Chinese scientists confirmed: 120 million years ago, there was still magma activity on the moon!

Author: Shi Xiangqi and Li Chuanfu

In the course of human exploration of the moon, a long-standing mystery is when the lunar geological activity stopped. Recently, a study conducted by researchers from the Institute of Geology and Geophysics of the Chinese Academy of Sciences has provided us with new clues. They used volcanic glass beads in the lunar soil samples brought back by the Chang'e-5 probe to confirm that there was still magma activity on the moon 120 million years ago. This discovery not only refreshes our understanding of the history of lunar geological activity, but also provides a new perspective for the study of the thermal evolution of the moon.

Schematic diagram of volcanic glass formed by lunar eruption Source: Institute of Geology and Geophysics

Magma activity: the "lifeline" of geological activity

Magma activity is one of the important signs of planetary geological activity. It can not only form new crust, but is also closely related to the thermodynamic processes inside the planet. Scientists have inferred that the volcanic activity on the moon occurred at least 3 billion years ago through lunar samples brought back by the Apollo program and the Luna mission, as well as lunar meteorite samples. However, with the samples brought back by the Chang'e 5 probe, this understanding has been constantly updated.

Chang'e 5's Valuable Discovery

In 2021, Chinese scientists used lunar soil samples brought back by Chang'e-5 to prove that the moon still had large-scale magmatic activity 2 billion years ago. The latest research has pushed this time point further back to 120 million years ago. The research team selected about 3,000 glass beads from the approximately 3 grams of lunar soil brought back by Chang'e-5, and identified three volcanic glass beads through high-precision scientific instruments such as scanning electron microscopes, electron probes, and ion probes. The formation time of these glass beads was determined to be 120 million years ago through uranium-lead isotope system measurements, representing a period of magmatic activity on the moon.

The difference between volcanic glass beads and impact glass beads

One of the biggest challenges in this study is how to distinguish volcanic glass beads from impact glass beads. Since asteroids and meteoroids can also form impact glass beads with similar appearance and composition when they hit the moon, this has brought considerable difficulties to scientists' identification work. Through the study of glass beads in the Apollo samples, scientists have formed some identification methods based on morphological structure, major and trace elements, etc. In this study, the research team used sulfur isotope characteristics as a new discrimination criterion and successfully distinguished volcanic glass beads from impact glass beads.

Distinguishing between volcanic glass beads and impact glass beads is a challenge in this study. Image source: Institute of Geology and Geophysics

Evidence for young lunar volcanism

The discovery of these young volcanic glass beads not only confirms that the moon still had magmatic activity 120 million years ago, but also provides new clues to the thermal evolution of the moon. The research team found that these volcanic glass beads are rich in potassium, rare earth elements and phosphorus, indicating that there are high levels of radioactive elements in their source area. The decay of these elements may be the cause of such late magmatic activity. Although no large-scale late magmatic activity has been observed on the moon, small-scale volcanic eruptions caused by local warming may still exist.

The results of this study not only provide us with new evidence of lunar geological activities, but also point out the direction for our future lunar exploration. With the implementation of subsequent missions such as Chang'e 6, we are expected to obtain more valuable information about the moon and uncover more secrets of the moon. These discoveries will help us better understand the origin, evolution and internal structure of the moon, and provide important scientific basis for future deep space exploration of mankind.

The moon, as the only natural satellite of the earth, has always been an important object for human exploration of the universe. This study by the Institute of Geology and Geophysics of the Chinese Academy of Sciences not only provides us with new evidence of lunar geological activities, but also opens a new door for our future lunar exploration and scientific research. With the advancement of science and technology and the deepening of exploration, we have reason to believe that the mystery of the moon will be gradually unveiled, bringing us a richer and deeper understanding of the universe.