JWST Discovers Semi-Heavy Water on a Faraway World, Revealing Its Water History
Astronomers using the James Webb Space Telescope detected semi-heavy water (HDO) in the atmosphere of the hot exoplanet WASP-39b and measured an elevated deuterium-to-hydrogen (D/H) ratio. This suggests WASP-39b’s water may have originated beyond the snow line and/or been shaped by atmospheric escape, offering insights into the planet’s formation and chemical history. WASP-39b is not habitable, but such isotopologue measurements help illuminate how giant planets acquire and lose water over time.
