摘要
The Chang’e-5 mission returned new lunar samples after the last sample mission of the Moon 44 years ago,and is also the first mission that China has completed the sampling of extraterrestrial bodies.Recently,independent teams from the Institute of Geology,Chinese Academy of Geological Sciences,and the National Astronomical Observatories and the Institute of Geology and Geophysics,Chinese Academy of Sciences reported the first batch of results of Chang’e-5 lunar samples.The basic physical properties of the Chang’e-5 soil are within the range of the Apollo and Luna samples though the Chang’e-5 soil is finer-grained,better sorted,and has a slightly lower true density than the mare basalt previosuly reported.The Pb-Pb dating of U-rich minerals in the Chang’e-5 basalt clasts indicated that they formed at about 2.0 Ga,800 million years younger than the youngest lunar sample recovered previously(2.8 Ga),confirming that lunar volcanic activity can last at least until 2 Ga.In-situ Sr-Nd isotope analyses suggested that the Chang’e-5 basalt originated from a depleted mantle source.The contribution of the KREEP component is less than 5%,which excluded the hypothesis that KREEP-rich sources provide an additional heat source for mantle melting.In addition,water contents and H isotopes of apatite and melt inclusions of the Chang’e-5 basalt suggested that the source region is not rich in water which can lower the melting point.Therefore,the reason why lunar volcanic activity can last so long is still unclear,which is a new direction for future lunar exploration and research.
