On October 19, the Chinese Academy of Sciences released the latest scientific research achievements of the Chang'e-5 lunar mission. These achievements are independently led and completed by China in the Chang'e-5 lunar research. One of the leading researchers, Academician Li Xianhua from the Institute of Geophysics, Chinese Academy of Sciences (hereinafter referred to as "the Institute"), revealed pride in his words: "All the research was completed in our institute, which fully demonstrates our scientific research strength and innovative capabilities." How were these [lunar] features studied? Let's take a look at the story behind lunar research. ### The "changes" of tiny samples Yang Wei from the Institute of Geology said: "The analysis of lunar samples can be affected in the air; we need to prevent contamination in research. We utilize [techniques to minimize] trace losses and, at the same time, employ high spatial resolution capabilities to ensure the accuracy of research results." Yang Wei introduced to reporters the thousand-level clean room in the institute's lunar sample cleanroom, where 3 sets of high-purity glove boxes are placed. Researchers operate inside these glove boxes. "Lunar water content is extremely low, and there is no volatile matter," Yang Wei explained, noting that they must ensure the content of water and volatile substances in the glove boxes is controlled. There was a touch of regret in his tone: "If only we could study [samples in their original] lunar environment."Lunar dust is finer than ordinary dust—how to find that "most storied" grain of lunar soilLunar dust is more like tiny stars. "The lunar soil brought back by Chang'e-5 is extremely fine, only 60 microns in size, finer than the lunar soil from the Apollo missions," Li Xianhua said, stretching out his palm and blowing gently to illustrate. Each grain of lunar dust may come from a distant past, but for scientific research, each grain tells a different story. How do we find the "most storied" one? Li Xianhua explained that, for example, in geological research, the most important dating minerals are key. "We use [radiometric] dating methods, and the best samples are those rich in [such] minerals. Thus, selecting the most suitable samples becomes crucial." Academician Wu Fuyuan proudly introduced their "secret weapon"—researcher Ma Hongxia. She has uniquely skilled hands, able to quickly and deftly process a sample as fine as dust into a usable form. "Our institute has long been engaged in such research; technicians like her are trained here and are 'treasures' of the institute. Now, many research institutions facing sample processing difficulties even ask us to lend her expertise," he said. Once the sample targets are prepared, the experiments can proceed.The best researchStudying the moon, being so far away, requires frugality. Li Xianhua said: "Our team was allocated 3 grams of samples, and we used 2.85 grams. With only 0.15 grams, we completed the first batch of research tasks." How to achieve the best results with minimal cost while reducing losses? Wu Fuyuan noted that the institute not only has a broad scientific vision in geological exploration but also prides itself on its "technology-first" experimental platform—the Public Technology Center, which is equipped with instruments such as ion probes and nano-analyzers. "This platform has gathered a stable team of engineers. In the research process, scientists and engineers collaborate to debug instruments to their optimal state with unique techniques and methods," Wu Fuyuan said, adding that this pushes the instruments to their "limit capabilities." Li Xianhua added: "For example, in the dating process, we improved key hardware of the imported probe instrument, achieving accurate testing with a beam spot as small as 3 microns. It can be said that few institutions internationally can achieve such precision; we have reached an international leading level." It is said that the second round of application for Chang'e-5 lunar samples has begun, and the moon will tell us more about its past. What good fortune! Chinese scientists are ready, and we are full of expectations for the future!Estimating the age of lunar rocksWhether Earth, the moon, or other planets, they are all actors on the cosmic stage. Over the long river of time, they have staged countless evolutionary stories. Planets like Earth and the moon are composed of rocks, and their evolutionary histories are recorded in the rocks formed during corresponding periods. To accurately place a lunar rock and the environmental information it records on the timeline, the first step is to determine the age of the rock. The moon is 380,000 kilometers away from Earth—how do scientists know when the rocks on the moon formed? The answer: count craters. Do the math. This is no child's play but a real scientific method. With an ordinary telescope with 5-8x magnification, we on Earth can clearly observe the pockmarked impact crater landscape on the moon's surface. When two impact craters overlap, it is obvious that "the new crater covers the old one." Thus, by observing the overlapping relationships of the dense impact craters on the moon's surface, we can determine the chronological order of rock layers in different regions of the moon. Moreover, the intensity and frequency of meteorite impacts on the moon varied