500 milligrams of the “native product” of the moon was used to do these three major things
The powder sample applied by the National Center for Space Science of the Chinese Academy of Sciences comes from the powder sample CE5C0400
Image courtesy of the scientific data and sample release system for lunar and deep space exploration
Approaching Lunar Soil Research ②
The lunar soil is formed by space weathering such as the impact of meteorites and micrometeorites, solar wind, and cosmic ray radiation on the lunar surface of the moon.
In addition to reflecting the material composition of the lunar surface itself, the lunar soil is also an important carrier for recording the history of solar wind and other interactions with the lunar surface and the proliferation of foreign matter.
Yang Yazhou, Special Research Assistant, National Center for Space Science, Chinese Academy of Sciences
On July 12, the National Space Administration's Lunar Exploration and Space Engineering Center held the first batch of lunar “local products” of the Chang'e-5 mission, and 31 applications from 13 scientific research institutions were approved.
21 samples totaled 17.4764 g, including 6 light flake samples totaling 157.6 mg, 13 cuttings samples totaling 868.8 mg, and 2 powder samples totaling 16.45 g.
This marked the official start of scientific research on lunar samples.
After review and voting by all members of the first lunar sample expert committee, the National Space Science Center of the Chinese Academy of Sciences successfully applied for a 500 mg lunar soil sample.
Based on these samples, what research will the National Space Science Center of the Chinese Academy of Sciences carry out?
How to deal with these precious lunar soil samples scientifically?
What scientific research results may be achieved in the future?
With these questions in mind, a reporter from Science and Technology Daily interviewed relevant experts from the National Space Science Center of the Chinese Academy of Sciences on August 8.
500 mg sample can meet the needs of analysis and testing
It is understood that the 500 mg lunar soil samples obtained by the National Space Science Center of the Chinese Academy of Sciences are all powder samples.
Why should I apply for all powder samples?
Liu Yang, a researcher at the National Center for Space Science of the Chinese Academy of Sciences, explained that because most of the lunar soil samples available for this release are surface scooped samples, there are mainly two types of debris samples and powder samples.
Among them, there are more powder samples, and the probability of application is relatively higher.
Therefore, in combination with its own research expertise and previous research foundations, all of the applications in this application are lunar soil powder samples.
500 mg, it sounds very small.
So, is this "local product" of the moon enough to carry out scientific research?
"When conducting analysis and research, the more samples are naturally the better. But because the lunar soil samples are more precious this time, in order to ensure that the sample application can be approved, most of the researchers will adopt more conservative strategies to evaluate what is needed when applying. The amount of sample." Liu Yang said, according to their assumptions, 500 mg of sample is enough to meet the needs of analysis and testing.
Zhu Rixiang, director of the Lunar Sample Expert Committee and academician of the Chinese Academy of Sciences, once said that there are three main results in the scientific research on the samples brought back by Chang'e-5: First, the training of talents. In the past, Chinese scientists were basically unable to obtain Apollo lunar samples for research. Now, relying on the lunar soil samples "backed" by Chang'e 5, we can also train our own research team; second, the Chang'e 5 sampling area has undergone a lot of research and demonstration, so we have The study of lunar soil samples may have a breakthrough understanding of the dynamic process of lunar evolution; third, it has an important guiding role for my country's follow-up lunar and deep space exploration.
However, scientific research is always full of unknowns.
"After analyzing all these samples, it is possible that we cannot find the phenomenon we want to see or answer the scientific questions we want to solve." Liu Yang said frankly, no matter what, the use of these samples to carry out scientific research will definitely Expand our understanding of the moon.
Different samples can reflect different information about the moon
Yang Yazhou, a special research assistant at the National Center for Space Science of the Chinese Academy of Sciences, said that the light sheet samples in the lunar samples released this time are powder or cuttings samples that have been pre-treated, usually after embedding the samples with epoxy resin, etc. The thin slice made by polishing, so the light sheet sample can be directly used for subsequent test analysis.
