Scientists at the University of Manchester have dated the South Pole-Aitken basin on the Moon to approximately 4.32 to 4.33 billion years ago.
The Moon is covered in impact craters from the continuous bombardment by asteroids and comets over billions of years. The South Pole-Aitken basin (SPA) is known as the largest and oldest impact site on the Moon, spanning nearly 2,000 km on the far side of the Moon.
Elevation data showing the Aitken-South Pole basin on the Moon, the largest and oldest impact basin on the Moon, depicted in blue and purple. (Photo: NASA/GSFC/University of Arizona).
Researchers from the University of Manchester analyzed the Northwest Africa 2995 lunar meteorite, discovered in Algeria in 2005. This meteorite contains uranium and lead that date back to this period. The study was published in the journal Nature Astronomy on October 16.
The proposed age of the SPA basin is about 120 million years older than previously expected. Dr. Joshua Snape, a researcher at the University of Manchester, stated: “For decades, it has been agreed that the most intense bombardment period peaked around 4.2-3.8 billion years ago. However, dating the South Pole-Aitken basin 120 million years earlier undermines this argument. This suggests a more gradual impact process over a longer period.”
This discovery also has implications for the early history of Earth. According to Dr. Romain Tartese, a senior lecturer at the University of Manchester, Earth and the Moon may have experienced similar impacts in their early history, although rock records from Earth have been lost. We can use what we have learned about the Moon to provide clues about conditions on Earth during that same time frame.
While dating the Northwest Africa 2995 meteorite has provided a good indication of the age of the SPA basin, the research team will need to confirm this data through sampling missions from within the crater.
