China News Service, Beijing, October 19 (Reporter Guo Chaokai) The Chinese Academy of Sciences released the latest research results of the Chang'e 5 lunar scientific research sample on the 19th.
The study found that the “youngest” basalt age of the moon is 2 billion years, and magma activity still existed on the moon until 2 billion years ago, which is about 800 million years longer than the magma activity stop time defined by previous lunar samples.
When will volcanic activity on the moon stop?
How to maintain the past magma activity?
How "dry" is the moon mantle?
What are the characteristics of the lunar sample of Chang'e 5?
Can you answer the above questions?
The Institute of Geology and Geophysics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of Geology and Geophysics) and the National Astronomical Observatory have jointly adopted three "Nature" papers and a "National Science Review" paper to report on these important scientific issues. Breakthrough progress.
The study proved that the Chang'e 5 lunar sample is a new type of lunar basalt, which gives a new understanding of the age of the magma in the landing zone and the nature of the source area. The age of the “youngest” basalt on the moon is 2 billion years, and its lunar mantle of late magmatic activity The source area is not rich in radioactive elements, and there is almost no water.
Studies on lunar samples from the United States and the Soviet Union and lunar meteorites on Earth have confirmed that one of the "life" features of the moon-magma activity lasted at least about 2.8 to 3 billion years ago, the black color left by ancient magma eruptions The basalt formed the "moon sea" seen.
However, there has been controversy in the scientific community about the exact time when the lunar magma activity ceased.
In the latest research, researchers used ultra-high spatial resolution uranium-lead (U-Pb) dating technology to determine more than 50 uranium-rich minerals (oblique zircons, perovskite zircons , Jinghaishi) analyzed and determined the age of basalt formation to be 2.030±0.04 billion years, confirming that the "youngest" basalt age on the moon is 2 billion years.
In other words, magma activity still existed on the moon until 2 billion years ago, which is about 800 million years longer than the time limit for magma activity stopped by previous lunar samples.
According to researchers, scientists have used a method of counting the size and number of impact craters in a region to infer that the Chang'e 5 landing area is one of the youngest basalt units on the moon. The age of this area is 1 to 3 billion years. There is great uncertainty.
The accurate dating data of the Chang'e-5 basalt provides a key anchor point for the statistical dating curve of impact craters, which will greatly improve the accuracy of statistical dating of impact craters on the surface of the inner solar system.
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.
At the same time, the cause of the most late magma activity on the moon has always been an unsolved mystery. At present, there are two possible explanations in the scientific community: magma is rich in radioactive elements to provide a heat source, or rich in water to lower the melting point.
The latest research is based on the ultra-high spatial resolution isotope analysis technology developed by Geology and Earth, and has achieved unexpected results: the initial melting of the Chang'e 5 basalt was not involved in the “Krip material enriched in potassium, rare earth elements, and phosphorus. "(These elements are called "incompatible elements" in geochemistry, meaning elements that are not easy to enter solids). The Chang'e-5 sample has elemental characteristics similar to the Krip material, but the isotopic results show This feature does not come from the lunar mantle source area, but the magma is formed through a large amount of mineral crystallization.
This result excludes the mainstream hypothesis that the Chang'e-5 basalt source area is rich in radioactive heat-generating elements and reveals the process of late lunar magmatism.
Regarding whether the magma source area is rich in water, the scientific research team used the analysis technology developed by the Institute of Geology and Earth's nano-ion probe to determine the water content and hydrogen isotopic composition in the Chang'e-5 basalt, and the water content in the lunar mantle source area was only 1 -5 micrograms/g, which means that the moon mantle is very "dry".
Researchers pointed out that this discovery also ruled out the hypothesis that the lunar mantle is rich in water and has a low melting point, leading to long-term magma activity in the region.
This series of results raises new scientific questions for the study of the lunar thermal evolution history. The reason why the lunar cooling is so slow is not clear. It requires a new theoretical framework and evolution model, and proposes a new direction for future lunar exploration and research.
This is the first batch of research results of the Chang'e 5 lunar scientific research samples led and independently completed by Chinese scientists, fully demonstrating the scientific research level and innovative ability of Chinese scientists.
These results have been highly praised by international experts. Charles Schiller, a senior researcher at the Lunar and Planetary Science Institute of the University of New Mexico, and Richard Garson, a researcher at the Carnegie Institute, believe that the series of results "provide the determination of the moon and the planet so far. “The youngest evidence of basalt”, “changed our understanding of the thermal history and magma history of the moon”, “has great significance for us to understand the origin and evolution of the moon”.
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