Identification of OSSO as a near-UV absorber in the Venusian atmosphere

The planet Venus exhibits atmospheric absorption in the 320-400 nm wavelength range produced by unknown chemistry. We investigate electronic transitions in molecules that may exist in the atmosphere of Venus. We identify two different S₂O₂ isomers, cis-OSSO and trans-OSSO, which are formed in significant amounts and are removed predominantly by near-UV photolysis. We estimate the rate of photolysis of cis- and trans-OSSO in the Venusian atmosphere and find that they are good candidates to explain the enigmatic 320-400 nm near-UV absorption. Between 58 and 70 km, the calculated OSSO concentrations are similar to those of sulfur monoxide (SO), generally thought to be the second most abundant sulfur oxide on Venus.