Magma ocean hint revealed by Chang'e 6

Recent research by Chinese scientists based on samples collected from the moon's far side has supported a major hypothesis about lunar history, said the China National Space Administration.

Organized by the CNSA, a group of researchers led by the Institute of Geology at the Chinese Academy of Geological Sciences used cutting-edge devices to analyze lunar dust retrieved by China's Chang'e 6 mission from the "dark side" of the moon.

Their study has revealed that basaltic samples from the moon's far side share similar compositions with those from the near side, with the primary basalt formation age determined to be approximately 2.82 billion years.

These findings validate the lunar magma ocean hypothesis, which states that the moon experienced global-scale melting shortly after its formation, creating a vast magma ocean. As the molten material cooled, lighter minerals rose to form the crust, while denser minerals sank to form the mantle. Residual melt enriched in incompatible elements, known as the KREEP layer, formed between the crust and mantle.

During their research, scientists confirmed the presence of the KREEP layer in the far side samples, suggesting that the magma ocean once spanned the entire moon. However, distinct evolutionary paths of lead isotopes in basalts from the far and near sides indicate regional differences in the mantle's post-crystallization development.

The research further highlights that large-scale impact events, particularly the collision that formed the South Pole-Aitken Basin, might have altered the physical and chemical properties of the lunar mantle.

The CNSA said that the research findings, published in the prestigious academic journal Science on Thursday, have provided critical evidence supporting the magma ocean hypothesis and shed light on the moon's early evolution.

The administration also emphasized its commitment to advancing lunar sample research and sharing scientific outcomes with the global science community.

The Chang'e 6 robotic mission, representing the world's first attempt to bring back samples from the far side of the moon, was launched on May 3 from Wenchang Space Launch Center in Hainan province.

After a series of complex maneuvers, the lander of the Chang'e 6 probe touched down at the South Pole-Aitken Basin on the lunar far side and then began to collect surface and underground samples.

The landing marked the second time a spacecraft ever arrived on the lunar far side. The vast region had never been reached by any spacecraft until January 2019, when the Chang'e 4 probe landed in the South Pole-Aitken Basin. Chang'e 4 surveyed areas surrounding its landing site, but did not collect samples.

The lander worked on the far side, using a mechanical arm and a drill to collect surface and underground materials.

The Chang'e 6 mission was successfully concluded on June 25 and a total of 1,935.3 grams of samples from the far side were retrieved.

The samples have unique scientific value and will further expand our knowledge about the moon's history, and help to gear up the exploration and exploitation of lunar resources, the CNSA said.