Kees C. WELTEN¹, Marc W. CAFFEE² , Monika E. KRESS^1,7, Marlene D. GISCARD⁴ , A. J. Timothy JULL⁴, Ralph P. HARVEY⁵ , and John SCHUTT^5,6
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14264]
¹Space Sciences Laboratory, University of California, Berkeley, California, USA
²Department of Physics, Purdue University, West Lafayette, Indiana, USA
³Department of Physics & Astronomy, San Jose State University, San Jose, California, USA
⁴NSF Arizona AMS Laboratory, University of Arizona, Tucson, Arizona, USA
⁵Department of Geology, Case Western Reserve University, Cleveland, Ohio, USA
⁶Geology & Geophysics, University of Utah, Salt Lake City, Utah, USA
⁷Stanford University, Stanford, California, USA

The US Antarctic Search for Meteorites (ANSMET) discovered a dense cluster of 88 ordinary chondrites with a total mass of more than 100 kg on a blue ice area (BIA) of 1.6 × 0.3 km² near the Otway Massif, Grosvenor Mountains, Antarctica. The larger masses (weighing up to 29 kg) were found at one end of an oval-shaped pattern and the smaller masses (50–200 g) at the other end. We measured concentrations of the cosmogenic radionuclides ¹⁰Be (half-life—1.36 × 10⁶ year) and ³⁶Cl (3.01 × 10⁵ year) in the metal fraction of 17 H chondrites, including 14 fragments of this cluster, to verify the hypothesis that this meteorite cluster on the Otway Massif BIA represents a meteorite strewn field produced by the atmospheric breakup of a single meteoroid. The ¹⁰Be and ³⁶Cl concentrations confirm that 10 out of 14 H chondrites from different locations within this small area are paired fragments of the same meteorite fall, while the four other H chondrites represent two additional—smaller—falls. The radionuclides suggest a pre-atmospheric mass of 200–400 kg for the large pairing group, suggesting that 25%–50% of the meteoroid survived atmospheric entry. Based on the distribution of the paired H chondrites and evidence of their common cosmic-ray exposure history in space, we conclude that most of the 88 meteorites within this small area represent a meteorite strewn field. The small size of the strewn field suggests that the meteoroid entered at a steep angle (>60°), while the low amount of fusion crust on most meteorite surfaces most likely indicates atmospheric break up at low altitude, while additional fragmentation of a large surviving fragment may have occurred during impact on the ice. This well-documented strewn field provides a good opportunity to apply model simulations of the atmospheric fragmentation of this object as a function of entry angle, velocity, and meteoroid strength. Cosmogenic ¹⁴C analyses in two members of the Otway Massif pairing group yield a terrestrial age of 15.5 ± 1.5 kyr, which represents the time elapsed since this meteorite fell on Earth. The excellent preservation of an Antarctic meteorite strewn field suggests that the Otway Massif BIA represents a relatively stagnant blue ice field.

R. J. CURTIS¹, T. J. WARREN¹, K. A. SHIRLEY¹, D. A. PAIGE², and N. E. BOWLES¹
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14266]
¹Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK
²Department of Earth and Space Sciences, University of California, Los Angeles, California, USA

A laboratory study was performed using the Visible Oxford Space Environment Goniometer in which the broadband (350–1250 nm) bidirectional reflectance distribution functions (BRDFs) of two representative Apollo regolith samples were measured, for two surface roughness profiles, across a range of viewing angles—reflectance: 0–70°, in steps of 5°; incidence: 15°, 30°, 45°, and 60°; and azimuthal: 0°, 45°, 90°, 135°, and 180°. The BRDF datasets were fitted using the Hapke BRDF model to (1) provide a method of comparison to other photometric studies of the lunar regolith and (2) to produce Hapke parameter values which can be used to extrapolate the BRDF to all angles. Importantly, the surface profiles of the samples were characterized using an Alicona 3D® instrument, allowing two of the free parameters within the Hapke model, φ and , which represent porosity and surface roughness, respectively, to be constrained. The study determined that, for , the 500–1000 μm size-scale is the most relevant for the BRDF. Thus, it deduced the following “best fit” Hapke parameters for each of the samples: Apollo 11 rough— = 0.315 ± 0.021,  = 0.261 ± 0.007, and  = 0.039 ± 0.005 (with  = 21.28° and φ = 0.41 ± 0.02); Apollo 11 smooth— = 0.281 ± 0.028,  = 0.238 ± 0.008, and  = 0.032 ± 0.006 (with  = 13.80° and φ = 0.60 ± 0.02); Apollo 16 rough— = 0.485 ± 0.155,  = 0.155 ± 0.083, and  = 0.135 ± 0.007 (with  = 21.69° and φ = 0.55 ± 0.02); Apollo 16 smooth— = 0.388 ± 0.057,  = 0.063 ± 0.033, and  = 0.221 ± 0.011 (with  = 14.27° and φ = 0.40 ± 0.02). Finally, updated hemispheric albedo functions were determined for the samples, which can be used to set laboratory measured visible scattering functions within thermal models.

