Found on the Moon: Candidate for Oldest Known Earth Rock

Explanation: Was the oldest known rock on Earth found on the Moon? Quite possibly. The story opens with the Apollo 14 lunar mission. Lunar sample 14321 , a large rock found in Cone crater by astronaut Alan Shepard , when analyzed back on Earth, was found to have a fragment that was a much better match to Earth rocks than other Moon rocks. Even more surprising, that rock section has recently been dated back 4 billion years, making it older , to within measurement uncertainty, than any rock ever found on Earth . A leading hypothesis now holds that an ancient comet or asteroid impact launched Earth rocks into the Solar System, some of which fell back to the Moon , became mixed with heated lunar soil and other rocks, cooled, and re-fragmented. The video features an internal X-ray scan of 14321 showing multiple sections with markedly different chemistries. Moon rocks will continue to be studied to learn a more complete history of the Moon , the Earth, and the early Solar System . Friday marks the 50th Anniversary of the Apollo 14 landing on the Moon .