Is the moon 100 million years younger?

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.

However, 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.

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."

Scientists keep getting better and better estimates, however, as they refine their techniques and technology improves. And those estimates are pushing the moon's formation date farther forward in time. The moon is thought to have harbored a global ocean of molten rock shortly after its dramatic formation. Currently, the most precisely determined age for the lunar rocks that arose from that ocean is 4.360 billion years, the researchers said.

And here on Earth, scientists have found signs in several locations of a major melting event that occurred around 4.45 billion years ago. So, evidence is building that the catastrophic collision that formed the moon and reshaped Earth occurred around that time, rather than 100 million years or so before, the researchers said.

To read more about the research and findings, click here.