¹Antonio Lanzirotti,^1,2Stephen R. Sutton,¹Matthew Newville,³Adrian Brearley,⁴Oliver Tschauner
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14130]
¹Center for Advanced Radiation Sources, The University of Chicago, Argonne, Illinois, USA
²Department of the Geophysical Sciences, The University of Chicago, Argonne, Illinois, USA
³Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, USA
⁴Department of Geoscience, University of Nevada Las Vegas, Las Vegas, Nevada, USA
Published by arrangement with John Wiley & Sons

This study describes the application of new synchrotron X-ray fluorescence (XRF) and diffraction (XRD) microtomographies for the 3-D visualization of chemical and mineralogical variations in unsectioned extraterrestrial samples. These improved methods have been applied to three compositionally diverse chondritic meteorite samples that were between 300 and 400 μm in diameter, including samples prepared from fragments of the CR2 chondrite LaPaz Icefield (LAP) 02342, H5 chondrite MacAlpine Hills (MAC) 88203, and the CM2 chondrite Murchison. The synchrotron-based XRF and XRD tomographies used are focused-beam techniques that measure the intensities of fluorescent and diffracted X-rays in a sample simultaneously during irradiation by a high-energy microfocused incident X-ray beam. Measured sinograms of the emitted and diffracted intensities were then tomographically reconstructed to generate 2-D slices of XRF and XRD intensity through the sample, with reconstructed pixel resolution of 1–2 μm, defined by the resolution of the focused incident X-ray beam. For sample LAP 02342, primary mineral phases that were visualized in reconstructed slices using these techniques included isolated grains of α-Fe, orthopyroxene, and olivine. For our sample of MAC 88203, XRF/XRD tomography allowed visualization of forsteritic olivine as a primary mineral phase, a vitrified fusion crust at the sample surface, identification of localized Cr-rich spinels at spatial resolutions of several micrometers, and imaging of a plagioclase-rich glassy matrix. In the sample of Murchison, major identifiable phases include clinoenstatite- and olivine-rich chondrules, variable serpentine matrix minerals and small Cr-rich spinels. Most notable in the tomographic analysis of Murchison is the ability to quantitatively distinguish and visualize the complex mixture of serpentine-group minerals and associated tochilinite–cronstedtite intergrowths. These methods provide new opportunities for spatially resolved characterization of sample texture, mineralogy, crystal structure, and chemical state in unsectioned samples. This provides researchers an ability to characterize such samples internally with minimal disruption of sample micro-structures and chemistry, possibly without the need for sample extraction from some types of sampling and capture media.

¹José C. Aponte,^1,2,3Frédéric Séguin,^1,4Ariel J. Siguelnitzky,¹Jason P. Dworkin,¹Jamie E. Elsila,¹Daniel P. Glavin,^5,6,7Harold C. Connolly Jr,⁵Dante S. Lauretta
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14118]
¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
²Department of Physics, The Catholic University of America, Washington, DC, USA
³Center for Research and Exploration in Space Science and Technology, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
⁴Sig Engineering LLC, Laurel, Maryland, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
⁶Department of Geology, School of Earth and Environment, Rowan University, Glassboro, New Jersey, USA
⁷Department of Earth and Planetary Science, American Museum of Natural History, New York, New York, USA
Published by arrangement with John Wiley & Sons

Volatile organic compounds (VOCs) are carbon-containing chemicals that may evaporate rapidly at room temperature and standard pressure. Such organic compounds can be preserved inside carbonaceous chondrite matrices. However, unlike meteoritic soluble organic matter (SOM) and insoluble organic matter (IOM), VOCs are typically lost (at least in part) during sample processing (meteorite crushing) and exposure to terrestrial atmosphere and/or solvents. Like SOM and IOM, VOCs can provide valuable insights into the chemical inventory of the meteorite parent body and even the presolar cloud from which our solar system formed, as well as the composition and processes that occurred during the early formation of our solar system and the asteroidal stage. Thus, in this work, we designed and built an instrument that allowed us to access the VOCs present in samples of the carbonaceous chondrites Murchison and Sutter’s Mill after mineral disaggregation by means of freeze–thaw cycling. We simultaneously evaluated the abundances and compound-specific 13C-distributions of the volatiles evolving after meteorite powdering at ~20, 60, and 100°C. Carbon monoxide (CO) and methane (CH4) were released from these meteorites as the most abundant VOCs. They were combusted together for analysis and showed positive δ13C values, indicative of their extraterrestrial origins. Carbon dioxide (CO2) was also an abundant VOC in both meteorites, and its isotopic values suggest that it was mainly formed from dissolved carbonates in the samples. We also detected aldehydes, ketones, and aromatic compounds in low amounts. Contrary to Murchison, which mostly yielded VOCs with positive δ13C values, Sutter’s Mill yielded VOCs with negative δ13C values. The less enriched 13C isotope composition of the VOCs detected in Sutter’s Mill suggest that they are either terrestrial contaminants, such as VOCs in compressed gas dusters and common laboratory solvents, or compounds disconnected from interstellar sources and/or formed through parent body processing. Understanding the relative abundances and determining the molecular distributions and isotopic compositions of free meteoritic VOCs are key in assessing their extraterrestrial origins and those of chondritic SOM and IOM. Our newly developed technique will be valuable in the study of the samples brought to the Earth from carbonaceous asteroid Bennu by NASA’s OSIRIS-REx mission.

