Planet's Rock Clouds Vanish Every Night, Webb Telescope Shows

Imagine waking up to clouds made of rock, then watching them completely vanish by sunset. That's everyday life on WASP-94A b, a giant planet astronomers just observed using the James Webb Space Telescope.

The planet sits nearly 700 light years away in the constellation Microscopium. Every morning, clouds made from magnesium silicate (the same mineral found in rocks on Earth) gather across its sky, only to disappear entirely by evening.

Scientists watched this dramatic weather cycle by observing the planet as it passed in front of its star. The telescope examined the planet's leading edge (its morning side) separately from its trailing edge (its evening side), revealing a stunning difference between the two.

The morning side appeared packed with mineral clouds, while the evening side looked almost completely clear. Researchers believe either powerful winds drag the clouds deep into the atmosphere on the scorching hot day side, or the clouds evaporate as temperatures exceed 1,000 degrees.

"I've been looking at exoplanets for 20 years, and general cloudiness has been a thorn in our side," said David Sing, a Bloomberg Distinguished Professor at Johns Hopkins University. "Not only have we been able to clear the view, but we can finally pin down what the clouds are made out of."

The clear evening skies gave scientists an unexpected gift. For the first time, they could examine the planet's atmosphere directly instead of viewing everything through a cloudy haze, like looking through a foggy window.

This clearer view solved a long standing mystery about what WASP-94A b contains. Earlier measurements suggested the planet had hundreds of times more oxygen and carbon than Jupiter, which didn't make sense. The new observations revealed it actually contains only about five times more oxygen and carbon than Jupiter, making it far more similar to our solar system's giant planet than anyone thought.

The team has already found similar cloud cycling on two more planets: WASP-39 b and WASP-17 b. They're planning a larger program to search for this pattern across many different worlds.

Why This Inspires

This discovery represents more than just cool alien weather. After decades of struggling to see through planetary clouds, scientists finally have the tools to peer into distant atmospheres with unprecedented clarity. The James Webb Space Telescope is opening windows we couldn't even peek through before, revealing that planets far beyond our solar system follow patterns we can understand and measure. Each observation brings us closer to understanding how planets form, how atmospheres behave, and ultimately, what makes worlds like ours possible. The universe is becoming less mysterious and more knowable, one cloudy morning at a time.

The findings were published in the journal Science in May 2026.