Venusian clouds may contain a highly efficient light absorber

An international research team has established new quantitative constraints on the mysterious material responsible for dark ultraviolet markings in Venus’s upper cloud deck. While Venus appears pale yellow in visible light, astronomers have observed high-contrast ultraviolet features that track the planet’s four-day superrotation since the 1920s.

Using a radiative-transfer model, researchers estimated the absorption coefficient required for the liquid inside Venusian cloud droplets to reproduce observed ultraviolet and blue reflectance. The study, published in Astrobiology, accounts for the fact that cloud particles scatter sunlight efficiently, which can mask the true absorption properties of the bulk liquid.

Lead author Dr. Jan Spacek of the Foundation for Applied Molecular Evolution noted that the model simulates what would happen if the cloud material were collected into a laboratory spectrometer. The findings suggest the unknown absorber must either possess remarkable light-absorption efficiency or exist in unusually high concentrations within the sulfuric acid clouds.