An Exploration of (SO)2 as a Source for Polysulfur within a simulated Venus Atmosphere with an overabundance of oxygen

Venus at ultraviolet (UV) wavelengths exhibits distinct light and dark markings [1]. The discovery of sulfur dioxide (SO2) using a ground-based high resolution spectrometer explained Venus’ albedo at wavelengths < 320 nm but not these dark markings at 320-500 nm ([2], [3], [4]). So, at least one other absorber must be important at these wavelengths. Radiative balance simulations suggest this unidentified absorber is responsible for about half of the solar energy absorbed by Venus’ atmosphere [5]. Polysulfur species (Sx) have been suggested but the pathway to how these polysulfur species are formed hasn’t been fully agreed on [6]. Pinto et al. proposed the production rate of Sx could be enhanced via production of disulfur, S2, from the photodissociation of SO dimer (SO)2 [7]. However, Francés-Monerris et al. found a much lower yield for S2 from photodissociation of (SO)2 in their ab initio simulations and proposed that S2 production could be enhanced instead via disulfur oxide (S2O) reacting with sulfur oxide (SO) [8]. The atmospheric model used by Francés-Monerris was highly simplified and did not include all important feedback processes. This present work evaluates, both the Pinto et al. and Francés-Monerris et al. pathways in a comprehensive 1-d photochemical model. This study demonstrates that elevated oxygen abundances suppress polysulfur formation in both the Pinto et al. and Francés-Monerris et al. pathways, resulting in optical depths for polysulfur that are too low to explain Venus’ “missing” UV absorber.