Chang’e-6 sample suggests that 42.5 billion years old impact forms the lunar Antarctic-aitken basin

Scientists have long sought to determine the age of the Antarctic-Polar (SPA) basin of the lunar, the largest and oldest known impact crater on the lunar surface. Recently, a research team led by Professor Chen Yi of the Institute for Geology and Geology at the Chinese Academy of Sciences dated the formation of the basin 4.25 billion years ago by analyzing the first rock samples that returned from the SPA basin by China’s Chang E6 mission.

The findings can be found in the National Science Review.

The Spa Basin, a vast impact structure that spans the other side of the moon, is believed to have been formed during the period of intense asteroid artillery that formed much of the solar system within the first hundreds of millions of years. Despite its importance, the exact age of the spa basin remains elusive, hampering efforts to understand its role in the history of the moon and planets.

Previous estimates of basin age vary widely, highlighting the need for direct analysis of spa-derived materials. The return of the lunar sample of the Chang’e-6 mission from the Spa Basin gave scientists the opportunity to solve this mystery. The researchers focused on impact molten rocks within these samples, providing important cues for the formation of the basin.

“The Spine Impact Event produced a large sheet of impact melt,” explained Professor Chen. “To accurately determine the age of the basin, we first had to identify this melt in the Chang’e-6 sample.”

The researchers meticulously analyzed approximately 1,600 fragments from the two soil samples to identify 20 noritecrusts with texture, mineralogy and geochemical features consistent with impact origin. Using dating of lead lead-lead minerals containing zirconium in these crusts, they revealed evidence of two different shock events, 4.25 and 3.87 billion years ago.

The 4.25 billion-year old norite exhibited structural and constitutive features suggesting that it crystallized at various depths within the common impact melting sheet produced by the Spa-Forming event.

“Our geological surveys and comparative lithological analysis strongly demonstrate that the age of 42.5 billion corresponds to the formation of the spa basin,” Professor Chen said.

This study provides direct sample-based evidence that the largest impact basin of the moon was formed approximately 320 million years after the creation of the solar system. The exact age of 4.25 billion years of the spa basin serves as a key anchor point for refinement of the lunar crater chronology and reconstructing the lunar early evolutionary timeline.

These discoveries not only promoted an understanding of the history of the moon, but also shed light on the dynamic processes that shaped the early solar system.