Late heavy bombardment (LHB) of extraterrestrial objects supplied carbon with metals to the prebiotic Earth. The early oceans were the major target of these impacts, followed by interactions among the atmosphere, oceanic water, and meteorite constituent materials under high-temperature and high-pressure conditions. Post-impact reactions of these hypervelocity impacts have the potential to produce reduced volatiles and organic compounds, including amino acids. Therefore, understanding the reactions in post-impact plumes is of great importance for the investigation of prebiotic organic compounds. The composition of post-impact plumes has been investigated with thermochemical calculations. However, experimental evidence is still needed to understand the reactions in dynamic systems of post-impact plumes. The present study investigates the effects of reaction temperature and availability of water on products from iron, nickel, graphite, nitrogen, and water in a dynamic gas flow system to investigate reactions in post-impact plumes. Results of this study indicate the formation of CO, H-2, NH3, and HCN by hypervelocity oceanic impacts of iron-rich extraterrestrial objects. The formation of methane was limited in the present experiments, suggesting that the quenching rate is an influential factor for methane formation in post-impact plumes. Availability of water vapor in the plume was also an influential factor for the formation of reduced volatiles that controlled the CO formation rate from graphite. These results provide experimental evidence for the formation of reduced volatiles in post-impact plumes, which influenced the formation of prebiotic organic compounds. (c) 2013 Elsevier Inc. All rights reserved.
