Hejiu Hui

Formation of the earliest evolved rocks on terrestrial planets remains poorly understood. The ancient Martian regolith breccia meteorite (MRB) contains feldspar-rich clasts, which could be evolved. Here, we report the first discovery of Martian sarcopside within an igneous clast (CS) of MRB. The mineral assemblage, the presence of sarcopside included in chlorapatite, and the equilibrium temperature of 774 ± 20 °C for plagioclase and alkali feldspar in clast CS collectively demonstrate that this clast crystallized from an evolved magma. A new U-Pb zircon age of 4525 ± 66 Ma places crystallization of these feldspar-bearing clasts within the first ∼100 Myr of Martian crust evolution. Furthermore, the equilibrium temperatures of all 16 two-feldspar-bearing clasts observed in small chips of MRB are < 1000 °C, and half are < 800 °C. The low equilibrium temperatures and mineral assemblages of different clasts are consistent with the interpretation that diverse evolved magmatism could have been present on early Mars. These ancient clasts provide a unique window into the timing and thermal regimes of evolved magmatism within the early Martian crust. More importantly, taken together with evidence from evolved lunar samples and asteroidal meteorites, the evolved lithologies on early Mars inferred from MRB indicate that evolved magmatism may have played an important role in the early Solar system.

Catastrophic disruptions of planetesimals occur in high-velocity collisions. Radioisotope dating of planetesimal disruption events recorded in meteorites confirms frequent catastrophic collisions in the first 10 Myr of the Solar System, reflecting a violent environment of the time. However, the nebula gas can damp the eccentricity of planetesimals and suppress the frequency of planetesimal collisions. Strong dynamical mechanisms that excited the protoplanetary disk are required. Here we show that the sweeping secular resonances of Jupiter and Saturn induced by the nebular gas dissipation, together with the mean motion resonances of Jupiter, can trigger a large number of catastrophic collisions, which occur episodically when the secular resonances are at 2–3 astronomical units and continue thereafter. After the gas dissipation completes, catastrophic collisions decrease in frequency, with scattering by planetary embryos becoming the major driving force of the collisions. Our results suggest that the violent environment excited by secular and mean motion resonances can be ubiquitous in protoplanetary disks during nebula dissipation.

Unraveling the origin of lunar farside-nearside asymmetry requires comparison of various lithologies from both hemispheres, a task long hindered by the absence of farside samples. Here, we present geochemical data for Chang’e 6 (CE6) lithologies from the farside, revealing systematic differences from their nearside counterparts. CE6 anorthosites are more magnesian, while CE6 Mg-suite samples contain lower potassium, rare earth element, and phosphorus (KREEP) contents. However, CE6 Mg-suite samples have Mg# values comparable to Apollo Mg-suite rocks. The mantle source of CE6 2.8-billion-year-old basalts is similar to that of Apollo low-Ti basalts. This systematic geochemical comparison of farside and nearside lithologies, which sample distinct lunar magma ocean (LMO) product layers, indicates that the mantle displays no clear compositional dichotomy. In contrast, the farside anorthositic crust is more magnesium-rich and thicker, while late-stage LMO products may be thinner on the farside. Therefore, we propose that the observed farside-nearside asymmetry originated from lateral thermal convection within a long-lived LMO on the tidally locked Moon.

The basalt clasts returned by the Chang'e‐5 (CE‐5) mission recorded a spatial diversity of cooling histories, with various cooling rates and timescales reported for different clasts. However, the temporal evolution of thermal conditions during cooling has received limited attention. Here, we report ∼0.3‰ and ∼0.8‰ in δ ⁵⁶ Fe and δ ²⁶ Mg variability at the mineral‐grain scale in a CE‐5 basalt clast, which are negatively correlated, unambiguously pinpointing kinetic isotope fractionation driven by inter‐diffusion in the minerals. Combined with systematic diffusion modeling and grain size analysis, the Mg–Fe isotopic variability reveals a substantial decrease in the cooling rate from 30–100°C/day to 1–10°C/day during the crystallization and cooling of the clast. The change in thermal conditions during eruption or magma overlaying caused the cooling rate to decrease. Our results highlight the importance of temporal evolution of thermal conditions in the crystallization and cooling history of magmatic systems.

