A groundbreaking study based on lunar samples collected by China’s Chang'e-6 mission has provided compelling evidence that the moon was once enveloped by a vast molten "magma ocean." Published in the latest issue of the journal Science, the research marks a significant advancement in our understanding of the moon's origin and evolution.
The Chang'e-6 mission, launched in 2024, achieved a historic milestone by conducting humanity's first-ever sampling from the far side of the moon. The mission successfully retrieved 1,935.3 grams of lunar material from the Apollo Basin within the South Pole-Aitken (SPA) Basin.
A research team from the Institute of Geology, Chinese Academy of Geological Sciences, was provided with two grams of these Chang'e-6 samples to conduct in-depth analysis. The study revealed that the composition of basalt, a type of volcanic rock, from both the far and near sides of the moon is remarkably similar. The basalt present in the Chang'e-6 samples is primarily 2.82 billion years old, supporting the lunar magma ocean model.
According to Liu Dunyi, a senior researcher at the institute, the research also suggests that the impact event that created the SPA Basin may have altered the moon's early mantle. The lunar magma ocean model, previously established based on samples from the moon's near side, proposes that the newborn moon underwent a global melting event, forming a vast magma ocean. As this ocean cooled and crystallized, less dense minerals floated to the surface to form the lunar crust, while denser minerals sank to form the mantle.
The new findings highlight that the KREEP layer, enriched with potassium, rare earth elements, and phosphorus, exists on the moon's far side as well. Che Xiaochao, an associate researcher at the institute, stated, "The similarity in basalt composition between the far and near sides indicates that a global magma ocean may have spanned the entire moon." This discovery fills a crucial gap, as prior to Chang'e-6, all lunar samples had come from the near side.
The SPA Basin, where Chang'e-6 landed, is no ordinary crater. Spanning 2,500 km in length and plunging to a depth of 13 km, it is the oldest and largest impact basin in the inner solar system, formed by a cataclysmic asteroid impact 4.3 billion years ago, according to scientists.
Interestingly, the study also reveals that the lead isotope evolution paths in basalt from the far and near sides differ, suggesting that different regions of the moon evolved uniquely after the magma ocean crystallized. Long Tao, another senior researcher on the team, explained, "The moon was once covered by a global magma ocean, but subsequent asteroid bombardments caused different evolution processes on the near and far sides."
The research team plans to further investigate the moon's early impact history. Che added, "The Chang'e-6 sampling site is in the largest and oldest impact basin in the inner solar system, so it may contain records useful for the study of early solar system impacts. We also hope to find materials from the moon's mantle."
Long Tao emphasized, "Studying the moon's impact history helps us understand Earth's own past, which has been obscured by tectonic activities."
The China National Space Administration (CNSA) reaffirmed its commitment to advancing lunar research and sharing scientific findings with the international community.
Reference(s):
Chang'e-6 samples provide evidence of "magma ocean" on early moon
cgtn.com
