New study challenges traditional Moon formation theory

A new analysis by scientists suggests that the Moon's formation may have occurred much closer to Earth's birth than previously thought. Led by researchers from the U.S., France, and Germany, the study proposes that the Moon formed about 4.53 billion years ago.

According to Francis Nimmo, a geologist at the University of California, Santa Cruz, this finding could explain several mysteries, such as why the Moon has fewer large impact craters than expected and contains less metal than Earth.

The study also offers new insights into the Moon's history and Earth's evolution. Scientists believe the Moon was created by a collision between a Mars-sized body and the young Earth. Debris from this impact formed a disk around Earth, which eventually coalesced to form the Moon.

After the impact, the Moon is thought to have had a magma ocean covering its surface, which quickly cooled and solidified. However, zircon crystals collected from the Moon challenge this scenario.

Zircon crystals, which allow for precise age calculations based on their uranium and lead content, were found to be between 4.46 and 4.51 billion years old—ages inconsistent with the magma ocean theory, as zircons would not survive in such an environment.

To resolve this, Nimmo and his team propose that the Moon underwent a secondary melting event around 4.35 billion years ago, likely due to tidal heating, when the Moon had a more eccentric orbit. This suggests the Moon's surface underwent partial remelting.

These new findings place the Moon's age between 4.43 and 4.53 billion years, which is nearly the same age as Earth, suggesting the Moon has been Earth's "sky companion" for almost the entire history of life on our planet.

The study, which could help explain the Moon's craters and lower metal content compared to Earth, was published in Nature magazine.