An early cosmic wallop for life on Earth?

Life on Earth either started with a bang or it suffered an unusually rocky childhood, a new study suggests.

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.

"This makes it more real that there could have been substantial editing of the biosphere and organisms...3.9 billion years ago," comments astrobiologist David J. Des Marais of NASA's Ames Research Center at Moffett Field, Calif.