◎Our reporter Lu Chengkuan
On February 15, when the Lantern Festival came, "Nature Astronomy" published an important result of lunar scientific research online.
Using the isotopic age of the "native products" of the Chang'e-5 lunar and the statistical results of the impact craters in the landing area, researchers from the Institute of Aerospace Information Innovation, Chinese Academy of Sciences and other units have established a new and more accurate lunar age on the basis of the currently commonly used lunar age function. functional model.
"The new chronological function model provides a more precise time scale for lunar and planetary science research," emphasized Yue Zongyu, the first author of the paper and a researcher at the Chinese Academy of Sciences.
Determining the age of important geological units and major geological events is critical in lunar and planetary science research.
Early Apollo and Luna missions collected samples on the lunar surface and obtained precise ages of these samples through isotopic dating methods, which represent the age of the geological unit in which the samples are located.
In order to apply these limited age information to the entire moon, scientists in Europe and the United States have established a statistical dating method for impact craters, including a yield function describing the size-frequency distribution of impact craters and a method describing the relationship between the normalized frequency of impact craters and absolute age. Age function, the former is obtained by the statistical analysis of remote sensing image impact craters, and the latter is obtained by the normalized frequency of the sample age and the impact crater in the geological unit.
Among them, the most famous and widely used is the yield function and chronological function established by Professor Gerhard Neukum of the Free University of Berlin in 1983.
However, "Unfortunately, the age of the samples collected by Apollo and Luna has a large gap in the age of about 3 billion to 1 billion years, accounting for almost half of the lunar geological history, which also makes the reliability of the chronological function always affected. Doubt." Yue Zongyu admitted frankly.
Therefore, finding samples of geological units on the lunar surface about 2 billion years old is of great significance to verify and improve the lunar age model, which has also become one of the scientific goals of the Chang'e-5 mission.
On December 1, 2020, Chang'e-5 landed safely in the vicinity of Lümke Mountain and Sharpyue Stream in the northern part of the Ocean of Storms on the front of the moon. The isotope measurement results of the samples brought back showed that its age was 2.03 billion years, which was in good agreement with expectations.
"The age of the Chang'e-5 sample provides a precious 'golden nail' for the improvement of the lunar age function, which is a unique contribution of the Chang'e-5 sample to lunar scientific research," said Di Kaichang, the corresponding author of the paper and a researcher at the Chinese Academy of Sciences.
The research team obtained the normalized crater frequency of the geological unit of the Chang'e-5 sampling point based on the statistical analysis results of the impact crater and the impact crater yield function of the high-resolution lunar remote sensing images, and established a lunar age function model based on the age composition of the Chang'e-5 sample. A new set of control data was used to update the chronological function established by Gerhard Newcomb through the nonlinear least square fitting algorithm, and a new lunar chronological function model was established.
Analysis shows that the dating results obtained from the new chronological function are older in most cases, with the largest difference being around 200 million years.
"Because of the addition of the key data points of Chang'e-5, the accuracy of the new lunar age function model is better than that of the classical Gerhard Newcomb model, and can be used for the future dating of lunar geological units. Further, according to The new lunar chronology function can deduce the new chronological functions of other exoplanets such as Mars and Mercury, and improve the dating accuracy." Di Kaichang said that the new lunar chronology function is a more accurate time scale and will be used in lunar and planetary science research. Play an important role.
More importantly, this achievement has also been highly praised by the reviewers.
One of the reviewers said: "This original work is significant and I think the entire planetary science community will be interested in this result."