However, in the preparation process of the light sheet sample, since the lunar soil particles need to be ground out of a plane for micro-area analysis, the grinding and polishing process will inevitably cause a very small amount of abrasion of the particle sample on the light sheet sample.
Detritus samples are the fragments formed by the fragmentation of early-formed lunar rocks after being affected by impacts, etc., which usually retain information such as the mineral composition of the original lunar rocks.
Yang Yazhou introduced that through petrographic, mineralogical, and geochemical analysis of cuttings samples, it is hoped that the rock genesis can be reversed.
In cuttings samples, it is relatively easy to find suitable minerals for isotopic chronological analysis.
The powder sample mainly refers to the lunar soil.
According to the analysis results of the returned samples from Apollo, the average particle size of lunar soil particles is on the order of tens of microns.
"Lunar soil is formed by long-term meteorite and micrometeorite impacts, solar wind, cosmic ray radiation and other space weathering on the lunar surface. Lunar soil not only reflects the material composition of the lunar surface itself, but also records the interaction of solar wind and the lunar surface. History and an important carrier of information about the proliferation of foreign substances.” Yang Yazhou said.
A detailed study of the lunar soil using microscopic analysis techniques
It is understood that the team of the National Space Science Center of the Chinese Academy of Sciences will carry out three studies on the 500 mg samples obtained in space weathering, solar wind injection and impact residues, in order to advance our understanding of the evolution of the moon and the solar system.
What research methods will researchers use to analyze, so as to "read out" the information they want?
Yang Yazhou explained that the research team will use some microscopic analysis techniques to conduct detailed microstructure analysis and geochemical analysis of lunar soil particles, and combine spectral analysis to explore the interaction process of lunar soil particles with solar wind, micrometeorites, etc. , And look for possible impact residues.
Yang Yazhou introduced that space weathering will strongly alter the surface microstructure of the lunar soil, forming a large number of cements and nano-iron, etc., and will have an impact on the reflectance spectrum at a macro level. It is to accurately interpret the mineral composition of the lunar surface through spectral data. The main obstacle to such information.
Researchers analyze the microscopic crystal structure and element distribution characteristics of lunar soil particles, and identify the types of space weathering products in lunar soil particles, such as nano-iron, amorphous coatings, etc., to explore the dominant mechanism of lunar surface space weathering.
At the same time, possible sources of lunar water include the water injected by the solar wind, the water added by the impact of small water-rich celestial bodies, and the water generated by the internal degassing of the moon.
Liu Yang said that the injection of solar wind will cause changes in lunar surface water content and hydrogen isotopes, but the current understanding of the specific formation and occurrence mechanism of lunar surface solar wind-causing water is still insufficient.
The study of solar wind injection on lunar soil samples may reveal this mechanism.
The impact residues of meteorites usually have different geochemical characteristics from the original lunar rocks, especially the composition of strong iron-philic elements.
"Therefore, we will first conduct a preliminary screening of lunar soil particles, and then conduct a micro-region strong iron-philic element analysis to infer the possible source of the impactor." Liu Yang said.
Liu Yang said that compared to other terrestrial planets, the lunar surface can preserve more complete evidence of impact events. Identifying the parent body of the impactor can provide geochemical and chronological constraints for the solar system dynamics model. However, due to the limitations of the previous lunar surface sampling points, The lack of younger geological records limits the understanding of the migration history of small celestial bodies in the solar system.
The landing zone of Chang'e 5 is located in the northern part of the dark lava plain called Storm Ocean on the front of the moon.
The storm ocean is the largest lunar sea on the moon. It has attracted the attention of the scientific community because it is in the KREEP terrane where the chemical abnormalities on the lunar surface are located.
Mount Rumke near the sampling point is a relatively young volcano located in a large-scale late basalt area on the moon.
Therefore, using the lunar return samples obtained by Chang'e-5 this time to obtain original scientific results in lunar volcanic activity and evolution history will provide us with an important reference for further understanding of the lunar geological evolution.
(Our reporter Lu Chengkuan)