¹Yuji Matsumoto,²Sota Arakawa
The Astrophysical Journal 948, 73 Open Access Link to Article [DOI 10.3847/1538-4357/acc57c]
¹National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan; yuji.matsumoto@nao.ac.jp
²Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001, Japan

Shock-wave heating is a leading candidate for the mechanisms of chondrule formation. This mechanism forms chondrules when the shock velocity is in a certain range. If the shock velocity is lower than this range, dust particles smaller than chondrule precursors melt, while chondrule precursors do not. We focus on the low-velocity shock waves as the igneous rim accretion events. Using a semianalytical treatment of the shock-wave heating model, we found that the accretion of molten dust particles occurs when they are supercooling. The accreted igneous rims have two layers, which are the layers of the accreted supercooled droplets and crystallized dust particles. We suggest that chondrules experience multiple rim-forming shock events.

¹Steven J. Desch,^2,3Emilie T. Dunham,¹Ashley K. Herbst,⁴Cayman T. Unterborn,¹Thomas G. Sharp,¹Maitrayee Bose,⁵Prajkta Mane,⁶Curtis D. Williams
The Astrophysical Journal 953, 146 Open Access Link to Article [DOI 10.3847/1538-4357/acdeed]
¹School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404, USA; steve.desch@asu.edu
²Department of Earth, Planetary and Space Sciences, University of California, Los Angeles, CA 90095, USA
³Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064, USA
⁴Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238, USA
⁵Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA
⁶Arctic Slope Regional Corporation Federal, 11091 Sunset Hills Road, Suite 800, Reston, VA 20190, USA

Most meteoritic calcium-rich, aluminum-rich inclusions formed from a reservoir with ²⁶Al/²⁷Al ≈ 5 × 10⁻⁵, but some record lower (26Al/27Al)0, demanding they sampled a reservoir without live ²⁶Al. This has been interpreted as evidence for “late injection” of supernova material into our protoplanetary disk. We instead interpret the heterogeneity as chemical, demonstrating that these inclusions are strongly associated with the refractory phases corundum or hibonite. We name them “low-²⁶Al/²⁷Al corundum/hibonite inclusions” (LAACHIs). We present a detailed astrophysical model for LAACHI formation in which they derive their Al from presolar corundum, spinel, or hibonite grains 0.5–2 μm in size with no live ²⁶Al; live ²⁶Al is carried on smaller (<50 nm) presolar chromium spinel grains from recent nearby Wolf–Rayet stars or supernovae. In hot (≈1350–1425 K) regions of the disk, these grains and perovskite grains would be the only survivors. These negatively charged grains would grow to sizes 1–10³μm, even incorporating positively charged perovskite grains, but not the small, negatively charged ²⁶Al-bearing grains. Chemical and isotopic fractionations due to grain charging was a significant process in hot regions of the disk. Our model explains the sizes, compositions, oxygen isotopic signatures, and the large, correlated ⁴⁸Ca and ⁵⁰Ti anomalies (if carried by presolar perovskite) of LAACHIs, and especially how they incorporated no ²⁶Al in a solar nebula with uniform, canonical ²⁶Al/²⁷Al. A late injection of supernova material is obviated, although formation of the Sun in a high-mass star-forming region is demanded.

^1,2Prajkta Mane,¹Maitrayee Bose,¹Meenakshi Wadhwa,^3,4Céline Defouilloy
The Astrophysical Journal 946, 37 Open Access Link to Article [DOI 10.3847/1538-4357/acb156]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA; pmane@lpi.usra.edu
²Lunar and Planetary Institute, Universities Space Research Association, Houston, TX 77058, USA
³WiscSIMS, Department of Geoscience, University of Wisconsin-Madison, Madison, WI 53706, USA
⁴CAMECA, F-92622 Gennevilliers Cedex, France

