Lunar dust suggests moon’s true age

The moon is 40 million years older than we thought, according to a new analysis of lunar samples collected by Apollo astronauts a half-century ago.

Latest research suggests the moon could have formed as long as 4.51 billion years ago.

The moon is 40 million years older than we thought, according to a new analysis of lunar samples collected by Apollo astronauts a half-century ago.

It is thought to have formed when a Mars-sized object, known as Theia, crashed into the Earth.

The debris from the collision became our planet’s only natural satellite, but the precise timing of the impact has been something of a mystery.

This research looked at moon dust brought back by the Apollo 17 mission in 1972, the last time ­humans set foot on the surface.

The results, published in the journal Geochemical Perspectives Letters, suggest it must be at least 4.46 billion years old and that it could have formed as long as 4.51 billion years ago.

A previous analysis of moon dust, published in 2019, had suggested a maximum age of 4.42 billion years.

“These crystals are the oldest known solids that formed after the giant impact,” said Philipp Heck of the Field Museum in Chicago, senior author of the study. “And because we know how old these crystals are, they serve as an anchor for the lunar chronology.”

The energy of the impact with Theia melted the rock that eventually became the moon’s surface. “When the surface was molten like that, zircon crystals couldn’t form and survive. So any crystals on the moon’s surface must have formed after this lunar magma ocean cooled,” Professor Heck said.

The study marks the first use of a technique called atom probe tomography to nail down the crystals’ age.

The research showed how many of the atoms inside the crystals had undergone radioactive decay, which happens when an atom has an unstable configuration of protons and neutrons in its nucleus. It sheds some of these protons and neutrons and transforms into a different element. For instance, uranium decays into lead. Scientists have established how long this process takes, and by looking at the proportion of different uranium and lead atoms (isotopes) present in a sample, they can tell how old it is.

The proportion of lead isotopes researchers found indicated the sample was about 4.46 billion years old. Therefore, the moon has to be at least that old.

It’s important to know when the moon formed, Professor Heck said, “(because) 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 Times