Chinese scholars have made progress in the space weathering characteristics and causes of Chang'e-5 lunar soil

Figure Laboratory spectral characterization, in situ detection and remote sensing observation of the lunar surface of Chang'e-5 lunar soil

With the support of the National Natural Science Foundation of China (approval numbers: 41972322, 11941001, 42102280), the team of Professor Ling Zongcheng of Shandong University, together with the team of Liu Jianzhong, a researcher from the Institute of Geochemistry, Chinese Academy of Sciences, and He Zhiping, a researcher from the Shanghai Institute of Technical Physics, have made new progress
in the study of space weathering of Chang'e-5 lunar soil 。 The results, titled "Mature lunar soils from Fe-rich and young mare basalts in the Chang'e-5 regolith samples," were published
online in Nature Astronomy on December 12, 2022 。 Link to paper: _istranslated="1">.

The interaction of the Earth's atmosphere, water and organisms with surface rocks and minerals has produced complex weathering that has long altered the topography of the earth's surface, causing rocks to break into loose soil
.
Although there is no dense atmosphere, large-scale liquid water, and no form of life on the moon, there is also a special process of "space weathering", even for billions of years
.
High-energy cosmic rays, solar wind and micrometeoroid impacts are the main factors
responsible for the weathering of the lunar surface in space.
Unlike weathering on Earth, lunar surface space weathering produces nano-sized metallic iron elements (nanoiron) at the edge of lunar soil particles, which can change the spectral characteristics
of lunar surface material.
Generally speaking, the longer the lunar soil is subjected to space weathering, the more nanoiron it contains, and the more mature
the lunar soil will be.

Due to the spatial (9°S−27°N) and time (3,04 billion years) limitations of the previous Apollo/Luna sample sampling sites, the study of space weathering of young basalts on the lunar surface still requires new samples
.
On December 1, 2020, China's Chang'e-5 mission successfully landed in the northern part of the lunar storm ocean (43.
06°N), returning the youngest (~2 billion years) and extremely iron-rich (iron oxide content percentage ~22.
5%) lunar sea basalt samples
to date.
In addition to available laboratory analysis of samples from lunar soil, Chang'e-5 performed in situ spectral measurements of the landing area before and after sampling (figure), which provides an important opportunity
to study the mechanism of space weathering in young basalts.
In this study, important lunar soil parameters such as the percentage (0.
48±0.
03%) and maturity index (~66±3.
2) of the lunar soil composition of the lunar soil layer of Chang'e-5 landing site were obtained, revealing that there is a special spatial weathering mechanism in young iron-rich basalt, that is, during space weathering, the lunar soil of this type will produce nanoiron faster and accelerate aggregation to form metal iron clusters
with larger particle sizes.
This provides a new perspective
on the interaction of lunar surface material with the space environment.
Although Chang'e-5 basalt is very young, Chang'e-5 lunar soil is more mature, even more mature than some Apollo lunar soil
.

Using the multispectral remote sensing images obtained by lunar orbital exploration, this study obtained a nanoiron abundance map (figure) around the Chang'e-5 landing site, clearly showing the indistinguishable sputter boundary
in the reflectivity image.
Chang'e-5 landed on the sputter pattern of Xu Guangqi Crater ( about 400 m in diameter ) , revealing that the Chang'e 5 lunar soil was mainly due to the excavation of Xu Guangqi Crater, and then experienced about 2430 million years of space weathering and cosmic exposure
.

This study comprehensively uses multi-source data such as Chang'e-5 lunar soil samples and lunar surface in situ spectroscopy to constrain the source and exposure age of Chang'e-5 lunar soil, reveals the unique space weathering characteristics of young lunar basalt, and provides new observational evidence
for the special space weathering mechanism in iron-rich lunar soil.