Journal Article

Is OSSO a Significant Contributor to the Unknown UV Absorber in Venus' Atmosphere?

Manners, James, Lefèvre, Franck, Stolzenbach, Aurélien, Plane, John M. C, Marsh, Daniel R, Lebonnois, Sébastien, Egan, Joanna V, Feng, Wuhu, James, Alexander D

2025

Overview

It has been proposed that two isomers of the SO dimer (cis‐ and trans‐OSSO) are candidates for the unknown UV absorber in Venus' atmosphere because they have a good spectral match with the absorber, despite the low concentrations predicted by 1D photochemical models. Here OSSO chemistry (production from SO and loss by photolysis, thermal decomposition, and reaction with O and Cl) has been included in the photochemistry scheme of a 3D planetary climate model (PCM‐Venus) along with sulfur injection due to meteoric ablation. 1D multiple scattering radiative transfer modeling is then used to predict the resulting top‐of‐the‐atmosphere reflectance produced by OSSO. The modeled OSSO concentrations are shown to be ∼3 orders of magnitude too low to explain the observed absorbance levels, and the predicted ratio of the OSSO isomers provides an unsatisfactory match to the spectral shape of the unknown absorber.

• Publisher: John Wiley & Sons, Inc
• Subject: Ablation / Absorbers / Absorption / Atmospheric chemistry / Climate models / Decomposition reactions / Dimers / Isomers / Kinetics / Low concentrations / MESSENGER Spacecraft / Modelling / Multiple scattering / Photochemical models / Photochemicals / Photochemistry / Photolysis / Planetary climates / Radiative transfer / Reflectance / Spacecraft / Specialty products / Sulfur / Sulphur / Thermal decomposition / Thermal degradation / Ultraviolet radiation / Venus / Venus atmosphere / Wavelength