Mass independent oxygen isotopic composition of atmospheric sulfate: Origin and implications for the present and past atmosphere of earth and mars

It is reported that atmospheric (aerosol and rainwater! sulfate possesses a mass independent isotopic composition, with excess O-17. Laboratory experi ments indicate that the oxidants, H2O2 and O-3, are the source of anomalous O-17 enrichments in atmospheric sulfate via aqueous phase S(IV) oxidation. The discovery of the oxygen anomaly in atmospheric sulfate, with definitio n of its origin, provides a new way to investigate atmospheric and general planetary processes. The observations provide new insight into atmospheric chemistry with application in studies of the evolution of the atmosphere an d surface-atmosphere interactions, both on Earth and Mars.