We found four alien worlds where it literally rains microscopic sand from high-altitude clouds.
arXiv · March 16, 2026 · 2603.13167
Why it matters
Using JWST data, researchers modeled the weather on these exoplanets and found that instead of water vapor, their atmospheres are filled with cluster-sized mineral particles. The study suggests that these planets have incredibly inefficient settling rates, meaning "sandy" clouds stay suspended in their skies far longer than expected.
From the abstract
The unprecedented accuracy of JWST has led to the detection of silicate clouds in exoplanet atmospheres, allowing for the first time to probe cloud formation in extreme environments. While parametrized cloud descriptions can fit these observations, the results do not fully agree with microphysical models. To bridge this gap, we developed Nimbus, a fast microphysical cloud model that can constrain cloud formation processes from observations and utilize Virga, an equilibrium condensation model bal