^1,2Rojas J et al. (>10)
Nature Astronomy  Link to Article [DOI 10.1038/s41550-024-02364-y]
¹Univ. Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
²Earth and Planets Laboratory, Carnegie Institution for Science, Washington DC, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

T. Mahlé^a, Y. Marrocchi^a, J. Neukampf^a, J. Villeneuve^a, E. Jacquet^b
Geochimica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.08.027]
^aUniversité de Lorraine, CNRS, CRPG, UMR 7358, Nancy, France
^bInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum national d’Histoire naturelle, Sorbonne Université, CNRS, CP52, 57 rue Cuvier, 75005 Paris, France
Copyright Elsevier

Among carbonaceous chondrites, the chondrules of CB and CH stand out by being dominated by skeletal barred olivine and cryptocrystalline textures. These non-porphyritic chondrules are thought to have formed within an impact-generated plume resulting from large-scale asteroidal collisions late in disk history. Porphyritic chondrules are also present, if rare, in CB and CH chondrites and might correspond to nebular objects formed earlier in the disk. We report on the mineralogy, petrology, and oxygen isotopic compositions of porphyritic chondrules in the Isheyevo CH/CB_b chondrite. These chondrules show minor element variations at both the chondrule and individual olivine grain scales, which are similar to those observed in other chondrites. In terms of oxygen isotopes, individual chondrules show contrasting behavior with either negligible, mass-dependent or mass-independent O-isotopic variations. They also display different average Δ¹⁷O, ranging from −6 ‰ to +4 ‰, anticorrelated with size, with most chondrules (8/13) showing Δ¹⁷O > 0 ‰. Our results show that porphyritic chondrules in CB (and CH) chondrites are of nebular origin and do not result from the collisional impact at the origin of other CB components. We propose that CB porphyritic chondrules originate from the chondritic impactor involved in the collision, similarly to hydrated matrix-rich clasts reported in Isheyevo. Altogether, this shows that two chondrule populations, formed by both nebular and planetary processes, co-exist in CB and CH chondrites. Isheyevo thus represents an archetypal chondrite lying at the transition between two dominant chondrule-forming regimes, nebular and impact-related.

^1,2P. J. Wozniakiewicz et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14251]
¹Physics and Astronomy, University of Kent, Canterbury, Kent, UK
²Earth Sciences Department, Natural History Museum, London, UK

The Kwajalein micrometeorite collection utilized high volume air samplers fitted with polycarbonate membrane filters to capture particles directly from the atmosphere at the Earth’s surface. This initial study focused on identifying cosmic spherule-like particles, conservatively categorizing them into four groups based on bulk compositional data: Group I exhibit a range of compositions designated terrestrial in origin; group II are Fe-rich and contain only additional O, S, and/or Ni; group III are silicate spherules with Mg-to-Si At% ratios less than 0.4; group IV are silicate spherules with Mg-to-Si At% ratios greater than 0.4. Spherules in groups I, II, and III have compositions that are also consistent with particles that are produced in great numbers by natural and/or anthropogenic terrestrial activities (e.g., volcanic microspherules, fly ash from coal fired power plants, etc.) and thus are assumed terrestrial in origin. Group IV spherules exhibit compositions closest to those of cosmic spherules identified in other collections and are, therefore, designated cosmic spherule candidates. Detailed analysis of seven group IV spherules found that whilst five exhibited morphology and compositions consistent with S-type cosmic spherules, two appear unique to this collection and could not be matched to either terrestrial or extraterrestrial spherules studied to date.

^a,bH. Li, ^bZ. Wang, ^cZ. Chen, ^bW. Tian, ^dW-R. Wang, ^bG. Zhang ^bL. Zhang
Geochimica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.09.002]
^aCenter for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100193, China

^bMOE Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China
^cLaboratory of Metallogeny and Mineral Assessment of MNR, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
^dKey Laboratory of Paleomagnetism and Tectonic Reconstruction of MNR, Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
Copyright Elsevier