drastically in different periods (the newly formed moon was bombarded with high intensity and frequency, while in the subsequent billions of years, only sporadic impacts occurred). By counting the size and frequency of impact craters, we can estimate the approximate age of a certain region on the moon. However, "counting craters" has a fatal flaw: it can only tell us the chronological order and approximate age range of rock layers but cannot provide an accurate age value. In the early 20th century, physicist E. Rutherford revealed an important law about radioactive elements—the law of radioactive decay. This law states that the decay rate of a radioactive element depends only on the number of radioactive atoms in the system. This law made Rutherford famous in the history of physics, and in the rest of the 20th century, his law underpinned nearly half of modern Earth and planetary sciences. Because it is the basic principle of "radiometric dating." Under natural conditions, many radioactive elements are lithophile elements, firmly locked in the microstructure of rocks—in the regular grids of small ions, i.e., crystal lattices. Radioactive elements trapped in crystal lattices decay according to the decay law, like a clock constantly ticking inside the rock. From the moment the "clock is set," the initial content of radioactive elements in the rock is fixed. As time passes, they continue to decay. The decay law tells us: each time node (t) corresponds strictly to a precise value of the remaining isotopes. By using a mass spectrometer to measure the remaining amounts of parent and daughter isotopes in the rock, and then reversing the decay equation to solve for the unknown t, we obtain the time elapsed during the entire decay process. Since this t starts counting from the moment the lattice was "formed," it naturally represents the formation age of its "host"—the rock itself. The lunar rock samples collected by humans so far are not many, but they can finally place a few "landmarks" with specific values in the massive sequence of "crater counting." The samples brought back by Chang'e-5 form one of the latest such "landmarks." Professor Liu Dunyi's team conducted lead (Pb) isotope dating and, combined with correlation correction using impact crater frequency statistics, finally confirmed that the rocks in the Chang'e-5 landing area (Oceanus Procellarum) formed 2 billion years ago. Today, the moon is a cold lump of rock. When did it become completely inactive? Previously, the scientific community generally believed it was 3 billion years ago. The latest research from Chang'e-5 has extended the active history of lunar geological activity by approximately 1 billion years. Considering that the total age of the moon is only about 4.5 billion years, 1 billion years is certainly not a small number. What evolutionary history does this huge time span represent? Different years, different storiesWhy did the moon cool down so early? The answer: it's too small. In the cold environment of space, smaller objects cool faster. When internal heat is insufficient to sustain active geological activity, the moon's surface becomes死寂. Earth, much larger, has excellent heat retention, so even today, we can still experience its vigorous geological activity on the surface. But who decides whether the moon had geological activity 2 billion years ago? Of course, lunar rocks—after all, the most intuitive products of geological activity are various rocks. If a lunar rock is dated to 2 billion years ago, it naturally indicates that there was active geological movement on the moon 2 billion years ago—at least, active volcanic activity. The lunar rocks involved in the research are basalts, formed when primitive mantle magma erupted onto the surface and solidified. This type of rock is not rare; it exists on both the moon and Earth. When we look up at the moon, those dark areas are basalts. Over 1,000 years ago, Li Bai admired the moon in Mount Emei and wrote poems about it, and the Golden Summit of Mount Emei is also made of basalt. When the moon first formed, it was in a magma ocean state, then gradually cooled. During the cooling process, the volume of magma shrank little by little, like a gradually drying-up pond. A drying-up pond often leads to "concentration." The most vivid example is fish that can only survive by moistening each other with their saliva. Some elements in magma (such as potassium, phosphorus, rare earth elements, etc., called "incompatible elements") behave similarly. As magma gradually cools, they refuse to solidify with the rock, preferring to concentrate in the remaining magma until the end. But as the lunar magma ocean finally dried up, they had nowhere to escape, destined to solidify into cold rocks. Thus, the latest residual magma products have extremely high contents of incompatible elements. The basalts collected by Chang'e-5 are not only 1 billion years younger than "the final drying-up period of the pond" but also show no signs of incompatible element concentration in their chemical characteristics. Piecing these puzzles together naturally reveals a new, sufficiently young period of lunar magma activity. A billion years after the lunar magma ocean completely solidified, it still contributed abundant fresh lava to the lunar surface (estimated at approximately 2,000 km³). Sources: Guangming Net, Guokr.com