Scientists at this week's Lunar and Planetary Science Conference propose that
a long-lost fifth terrestrial planet could have induced a period of
bombardment in the early solar system.
by Vanessa Thomas
About 3.9 billion years ago — when our solar system was still very young —
a torrent of debris rained down on Earth's moon. At least that's the story
pieces of the moon (lunar meteorites and samples returned by Apollo and
Russian Luna missions) have been telling planetary scientists for decades.
