JWST May Have Just Found Heavy Water on an Alien World

JWST observations of exoplanet WASP-39b suggest the presence of semi-heavy water, or HDO, in its atmosphere.

The signal points to a higher deuterium-to-hydrogen ratio than seen in Solar System gas giants.

That could indicate atmospheric escape or that the planet formed farther out before migrating inward.

The finding helps scientists trace how hot exoplanets form and evolve, and tests JWST’s ability to probe atmospheric chemistry.