Sulfur chemistry in the middle atmosphere of Venus

► We use a 1-D photochemistry-diffusion model to simulate the chemical system in the middle atmosphere of Venus. ► A sulfur source is required to explain the SO and SO 2 profiles observed by Venus Express. ► The evaporation of the aerosols composed of sulfuric acid or polysulfur above 90 km could provide the sulfur source. ► Measurements of SO 3 abundance and SO ( a 1Δ → X 3Σ -) emission at 1.7 μm may be the key to distinguish between the two models. Venus Express measurements of the vertical profiles of SO and SO 2 in the middle atmosphere of Venus provide an opportunity to revisit the sulfur chemistry above the middle cloud tops (∼58 km). A one dimensional photochemistry-diffusion model is used to simulate the behavior of the whole chemical system including oxygen-, hydrogen-, chlorine-, sulfur-, and nitrogen-bearing species. A sulfur source is required to explain the SO 2 inversion layer above 80 km. The evaporation of the aerosols composed of sulfuric acid (model A) or polysulfur (model B) above 90 km could provide the sulfur source. Measurements of SO 3 and SO ( a 1Δ → X 3Σ -) emission at 1.7 μm may be the key to distinguish between the two models.