Apatite is ubiquitous in lunar samples and has been used widely for estimating volatile abundances in the lunar interior. However, apatite compositional and isotopic variations within and between samples have resulted in varying and ambiguous results. Understanding apatite petrogenesis will help with both identifying the appropriate composition for volatile estimation and interpreting isotopic variations. Here we report a comprehensive petrogenetic investigation of apatite in Chang’E-5 (CE5) basaltic sample CE5C0800YJYX013GP. Apatite displays both intra-grain and inter-grain compositional variations with F and Cl contents falling in the ranges of 0.97–2.47 wt% and 0.24–1.09 wt%, respectively. These apatite compositions show relatively low F and high Cl characteristics in comparison to apatites of Apollo high-Ti and low-Ti mare basalts, but are similar to those reported for lunar meteorites LAP 04841 and MIL 05035. We discern three zoning profiles: fractional crystallization (FC)-dominated, degassing-induced and a third indicated by REE-enriched cores, which are interpreted as representing different generations of apatite. FC-dominated zoning is characterized with decreasing F and increasing Cl and S contents from core to rim; while the opposite is true for the degassing-induced zoning. Regardless of the zoning patterns, apatite Cl and S contents display positive correlations, with S contents up to ∼ 3000 ppm, much higher than previous reports for Apollo samples (up to ∼ 600 ppm). We demonstrate that the fractional crystallization model proposed by Boyce et al. (2014) in combination with H₂O degassing and high S contents in melt (likely at sulfide saturation) can explain these high Cl and S contents observed in CE5 apatite.

Based on the core composition of the FC-dominated zoning profile, which has the lowest incompatible element concentrations, bulk F, Cl and H₂O contents in the parental melt are estimated to be ∼ 72 ± 21, ∼43 ± 14 and ∼ 1576 ± 518 ppm, respectively. These estimates have lower F/Cl ratios than those measured in olivine-hosted melt inclusions from Apollo mare basalts. By adopting the petrogenetic model for CE5 basalt proposed by Su et al. (2022), i.e., 10 % partial melting of a hybrid mantle source, followed by ∼ 30–70 % fractional crystallization (∼50 % for our sample), we estimate the F, Cl, H₂O and S contents in the mantle source are in the ranges of ∼ 2.5–4.6, ∼0.7–1.4, ∼53–105 and ∼ 38–125 ppm, respectively, similar to estimates for both depleted Earth mantle and primitive lunar mantle. However, by adopting the model of Tian et al. (2021), 2–3 % partial melting of a mantle source composed of 86 PCS+2% TIRL (PCS, percent crystallized solid; TIRL, trapped instantaneous residual liquid), followed by 43–88 % fractional crystallization, these estimates will be 5–10 times lower. To be certain whether the relatively low F and high Cl characteristics of CE5 apatite imply an enriched mantle source requires further evaluation of the petrogenetic models for CE5 basalt.

^1,2A. Kereszturi et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14255]
¹Konkoly Thege Astronomical Institute, HUN-REN Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
²CSFK, MTA Centre of Excellence, Budapest, Hungary

A medium-grade, poorly weathered CO3-type meteorite was subjected to artificial space weathering by 1 keV protons in three subsequent steps, with gradually increasing doses from 10¹¹ to 10¹⁷ protons per cm². The resulting mineral modifications were identified by Raman spectroscopy, with specific emphasis on main minerals such as olivine (bands: 817, 845 cm⁻¹), pyroxene (1007 cm⁻¹), and partly amorphous feldspar (509 cm⁻¹), considering variation in band shift and bandwidth (full width at half maximum, FWHM). After the first and second irradiations, variable band position changes were observed, probably from metastable alterations by Mg loss of the minerals, while the third stronger irradiation showed band shift dominated by amorphization. The olivine and pyroxene show weak increase in FWHM after the first irradiation, while more changes happened after the second and third irradiations. The flux after the third irradiation was higher than in other works, caused stronger damage in crystal lattice, partly resembling to dimerization as described by shock metamorphism. The glassy feldspar was characterized by high FWHM values already at the beginning, indicating weak crystallinity already that become even less crystallized, thus their bands disappeared after the third irradiation. Bands of hydrous minerals (goethite clay, chlorite) were not visible after the third irradiation, confirming some earlier results in the literature. Based on our results, moderately fresh surfaces could show stochastic but small spectral differences compared to the fresh most meteorites by metastable mineral alterations. The interpretation of Raman spectra of heavily space-weathered surfaces could further benefit from the joint evaluation of alteration induced by both shock impact alteration and space weathering.

^1,2Wang, Bi-Wen et al. (>10)
Science 385, 1077-1080 Link to Article [DOI: 10.1126/science.adk6635]
¹State Key Laboratory of Lithospheric and Environmental Coevolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
²College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Reprinted with permission from AAAS

There is extensive geologic evidence of ancient volcanic activity on the Moon, but it is unclear how long that volcanism persisted. Magma fountains produce volcanic glasses, which have previously been found in samples of the Moon’s surface. We investigated ~3000 glass beads in lunar soil samples collected by the Chang’e-5 mission and identified three as having a volcanic origin on the basis of their textures, chemical compositions, and sulfur isotopes. Uranium-lead dating of the three volcanic glass beads shows that they formed 123 ± 15 million years ago. We measured high abundances of rare earth elements and thorium in these volcanic glass beads, which could indicate that such recent volcanism was related to local enrichment of heat-generating elements in the mantle sources of the magma.

