Lunar igneous activities, which encompass both intrusive and extrusive magmatism, offer valuable insights into the Moon’s interior and its thermal conditions. The distribution of these activities is not uniform between the nearside and farside, highlighting a global divide known as lunar dichotomy. While previous lunar samples have all been collected from the nearside (including those from Apollo, Luna, and Chang’e-5), the samples obtained from the farside’s South Pole-Aitken (SPA) basin are believed to be crucial in balancing our understanding of the Moon and addressing the lunar dichotomy puzzle.
Lunar igneous activities, which encompass both intrusive and extrusive magmatism, offer valuable insights into the Moon’s interior and its thermal conditions. The distribution of these activities is not uniform between the nearside and farside, highlighting a global divide known as lunar dichotomy. While previous lunar samples have all been collected from the nearside (including those from Apollo, Luna, and Chang’e-5), the samples obtained from the farside’s South Pole-Aitken (SPA) basin are believed to be crucial in balancing our understanding of the Moon and addressing the lunar dichotomy puzzle.
Earlier this year, the Chang’e-6 mission from China’s Lunar Exploration Program launched successfully on May 3, landed on the Moon’s surface on June 2, and returned to Earth on June 25 with a total of 1935.3 grams of lunar soil. This mission marks the world’s first sample-return operation from the lunar farside, specifically landing in the southern part of the Apollo basin in the SPA basin. These valuable samples are expected to provide essential insights to tackle the enduring mysteries of lunar dichotomy and could even transform our understanding of our nearest celestial neighbor. However, compared to the well-known volcanic activities in the mare regions near the Chang’e-6 landing site, intrusive magmatic activities are less evident and their origins remain unclear, which may hinder future analyses once the samples are accessible.
A recent paper published in The Astrophysical Journal Letters by Dr. Yuqi QIAN, Professor Joseph MICHALSKI, and Professor Guochun ZHAO from the Department of Earth Sciences at The University of Hong Kong (HKU), along with their national and international collaborators, offers a detailed examination of the intrusive magmatism around the Chang’e-6 landing zone using remote sensing data. This research uncovered the widespread and elusive characteristics of these magmatic activities, shedding light on the formation of lunar plutonic rocks and the Chang’e-6 mission’s findings, which will help advance scientific exploration of the lunar farside.
The study indicates that intrusive magmatism is prevalent in the SPA basin. These magmatic forms include sills found under craters, linear and ring dikes indicated by gravity data, and Mg-suite intrusions recognized by their distinctive spectral features. These findings align with the thick intermediate crust of the SPA, where such intrusions are likely. Since Chang’e-6 landed in the SPA basin, it is probable that the mission gathered plutonic rocks that were excavated and moved by surrounding impact craters to the sample site, which can now be studied further. The researchers identified two heavily eroded craters with fractured floors, suggesting the potential for discovering more similar geological features on the Moon. This all points to a rich presence of intrusive magmatism in the area sampled by Chang’e-6.
The research traced possible plutonic materials in the Chang’e-6 samples, suggesting a strong likelihood of Mg-suite materials, primarily sourced from the western peak ring of the Apollo basin, delivered by impacts from the Chaffee S crater. These magnesium-rich materials could provide crucial insights into the enigmatic KREEP-poor Mg-suite rocks. Collecting samples from both intrusive and extrusive magmatism on the unvisited farside, particularly the enigmatic Mg-suite rocks, could enhance our understanding of the lunar dichotomy and address key scientific questions related to the formation of secondary crusts and the Moon’s early evolution.
Professor Xianhua LI, a member of the Chinese Academy of Sciences (CAS) and a leader in lunar sample studies from the Institute of Geology and Geophysics (CAS), remarked, ‘The findings of this research establish a vital geological framework for studying plutonic rocks in the Chang’e-6 samples, especially those related to the Mg-suite.’ He underscored the current uncertainties surrounding their petrogenesis and timing, adding that this research would considerably contribute to understanding their origins.
‘This research exemplifies HKU’s deep engagement in China’s Lunar Exploration Program,’ asserted Professor Guochun ZHAO, an academician of the Chinese Academy of Sciences and Chair Professor of Earth Sciences at HKU. ‘Lunar and space exploration is a significant facet of China’s ambition to emerge as a scientific and technological leader, and HKU’s active role in these initiatives will help elevate Hong Kong as a global hub for science and innovation,’ he noted.
HKU was the first university in Hong Kong to acquire lunar samples from the Chang’e-5 mission. Building on this foundation, HKU geologists will seek further opportunities to study the Chang’e-6 samples and enhance their involvement in the Chinese Lunar Exploration Program.
