Experimental observation of the breakdown products of SO2 by electrical discharge under the conditions relevant to the Venus cloud layer and the implication for Venus UV observation [dataset]

Sulfur-containing species are suggested as the UV absorbers in Venus’s atmosphere, which can be generated by photochemistry or electrochemistry. Here we report an electrical discharge experiment in the mixtures of SO2 with SO2 + N2, under the conditions relevant to the Venus cloud layer. We directly observed the primary breakdown products of SO2 as free radicals SO*, SI*, SII*, S2*, OI*, OII*; and the stable ending products as S8 particles and H2SO4 droplets. The observation of these products in a short-duration (minutes) experiment implies the formation of short-lived intermediate phases, including (SO)2 and polysulfur, as recognized candidates for the 2nd UV absorber. The simultaneous occurrence of SO* and S2* under all experimental conditions indicates an equal probability for two reaction paths and two groups of products. Compared with photochemistry, the high yields of electrochemistry could be responsible for the inhomogeneous distribution and temporal changes of UV features in Venus images observed by ground-based telescopes and spacecraft.