Astronomers using the James Webb Space Telescope (JWST) have discovered a dramatic weather cycle and massive “rock clouds” on a distant giant planet, revealing how mineral clouds form and disappear under extreme heat conditions.
The planet, known as WASP-94A b, is a “hot Jupiter” — a gas giant that orbits extremely close to its host star. Scientists found that mineral clouds gather in the planet’s cooler morning atmosphere before vanishing later in the day as temperatures rise.
Researchers said the discovery provides one of the clearest views yet of changing weather patterns on a planet outside Earth’s solar system.
WASP-94A b lies nearly 700 light-years away in the constellation Microscopium. Because the planet is too distant to photograph directly, scientists studied it by tracking small changes in starlight as the planet passed in front of its star.
Scientists observed different conditions across the planet
Using JWST, researchers examined both sides of the planet during the transit. The leading edge represented morning conditions as atmospheric gases moved from the cooler nightside into the hotter dayside. The trailing edge reflected evening conditions as air shifted back toward darkness.
The difference between the two sides was striking. Scientists found thick clouds made of magnesium silicate — a rock-forming mineral — covering the morning side of the planet. The evening side, however, appeared mostly clear.
Astronomers using the James Webb Space Telescope discovered massive “rock clouds” on a distant giant planet nearly 700 light-years from Earth.
Scientists found clouds made of vaporized minerals forming in the planet’s cooler morning atmosphere. pic.twitter.com/xKbRE14RiI
— Tom Marvolo Riddle (@tom_riddle2025) May 26, 2026
Researchers proposed two possible explanations. Strong winds may push clouds high into the atmosphere on the cooler side before forcing them deeper into the hotter regions, making them difficult to detect.
Another theory suggests the clouds form on the nightside and quickly vaporize after moving into the scorching dayside, where temperatures rise above 1,000 degrees Celsius (1,832 degrees Fahrenheit).
“It was a huge surprise,” said David Sing of Johns Hopkins University. “What we saw was a real dichotomy between the weather on both sides of the planet, and huge differences in cloud coverage.”
Clearer skies revealed new chemical details
The cloud-free evening atmosphere also allowed researchers to examine the planet’s chemistry in greater detail. Earlier observations suggested WASP-94A b contained hundreds of times more oxygen and carbon than Jupiter, a result that challenged existing planet formation theories.
The new study found the planet contains only about five times more oxygen and carbon than Jupiter, making it far more similar to the giant planet in Earth’s solar system than previously believed.
Researchers also identified similar cloud cycles on two other hot Jupiters, WASP-39 b and WASP-17 b. The findings, published in Science, suggest dynamic cloud patterns may be common on these extreme worlds.
See all the latest news from Greece and the world at Greekreporter.com. Contact our newsroom to report an update or send your story, photos and videos. Follow GR on Google News and subscribe here to our daily email!
