Surprising signatures in WASP-121b's dynamic atmosphere challenge understanding of how 'roasting marshmallows' form

Nearly one third of known exoplanets are enormous gas giants, similar to Jupiter or Saturn. But whereas our solar system developed with gas giants far from our sun, some planetary systems consist of so-called 'hot—or even ultra-hot—Jupiters' orbiting very close to their star, some as close as Mercury is to the sun. These hot, puffy giants endure extreme temperatures and are sometimes nicknamed "roasting marshmallows."