Rock Clouds Wake in the Morning, Clear at Night on Distant Gas Giant, JWST Finds

JWST observations of WASP-94A b reveal a day-night atmospheric cycle: the planet’s morning limb is cooler and cloudier due to mineral silicate clouds forming at low pressure, while the evening limb is hotter and clearer with stronger water absorption. The clouds form and evaporate as air circulates from night to day and back, a rock-based weather system on a tidally locked gas giant about 700 light-years away. This limb-resolved spectroscopy highlights why averaging spectra can mislead about atmospheric composition and demonstrates JWST's ability to map exoplanet weather.