CCTV, Beijing, October 20 (Reporter Zhu Min) When will the volcanic activity on the moon stop? How to maintain the previous magma activity? How “dry” is the moon mantle? These are the questions that humans have to answer when studying the moon. On the afternoon of the 19th, Beijing time, the international academic journal “Nature” simultaneously published three online research results from the Institute of Geology and Geophysics, Chinese Academy of Sciences. The study proved that the lunar sample of Chang’e-5 is a new type of lunar basalt, which fills the “blank” in lunar sampling missions of the United States and the former Soviet Union. Give a new understanding of the age of the magma in the landing zone and the nature of the source area.
The study found that the moon was “alive” just 2 billion years ago, and hot magma erupted, which was about 800 million years longer than the magma activity stop time limited by lunar samples in the past. So, what made the moon “live” at least 2 billion years ago? What surprises do the lunar samples brought back by Chang’e-5 bring us?
The moon is the only natural satellite of the earth and the first target celestial body for mankind to explore the universe. The massive distribution of basalt on the front of the moon indicates that it has experienced an active volcanic eruption period. Li Xianhua, an academician of the Chinese Academy of Sciences and a researcher at the Institute of Geology and Geophysics of the Chinese Academy of Sciences, said that the study of lunar basalt can reveal the chemical composition and thermodynamic evolution history of the moon. “Basalt is formed by partial melting of the rocks of the moon’s mantle in the deep part of the moon, and then magma is formed, and then the surface of the moon is ejected to form the basalt that we see. Volcanic activity is a very important thing on the moon, and it represents us. The internal vitality of the moon represents a process of recycling energy and material inside the moon. Therefore, studying volcanic rocks can reveal the evolutionary history of the moon’s chemical composition and thermodynamics.”
Previously, studies on lunar samples from the United States and the former Soviet Union and lunar meteorites on Earth have confirmed that the lunar magma activity lasted at least about 2.8 to 3 billion years ago, and the black basalt left by the ancient magma eruption formed what was seen “Moon Sea”. However, there has been controversy in the scientific community about the exact time when the lunar magma activity ceased. The moon was formed about 4.5 billion years ago. Ouyang Ziyuan, an academician of the Chinese Academy of Sciences, said that human beings are still unclear about its complete history. “Existing studies, including Apollo and Luna of the former Soviet Union, all age activities are from 4 billion to 3 billion years ago. This period of history is clear, but the two ends are blank. It should be said that the moon There are two problems in the history of “One old”, 4 billion years ago; “One new”, 3 billion years later, it is not clear. Can we break through it? How can we break through? Restore the true evolutionary history of the moon, this Is an important task for scientists.”
On December 17, 2020, the Chang’e-5 sample module successfully landed in Siziwang Banner, Inner Mongolia, and brought back 1731 grams of lunar samples. This is the first time that China has completed the collection of extraterrestrial celestial bodies. It is also the first time that humans have collected samples from the moon after a lapse of 44 years. The landing site of Chang’e 5 on the moon is near Mount Rumke, northwest of the Storm Ocean, where there is the youngest lunar basalt on the moon. Li Xianhua said that in the latest research, researchers analyzed more than 50 uranium-rich minerals in the basalt cuttings of the Chang’e-5 lunar sample, and confirmed that the “youngest” basalt on the moon is 2 billion years old. He said: “We put these samples together for statistics, and got a very accurate basalt age of 20.3±0.04 billion years. This age is the eruption age of our Chang’e 5 sample basalt, which is the oldest one on the moon. The magmatic and volcanic activities that ended late are 800 to 900 million years late.”
So, how does the “life” of the moon last 800 million years? The cause of the most late magma activity on the moon has always been an unsolved mystery in planetary science. At present, scientists believe that there are two possible explanations: one is that the lunar magma source area is rich in heat generating elements to provide a heat source, and the other is that the area is rich in water to lower the melting point. However, the results of the research on the Chang’e 5 lunar soil sample by researchers were unexpected: the Chang’e 5 sample was enriched after a large amount of minerals crystallized and solidified in the later stage of magma, and the initial magma of the rock in the Chang’e 5 landing area was excluded. The melting heat source comes from the mainstream hypothesis of radioactive heat-generating elements. Moreover, they also discovered that the magma source area of the Chang’e-5 basalt is not rich in water, and the moon mantle is very “dry”.
“As time evolves, it seems that the water in the mantle source area of our month is at least very low, and even has a tendency to decrease. Why is this? It may be multiple melting, each time a little water is pumped, the more the water is pumped, the drier the water is. , This is our understanding.” Li Xianhua said.
The ultra-high spatial resolution dating and isotope analysis technology used in this study is at the international leading level, providing new technical methods for the chronology of precious extraterrestrial samples. Academician Ouyang Ziyuan commented on this: “Our team is working in hours after getting the samples. The instruments used are the best dating in the world, and the composition and quality of the team are the best in China. Top-notch, 2.030 billion years! I am sure that this data must be the best. They have relatively high accuracy and a large number of samples, which can withstand all kinds of doubts.”
These series of results have raised new scientific questions for the study of the lunar thermal evolution history. The reason why the lunar cooling is so slow is not clear. A new theoretical framework and evolution model are needed, and a new direction for future lunar exploration and research is proposed. Exploring the vast universe is the common dream of mankind. Zhou Qi, vice president of the Chinese Academy of Sciences, revealed: “The Academy of Sciences is actively promoting international cooperation in the study of lunar samples. At present, China and France are based on long-term friendly cooperation in the space field. A preliminary consensus has also been reached on the cooperative study of lunar samples.”
The Chang’e-5 lunar sample gives us a clearer understanding of the moon’s recent history. However, how the moon was formed in the first place is still a mystery, and more lunar samples from different regions are needed to study. Regarding the future sample retrieval plan of China’s lunar exploration project, Li Chunlai, a researcher at the National Astronomical Observatory, revealed that the most recent one is Chang’e 6, which has entered the implementation stage. “Where will Chang’e-6 sample? We are still in the process of demonstration and confirmation. The launch time and where to sample? What can be sampled? We are still further confirming. Of course we hope to sample more or more. For special samples, we also hope to sample on the back of the moon, and we are working hard in this direction. We should have a definite result soon for the specific location and whether it is like this.”Return to Sohu to see more
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