The Moon in a "Cradle"? Chang'e 5 "brought back" the secrets of the early formation of the lunar crust

Author Li Chuanfu

On July 27, 2024, a groundbreaking study conducted by a research team led by Professor Wang Shuijiong of China University of Geosciences (Beijing) and domestic collaborators provided a new perspective for our understanding of the early history of the moon.

Through in-depth analysis of lunar soil samples brought back by the Chang'e-5 mission, scientists have discovered an initial melt similar to the magnesian suite in a piece of anorthosite rock debris, which provides direct petrographic evidence for the simultaneous formation of the parent magma of lunar anorthosite and magnesian suite. This research result has been published in the journal Communications - Earth and Environment, revealing a key link in the early evolution of the moon.

The formation of the moon can be traced back to a giant impact event about 4.5 billion years ago. According to the classic magma ocean model, the early formation and evolution of the moon's crust went through two main stages. In the first stage, as the magma ocean cooled, plagioclase gradually floated and gathered to form the original lunar crust. Subsequently, after the magma ocean solidified, the lunar mantle flipped over and melted again, producing a magnesian rock suite, which led to the reshaping of the lunar crust.

Chronological studies show that the formation time of anorthite and magnesian rock suites is almost the same, which suggests that the formation and reshaping of the lunar crust may be a continuous evolutionary process, but the specific mechanism of this process has always been an unsolved mystery.

In this latest study, the research team conducted geochemical and thermodynamic simulations on the melts in the Chang'e-5 lunar soil samples. The results show that the parent magma of the magnesian rock suite may have originated from the melting of the orthopyroxene-rich upper mantle containing plagioclase, rather than the decompression melting of the olivine-rich lower mantle as traditionally believed. Based on this discovery, the researchers put forward a new view: the formation of the lunar crust is a continuous process.

During the cooling of the lunar magma ocean, the plagioclase crust was formed. Due to the instability of gravity, the high-density ilmenite crystal layer caused a small-scale in-situ overturn of the upper mantle. This overturn caused the orthopyroxene layer in the upper mantle to rise and mix with plagioclase, forming the source area of ​​the magnesian suite. Over time, the continuous sinking and aggregation of ilmenite crystals eventually triggered a large-scale overturn of the lunar mantle, resulting in the decompression melting of the olivine-rich lower mantle and the formation of the relatively young parent magma of the magnesian suite.

This study not only provides us with a new understanding of the early evolution of the Moon, but also shows that the melting of the lunar mantle is a bridge between the formation of the original lunar crust and the reshaping of the lunar crust. These findings are of great significance to our understanding of the geological history of the Moon and the comparative planetary studies of the Moon and other celestial bodies. With further research and analysis of lunar samples, we are expected to uncover more secrets about the formation and evolution of the Moon and provide a scientific basis for future human exploration and utilization of the Moon.

Through this research, we have once again witnessed the power of scientific exploration. It is these unremitting efforts and innovative scientific methods that allow us to transcend the limitations of time and space and explore the mysteries of the universe. As our closest celestial neighbor, the study of the moon not only enriches our understanding of the world outside the earth, but also provides us with valuable information for studying the early history of the solar system. With the advancement of science and technology and the continuous development of detection technology, we look forward to more discoveries in the future, which will reveal a corner of the mystery of the moon for us and further expand the boundaries of human cognition of the universe.