Venus is shrouded in a veil of mystery. The yellowish “lower haze” at the bottom of its atmosphere was discovered by the Venera and Pioneer Venus probes in the 1970s. These spacecraft were some of the first to successfully send images of the planet back to Earth, but the haze they saw went unexplained for decades. Now the mystery Venus was keeping has been unveiled.

What nobody knew then was that the haze is an accumulation of particles from meteorites. “Shooting stars” that burn up in the atmosphere leave behind cosmic dust particles, and after sulfuric acid interacts with these particles, it leaves behind a haze. Planetary scientist Hiroki Karyu and his research team at Tohoku University in Sendai City, Japan, finally figured out how the haze formed using a microphysical model. This type of model involves microphysics—the micro-scale processes that create clouds and precipitation on Earth and other bodies.

“The continuous influx of cosmic dust is sufficient to sustain this lower haze layer with the particle size distribution observed by the entry probes,” Karyu said in a study published in Nature Astronomy. “These haze particles of cosmic origin act as efficient condensation nuclei, promoting cloud formation in the main cloud deck even far from their initial source.”