China's Chang'e-6 robotic spacecraft made history in June by retrieving the first surface samples from the far side of the moon, an area that perpetually faces away from Earth. The material collected is providing new insights into the moon's geological history, including the oldest evidence of lunar volcanism to date. Researchers reported on Friday that the soil returned from the Chang'e-6 landing site contains fragments of volcanic rock—basalt—dating back 4.2 billion years and 2.8 billion years.
This suggests a prolonged period of volcanic activity, lasting at least 1.4 billion years, on the far side of the moon during its early history, indicating it was more geologically active during that time.
The moon, like Earth, formed approximately 4.5 billion years ago. Volcanism occurs through the eruption of molten rock from the mantle, the layer beneath the outer crust, onto the surface. The landing site, located in the South Pole-Aitken Basin, is characterised by its thinnest crust on the moon, facilitating the search for evidence of volcanism.
The Chang'e-6 probe collected about 4-1/4 pounds (1,935 grams) of soil using a scoop and drill before returning the material to Earth, landing in Inner Mongolia.
The samples included various volcanic rock fragments, and researchers employed a method called radioisotope dating to ascertain their ages. Previous lunar basalt samples obtained from the moon's near side—during U.S. Apollo, Soviet Luna, and Chinese Chang'e-5 missions—indicated that volcanism on the near side occurred as long ago as 4.0 billion years and continued for at least two billion years.
The study also revealed that the basalt samples dating to 4.2 billion years ago differ in composition from those dating to 2.8 billion years ago, suggesting they originated from different sources of molten rock (magma) in the mantle. Additionally, the Chang'e-6 samples display compositional differences compared to previously collected lunar samples from the near side.
Currently, there is no evidence of active volcanism on the moon, unlike other locations within the solar system, such as Venus and Earth.
ALSO READ: COP29: India, developing nations push for fair climate finance
Inputs from Reuters
