¹Lingzhi Sun,¹Paul G. Lucey
Earth and Planetary Science Letters 643, 118931 Link to Article [https://doi.org/10.1016/j.epsl.2024.118931]
¹Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
Copyright Elsevier

The South Pole-Aitken (SPA) basin, excavating more than 100 km depth, must have exposed extensive lunar mantle materials, making it a promising location for sampling mantle material. To investigate the distribution of potential mantle materials across the SPA basin, we mapped the distribution of Mg# and major minerals contents using Moon Mineralogy Mapping data and radiative transfer modeling. We found that the potential mantle material exposed by SPA is Mg-rich orthopyroxenite, and we identified the locations of seven mantle candidate sites. The Chang’E-6 sample return site is located near mantle candidate sites within the Apollo basin, making it promising to return the first unambiguous mantle sample. Our Mg# and mineral mapping results show that the SPA ejecta is enriched in low-Ca pyroxene (LCP) with Mg#≥85, consistent with a post-overturn upper mantle composition. The enrichment of LCP in the SPA upper mantle may result from a low content of dunite or incomplete overturn.

¹C. J. Floyd,²S. Benito,¹P.-E. Martin,¹L. E. Jenkins,³E. Dunham,^1,4,5L. Daly,¹M. R. Lee
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14250]
¹School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK
²Ruhr-Universität Bochum, Chair of Materials Technology, Bochum, Germany
³Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, California, USA
⁴Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales, Australia
⁵Department of Materials, University of Oxford, Oxford, UK
Published by arrangement with John Wiley & Sons

The sizes of chondrules are a valuable tool for understanding relationships between meteorite groups and the affinity of ungrouped chondrites, documenting temporal/spatial variability in the solar nebula, and exploring the effects of parent body processing. Many of the recently reported sizes of chondrules within the CM carbonaceous chondrites differ significantly from the established literature average and are more closely comparable to those of chondrules within CO chondrites. Here, we report an updated analysis of chondrule dimensions within the CM group based on data from 1937 chondrules, obtained across a suite of CM lithologies ranging from petrologic subtypes CM2.2 to CM2.7. Our revised average CM chondrule size is 194 μm. Among the samples examined, a relationship was observed between petrologic subtype and chondrule size such that chondrule long-axis lengths are greater in the more highly aqueously altered lithologies. These findings suggest a greater similarity between the CM and CO chondrites than previously thought and support arguments for a genetic link between the two groups (i.e., the CM-CO clan). Using the 2-D and 3-D data gathered, we also apply numerous stereological corrections to examine their usefulness in correcting 2-D chondrule measurements within the CM chondrites. Alongside this analysis, we present the details of a standardized methodology for 2-D chondrule size measurement to facilitate more reliable inter-study comparisons.

¹L.E. McGraw,¹J.P. Emery,¹C.A. Thomas,²A.R. Rivkin
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116252]
¹Northern Arizona University, Department of Astronomy and Planetary Science, P.P. Box 6010, Flagstaff, AZ 86011, USA
²JHU/APL, 211100 Johns Hopkins Road, Laurel, MD 20723, United States of America
Copyright Elsevier

Near-Earth Asteroids (NEAs) are excellent laboratories for processes that affect the surfaces of airless bodies. Most NEAs were not expected to contain OH/H2O on their surfaces because they are primarily S-complex objects and sourced from the inner Main Belt, which is interior of the frost line, and their surface temperatures are high enough to remove these volatiles. However, a 3-μm feature typically indicative of OH/H2O was identified on other seemingly dry bodies in the inner Solar System, such as the Moon and Vesta, and more recently on the NEAs (433) Eros, (1036) Ganymed, and (3122) Florence. The most likely sources for OH/H2O on these bodies include carbonaceous chondrite impacts or interactions with protons implanted by solar wind. We investigated the causes of band depth and shape variations on NEAs by comparing new observations of Eros and Ganymed to those previously published and conducting a rotationally-resolved spectral study on Florence. All spectra discussed were collected by SpeX on NASA’s IRTF using the LXD_short (1.67–4.2 μm) mode to characterize the 3-μm region. Some observations also used the prism (0.7–2.52 μm) mode to characterize asteroid spectral type and investigate silicate composition dependencies. All three asteroids possess exogenously sourced OH/H2O and have spectra that show potential spatially correlated variations in band depth or shape. Eros’ band is slightly wider at the poles than at lower sub-observer latitudes, possibly due to its high obliquity, which ensures that each polar region is oriented toward the Sun over a significant part of its orbit. Ganymed’s trends in hydration band depth with sub-solar longitude and band I center suggest a carbonaceous or cometary impactor that struck the surface around 0° relative longitude, excavating a relatively magnesium- and olivine-enriched layer. Florence’s total hydrogen concentration remains stable across the surface even as the OH-to-H2O ratio changes as the asteroid rotates. These three examples suggest that non-native OH/H2O on other bodies will likely also be spatially dependent, regardless of delivery mechanism.

