Constraining the formation and transport of lunar impact glasses using the ages and chemical compositions of Chang'e-5 glass beads.

Impact glasses found in lunar soils provide a possible window into the impact history of the inner solar system. However, their use for precise reconstruction of this history is limited by an incomplete understanding of the physical mechanisms responsible for their origin and distribution and possible relationships to local and regional geology. Here, we report U-Pb isotopic dates and chemical compositions of impact glasses from the Chang'e-5 soil and quantitative models of impact melt formation and ejection that account for the compositions of these glasses. The predominantly local provenance indicated by their compositions, which constrains transport distances to <~150 kilometers, and the age-frequency distribution are consistent with formation mainly in impact craters 1 to 5 kilometers in diameter. Based on geological mapping and impact cratering theory, we tentatively identify specific craters on the basaltic unit sampled by Chang'e-5 that may have produced these glasses and compare their ages with the impact record of the asteroid belt.

Age and composition of young basalts on the Moon, measured from samples returned by Chang'e-5.

Orbital data indicate that the youngest volcanic units on the Moon are basalt lavas in Oceanus Procellarum, a region with high levels of the heat-producing elements potassium, thorium, and uranium. The Chang'e-5 mission collected samples of these young lunar basalts and returned them to Earth for laboratory analysis. We measure an age of 1963 ± 57 million years for these lavas and determine their chemical and mineralogical compositions. This age constrains the lunar impact chronology of the inner Solar System and the thermal evolution of the Moon. There is no evidence for high concentrations of heat-producing elements in the deep mantle of the Moon that generated these lavas, so alternate explanations are required for the longevity of lunar magmatism.

The fractional patterns of polybrominated diphenyl ethers in the soil of the central Tibetan Plateau, China: the influence of soil components.

Sixteen soil samples were collected from the central Tibetan Plateau (CTP). The soil concentrations of polybrominated diphenyl ethers (PBDEs) in CTP were analyzed. The detected 42 congeners were divided into light, intermediate and heavy fractions. In addition to the various minerals, other soil properties were also characterized, including the content of soil organic carbon (SOC) and the particle size distribution. The clay content is positively related to the intermediate fraction of the PBDEs and negatively related to the light and heavy fractions. Similar correlations were observed for SOC and the fine-particle fraction (size < 2 µm). The coefficient of determination (r(2)) associated with a linear regression indicated that the clays were more highly correlated with the fractional pattern of the PBDEs than with the other properties, such as SOC and the fine-particle fraction. The values of r(2) between clays and three fractions of PBDEs are 0.70, 0.69 and 0.58.

Altitudinal distribution of polybrominated diphenyl ethers (PBDEs) in the soil along Central Tibetan Plateau, China.

The distribution of PBDEs in the mountains of the Central Tibetan Plateau (CTP) was determined by sampling soil along an elevation transect. The analysis of soil extracts was performed by gas chromatography and high-resolution mass spectrometry, through which 42 congeners were detected. The samples were also characterized with respect to the soil organic carbon (SOC) and mineral contents. The logarithmic concentration for three of the fractions and the ΣPBDEs increased significantly and exponentially with altitude. The slope value of the linear regression between the logarithm of the clay-normalized three fractional concentrations and the altitude is in the following order: light>intermediate