The English word ‘cloud’ stems from the Old English clūd, meaning ‘boulder’. It is therefore fitting that the clouds on distant exoplanet WASP-107b are made of particles of silicate – minerals that are often the main constituents of sand. It is thought that the sand on WASP-107b behaves in a way reminiscent of Earth’s own water cycle: particles of silicate form clouds in the upper atmosphere. These particles then rain back down into the hotter layers of the planet’s atmosphere below, where they evaporate. In its gaseous phase, the silicate then rises and condenses back into the solid particles of cloud. This process then repeats in cycles, rather like the water cycle on Earth – but with sand!
NASA’s James Webb Space Telescope was used to carry out this research. It is the first time the chemical composition of another planet’s clouds has been detected, and its findings provide a unique insight into both the differences and similarities that can exist on planets other than our own.
You can read more about these clouds of sand in this NPR article.
Image: What would clouds of sand look like? Nobody knows, but probably not like the above since it’s an upside-down photo of the Sahara Desert. Image © Pierre André CC BY-SA 4.0.