¹J.O. Edgar,²J.A. Gould,³K. Badreshany,²S.P. Graham,¹J. Telling
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116238]
¹School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
²Faculty of Sciences, Agriculture and Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
³Department of Archaeology, Durham University, Durham DH1 3LE, United Kingdom
Copyright Elsevier

The aeolian transport of sand generates fine material through abrasion. On Mars this process occurs at lower temperatures than on Earth, however, there is minimal data on the effects of temperature on aeolian abrasion rates. Here, results are reported of laboratory experiments where a suite of single-phase, Mars relevant minerals (feldspar, olivine, pyroxene, quartz and opal) were exposed to conditions simulating aeolian abrasion at temperatures common to the Martian surface (193 to 293 K). Our results suggest that mineral specific differences in solid phase parameters result in non-similar changes in abrasion rates with temperature. We propose this will ultimately exert a control on the composition and reactivity of the Martian surface.

^1,2Tao Anna Zhang,^1,3,4ShiYong Liao,^5,6RongChang Wu,^1,4Birger Schmitz
Earth and Planetary Science Letters 643, 118891 Link to Article [https://doi.org/10.1016/j.epsl.2024.118891]
¹Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
²School of Astronomy and Space Sciences, University of Science and Technology of China, Hefei, China
³Chinese Academy of Sciences Center for Excellence in Comparative Planetology, Hefei, China
⁴Astrogeobiology Laboratory, Lund University, Lund, Sweden
⁵Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
⁶Key Laboratory of Palaeobiology and Petroleum Stratigraphy, Nanjing, China
Copyright ELsevier

More than a quarter of all meteorites falling on Earth today originate from the breakup of the L-chondrite parent body (LCPB) ∼470 Ma ago, the largest documented asteroid breakup in the past ∼3 Ga. The event had a profound impact on the inner Solar System, resulting in an orders-of-magnitude increase in L-chondritic material in mid-Ordovician sediments on Earth. Here we show based on Ordovician strata at Puxi River, China, and Hällekis, Sweden, that the first arrival of LCPB dust to Earth can be used for global high-resolution correlation. The approach unravels a remarkable parallelism in facies development between distant paleocontinents and environmental perturbations on a global scale, possibly related to cooling of Earth by LCPB dust. In the Puxi River section, the first L-chondritic dust coincides with volcanic ash zircons, allowing U-Pb dating of the LCPB breakup. Ages determined from both sedimentary ash and recent L chondrites are consistently close to 470 Ma. A more precise age assessment is method-dependent, but the dual and independent dating options allow unique calibration possibilities. A similar increase in LCPB-derived dust as in Earth’s sediments may exist in coeval layered deposits on Mars, the Moon, and large asteroids and may be used as a chronostratigraphic tie point on an astronomical scale.

¹Takaaki Noguchi et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.07.038]
¹Division of Earth and Planetary Science, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
Copyright Elsevier

Chondrules and Ca-Al-rich inclusions (CAIs) have been considered characteristic constituents of chondritic meteorites, although the outward transportation of CAIs has been theoretically pointed out. Stardust samples recovered by the Stardust mission from the 81P/Wild2 comet contained chondrule-like objects (CLOs) and refractory inclusions that include CAIs and amoeboid olivine aggregates (AOAs). However, it was not proven that the CLOs, AOAs, and CAIs coexist with fine-grained materials equivalent to chondritic porous interplanetary dust particles (CP IDPs) containing abundant glass with embedded metal and sulfides (GEMS). Here we report on two type II CLOs, containing <90 Mg# in ferromagnesian silicates, enclosed in GEMS-rich CP Antarctic micrometeorites (AMMs) (CP IDPs that reached the surface of the Earth) and one igneous object rich in kosmochloric (Ko-rich: NaCrSi2O6-rich) high-Ca pyroxene and Fe-bearing olivine (KOOL) that is enclosed in a CP IDP. KOOL grains have also been found in Stardust samples and CP IDPs. These three igneous objects are embedded in fine-grained matrices that do not show any evidence of aqueous alteration. The low Mg# and elevated Δ17O of olivine and pyroxene in these CLOs and the KOOL grain are consistent with previously studied CLOs from comet 81P/Wild 2 and a giant cluster IDP. These results support the view that CP IDP- and CP AMM-like materials constitute samples from comets or comet-like icy bodies. The CLOs were formed in oxidizing environment beyond the snow line and then transferred to the comet-forming region. In contrast, a spinel-hibonite (SHIB) fragment found in an AMM experienced aqueous alteration of its rim. The SHIB fragment contains ultrarefractory oxides and refractory metal nuggets and has a 26Mg excess like typical meteoritic CAIs. The mineralogy of the fine-grained matrix is very similar to CP IDPs and CP AMMs. However, because “GEMS” in the matrix lacks Fe-Ni metal and amorphous silicate in it contains Fe, it is clear that the matrix weakly experienced aqueous alteration. Olivine / (Olivine + low-Ca pyroxene) ratios in the matrices of the four samples range from 0.4 to 0.6, which are comparable with those of anhydrous CP IDPs and CP MMs (around 0.5), and those of P- and D-type asteroids and Jupiter-family comets (around 0.5).

