The Chang'e‐5 (CE‐5) materials represent the youngest returned lunar samples. We performed a detailed Raman spectroscopic survey (1259‐point Raman modal analysis) to evaluate the mineralogical characteristics of CE‐5 soils, constraining the source materials and shock effects of these unique samples. The mineral chemistry (e.g., Mg#3‐60 for mafic minerals) and modal abundance (first distinguishing basaltic and feldspathic glasses) of CE‐5 mare soils are different from those of Apollo high‐ and low‐Ti basalts, possibly representing an intermediate‐Ti mare basalt. The occurrence of minor Mg‐rich materials (Mg# > 70) provides evidence of contamination from ∼5% to 7% exogenous materials, possibly related to Mg‐suite rocks. The microimage analyses suggest that the CE‐5 soils are fine‐grained, mature, and unimodal particle‐size distribution, highlighting that micrometeorite reworking dominates the CE‐5 regolith evolution with minor mixing from nonmare materials. The pressure‐sensitive minerals (quartz and maskelynite) indicate that 17–25.8 GPa shock pressures might be the higher limit in a relatively young lunar terrain.
A remote Raman prototype with a function of excitation energy adjusting for the purpose of obtaining a Raman signal with good signal-to-noise ratio (SNR), saving power consumption, and possibly avoiding destroying a target by high energy pulses, which may have applications for Chinese planetary explorations, has been setup and demonstrated for detecting different minerals. The system consists of a spectrograph equipped with a thermoelectrically cooled charge-coupled device (CCD) detector, a telescope with 150 mm diameter and 1500 mm focus length, and a compact 1064 nm Nd:YAG Q-switched laser with an electrical adjusted pulse energy from 0 to 200 mJ/pulse. A KTP crystal was used for second harmonic generation in a 1064 nm laser to generate a 532 nm laser, which is the source of Raman scatting. Different laser pulse energies and integration time were used to obtain distinguishable remote Raman spectra of various samples. Results show that observed remote Raman spectra at a distance of 4 m enable us to identify silicates, carbonates, sulfates, perchlorates, water/water ice, and organics that have been found or may exist on extraterrestrial planets. Detailed Raman spectral assignments of the measured planetary materials and the feasible applications of remote Raman system for planetary explorations are discussed.
Mare basalts from lunar farside are pivotal for unraveling lunar nearside-farside dichotomies and global thermal history. The Chang’e-6 (CE-6) mission conducted the first sampling from a young basaltic unit within the Apollo basin on the lunar farside. Here, we performed comprehensive petrological and geochemical analyses on the CE-6 basalt clasts. The CE-6 basalt is a low-titanium basalt (about 5 wt% TiO2) depleted in KREEP components. The absence of olivine, particularly magnesium-rich olivine, suggests that the basaltic magma underwent extensive fractional crystallization. Thermodynamic modeling supports that there may be 10%–20% late-stage cumulates of magma ocean (clinopyroxene and ilmenite) present in the source region of CE-6 basalt. The magma derived from the partial melting of such lunar mantle may undergo fractional crystallization dominated by olivine and clinopyroxene within a shallow magma cg1hamber, followed by eruption. Modeling of the REE pattern further indicates that 3%–7% batch melting of a depleted lunar mantle source, combined with 21%–59% fractional crystallization, achieves the observed REE abundances of CE-6 basalt. The genesis of CE-6 basalt could be attributed to the synergistic influence of a readily fusible mantle source, resulting from the incorporation of late-stage cumulates, and the crust-mantle deformation induced by large impacts. This could serve as a paradigm for the formation of other young basalts on the Moon.
Lunar materials were believed to have formed and been preserved in a reducing environment, with only Fe 2+ and Fe 0 present. Native oxidized minerals, such as hematite, have not been validated in previously returned lunar samples. In this work, we report the discovery of micrometer-scale crystalline Fe 2 O 3 in the forms of hematite (α-Fe 2 O 3 ) and maghemite (γ-Fe 2 O 3 ) overgrowing troilite in the recently returned Chang’e-6 (CE6) lunar soils. It is possible that impact-induced oxygen release created localized micrometer-scale regions of elevated oxygen fugacity, facilitating the formation of Fe 2 O 3 at temperatures between ~700° and 1000°C. This finding provides credible evidence for the presence of Fe 2 O 3 on the lunar surface, challenging the traditional understanding of lunar surface redox states. In addition, the Fe 2 O 3 in the form of maghemite may be the mineralogical reason for the generation of the magnetic anomalies observed around the South Pole–Aitken basin.