The largest collision on the Moon was more than 4 billion years ago

The Moon is full of impact craters caused by constant bombardment by asteroids and comets over billions of years. The South Pole-Aitken (SPA) basin is the largest and oldest known impact site on the Moon, stretching nearly 2,000 km on the far side of the Moon.

Scientists at the University of Manchester, analyzed the lunar meteorite Northwest Africa 2995, found in Algeria in 2005. The meteorite contains uranium and lead dating from this period. The research was published in the journal Nature Astronomy on October 16.

The proposed age of the SPA basin is about 120 million years larger than expected. Dr Joshua Snape, research fellow at the University of Manchester, said: “For decades it has been agreed that the period of heaviest bombardment was concentrated around 4.2-3.8 billion years ago. However, dating the South Pole-Aitken basin earlier than 120 million years weakens this argument, suggesting a more gradual collision process over a longer period of time.”

This discovery is also related to the early history of the Earth. According to Dr Romain Tartese, senior lecturer at the University of Manchester, the Earth and Moon may have experienced similar impacts in their early history, but the rock record from Earth has been lost. We can use what we learn about the Moon to provide clues about conditions on Earth during the same time period.”

Although dating from the Northwest Africa 2995 meteorite has provided a good indication of the age of the SPA basin, the team will have to confirm this data with a mission to sample from inside the crater.