Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The lower sulfur oxides are a group of chemical compounds consisting of: SO, sulfur monoxide and its dimer S2O2; S2O; sulfur monoxides, SnO, based on cyclic Sn rings where n is 5-10; S7O2; polymeric oxides, polysulfuroxides sometimes termed PSO''s. Interest in the lower sulfur oxides has increased because of the need to understand terrestrial atmospheric sulfur pollution and the finding that the extraterrestrial atmospheres of Io, one of Jupiters moons, and Venus contain significant amounts of sulfur oxides. Some compounds reported by early workers such as the blue "sesquioxide", S2O3, formed by dissolving sulfur in liquid SO3 appears to be a mixture of polysulfate salts of the S42+ and S82+ ions.