How old is the moon?

The moon may be more than 100 million years older than some scientists previously thought, according to a new study.

The research, published in the journal Nature, challenges the long-held idea that the Moon formed roughly 4.35 billion years ago, after a Mars-sized object slammed into the early Earth and created our natural satellite.

This timeline is based on analyzes of lunar rock samples from NASA's Apollo missions.

But the new study suggests that the Moon formed earlier — about 4.51 billion years ago — and then experienced a dramatic "remelting" event around the time other scientists had assumed it formed first.

The melting occurred as the Moon was moving away from Earth, the authors say, when the planet's constant gravitational tugs warped it in a way that caused it to superheat.

The process changed the lunar surface and thus hid the moon's real age, according to the study.

Francis Nimmo, lead author of the study and a professor in the Department of Earth and Planetary Sciences at the University of California, Santa Cruz, said extreme warming is likely to melt the surface of the moon again.

"So the rocks don't tell us when the Moon formed, but they are telling us when a later event occurred that warmed it up," Nimmo said.

Within the scientific community, there has been disagreement about the exact age of the satellite for decades; Nimmo and his colleagues are not the first to posit an older estimate, he writes yahoonews, the Telegraph reports.

The new findings add to a growing consensus that there may be more to the Moon's history than what the Apollo samples revealed.

Planetary scientists, for example, have struggled to explain how a large collision created the moon 4.35 billion years ago, at a time when most large celestial objects were thought to have already accreted to form planets.

The timeline from Nimmo's team may also help explain why minerals on the moon—called zircon—were estimated to be roughly 4.5 billion years old.

Lunar zircon, like other minerals on the Moon, was thought to have crystallized from extreme temperatures when the Moon formed, but its much older age has long puzzled scientists.

Similar heating is thought to occur between Jupiter and its moons.

A 2020 study found that the gas giant's gravity could stretch and squeeze some of its icy moons enough to heat their interiors or even melt the rocks.

This is thought to be the case with the Jovian moon Io.

Recent and future lunar missions may provide better insights into the moon's evolutionary history, according to Nimmo.

Otherwise, although the difference between 4.35 billion years and 4.51 billion years may seem relatively small when it comes to time scales in the universe, figuring out what happened in those chaotic early days of the solar system is key to understanding how the planets came to be . /Telegraph/