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 S 2 O 2 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.