late heavy bombardment
Based on the visible impact history on other worlds, computer estimates suggest that during the 200-million-year period of the late heavy bombardment, Earth suffered over 22,000 impact craters larger than 20 km, about 40 impact basins larger than 1,000 km, and several continent-sized, 5,000-km basins. There would have been an impact that affected global conditions every century or so. Yet amid this cosmic blitzkrieg, life managed to get started on our world. In fact, it may be that impact-generated hydrothermal systems made excellent incubators for prebiotic chemistry and the early evolution of life, an idea that is consistent with other evidence that shows life may have originated in hot water systems around or slightly before 3.85 billion years ago.
Related entries• life, origin
• Earth, early history
Related categories• ORIGIN AND EVOLUTION OF LIFE
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