Accurate isotope compositions of nanoparticles in planetary materials provide critical constraints on the evolution of the early solar system. Atom probe tomography (APT) can analyze isotopes in situ with the highest spatial resolution, making it ideal for nanoscale planetary materials. However, significant deviations between isotope ratios determined using APT and a traditional mass spectrometer have hindered the wide application of APT in isotope analysis. Here, we propose that these isotope ratio discrepancies arise from different uncounted rates of the isotopes in APT analysis. Theoretical assessment indicates that such discrepancies can be corrected using a suite of reference materials. Iron isotope analyses of Fe–Mn–Ni steels and meteoritic irons using APT and a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) confirm a strong linear correlation between the two data sets, supporting the establishment of ⁵⁶Fe/⁵⁴Fe and ⁵⁷Fe/⁵⁴Fe calibration curves for APT data correction. The calibration curves were subsequently validated using four meteoritic irons with known Fe isotope ratios. Combining all of the errors, our corrected APT results achieve a 2σ uncertainty of 56Fe. This precision demonstrates that our calibrated APT protocol enables accurate isotope determination, unlocking the potential of APT for precise isotope analysis of nanoscale planetary materials.

The absolute age of the Moon’s largest impact basin, the South Pole-Aitken (SPA) basin, remains unconfidently constrained due to the absence of datable materials directly linked to its formation. Basaltic magma can erupt on the Moon’s surface only after an impact event has sufficiently thinned the thick lunar crust. Therefore, identifying the oldest basalts in the SPA basin could provide key constraints on the its formation age. We report the oldest basalt yet returned, dated at 4.341±0.003 Ga, from the SPA basin sampled by the Chang’e 6 mission. Eruption of this high-alumina basaltic magma requires an extremely thin crust, which must have occurred within an impact basin exceeding 800 km in diameter. Only the SPA basin satisfies both crater scale and basaltic eruption age. Consequently, this basalt age yields a tight lower age limit for the SPA basin. Accounting for impact melt solidification timescale, the SPA basin formed at 4.37±0.03 Ga. Furthermore, trace element and Pb isotopic compositions of this basalt suggest a relatively fertile mantle source barely melted by the SPA-forming impact. This fertile source indicates that lunar interior may have remained partially molten before impact, thereby preventing it from extensive impact-induced melting, a mechanism supported by numerical simulations. Our results suggest that the SPA-forming impact may have limited effects on mantle structure and composition in the Moon.

The lunar mantle remains enigmatical due to the absence of unequivocally identified mantle materials. The South Pole-Aitken (SPA) basin, as the largest impact structure on the Moon, holds great potential to have excavated lunar mantle materials. The samples returned from the SPA basin by Chang’e 6 (CE6) mission, thus, provide an unprecedented opportunity to search for mantle materials. We report lunar mantle olivine and orthopyroxene hosted in a 4.1-Ga high-alumina CE6 basalt. These mantle crystals with reaction rims are highly magnesian and are in equilibrium with the bulk melt, indicating that they are residues of mantle partial melting occurring at depths of 170–190 km below the Moon's surface. The extreme enrichment of rare earth elements (REEs) in the residual orthopyroxene coupled with a high μ value in the mantle source provides compelling evidence that this farside mantle was metasomatized by potassium, REEs, and phosphorus (KREEP) melt. These mantle mineral residues thus directly demonstrate the presence of KREEP melt on the Moon’s farside. Moreover, the KREEP melt must have migrated downward into the deep mantle before partial melting. This finding suggests that KREEP was likely distributed globally, supporting the existence of a magma ocean on the early Moon.

Catastrophic disruptions of planetesimals occur in high-velocity collisions. Radioisotope dating of planetesimal disruption events recorded in meteorites confirms frequent catastrophic collisions in the first $\sim$10 Myr of the Solar System, reflecting a violent environment of the time. However, the nebula gas can damp the eccentricity of planetesimals and suppress the frequency of planetesimal collisions. Strong dynamical mechanisms that excited the protoplanetary disk are required. Here we show that the sweeping secular resonances of Jupiter and Saturn induced by the nebular gas dissipation, together with the mean motion resonances of Jupiter, can trigger a large number of catastrophic collisions, which occur episodically when the secular resonances are at $\sim$2-3 au and continue thereafter. After the gas dissipation completes, catastrophic collisions decrease in frequency, with scattering by planetary embryos becoming the major driving force of the collisions. Our results suggest that the violent environment excited by secular and mean motion resonances can be ubiquitous in protoplanetary disks during nebula dissipation.