Meteoritics & Planetary Science最新文献

Angrites and eucrites are among the oldest basaltic rocks in the solar system. However, the shock histories of these meteorite groups differ markedly, as most angrites show little to no evidence of shock metamorphism. While some angrites exhibit weak wavy extinction in olivine, indicative of low-level shock, only two—Northwest Africa (NWA) 1670 and NWA 7203—are known to preserve significant shock features such as shock melt veins. To better constrain the shock history of angrites, we performed noble gas analyses on the rare shock-metamorphosed angrite NWA 7203 to determine its cosmic ray exposure and gas retention ages. Neon in NWA 7203 is entirely cosmogenic, and combined neon and argon data yield a cosmic ray exposure age of 22.7 ± 3.1 Ma (2σ). This age nominally differs from that of the other shocked angrite, NWA 1670, but is comparable to that of the unshocked angrite NWA 7812. NWA 7203 may have been ejected from a rubble pile-like asteroid composed of both shocked and unshocked materials. Two distinct ⁴⁰Ar/³⁹Ar apparent ages, 3.38 ± 0.10 Ga and 1.41 ± 0.11 Ga, were obtained, likely reflecting variable argon loss during a single impact-induced thermal event that occurred no earlier than 1.41 ± 0.11 Ga (2σ). This is the first report for the shock metamorphic age of an angrite. Our results reinforce the view that even shocked angrites lack clear evidence of a catastrophic disruption of their parent body (>100 km) hypothesized to have occurred in the early solar system. To resolve this conundrum, we propose that angrites may have experienced extensive melting during such an event, which suppressed or erased conventional shock features. If this impact occurred near the time of their crystallization (>4564 Ma), it may have been a “hot shock” event driven by heat from short-lived radionuclides. Such an event could have generated large volumes of shock melt, from which quenched angrites subsequently formed. We suggest that differentiated planetary bodies may have commonly undergone such early-stage disruption events during the formative epoch of the solar system.

The lunar regolith contains a rich history of Solar System impact events and solar activity. Many future missions will land in the south polar region of the Moon, a heavily impact cratered highland terrain, similar to the Apollo 16 landing site. In preparation, it is important to understand regolith processes and the upper stratigraphy of the regolith in typical highlands regions. In this study, we used a nondestructive scanning electron microscope with the QEMSCAN software to analyze the mineralogical compositions and maturities of regolith samples from various depths within four Apollo 16 double drive tubes. Our results support previous analyses made using other techniques that there is a lack of stratigraphic correlation across the central and southern regions of the Apollo 16 landing site, where the cores show lateral and vertical heterogeneities. Our results also show that QEMSCAN is a powerful tool for rapid, quantitative assessment of regolith characteristics. Our findings can serve as an analog for south polar regolith, providing context for upcoming missions looking to sample the subsurface regolith in the south polar region.

Instrumentally determined pre-atmospheric orbits of meteorites offer crucial constraints on the provenance of extraterrestrial material and the dynamical pathways that deliver it to Earth. However, recovery efforts are focused on larger and slower impacts due to their higher survival probabilities and ease of detection. In this study, we investigate the prevalence of these biases in the population of recovered meteorites with known orbits. We compiled a data set of 75 meteorites with triangulated trajectories and compared their orbits to 538 potential $��>�$1 g meteorite-dropping fireballs detected by the Global Fireball Observatory, the European Fireball Network, and the Fireball Recovery and InterPlanetary Observation Network. Our results reveal that objects with small semi-major axis values (a$��<�$1.8 au) appear 2–3$��\times �$ more often than expected. The current sample of meteorites with known orbits does not reflect the sources of meteorites in our collections, and it is essential to account for search and recovery biases to obtain a more representative understanding of meteorite source contributions.

Saper, L., Liu, Y., Kipp, M. A., Burney, D., Ma, C., Tissot, F. L. H., Young, E., Treffkorn, J. and Farley, K. A. (2025) Chemical, Isotopic (O, He, U), and Petrological Characteristics of a Slowly Cooled Enriched Gabbroic Shergottite, Northwest Africa 13134. Meteoritics & Planetary Science, 60: 1119–1150. https://doi.org/10.1111/maps.14345

In Table 6, the two glasses analyzed using the phosphate EPMA routine had Na₂O contents erroneously reported as K₂O contents. We have provided an updated Table 6 corrected for these two entries.

We apologize for this error.

Climate change is inducing a global atmospheric contraction above the tropopause (~10 km), leading to systematic decrease in neutral air density. The impact of climate change on small meteoroids has already been observed over the last two decades, with documented shifts in their ablation altitudes in the mesosphere (~50–85 km) and lower thermosphere (~85–120 km). This study evaluates the potential effect of these changes on meteorite-dropping fireballs, which typically penetrate the stratosphere (~10–50 km). As a case study, we simulate the atmospheric entry of the fragile Winchcombe carbonaceous chondrite under projected atmospheric conditions for the year 2100 assuming a moderate future emission scenario. Using a semi-empirical fragmentation and ablation model, we compare the meteoroid's light curve and deceleration under present and future atmospheric density profiles. The results indicate a modest variation of the ablation heights, with the catastrophic fragmentation occurring 300 m lower and the luminous flight terminating 190 m higher. The absolute magnitude peak remains unchanged, but the fireball would appear 0.5 dimmer above ~120 km. The surviving meteorite mass is reduced by only 0.1 g. Our findings indicate that century-scale variations in atmospheric density caused by climate change moderately influence bright fireballs and have a minimal impact on meteorite survival.

We used trace element analyses of plagioclase from Mg-suite troctolite 76535 to estimate the Rare Earth Element (REE) concentrations of its parental liquid and assess the feasibility of an urKREEP contribution to the Mg-suite parental liquid. We measured 33 trace elements in 76535 plagioclase separates. Our measurements revealed enrichments in incompatible elements consistent with previous analyses. Using the measured REE concentrations, we estimated the REE concentrations of the unfractionated Mg-suite parental liquid using a RhyoliteMELTS-based forward model. Compared to chondritic concentrations, the Mg-suite parental liquid is ~100 times more enriched in light REEs and ~10 times more enriched in heavy REEs. We sought to explore the feasibility of reproducing these enrichments in the parental liquid through assimilation of urKREEP by a partial melt of rising LMO cumulates during cumulate mantle overturn. We show that these enrichments can be reproduced by a 30%–50% addition of fully molten urKREEP to the LMO cumulate melt, if the LMO cumulate melt and urKREEP are in thermal equilibrium with each other. However, the Mg# of these mixtures (57–68) is too low to produce the most Mg-rich olivine (Fo 91) observed in Mg-suite troctolites. Alternatively, assuming that the LMO cumulate melt and urKREEP are in thermal disequilibrium, we reproduced both the REE abundances and Mg# of the Mg-suite parental liquid with only a 10% addition of the urKREEP partial melt. These results support the feasibility of urKREEP assimilation as a mechanism for generating the incompatible element enrichments in Mg-suite magmas while preserving their major element chemistry.