The calcium–aluminum-rich inclusions (CAIs) from chondritic meteorites are the first solids formed in the solar system. Rim formation around CAIs marks a time period in early solar system history when CAIs existed as free-floating objects and had not yet been incorporated into their chondritic parent bodies. The chronological data on these rims are limited. As seen in the limited number of analyzed inclusions, the rims formed nearly contemporaneously (i.e., <300,000 yr after CAI formation) with the host CAIs. Here we present the relative ages of rims around two type B CAIs from NWA 8323 CV3 (oxidized) carbonaceous chondrite using the 26Al–26Mg chronometer. Our data indicate that these rims formed ∼2–3 Ma after their host CAIs, most likely as a result of thermal processing in the solar nebula at that time. Our results imply that these CAIs remained as free-floating objects in the solar nebula for this duration. The formation of these rims coincides with the time interval during which the majority of chondrules formed, suggesting that some rims may have formed in transient heating events similar to those that produced most chondrules in the solar nebula. The results reported here additionally bolster recent evidence suggesting that chondritic materials accreted to form chondrite parent bodies later than the early-formed planetary embryos, and after the primary heat source, most likely 26Al, had mostly decayed away.

¹Kelsey B. Prissel,¹Michael J. Krawczynski,²Nicole X. Nie,²Nicolas Dauphas,
²Sarah M. Aarons,²Andy W. Heard,³Michael Y. Hu,³E. Ercan Alp,³Jiyong Zhao
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.01.006]
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, 1 Brookings Drive, St. Louis, 63123, MO, USA
²Origins Laboratory, Department of Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, 60637, IL, USA
³Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, 60439, IL, USA
Copyright Elsevier

Basaltic volcanism on the Moon produced low- and high-Ti mare basalt suites that are also distinct with respect to their iron, titanium, and magnesium isotopic compositions. Here, the equilibrium fractionation of Fe and Ti isotopes between ilmenite and melt was experimentally investigated in order to evaluate the role of ilmenite in generating the isotopic compositional variability among the lunar mare basalts. Ilmenite crystallization experiments were conducted using two bulk compositions: an ilmenite-saturated basaltic andesite and an ilmenite-saturated Apollo 14 black glass, and the Fe and Ti isotopic compositions of the experimental ilmenites and glass (quenched melt) were analyzed using solution MC-ICPMS after hand-picking. Additionally, Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements on synthetic ilmenite were conducted and compared to previous NRIXS measurements on synthetic lunar glasses in order to derive temperature-dependent equilibrium ilmenite-melt Fe isotopic fractionations. Experimentally determined ilmenite-melt fractionations were then incorporated into a lunar magma ocean crystallization model that tracks the major element and isotopic compositional evolution of lunar magma ocean cumulates and residual liquid. There is good agreement between the Fe equilibrium isotopic fractionation measured by NRIXS and the laboratory equilibration experiments, and we find that the isotopic fractionation is sensitive to ilmenite compositional differences (0 vs. 10% Fe³⁺). Further, the light Ti isotopic composition of ilmenite relative to the melt (Δ49Ti‰=ilmenite-melt−0.09±0.03‰ at 1100 ^∘C) is consistent with the higher coordination of Ti in ilmenite relative to melts and results of previous studies. The modeled Ti isotopic compositions for lunar magma ocean cumulates display Ti isotopic variability sufficient to explain the low- and high-Ti mare basalt sources. However, the difference in Fe isotopic composition between the low- and high-Ti mare basalts cannot be attributed solely to ilmenite fractionation. Instead, Fe isotopic fractionation by additional products of lunar magma ocean crystallization, such as clinopyroxene, is required to generate the inferred Fe and Mg isotopic variability in the lunar mantle. Alternatively, the Fe and Mg isotopic compositions of the lunar mare basalts may indicate Fe-Mg interdiffusion has occurred in the Ti-rich component of the mare basalt source regions via reaction between ilmenite cumulates and the olivine- and pyroxene-rich lunar mantle.

^1,2Hasnaa Chennaoui Aoudjehane
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14126]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
²ATTARIK Foundation for Meteoritics and Planetary Science, Casablanca, Morocco
Published by arrangement with John Wiley & Sons

Morocco is known for the high number of meteorites collected in its territory, including finds and falls. This is explained by the large size of the Moroccan Sahara, the guarantee of security in this desert, and the large community of well-trained Moroccan hunters and nomads who roam through it. Despite this richness, most meteorites collected in Morocco are sold abroad and exported. The exportation of meteorites as well as other geoheritage samples such as fossils and minerals was not completely legal or illegal as there was no dedicated regulation. Since 2000, the APPGM (Association pour la Protection du Patrimoine Géologique du Maroc) a Non-Governmental Organization (NGO) dedicated to the preservation of the Moroccan geoheritage began working with the Moroccan Geological Survey, on a draft of a specific law dedicated to geoheritage. It was fundamental to benefit from the experience of other countries with a high number of meteorites where exportation is not allowed and that are losing their meteorites to illegal exportation. The author recommended a win-win regulation that would allow the legal collection and exportation of meteorites under clear rules benefiting both hunters and scientists but also the country. In 2014, Morocco updated its law regarding mines. One article cited geoheritage as including fossils, minerals, and meteorites and mentioned that their collection and exportation would be regulated by decree. In 2019, the Moroccan Geological Survey and APPGM prepared the application decree of this article that has been discussed and approved by the Moroccan government and implemented in February 2020. This situation is unique in the region as well as compared to the other countries with a high potential of meteorites collection. Meteorite researchers and collectors all over the world should be aware of this regulation in Morocco to make their acquisitions legal. They should request a copy of the “End of the work” from local traders, the receipt from the Geological survey, and the certificate of export from customs. It is an important ethical and scientific responsibility of our community.

