The massive wave of extinctions on Earth 250 million years ago appears to have been triggered by an impact from space, according to an analysis of rocks from Japan and China.
The die-offs at the end of the Permian period exterminated almost 95 percent of the species in the ancient oceans, as well as many land animals, and set the stage for the rise of the dinosaurs. Scientists have proposed varying causes for the widespread extinctions, including changes in ocean chemistry and widespread volcanic activity (SN: 2/1/97, p. 74). Although recent studies hadn't identified a specific cause, they suggested the deaths occurred suddenly on the geologic time scale--possibly in as little as 8,000 years (SN: 7/15/00, p. 39).
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