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the reporter learned from the national astronomical observatory of the chinese academy of sciences that on september 17, a joint research team led by li chunlai of the national astronomical observatory of the chinese academy of sciences, hu hao of the china lunar exploration and space engineering center, and yang mengfei of the beijing institute of control engineering published a paper in the national science review (nsr).the first research paper on the chang'e-6 returned samples was published, elaborating on the physical, mineralogical and geochemical characteristics of the returned samples.

characteristics of lunar soil and rock debris

the paper points out that the samples returned by chang'e 6 havelower density, indicating that its structure is relatively loose and has a high porosity. particle analysis shows that the lunar soilparticle size shows bimodal distribution, suggesting that the samples may have experienced a mixture of different sources.the content of plagioclase increased significantly, while the content of olivine decreased significantly., indicating that the lunar soil in this area is obviously affected by non-basaltic materials.

in addition, the rock fragments collected by chang'e-6 are mainly composed of basalt, breccia, cementite, light-colored rocks and glassy materials. among them, basalt fragments account for 30% to 40% of the total, and its minerals are mainly pyroxene, plagioclase and ilmenite, with extremely low olivine content. breccia and cementite are composed of basalt fragments, glass beads, glass fragments and a small amount of light-colored rock fragments such as plagioclase and syenite, further revealing the complexity of the source of the samples.

△ typical images of samples returned by chang'e-6. (a) some rock debris particles larger than 1 mm selected from the samples scooped up by chang'e-6. (b) backscatter images (bse) of basalt debris with different structural characteristics, (fg) breccia, and (h) cementite. microscope photos of typical basalt (i and j), cementite (k), light-colored rock debris (l), and glass (m and n).

mineralogy and geochemical characteristics

mineralogical analysis shows that the main phases of the chang'e-6 lunar soil samples areplagioclase (32.6%), pyroxene (33.3%) and glass (29.4%), where the glass content is close to the lower limit of apollo samples. in addition, a small amount of orthopyroxene was detected in the sample, suggesting the presence of non-basaltic materials.

geochemical analysis further revealed that the samples from chang'e 6 containedthe content of aluminum oxide (al₂o₃) and calcium oxide (cao) is high, while the content of iron oxide (feo) is relatively low, which is consistent with the characteristics of a mixture of lunar mare basalt and anorthosite.the contents of trace elements such as thorium (th), uranium (u) and potassium (k) are significantly lower than those in kreep basalt., which showed huge differences from samples from the apollo mission and the chang'e-5 mission located in the klip terrane in the ocean of storms on the front side of the moon.

a new chapter in lunar science

△ schematic diagram of the landing points of chang'e 6, chang'e 5, the us apollo program and the soviet luna program

it is understood that in the vast journey of exploring the moon, humans have brought back more than 380 kilograms of samples from the lunar surface through 6 apollo missions, 3 luna missions and 1 chang'e 5 mission. however, all these samples came from the front of the moon. china's chang'e 6 missionthe first human feat of collecting samples from the far side of the moon, bringing back 1935.3 grams of precious samples. the landing point of this sampling mission is located in the south pole-aitken (spa) basin on the far side of the moon. the sampling point is located at the edge of the apollo impact crater inside the spa basin. the lunar crust in this area is extremely thin, and it is expected to reveal the original material of the early impact basin on the far side of the moon.

the chang'e-6 samples include not only basalts that record the history of volcanic activity, but also non-basaltic materials from other regions. these samples, like "messengers" from the ancient moon, provide important first-hand information for our study of the early impact history of the moon, volcanic activity on the far side of the moon, and the composition of the moon's interior.

the samples from the far side of the moon brought back by chang'e-6 not only fill the historical gap in the study of the far side of the moon, but also provide direct evidence for our study of the early evolution of the moon, the volcanic activity on the far side and the impact history, and open up a new perspective for understanding the geological differences between the far side and the near side of the moon. with the in-depth study of these precious samples, it is expected that we will continue to deepen our understanding of the internal structure, material composition and formation and evolution process of the moon, and promote the vigorous development of lunar and planetary science.

(cctv reporter shuai junquan and chu erjia)