^1,4Jangmi Han, ²Kazuhide Nagashima, ¹Changkun Park, ²Alexander N. Krot, ¹Lindsay P. Keller
Geochimica et Cosmochimica acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.09.001]
¹Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA
²Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
³Division of Glacier and Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990, South Korea
⁴ARES, NASA Johnson Space Center, 2101NASAParkway, Houston, TX 77058, USA
Copyright Elsevier

We report the results of coordinated mineralogical, microstructural, and oxygen isotopic analyses of grossite-bearing refractory inclusions from reduced CV (Vigarano type) chondrites to obtain a more complete picture of secondary parent body alteration processes and conditions. Grossite (CaAl₄O₇) occurs in cores of nodules in fine-grained Ca,Al-rich inclusions (CAIs) that likely represent aggregates of nebular condensates. In many occurrences, grossite has been partially replaced by hercynite [(Fe,Mg,Zn)Al₂O₄], which displays complex microstructures and compositions, and magnetite nanoparticles. The alteration of grossite was a crystallographically-controlled, fluid-driven process that occurred via partial dissolution of grossite and subsequent precipitation of hercynite and magnetite during short-lived and low-temperature metasomatic alteration on the CV chondrite parent body. The constituent phases of grossite-bearing CAIs show heterogeneous oxygen isotopic compositions, with grossite and perovskite displaying systematically ¹⁶O-depleted compositions (Δ¹⁷O= − 12 ‰ to − 1 ‰) relative to uniformly ¹⁶O-rich hibonite and spinel (Δ¹⁷O= − 25 ‰ to − 21 ‰). Melilite is variably ¹⁶O-depleted (Δ¹⁷O= − 25 ‰ to − 2 ‰). The observed oxygen isotopic distribution is interpreted as a result of mineralogically controlled oxygen isotopic exchange with an ¹⁶O-poor fluid on the CV chondrite parent body. Collectively, the presence of limited fluids played an important role in preferential alteration of grossite to hercynite and magnetite and various degrees of ¹⁶O depletion in grossite, perovskite, and melilite during thermal metamorphism. We conclude that, among refractory phases in the inclusions, grossite was the most susceptible to metasomatic reactions with Fe-rich fluids and the second most susceptible, after perovskite, to oxygen isotopic exchange with an ¹⁶O-poor fluid during the thermal history of the CV chondrite parent asteroid.

¹Aindrila Pal, ¹Rajdeep Dasgupta
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.08.026]
¹Department of Earth, Environmental and Planetary Sciences, Rice University, Houston TX-77005, USA
Copyright Elsevier

Nitrogen is an essential element for life. Yet the processes of planet formation and early planetary evolution through which rocky planets like Earth obtained their atmospheric and surface nitrogen inventory are poorly understood. In order to understand the effect of early silicate differentiation of the rocky bodies on N inventory, here we study the elemental partitioning of N between the silicate minerals and melts. We conducted laboratory experiments using tholeiitic basalts and Fe + Si alloy mixtures at 1.5–4.0 GPa and 1300 to 1550 ⁰C under graphite saturation at an oxygen fugacity range of IW–1.1 to IW–3.0. The experiments yielded an assemblage of Fe-rich alloy melt (am) + silicate melt (sm) + clinopyroxene (cpx) ± garnet (grt) ± orthopyroxene (opx) ± plagioclase (plag). Using electron microprobe, we determine that under the experimental conditions, N act as an incompatible element with DNcpx/sm (0.11–––0.47) > DNplag/sm (0.40) >DNopx/sm (0.25) >DNgrt/sm(0.06–––0.21). The DNmineral/sm do not show any strong dependence on temperature, pressure, and melt composition. However, through comparison with previous estimates, it appears that with decreasing fO₂, N becomes less incompatible. Under our experimental conditions of alloy melt-mineral equilibria, N behaves as a siderophile element (DNam/mineral ranging from 4.1 to 60.6) with fO₂ playing the strongest control on DNam/mineral. Our data suggest that under reducing conditions, in the early stages of a magma ocean (MO) and/or deeper mantle, silicate minerals would hold a non-negligible fraction of N as N becomes less atmophile and siderophile. Therefore, reduced parent bodies could also retain substantial N in the residual mantle during partial melting. The extraction of N from an internal MO or a solid planetary mantle is thus enhanced only as the system becomes more oxidizing, enriching the surficial reservoirs in N. Thus, Earth’s N₂-rich atmosphere may be intrinsically linked to its mantle oxidation, whereas other rocky planets of the Solar System, such as Mars and Mercury, may have retained a significant portion of their N inventory in nominally N-free mantle silicates through episodes of MO crystallization and mantle melting.