Meteorite Impacts are Cool

Ever since Luis Alvarez got famous for proposing that the impact of an asteroid wiped out the dinosaurs, a merry band of geologists has been searching the world for impact craters that would explain every other mass extinction and rapid climate change. A few years ago we got the theory that a meteorite impact in the Great Lakes area caused the Younger Dryas cold snap at the end of the last Ice Age. Now another geologist says that a meteorite impact off Australia caused the cold period of AD 536 to 545. So many impacts have been proposed that astrophysicists are starting to wonder where all these rocks could have come from:

Members of an informal association called the Holocene Impact Working Group are finding evidence for more impact events than astronomers calculate should be possible. [They] argue that several climate events during the Holocene epoch—11,500 years ago to the present—were actually triggered by impacts, and therefore such large impacts are more common than currently believed.

Physicist Mark Boslough and other experts, meanwhile, have been cataloging asteroids and other bodies that cross Earth's orbit and calculating how frequently space rocks should strike the planet.

"We have a pretty good idea about how many there are and what the frequency of impact should be, and the abundances based on [the working group's claimed crater count] are orders of magnitude greater than what astronomers observe," Boslough said.

"It's pretty hard to imagine where these things could be coming from so that astronomers wouldn't see them."