Bolide impacts

Prinn, R. G. and Fegley, B. (1987). Bolide impacts, acid rain, and biospheric traumas at the Cretacious-Tertiary boundary. Earth Planet. Sci. Lett. 83,1-15. 

Life evolved soon after Earth s formation, befiare any continents were present, during a time when the oceans were chemically and thermally controlled by tectonic processes. Thus, it has been proposed that the life evolved in hot anaerobic submarine environments similar to present-day hydrothermal vent systems. This hypothesis is supported by the observation of structures, thought to be the remains of protocells, in rocks formed by hydrothermal processes 3.5 to 3.8 billion years ago. Thus, the first organisms on Earth were probably anaerobic hyperthermophiles. Hydrothermal vent habitats probably offered an additional benefit by providing a stable environment relatively isolated from the catastrophic effects of bolide impacts. In other words, submarine hydrothermal vents coifld have acted as refugia enabling survival of early life forms. 

Besides being desiccated and irradiated, microorganisms traveling in space will be exposed to space vacuum that can reach 10-14 pascal (a unit of pressure—100 Pa = 1 mbar).57 The result is extreme dehydration, and naked spores can survive for only days if exposed to space vacuum. Survival of spores is increased if they are associated with various chemicals such as sugars, or are embedded in salt crystals. Nicholson et al. (2000) discuss the various stresses that a microbial cell or spore would have to endure to survive interplanetary travel.58 They include the process that transports them out of Earth s atmosphere, such as volcanic eruptions and bolide impacts, long periods of transit in the cold of space, and atmospheric entry into a new planetary home. Spores have been shown to survive the shock conditions of a meteorite impact and the ultraviolet radiation and low temperature of space.59 It is clear that panspermia is possible and even probable if bacterial spores become embedded in rocks that are ejected from one planet and eventually enter the atmosphere of another. Bacterial... 

Kasting, J.F. 1990. Bolide impacts and die oxidation state of carbon in the Earth s early atmosphere. Origins Life 20 199-231. See also Schaefer, L., and Fegley Jr., B., 2007, Outgassing of ordinary chondritic material and some of its implications for the chemistry of asteroids, planets, and satellites, Icarus 186.2 462-483. 

Alvarez L. W. (1987) Mass extinctions caused by large bolide impacts. Phys. Today 40, 24-33. 

Kaiho K., Kajiwara Y., Nakano T., Miura Y., Kawahata H., Tazaki K., UeshimaM., Chen Z., and Shi G. R. (2001) End-Permian catastrophe by a bolide impact, evidence of a gigantic release of sulfur from the mantle. Geology 29, 815-818. 

Kasting J. F. (1990) Bolide impacts and the oxidation state of carbon in the Earth s early atmosphere. Origins Life Evol. Biosphere 20, 199-231. 

Atmospheric pC02 is likely to have increased as a result of equilibration between the air and Strangelove ocean, and the terrestrial wild fires triggered by the bolide impact (Wolbach et al. 1988). However, the periodic phytoplanktonic blooms would have drawn down significant amounts of C02. Consequently, it is likely that there were dramatic climatic swings during the recovery phase, until atmospheric C02 levels stabilized (Wolfe Upchurch 1986). 

Koeberl C, GUmour I, Reimold WU, Claeys P, Ivanov B (2002) End-Permian catastrophe by bolide impact Evidence of a gigantic release of sulfur from the mantle Comment. Geology 30(9) 855-856... 

Bolide impact Biologic activity Fossil fuel burning Land use activity Metamorphism Seafloor volcanism Flood basalts... 

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