The samples brought back from the back of the moon by Chang'e-6 for the first time are still bringing us surprises!Researchers from the National Space Science Center of the Chinese Academy of Sciences systematically analyzed the exposure of anorthosite in the lunar Apollo Basin, and successfully identified 51 pure anorthosite exposure points, distributed on the northern edge, southern edge, basin floor, and central peak ring structure of the Apollo Basin.
This means,The lunar samples brought back from the Apollo Basin by Chang'e-6 may contain anorthosite representing the original lunar crust composition!
Everyone knows that the front and back of the moon are completely different, but the reason has always been a mystery.
Scientists believe that the early moon was like a sea of boiling magma. When it cooled, calcium-rich anorthosite floated to the surface due to its lighter weight, forming the oldest primitive lunar crust.
In the past, U.S. Apollo missions have brought back such anorthosite samples from the lunar front, but the samples were underrepresented and had limited spatial coverage.
Whether the original lunar crust on the far side of the moon is the same as that on the front side has not been clear to the academic community.
▲(a) Digital elevation model of the moon with the SPA South Pole-Aitken Basin as the projection center. (b), (c), and (d) respectively represent the lunar crust thickness, images, and MI data false color images in the Apollo Basin region. In (d), the R, G, and B channels are the absorption depths of 900nm, 1050nm, and 1250nm respectively.
The samples brought back by Chang'e-6 from the Apollo Basin on the far side of the moon bring hope to answer this question.
In this latest study, researchers used observation data obtained by the "Moon Goddess" lunar probe's multi-band imager and compared it with known lunar rock databases, simulated spectra, and anorthosite samples brought back by the Apollo missions. They successfully found 51 rock outcrops that clearly contain anorthosite.
Analysis shows,The plagioclase in these places is extremely pure and belongs to pure anorthosite. It is mainly exposed on the walls and central peak of impact craters formed later, as if they were excavated by impact events.
▲The decontinuum spectra of 51 identified anorthosite outcrops are divided into four groups according to their geographical location: (a) northern basin margin, (b) basin floor, (c) peak ring, (d) southern basin margin
The Chang'e-6 landing area is located in the maria plain area in the southern part of the Apollo Basin, and is surrounded by multiple impact craters containing pure anorthosite outcrops.
Simulation calculations show that,The material sputtered from these anorthosite-containing impact craters accumulated more than 10 centimeters thick at the Chang'e-6 landing site.
This means that when Chang'e-6 digs out lunar soil, it is very likely that it will dig up these fragments from the moon's oldest crust.
At the same time, there are also some low-calcium pyroxenes that may come from the lunar mantle in the Apollo Basin.
therefore,The "lunar specialties" brought back by Chang'e-6 are likely to contain both primitive lunar crust and lunar mantle materials.
▲Partial enlargements of five representative anorthosite exposure points displayed on the Chang'e-2 CCD image (left) and MI false color image (right). Blue dots mark exposures of iron-rich anorthositic rocks, arrows point north
Liu Yang, a researcher at the National Space Science Center of the Chinese Academy of Sciences, said that this study deepens our understanding of the distribution of the original lunar crust in this area on the far side of the moon, can strongly support the study of Chang'e-6 samples, and provides an important reference for studying the cooling process of the lunar magma ocean, the evolution of the lunar crust and the lunar mantle, and other early lunar history.