How Old Is The Moon? 100 Million Years Younger Than Previously Thought, Says Researcher
The moon is 100 million years younger than the leading theory says it is, planetary scientist Richard Carlson announced yesterday at a discussion of the Royal Society. The current leading theory dates the moon's creation to 4.56 billion years ago, when an unknown planet slammed into Earth, sending into space debris that formed the moon. Carlson says that this event -- the "giant impact," as it's known -- actually happened between 4.4 billion and 4.45 billion years ago. (Whatever the case, the moon looks pretty good for its age, so be sure to mention that next time you see it.)
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New and improved technology for dating lunar rocks points to evidence of a younger moon, Carlson told the Society. Earlier technology "couldn't distinguish between 4.45 and 4.55 billion years," Carlson said, but with a smaller margin of error nowadays, "everything we are seeing suggests the 4.4 billion number."
Carlson based his number on radioactive dating analysis of lunar rocks from the Apollo missions, and by analyzing zircon samples from Western Australia. Zircon is a durable mineral which offers geological clues into early Earth history. Carlson said that the Australian zircon shows evidence of a "major differentiation event" that happened around the same time as the giant impact. The zircon on Earth, Carlson believes, is the result of Earth and the unknown planet colliding.
"There are several important implications of this late moon formation that have not yet been worked out," said Carlson. "For example, if the Earth was already differentiated prior to the giant impact, would the impact have blown off the primordial atmosphere that formed from this earlier epoch of Earth history?" In other words, if the Earth was already formed before the giant impact, Carlson wonders whether the event would have destroyed Earth's first atmosphere.
The discussion, titled "Origins of the moon," took place yesterday at the Royal Society's meeting in London. The conference continues with "Origins of the Moon -- Challenges and Prospects," scheduled for both today and tomorrow.
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