A new study by Nature reveals that the moon may be over 100 million years older than we thought. For years, scientists believed that the moon was formed about 4.35 billion years ago after a collision with a Mars-sized object. However, new research indicates it may have formed around 4.51 billion years ago, with a major "re-melting" event happening later.

What is re-melting

As the moon moved away from Earth, the planet's gravity caused extreme heat, changing the moon's surface. Francis Nimmo, a professor at the University of California, Santa Cruz, explained that this heat likely reset the "clocks" in the moon's rocks, making it harder to determine the moon's true age. He said, "The moon rocks didn’t show when the moon was formed, but when this heating event happened."

Scientists were not sure about the moon's age for a long time. The samples brought back by the Apollo missions argue that the moon was younger, but some researchers questioned this idea. They argued that, 4.35 billion years ago, the solar system probably didn’t have the large objects needed for the collision that is believed to have created the moon.

The study also revealed some other findings including minerals like zircon, found in Apollo samples.These minerals were once thought to have formed during the moon's creation, but their age (4.5 billion years) has confused researchers.Nimmo's team explains this by a process called "tidal heating," where Earth's gravity pulls on the moon, stretching and squeezing its orbit, causing it to heat up significantly.

Other factors

Other than this, tidal heating, like the kind observed on Jupiter's moon Io, also affects the Moon, causing it to heat up and alter its surface. This heating process, which occurred as the Moon moved away from Earth, complicates the determination of the Moon's true age. Upcoming lunar missions, such as China's Chang'e 6 and NASA's Artemis program, could provide more information. A scientist, Carsten Munker, praised the new research for helping reconcile different theories about the Moon's age.

Munker pointed out that this study was written by researchers who once believed the Moon was younger, but now they agree on an older age. He emphasized that refining the timeline of these early solar system events is essential for understanding planetary formation.

Although the difference between 4.35 billion and 4.51 billion years may seem small, it is crucial for understanding the chaotic early days of the solar system. Munker explained, "The solar system evolved rapidly. Within tens of millions of years, the celestial bodies we know today took shape." He added that pinpointing these early events is key to understanding the formation of the Earth-Moon system and our cosmic neighborhood.