Toxins produced by meteorite impacts and their possible role in a biotic mass extinction

Chemical contamination of ecosystems due to the production of toxic gases by large impacts is a possible cause of biotic mass extinctions. Some globally distributed toxins are hazardous even at low concentrations. This extinction mechanism has not been studied in detail due to the lack of chemical models of the effects of an impact event. This chapter presents experimentally derived information about the chemistry of impacts and considers the possible effect of chemical contamination on the biosphere, with special reference to the Chicxulub impact and the Cretaceous-Tertiary mass extinction. The Chicxulub impact released CO, SO2, CS2, H2S, and other gases that spread from the point of the impact, dissolved in the atmosphere, and may have produced lethal concentrations over large areas. The global concentrations of many gases were probably orders of magnitude above permissible exposure levels for human beings and may have resulted in long-term mortal effects by carcinogenesis, mutagenesis, or teratogenesis. Production of toxins during a large impact may be a sufficient mechanism for some extinctions.