Researchers at the Chinese Academy of Sciences conducted radioisotope dating on 108 basalt fragments returned by China’s Chang’e-6 from the lunar surface. This analysis has revealed the persistence of volcanic activity on the far side of the moon, from 4.2 to 2.8 billion years ago.
Astronomers have long established the cratering chronology of the nearside of the moon. This evidence was used to suggest volcanic activity on the far side of the moon but without sample verification. Thanks to the samples returned by the Chang’e-6 mission, researchers confirmed two new episodes of basaltic volcanism on the dark side of the moon.
Moon’s nearside and farside encompass stark differences in topography, thorium concentration, and crustal thickness. A better understanding of volcanic history could offer better insights into the hemispheric dichotomy of the Moon.
“Unraveling the volcanic history of the lunar farside is crucial for understanding the hemispheric dichotomy of the Moon,” said Prof. LI.
The lead author, Li, conducted systematic radioisotope dating on those 108 samples. Among them, 107 fragments were formed just 2.8 billion years ago. This indicated that the Chang’e-6 probe’s landing site was once the eruption zone.
Notably, no near side of the moon’s fragments dates to volcanic episodes 2.8 billion years. One of these rock samples with a high aluminum content dates back 4.2 billion years. This indicates that the volcanic activity on the far side of the lunar surface could have endured for at least 1.4 billion years.
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The isotope analysis suggests that the 4.2 billion-year-old mantle was rich in Potassium (K), rare earth elements (REE), and phosphorous (P). KREEP is an acronym for this. However, the 2.6 billion years old samples emerged KREEP-poor.
This close alignment between the 2.8 Ga basalt rock and crater-counting calculations indicates that the nearside observations are applicable to the farside as well.
“The radioisotope ages of the Chang’e-6 basalts provide an essential calibration point for refining lunar crater-counting chronology, thus enhancing its accuracy,” says Prof. LI.
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Journal Reference
- Zhang, Q. W., Yang, M., Li, Q., Liu, Y., Yue, Z., Zhou, Q., Chen, L., Ma, H., Yang, S., Tang, X., Zhang, G., Ren, X., & Li, X. (2024). Lunar farside volcanism 2.8 billion years ago from Chang’e-6 basalts. Nature, 1-2. DOI: 10.1038/s41586-024-08382-0
