The moon, formed when a rock the size of Mars hit the Earth, was thought to be 4.3 billion years old. It's actually older, say scientists at University of California, Los Angeles, who studied moon rocks retrieved by U.S. astronauts. It's at least 4.51 billion years old, they say, which explains how the Earth could recover from the collision and become hospitable to life when it did. Kevin Enochs reports.
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