Recently, the scientific research team of the National Space Science Center of the Chinese Academy of Sciences, based on the ultra-high spatial resolution image and spectral data obtained by the "Chang'e-4" patrol device, has identified carbonaceous materials that are less than 1 million years old in situ on the lunar surface for the first time. Remnants of chondrite impact bodies.
Previous studies have found fragments of carbonaceous chondrites in "Apollo samples", but the impact residues of carbonaceous chondrites have never been directly observed on the lunar surface through remote sensing.
The findings of the scientific research team indicate that the impact of carbonaceous asteroids rich in volatile matter may still provide water for the current moon.
At the same time, studies have shown that there is the possibility of impactor residues in relatively young lunar surface materials (such as the return sample of "Chang'e 5").
The direct analysis of these impactor residues that may be present in the "Chang'e 5" sample will provide an important reference for the evolution history of the composition and type of the Earth-Moon system impactor, and is expected to further restrict the orbital dynamics of the solar system. Improve understanding of the history of impacts in the inner solar system.
Relevant research results were recently published in the international academic journal "Nature-Astronomy".
The "Chang'e-4" probe successfully landed in the Von Kamen impact crater in the South Pole-Aiken Basin on the back of the moon in January 2019. The "Yutu-2" patrol device carried on it subsequently carried out continuous inspections on the lunar surface. .
The panoramic camera and visible-near-infrared imaging spectrometer equipped on "Yutu-2" can acquire ultra-high-resolution images of the moon's surface and hyperspectral data.
During the patrol of the lunar surface, "Yutu 2" discovered a small fresh impact crater, and carried out detailed spectral detection of the impact crater on the 9th day of the month.
Based on the crater images obtained by the panoramic camera at close range, the scientific research team found that there are some materials in the center of the crater that are significantly different from the crater wall and the lunar soil outside the crater.
The study analyzed the hyperspectral image data obtained by the imaging spectrometer and found that the spectra of the suspected "residue" in the center of the impact crater and the typical lunar soil and rock fragments in and outside the crater showed distinct characteristics. Foreign impactor materials with blue spectral characteristics are mixed into it.
The study collected a large number of spectra of carbonaceous chondrites. After careful comparison, it was found that the residue did have a high degree of similarity with the spectra of carbonaceous meteorites.
The analysis results indicate that the impact crater may have been formed after the impact of a small carbonaceous meteorite.
The impact transport process is considered to be one of the main contributors to the water on the moon's surface and the water ice in the permanent shadow zone. Carbonaceous asteroids are a type of small celestial bodies that are relatively rich in water and volatile matter, and they carry them during the impact. Some of the water may be retained on the monthly table.
Based on the crater degradation model, the research team estimated the age of the crater, and the results showed that the crater should have been formed within one million years.
This direct observation of carbonaceous impact residues indicates that similar carbonaceous meteorite residues may be very common on the lunar surface, and there will be some in the samples collected and returned from a relatively young basalt unit on the lunar surface by "Chang'e 5". There is a high probability that similar impact residues will be found.
By then, combined with major trace elements and isotope chronology analysis, it will be possible to better define the composition and type evolution of the impactor.
In the future, using higher spatial resolution telemetry spectral data, it will be possible to find similar impact residue distributions in more places on the lunar surface, thereby further deepening the understanding of the source and distribution of lunar water.
(CCTV reporter Shuai Junquan)