¹Ryota Fukai et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14121]
¹Japan Aerospace Exploration Agency, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Japan Aerospace Exploration Agency’s Martian Moons eXploration (MMX) mission will launch a spacecraft in 2024 to return samples from Phobos in 2029. Curatorial work for the returned Phobos samples is critical for the sample allocation without degrading the sample integrity and subsequent sample analysis that will provide new constraints on the origin of Phobos and the evolution of the circum-Mars environment. The Sample Analysis Working Team of the MMX is designing the sample curation protocol. The curation protocol consists of three phases: (1) quick analysis (extraction and mass spectrometry for gases), (2) pre-basic characterization (bulk-scale observation), and (3) basic characterization (grain-by-grain observation and allocation of the sample aliquots). Nondestructive analyses within the clean chamber (e.g., visible and near-infrared spectral imaging) and outside the chamber (e.g., gas mass spectrometry) are incorporated into the curation flow in coordination with the MMX mission instrument teams for ground-truthing the remote-sensing data sets. The MMX curation/sample analysis flow enables the seamless integration between the sample and remote-sensing data sets to maximize the scientific value of the collected Phobos samples.

¹Aruto Kashima,^1,2Shu-hei Urashima,^1,2Hiroharu Yui
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14123]
¹Department of Chemistry, Faculty of Science, Tokyo University of Science, Tokyo, Japan
²Water Frontier Research Center, Research Institute for Science and Technology, Tokyo University of Science, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Chemical states of carbon in terrestrial (meta) sediments and carbonaceous chondrites gather attention as a geothermometer. As a nondestructive analytical method, Raman spectroscopy has been widely used to study their electronic properties, crystallinity, and structural defects through so-called D and G bands. For the analysis of Raman spectra, a common problem is coexistence of a fluorescence background, which should be subtracted prior to the peak-fitting analysis. However, we recently faced a problem that the band shape noticeably changed depending on the background function assumed although the background seemed to be well subtracted at a first glance regardless of the choice of the background function. For the application of the Raman spectroscopy as a geothermometer, a standard background subtraction method must be established to suppress the arbitrariness. In the present study, Raman spectra of seven carbon-containing natural samples, whose background intensities were significantly different, were measured, and their background shape was evaluated by first-, second-, and third-order polynomials. The results indicated that the third-order polynomial was necessary and sufficient as a standard background function. Importantly, although lower order polynomials seem to successfully fit the background at a first glance, they falsely caused dispersion of the shoulder band shape.

¹Van T. H. Phan et al.(>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14122]
¹Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), CNRS, Université Grenoble Alpes, Grenoble, France
Published by arrangement with John Wiley & Sons

The Hayabusa2 mission from the Japan Aerospace Exploration Agency (JAXA) returned to the Earth samples of carbonaceous asteroid (162173) Ryugu. This mission offers a unique opportunity to investigate in the laboratory samples from a C-type asteroid, without physical or chemical alteration by the terrestrial atmosphere. Here, we report on an investigation of the mineralogy and the organo-chemistry of Hayabusa2 samples using a combination of micro- and nano-infrared spectroscopy. Particles investigated with conventional FTIR spectroscopy have spectra dominated by phyllosilicate-related absorption, as observed for samples of CI-chondrites, selected ungrouped carbonaceous chondrites, and selected hydrated micrometeorites. Ryugu samples show smaller sulfate-related absorption than CI-chondrites. Our samples that were only briefly exposed to the Earth atmosphere show absorptions related to molecular water, revealing fast terrestrial contamination of the spectral signature at 3 μm. Overall, our FTIR data are in agreement with other work done on Ryugu samples, revealing a low degree of mineralogical variability across Ryugu samples. AFM-IR mapping of the grains shows the presence of a micrometer-sized organic globule in one of our analyzed grains. The AFM-IR spectra obtained on this globule are similar to IR spectra obtained on IOM suggesting that it is constituted of refractory organic matter. This globule may host silicate in its interior, with a different mineralogy than bulk Ryugu phyllosilicate. The shape, presence of peculiar silicate, and the nature of organic constituting the globule point toward a pre-accretionary origin of this globule and that at least part of Ryugu organics were inherited from the protosolar nebulae or the interstellar media. Altogether, our results show the similarities between Ryugu samples and CI chondrites.