Narrator: This is Science Today. By dating tiny droplets of molten rock scooped up from the moon during the 1971 Apollo 14 mission, researchers have come up with a new chronology of the Earth's history. Paul Renne, a geologist at the University of California, Berkeley says the molten rock, which resemble tiny glass beads, were the result of violent meteoroid impacts on the moon billions of years ago that created huge craters on its surface.
Renne: It's pretty clear that the really big impacts that would've been the most destructive to life on Earth or anywhere else, occurred early on.
Narrator: But Renne's group discovered evidence of another peak of cratering activity about 500 million years ago. This coincides with the "Cambrian explosion", a period in which life on Earth dramatically diversified.
Renne: So clearly, turning up the cratering rate doesn't snuff out life - if anything it seems to stimulate it, if there's a causal relationship there. It may be just coincidence, but it's certainly a striking possibility.
Narrator: For Science Today, I'm Larissa Branin. .