The moon is quite a bit younger than scientists had previously believed, new research suggests.
The leading theory of how the moon formed holds that it was created when a mysterious planet — one the size of Mars or larger — slammed into Earth about 4.56 billion years ago, just after the solar system came together. But new analyses of lunar rocks suggest that the moon, which likely coalesced from the debris blasted into space by this monster impact, is actually between 4.4 billion and 4.45 billion years old.
The finding, which would make the moon 100 million years younger than previously thought, could reshape scientists’ understanding of the early Earth as well as its natural satellite, researchers said.
“There are several important implications of this late moon formation that have not yet been worked out,” Richard Carlson, of the Carnegie Institution for Science in Washington, D.C., said in a statement.
“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?” added Carlson, who is presenting the new results Monday (Sept. 23) in London at a meeting organized by the Royal Society called “Origin of the Moon.”
Scientists know the solar system’s age (4.568 billion years) quite well. And they can pin down the formation times of relatively small bodies such as asteroids precisely, too, by noting when these objects underwent extensive melting — a consequence, in part, of the heat generated by the collision and fusion of these objects’ building-block “planetesimals.”
For example, analysis of meteorites that came from the asteroid Vesta and eventually rained down on Earth reveals that the 330-mile-wide (530 kilometers) space rock is 4.565 billion years old. Vesta cooled relatively quickly and is too small to have retained enough internal heat to drive further melting or volcanism, Carlson explained.
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