¹Joanna V. Egan, ^1,2Wuhu Feng, ¹Alexander D. James, ³James Manners, ^1,4Daniel R. Marsh, ⁵Sébastien Lebonnois, ⁶Franck Lefèvre, ⁷Aurélien Stolzenbach, ¹John M. C. Plane
Journal of Geophysical Research: Planets, 131, e2025JE009634 Open Access Link to Article [DOI: 10.1029/2025JE009634]
¹School of Chemistry, University of Leeds, Leeds, UK
²NCAS, University of Leeds, Leeds, UK
³Met Office, Exeter, UK
⁴School of Physics and Astronomy, University of Leeds, Leeds, UK
⁵Laboratoire de Météorologie Dynamique, Sorbonne Université, ENS, PSL Research University, École Polytechnique, Institut Polytechnique de Paris, CNRS, Paris, France
⁶LATMOS, Sorbonne Université, UVSQ Paris-Saclay, CNRS, Paris, France
⁷Instituto de Astrofisica de Andalucia (IAA/CSIC), Granada, Spain
Published by arrangement with John Wiley & Sons

Near-ultraviolet imaging of the planet Venus reveals inhomogeneous absorption features in the otherwise bright clouds. This absorption has been studied for nearly 100 years, but identification of the near-UV absorber remains one of the largest open questions in Venusian research. Based on a multiple scattering radiative transfer model, the observed absorption between 300 and 600 nm can be produced by 1.0–1.2 wt% ferric chloride (FeCl₃) in the mode 1 (∼0.2 μm radius) sulfuric acid cloud droplets—less than the in-cloud iron mass loading measured during the Venera-12 mission. We present a novel chemical network within a global chemistry-climate model, which provides the required source of FeCl₃ in the upper cloud region from the reaction of Fe-containing molecules, produced by the ablation of cosmic dust particles, with atmospheric HCl. A residence lifetime of ∼3,000 years is required to provide sufficient optical absorption from a purely meteoric source of FeCl₃.