Geochemical evidence from high-sulfur impact glass spherules at the Cretaceous/Tertiary (K/T) boundary indicates that a bolide impact occurred on evaporite sediment terrane, resulting in major emission to the atmosphere. PIs will study the consequences of bolide impact on such terrane, the resulting degassing of sulfurous gases to the atmosphere, formation of sulfuric acid aerosol, and effects on the atmosphere and land. Sulfuric acid aerosol and possibly acid rain may have been key factors in the global extinction at the K/T boundary. The severity of the extinctions may thus be largely a function of the unusual geology of the target terrane. During the first year PIs will determine experimentally the processes of degassing of anhydrite and gypsum sediments and the speciation of sulfur gases emitted. In the second year PIs will model the environmental effects of an impact-induced sulfuric acid aerosol. These effects may include: (a) alkalinity crisis due to the fallout of CaO derived from dissociation of anhydrite, (b) global cooling due to stratospheric sulfate aerosol, and (c) acid rain from fallout of sulfate aerosol.
