Earth's moon is much older than we thought, according to new evidence

The Moon, Earth’s eternal companion, continues to captivate scientists. Despite decades of research and lunar missions, one fundamental question remains unresolved: how old is the Moon?

Current estimates suggest the Moon formed around 4.35 billion years ago, but some evidence hints at an older age that is closer to 4.51 billion years.

This discrepancy has fueled debates and inspired new research, including a recent study proposing that the Moon underwent a “volcanic facelift” billions of years ago.

Mystery of the Moon’s age

Lunar rock samples brought back by missions like Apollo have provided crucial insights. These samples indicate that the Moon formed about 200 million years after the solar system’s formation.

However, this timeline seems inconsistent with the chaotic early days of the solar system, during which debris coalesced into planets.

By the time the Moon supposedly formed, most debris had already merged into larger celestial bodies, making a late-forming Moon improbable.

Adding to the mystery, zircon minerals on the Moon suggest an age of up to 4.51 billion years. This mismatch between lunar rock ages and thermal models has puzzled researchers for years.

Now, scientists may have an explanation: a massive remelting event caused by tidal forces could have “reset” the Moon’s geological clock.

The role of tidal heating

In a paper published in the journal Nature, a team led by Professor Francis Nimmo from UC Santa Cruz explored how tidal forces may have reshaped the Moon’s geological history.

“We predict that there shouldn’t be any lunar rocks that are older than 4.35 billion years because they should have experienced the same resetting,” said Nimmo.

Tidal heating occurs when gravitational forces create internal friction within a celestial body, which generates heat. In the Moon’s early history, its proximity to Earth likely amplified these effects.

The researchers propose that around 4.35 billion years ago, the Moon’s orbit became unstable, leading to intense tidal forces. This caused widespread volcanic activity that altered the Moon’s surface and reset the age of its rocks.

Insights from Jupiter’s moon Io

The study draws parallels between the Moon’s past and the current volcanic activity on Jupiter’s moon Io, the most volcanically active body in the solar system.

Io’s elliptical orbit around Jupiter creates tidal forces that heat its interior, driving constant eruptions. Similarly, early tidal heating could have caused the Moon’s mantle to churn, thus melting and reshaping its crust.

The intense volcanic activity likely erased evidence of earlier impacts and geological features.

According to the researchers, this explains why fewer impact basins are visible on the Moon’s surface than are predicted by models for an older Moon.

New perspective on the Moon’s age

Using advanced modeling, Nimmo’s team showed that tidal heating events could have melted significant portions of the Moon’s crust, resetting the ages of most lunar rocks to around 4.35 billion years.

This process left only a few heat-resistant zircons as remnants of the Moon’s earlier history.

“The strong volcanism likely reset the Moon’s geological clock,” said Thorsten Kleine, a co-author of the study.

The findings suggest that the Moon itself formed between 4.43 and 4.51 billion years ago, but intense volcanic activity reshaped its crust around 4.35 billion years ago.

This revised timeline resolves contradictions between lunar rock samples, thermal models, and the scarcity of impact basins.

Valuable data from unexplored lunar regions

The study highlights the importance of tidal heating in shaping the Moon’s geological history.

Nimmo emphasized the need for more detailed simulations and new lunar samples to refine these findings. “We hope that our findings will spark further discussion and exploration,” he said.

Upcoming missions, like China’s Chang’e 6, are expected to provide valuable data from previously unexplored lunar regions.

These fresh samples could confirm whether a global remelting event did indeed reset the Moon’s geological clock.

The researchers also plan to investigate how tidal heating affected the Moon’s interior and surface composition.

Volcanism reset the Moon’s age

The new findings offer a unifying explanation for several longstanding lunar mysteries. They indicate that volcanism may have reset the ages of lunar rocks and also erased evidence of early impacts and altered the composition of the Moon’s mantle.

“The new results mean that all the pieces of the puzzle that previously didn’t fit together now form a coherent overall picture of the Moon’s formation,” said Kleine.

Determining the Moon’s age is crucial for understanding not just its history but also the broader story of the solar system.

If the Moon’s true age remains elusive, it raises questions about the accuracy of dating methods used for other celestial bodies.

With ongoing and future lunar missions, scientists are hopeful that the Moon will finally reveal its secrets, illuminating the early history of our cosmic neighborhood.

The study is published in the journal Nature.

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