Lunar farside volcanism 2.8 billion years ago from Chang'e-6 basalts.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39547260.
- Also identified by DOI 10.1038/s41586-024-08382-0 and PMC identifier 12240805.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Unravelling the volcanic history of the enigmatic lunar farside is essential for understanding the hemispheric dichotomy of the Moon<sup>1-3</sup>. Cratering chronology established for the lunar nearside has been used to suggest long-lived volcanism on the farside of the Moon<sup>3,4</sup> but without sample verification. We describe two episodes of basaltic volcanism identified by Pb-Pb dating of basalt fragments returned by the Chang'e-6 mission. One high-Al basalt fragment, dated at 4,203 ± 4 million years ago (Ma), has a source <sup>238</sup>U/<sup>204</sup>Pb ratio (µ value) of approximately 1,620, implying a KREEP-rich (K, rare earth elements and P) source for this oldest-known example of basaltic volcanism among returned samples. The main volcanic episode of the Chang'e-6 basalt documents a surprisingly young eruption age of 2,807 ± 3 Ma, which has not been observed on the nearside of the Moon. The initial Pb isotope compositions of these younger basalts indicate a derivation from a source with a µ value of approximately 360, indicating a KREEP-poor mantle source. Mare volcanism on the lunar farside thus persisted for over 1.4 billion years, even if the source was depleted in heat-producing elements. The consistency between the 2.8-billion-year basalt age and the crater-counting age indicates that the cratering chronology model established for the lunar nearside is also applicable to the farside of the Moon.