¹Craig R. Hulsey,¹Katie M. O’Sullivan
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14248]
¹Department of Geological Sciences, California State University, Bakersfield, California, USA
Published by arrangement with John Wiley & Sons

The first in-depth geochemical and petrological analyses of new lunar meteorite Northwest Africa (NWA) 11788 were conducted with the aim of better understanding the diversity of lunar rock types. Petrography, microcomputed tomography, electron probe microanalysis, and laser ablation inductively coupled plasma mass spectrometry were employed to analyze mineralogic/elemental makeup, petrologic profile, melt history, and inferred composition of the lunar mantle from which the crystals in this sample originated from. Geochemical maps of the lunar surface were generated to constrain potential lunar launch locations for NWA 11788. Potential launch locations are concentrated in the outer rims of impact basins on the lunar Eastern nearside limb (e.g., Crisium, Fecunditatis, Marginis, Smythii) and around the South Pole–Aitken Basin. Similarities in the major, minor, and trace element chemistry of NWA 11788 along with its potential launch locations suggest a petrogenetic relationship with regolith samples returned from the Luna 20 mission and the Apollo 16 and 17 magnesian granulites. Additionally, the results of this study add to the growing body of evidence that KREEP (potassium, rare earth elements, phosphorous)-poor, Mg-suite-“like” lithologies are common in non-Apollo-type locales, that KREEP may not be required to generate lithologies like the Mg-suite, and that KREEP is not globally distributed at present.

¹Addi Bischoff et al.(>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14245]
¹Institut für Planetologie, University of Münster, Münster, Germany
Published by arrangement with John Wiley & Sons

n 1889 the German poet and novelist Theodor Fontane wrote the popular literary ballad “Herr von Ribbeck auf Ribbeck im Havelland.” The Squire von Ribbeck is described as a gentle and generous person, who often gives away pears from his pear trees to children passing by and continued donating pears after his death. Now, 135 years later the rock called Ribbeck is giving us insight into processes that happened 4.5 billion years ago. The meteorite Ribbeck (official find location: 52°37′15″N, 12°45′40″E) fell January 21, 2024, and has been classified as a brecciated aubrite. This meteoroid actually entered the Earth’s atmosphere at 00:32:38 UTC over Brandenburg, west of Berlin, and the corresponding fireball was recorded by professional all sky and video cameras. More than 200 pieces (two proved by radionuclide analysis to belong to this fresh fall) were recovered totaling about 1.8 kg. Long-lived radionuclide and noble gas data are consistent with long cosmic ray exposure (55–62 Ma) and a preatmospheric radius of Ribbeck between 20 and 30 cm. The heavily brecciated aubrite consists of major (76 ± 3 vol%) coarse-grained FeO-free enstatite (En99.1Fs<0.04Wo0.9), with a significant abundance (15.0 ± 2.5 vol%) of albitic plagioclase (Ab95.3 An2.0Or2.7), minor forsterite (5.5 ± 1.5 vol%; Fo99.9) and 3.5 ± 1.0 vol% of opaque phases (mainly sulfides and metals) with traces of nearly FeO-free diopside (En53.2Wo46.8) and K-feldspar (Ab4.6Or95.4). The rock has a shock degree of S3 (U-S3), and terrestrial weathering has affected metals and sulfides, resulting in the brownish appearance of rock pieces and the partial destruction of certain sulfides already within days after the fall. The bulk chemical data confirm the feldspar-bearing aubritic composition. Ribbeck is closely related to the aubrite Bishopville. Ribbeck does not contain solar wind implanted gases and is a fragmental breccia. Concerning the Ti- and O-isotope compositions, the data are similar to those of other aubrites. They are also similar to E chondrites and fall close to the data point for the bulk silicate Earth (BSE). Before the Ribbeck meteoroid entered Earth’s atmosphere, it was observed in space as asteroid 2024 BX1. The aphelion distance of 2024 BX1’s orbit lies in the innermost region of the asteroid belt, which is populated by the Hungaria family of minor planets characterized by their E/X-type taxonomy and considered as the likely source of aubrites. The spectral comparison of an average large-scale emission spectrum of Mercury converted into reflectance and of the Ribbeck meteorite spectrum does not show any meaningful similarities.

