On Earth, it mostly rains water. But according to a new discovery published in Nature, it may rain sand on other planets.
WASP-107b is a “fluffy” planet located 211 light years away. It orbits its host star (a K-type star, larger and cooler than our own sun) in just 5.7 days. While it has a mass similar to our resident ice giant Neptune, it’s much, much larger—approximately the size of Jupiter. That’s why scientists describe WASP-107b as “fluffy.” It’s also been referred to as a “cotton candy” planet and a “super puff.”
It sounds silly, but there are advantages to a planet being fluffy. It enables scientists to peer much deeper into the atmosphere than we can for a large, much more massive planet like Jupiter. For the first time, scientists were able to analyze the clouds of an exoplanet and discovered something surprising: high-altitude clouds were composed of tiny silicate particles, better known as the primary ingredient of sand.
Scientists accomplished this thanks to MIRI, or the Mid-Infrared Instrument, on the James Webb Space Telescope (JWST). In addition to the silicate clouds, they identified water vapor and sulfur dioxide in the atmosphere.
Why are there sand clouds in WASP-107b’s upper atmosphere?
At around 1,000 degrees C, silicate particles form clouds within an atmosphere—or so scientists thought. But they were baffled by the presence of these silicate clouds in the upper atmosphere of WASP-107b, because the temperature is only about 500 degrees C. As a result, these clouds should have formed lower in the atmosphere where it’s warmer. The question is, then, how do these silicate clouds form?
The answer may be that WASP-107b has a mechanism similar to Earth’s water vapor. On our own planet, water is constantly cycling through the atmosphere. Clouds form, are affected by wind, and then precipitation falls back to the Earth as rain or snow. The water then evaporates, travels back into the atmosphere, and condenses as clouds.
Scientists think that a similar cycle may be occurring on WASP-107b, but with these silicate particles—a kind of sand vapor, instead of water vapor. The small particles must evaporate within a very hot lower atmosphere, and then travel back up through some sort of vertical updraft mechanism. They then condense into these silicate clouds, and then travel back into the lower atmosphere as some sort of sand-rain.