Letters indicate the areas examined most extensively.
Analyzing lunar meteorites, researchers have found new evidence that a swarm of debris bombarded the moon some 3.9 billion years ago. That's about the same time that life may have formed on Earth. If our planet suffered a similarly catastrophic bombardment, as scientists claim, it could have dramatically affected the evolution of life here. Calif. Indications that the moon underwent a heavy bombardment date to the early 1970s. That's when researchers analyzed age-revealing isotopes in moon rocks collected by spacecraft.