¹E. V. Petrova,¹A. V. Chukin,²G. Varga,²Z. Dankházi,³G. Leitus,⁴I. Felner,⁵E. Kuzmann,⁵Z. Homonnay,¹V. I. Grokhovsky,¹M. I. Oshtrakh
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14249]
¹Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russian Federation
²Department of Materials Physics, Eötvös Loránd University, Budapest, Hungary
³Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
⁴Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
⁵Laboratory of Nuclear Chemistry, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
Published by arrangement with John Wiley & Sons

Fragment of Calama 009 L6 ordinary chondrite recovered in the Atacama Desert was chosen for a complex study of the bulk interior and the fusion crust by scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), magnetization measurements, and Mössbauer spectroscopy. SEM demonstrated the presence of Fe-Ni-Co grains, troilite and chromite inclusions in both the bulk interior and the fusion crust as well as many veins with ferric compound. EDS showed variations in the Ni concentration within the metal grains and within one metal phase in the grain. XRD revealed some differences in the contents of various phases in the bulk interior and in the fusion crust. XRD indicated the presence of magnesioferrite in the fusion crust as well as the formation of goethite nanoparticles with the mean size of 9 nm in both the bulk interior and the fusion crust. Magnetization measurements demonstrated the ferrimagnetic–paramagnetic phase transition in chromite at 44 K and low values of the saturation magnetization moments (6.46 and 3.26 emu g−1 at 100 K) for the bulk interior and the fusion crust, respectively, due to the lack of Fe-Ni-Co alloy as a result of weathering. The Mössbauer spectra of the bulk interior and the fusion crust showed some differences in the number and relative areas of spectral components. The revealing of the Mössbauer spectral components related to 57Fe in the M1 and M2 sites in olivine and orthopyroxene as well as determining the Fe2+ occupations of these sites from XRD permitted us to estimate the temperature of equilibrium cation distribution for these silicates which are (i) 662 K (XRD) and 706 K (Mössbauer spectroscopy) for olivine and (ii) 893 K (XRD) and 910 K (Mössbauer spectroscopy) for orthopyroxene.

¹Daniela Guerrero,¹Wolf Uwe Reimold,¹Natalia Hauser,²Igor Figueiredo,²Lucas Kenni,³Philippe Lambert
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14247]
¹Postgraduate Program in Geology, Laboratory of Geochronology, Geosciences Institute, University of Brasília, Brasília, Brazil
²Department of Geology—Escola de Minas, Federal University of Ouro Preto, Ouro Preto, Brazil
³CIRIR—Centre International de Recherche et de Restitution sur les Impacts et sur Rochechouart, Rochechouart, France
Published by arrangement with John Wiley & Sons

The Rochechouart impact structure in the northwestern part of the French Massif Central (FMC) has a great diversity of impactites, including monomict impact breccias, suevite, and impact melt rocks (IMRs). The structure is strongly eroded, which allows the study of impactites of the crater fill and the transition into the crater floor. The FMC has had a multistage geological evolution from the late Neoproterozoic to the Ordovician (600–450 Ma) until the later stages of the Variscan orogeny (~300 Ma). Previous geochronological work on Rochechouart has been focused mainly on the impactites and constraining the impact age, and scarce work has been done on the FMC-related target rocks. Here, U-Pb isotope analysis by LA-MC-ICP-MS has been conducted on zircon from two IMRs from the Recoudert and Montoume localities, and from a monzodiorite, a paragneiss, and two amphibolite samples of the basement to the impact structure. Zircon from the target rocks yielded mainly Neoproterozoic to Carboniferous ages (~924 to ~301 Ma) that can mostly be correlated to different stages of the geological evolution of the FMC. The monzodiorite also yielded a Permian age of 272 ± 12 Ma. Zircon from the IMRs, and especially from the Montoume sample, gave a comparatively higher diversity of Neoproterozoic to Jurassic ages (~552 to ~195 Ma). Provenance analysis for the zircon age populations of the impactites compared to those of the basement rocks shows overall poor correlation between the two age groups. This suggests that other target lithologies were involved in the formation of these impact melts as well. Post-Variscan and preimpact ages (281–226 Ma) obtained for both melt rocks probably reflect a previously unconstrained event in the evolution of the regional geological history. Ages similar to the currently most widely accepted impact age of ~204–206 Ma were obtained from both IMR samples. In addition, the Montoume melt rock yielded several post-204 Ma ages, which might reflect a to date unconstrained, about 194 Ma postimpact thermal/hydrothermal event.