Lunar crystals show Moon is 40 million years older than previously thought

The Moon is 40 million years older than previously thought, lunar crystals brought back by the Apollo astronauts have shown.

Scientists from the University of Glasgow and the Field Museum, in Chicago, have been studying samples collected during the last Moon landing by Nasa in 1972.

They discovered that the zircon crystals are 4.46 billion years old, meaning that the Moon must be at least that age.

Experts believe that the Moon formed when a giant object the size of Mars crashed into the early Earth, knocking off a huge chunk, which would have taken millions of years to cool before the crystals could form.

It means that the Earth and the Moon have been locked together for much longer than previously thought – from about 150 million years after the Earth formed 4.6 billion years ago.

“These crystals are the oldest known solids that formed after the giant impact,” said Prof Philipp Heck of the Field Museum and University of Chicago.

“And because we know how old these crystals are, they serve as an anchor for the lunar chronology.

“When the surface was molten, zircon crystals couldn’t form and survive. So any crystals on the Moon’s surface must have formed after this lunar magma ocean cooled.

“The Moon is an important partner in our planetary system – it stabilises the Earth’s rotational axis, it’s the reason there are 24 hours in a day, it’s the reason we have tides. Without the Moon, life on Earth would look different.”

The samples of lunar dust used in the study were brought back by Apollo 17 astronauts in the last crewed mission to the lunar surface.

Experts used a technique called atom probe tomography, which uses lasers to evaporate atoms from the surface, so they can be weighed and identified.

Once the atoms were known, the team measured how many had undergone radioactive decay.

Radioactive decay happens in a continuous fashion, so it can be used as a clock to age the samples.

“It’s amazing being able to have proof that the rock you’re holding is the oldest bit of the Moon we’ve found so far,” said Dr Jennika Greer, a research associate of the University of Glasgow.

“It’s an anchor point for so many questions about the Earth. When you know how old something is, you can better understand what has happened to it in its history.”

The study was published in the Geochemical Perspectives Letters journal.