Martha Kehagias
While we have long known that the Moon was formed by a massive collision with Earth around 4.5 billion years ago, a new study reveals that a major event of remelting around 4.35 billion years ago has been hiding the true age of the Moon.
In this groundbreaking research, scientists discovered that the Moon’s crust underwent a significant remelting event caused by tidal forces—a phenomenon that occurs when a planet’s gravity causes stretching and compression in its orbit. This event, tied to a transition in the Moon’s orbit, may have reset the Moon’s geological clock, making it appear younger than it really is.
By analyzing lunar rocks and ancient zircons, scientists have found that the Moon’s surface was extensively reshaped by the tidal heating around 4.35 billion years ago, much later than its original formation. This remelting didn’t just affect one part of the Moon—it was a widespread process, possibly causing the entire lunar surface to undergo dramatic changes. It was like a cosmic reboot, resetting much of the Moon's geological history.
The implications of this discovery are huge. The 4.35 billion-year-old ages recorded in many of the Moon’s rocks had previously suggested that the Moon was formed later than some models predicted. But this new tidal heating model reconciles these differences, pointing to a Moon that likely formed much earlier—between 4.43 to 4.53 billion years ago.
In addition to helping clarify the Moon’s true age, this tidal heating event could explain several of the Moon’s other mysteries, such as the absence of more ancient impact basins and the unique chemical composition of its surface. It also provides new insights into how the Earth-Moon system evolved over time, giving us a clearer picture of the dynamic forces that shaped not only the Moon but our entire solar system.
This research highlights how the Moon continues to reveal its secrets. With the new understanding of tidal forces reshaping the Moon, we are one step closer to unlocking the full history of our celestial neighbor, pushing the boundaries of what we know about the early days of the Earth-Moon system. The Moon may still have many surprises in store as scientists continue to probe its ancient rocks.
Read the original study, available from Nature, here: Tidally driven remelting around 4.35 billion years ago indicates the Moon is old
