JWST detected the signature of water while the rocky exoplanet GJ 486 b crossed its star, raising hopes of a steam-rich atmosphere just 26 light-years away. But cool patches on the star can imitate exactly the same signal—and follow-up observations now suggest the planet is probably airless.

NIRSpec found a water-shaped transit signal at GJ 486 b, but two MIRI eclipses measured a nearly bare-rock dayside, making cool stellar patches the stronger explanation. The post JWST detected the signature of water while the rocky exoplanet GJ 486 b crossed its star, raising hopes of a steam-rich atmosphere just 26 light-years away. But cool patches on the star can imitate exactly the same…