Scientists say giant crater on dark side of the Moon is 4.32 billion years old

Scientists from Manchester believe they have solved the mystery of the age of a giant crater on the Moon - with analysis showing it to have been created 4.32 billion years ago.

The team of researchers investigated the formation of the massive South Pole-Aitken (SPA) basin, which is located on the far side of the Moon and stretches more than 2,000 kilometres. The Moon has been bombarded by asteroids and comets throughout time and they have left behind craters, with the larger ones known as basins.

The exact timing of the creation of the SPA was unknown until this research, which was carried out by scientists from the universities of Portsmouth and Manchester. To find out the basin’s age, they analysed a lunar meteorite known as Northwest Africa 2995, which was found in Algeria in 2005.

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The meteorite is a regolith breccia, which means it contains fragments of different rock types that were once a lunar soil and have been fused together by the heat and pressure involved in an impact event.

James Darling, professor of earth and planetary science at the University of Portsmouth, explained: “By analysing the isotopes of uranium and lead found in a range of mineral and rock fragments within the meteorite, we were able to determine the materials dated back to between 4.32 and 4.33 billion years ago. Importantly, evidence from the internal structure of minerals suggests that this is the timing of an extreme event that reset the ages of the sample.”

The proposed date, published in the journal Nature Astronomy, is about 120 million years earlier than what is believed to be the most intense period of impact bombardment on the Moon.

Dr Joshua Snape, Royal Society University Research Fellow at The University of Manchester, said: “Over many years scientists across the globe have been studying rocks collected during the Apollo, Luna, and Chang’e 5 missions, as well as lunar meteorites, and have built up a picture of when these impact events occurred. For several decades there has been general agreement that the most intense period of impact bombardment was concentrated between 4.2-3.8 billion years ago – in the first half a billion years of the Moon’s history.

“But now, constraining the age of the South-Pole Aitken basin to 120 million years earlier weakens the argument for this narrow period of impact bombardment on the Moon and instead indicates there was a more gradual process of impacts over a longer period.”

The researchers explained that they compared their results to data collected by Nasa’s Lunar Prospector mission, which orbited the Moon studying its surface composition between 1998 and 1999. They said that the comparison revealed many chemical similarities between the meteorite and the rocks within the SPA basin, confirming their link and enabling the new age estimate.

Dr Romain Tartese, senior lecturer at the University of Manchester, said: “The implications of our findings reach far beyond the Moon. We know that the Earth and the Moon likely experienced similar impacts during their early history, but rock records from the Earth have been lost.

“We can use what we have learnt about the Moon to provide us with clues about the conditions on Earth during the same period of time.”

In June this year, China’s Chang’e 6 probe was the first to land in the SPA to directly bring back samples from the Moon’s far side.