing planetary formation and atmospheric evolution, applicable to temperate rocky worlds in the future.