Meteorite impacts played a fundamental role in the evolution of planetary surfaces in the early Solar System. The present record of the early bombardment history of the Earth and terrestrial planets derives largely from studies of lunar rocks and cratering. Studies to date by the principal investigator of distinctive spherule layers in rocks of the Barberton Greenstone Belt provide substantial evidence that they are parts of distal ejecta and condensate blankets produced by giant meteorite impacts on the Earth 3.2 to 3.5 billion years ago. These deposits provide a direct source of information on impact mechanics, the processes by which impact debris is generated, dispersed and accumulates and the latest stages of terrestrial and planetary accretion. Comparison of the thickness of these Early Archean distal debris blankets, commonly 30 to 50 cm of virtually pure spherules, with terminal Cretaceous boundary spherule and clay layers suggests that the Archean impacts were of enormous size and must have had profound effects on early terrestrial depositional and biological systems. The objective of the proposed research program is to evaluate through both field and laboratory studies the nature of these effects.
