Webb Spots Rock-Forming Clouds On One Hemisphere Of A Distant Hot Jupiter

NASA’s James Webb Space Telescope analyzed WASP-94A b by splitting its transit into the cooler, cloudier morning limb and the hotter, clearer evening limb. The observations suggest mineral clouds (likely magnesium silicate) form as gas cools on the morning side and evaporate on the scorching dayside, leaving the evening limb relatively clear and rich in water absorption. This limb-by-limb spectroscopy reveals a weather-driven 3D structure that a single averaged atmospheric model would miss, highlighting a mineral-cloud cycle on a tidally locked exoplanet and showcasing a method to map exoplanet weather even when the planet isn’t spatially resolved.