The moon is 40 million years OLDER than scientists thought, study claims

Despite being Earth’s closest celestial companion, there has long been doubt about how and when the moon formed.

Now there are indications that the moon is 40 million years older than scientists previously thought.

The most widely accepted explanation for the moon’s existence is the “giant impact theory,” which suggests that a planet the size of Mars smashed into Earth.

It is believed that the debris released from the collision recombined to form the moon.

Now, moon crystals brought back from the last Apollo mission in 1972 have been used to estimate the moon’s exact age.

The crystals must have formed after the giant impact that created the moon, researchers say, because that high-energy collision melted the rock that eventually became the moon’s surface, creating a magma ocean that would also have melted any crystals .

Assuming that the zircon crystals came later, scientists used radiometric dating, which looks at the rate of decay of the crystal atoms, to determine their age.

Their results push back the moon’s age by 40 million years to at least 4.46 billion years old.

Professor Philipp Heck, senior author of the study, from the University of Chicago, explained why it is important to know the age of the moon, saying: ‘The moon is an important partner in our planetary system – it stabilizes the rotation axis of the earth, 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 be different.

‘It’s a part of our natural system that we want to understand better, and our research provides a small piece of the puzzle in that whole picture.’

More than four billion years ago, when the moon is thought to have formed, our solar system was still young and the Earth was still growing.

To determine the age of the moon, scientists used a sample of lunar dust brought back by Apollo 17 astronauts from the last manned mission to the moon in 1972.

The dust contained small crystals that formed billions of years ago.

Professor Heck said: ‘These crystals are the oldest known solids to have formed after the giant impact.

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

An earlier study had suggested the age of the crystals, but a ‘nanoscale’ look at the samples was needed to fully understand them.

Scientists used a method called atomic probe tomography, which works like a ‘pot grinder’ to reduce the lunar sample to a fine point, before using ultraviolet lasers to vaporize atoms from the surface of that point.

The atoms traveled through a mass spectrometer, with their speed indicating how heavy they were, and therefore their composition.

An atom-by-atom analysis showed how many of the atoms in the zircon crystals had undergone radioactive decay, which can turn uranium into lead, for example.

By looking at the ratio of different uranium and lead atoms, called isotopes, scientists can tell how old a sample is.

The proportion of lead isotopes found indicates that the sample was about 4.46 billion years old, so the moon must be at least that old.

Dr. Jennika Greer, lead author of the study, published in the journal Geochemical Perspectives Letters, who conducted the study when she was at the University of Chicago but is now at the University of Glasgow, said: ‘It’s amazing to be able to have evidence that the stone you are holding is the oldest piece of the moon we have found so far.

‘It is an anchor point for so many questions about the Earth. If you know how old something is, you can better understand what happened to it in history.’