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On September 24, 2023, NASA’s OSIRIS-REx mission returned pristine carbonaceous material from asteroid Bennu. One key aspect required to understand this returned material is to establish its bulk chemical composition. This is primarily due to each chondrite group having a distinct elemental composition, which is important both as a classification tool and for establishing the connections between the different chondrite groups. As the carbonaceous and non-carbonaceous chondrites are thought to have formed in the inner and outer protoplanetary disk, respectively, measuring the bulk elemental composition of Bennu material will help test the mission hypothesis that “Bennu's parent body formed beyond the snow line by accretion of material in the protoplanetary disk”. In addition, two further mission hypotheses — paraphrased as Bennu’s bulk elemental composition reflects that of its parent asteroid and is similar to the composition of the Sun and Bennu’s dominant lithologies are comparable in composition to the most aqueously altered carbonaceous chondrites — can be directly tested by bulk elemental analyses. Elemental analyses were undertaken on sample OREX-803015-0, a 20.66 mg aggregate sourced from inside the sample collector. All analyses were conducted using an iCAP Q ICP-MS. Overall, all 54 elements analyzed for the Bennu aggregate sample show similar abundances to those of the average CI chondrite, and thus the solar photosphere composition and some of the most aqueously altered carbonaceous chondrites. The elemental data also show that Bennu is indeed a carbonaceous asteroid that formed beyond the snow line by accretion of material in the protoplanetary disk. This Bennu aggregate sample appears similar in elemental composition to samples of asteroid Ryugu, yet without the small refractory element enrichments seen in Ryugu. more...

On September 24, 2023, NASA’s OSIRIS-REx mission delivered to Earth ~121 g of pristine carbonaceous regolith from asteroid Bennu. A first series of mineralogical observations and chemical/isotopic analyses of Bennu aggregate samples (fine to coarse particles up to a few mm) revealed that this material resembles the most chemically primitive chondrites and the samples returned by the JAXA’s Hayabusa2 mission from the carbonaceous asteroid Ryugu. Laboratory studies have confirmed the story gleaned from the spacecraft encounter that Bennu’s rock fragments underwent extensive aqueous alteration and are predominantly composed of hydrated minerals (serpentine, smectite) and other secondary minerals (e.g., magnetite, carbonates). The secondary phases were likely formed under the presence of liquid water on Bennu’s parent asteroid. The isotopic compositions of hydrous minerals and secondary phases can increase our understanding of the source and distribution of water and volatile elements in the protoplanetary disk [e.g., 5-8]. However, direct estimates of the hydrogen isotopic ratios (D/H) in hydrous minerals cannot be obtained easily in primitive rocks due to the difficulty in estimating the organic matter (OM) contribution to the whole H budget. In order to obtain hints on the initial constituents of Bennu’s parent asteroid and to test if Bennu's parent asteroid have formed beyond the snow line (hypothesis 4 of [9]), we measured the D/H and C/H ratios in chondritic matrices by secondary ion mass spectrometry (SIMS) and obtain information on the D/H ratio of water retained in the hydrated minerals. The method also gives clues on the hydrogen isotope variability among different Bennu rock fragments made available for measurement. more...

The OSIRIS-REx sample return mission visited the B-type asteroid Bennu and delivered 121.6 gof pristine material to Earth in September 2023. Genetic links between this pristine material and different meteorite groups can be determined using nucleosynthetic isotope variations. These variations reflect the heterogeneous distribution of isotopically distinct dust from different stellar environments within the protoplanetary disk. They can therefore be used to constrain different formation locations of parent asteroids [e.g., 1]. In addition, isotope variations are powerful tracers to establish the nucleosynthetic heritage of returned samples [e.g., 2] and to evaluate mixing and reservoir formation within the disk. Here we present nucleosynthetic Ti and Fe isotope data for samples from Bennu and several carbonaceous chondrites. We also report the Ti isotope composition of hand-picked matrix fractions from CR and CV meteorites. more...

Primitive chondrites, including CI and CM types, are known to contain a rich variety of presolar grains that were seeded into the protoplanetary disk from neighboring stars and stellar objects prior to aggregation into asteroidal parent bodies. Stepped combustion using the FINESSE instrument at the Open University (OU) was employed to determine whether material from Bennu contains populations of presolar grains similar to those of CI and CM chondrites as well as recently returned samples from Ryugu. more...

Granitic clasts with unique ternary feldspar compositions have been identified within samples of the layered impact melt breccia from Apollo 17 Station 2 Boulder 1 (72215, 72235, 72255 and 72275), and in a felsite clast from station 3 (73215). These “ternary” compositions seemingly plot within the miscibility gap of the albite-anorthite-orthoclase (Ab-An-Or) system. Feldspars with these compositions have not been identified in terrestrial samples, and equilibrium feldspar compositions from laboratory experiments indicate they would not be thermodynamically stable. Thus, the physiochemical processes involved in forming these unique ternary feldspars remain poorly understood. To better constrain the formation of ternary feldspar within lunar breccias, we have undertaken a coordinated scanning electron microscope (SEM)-based coupled electron backscatter diffraction (EBSD) and energy dispersive spectrometry (EDS), electron microprobe analyzer (EPMA) wavelength dispersive spectrometry, and transmission electron microscopy (TEM) study. The goals of this study are twofold: 1) confirm whether ternary feldspar is present as coherent, single-crystals or sub-microscopic intergrowths of normal compositions, and 2) better constrain the formation conditions of clasts containing ternary feldspar. more...

The apatite group minerals [Ca5(PO4)3(F,Cl,OH)] are some of the primary mineralogical reservoirs for phosphorus on Earth and a common phosphate mineral within a broad range of extraterrestrial samples. Naturally occurring apatite hosts F, Cl, and OH as essential structural constituents, and all three make up the apatite endmembers fluorapatite, chlorapatite, and hydroxylapatite, respectively. Although apatite is one of the most common phosphate minerals in meteorites and rocks from Earth, it typically occurs at minor to trace abundances. Apatite has been widely used as a mineralogical tool to probe the interiors of both differentiated and undifferentiated parent bodies for information about volatiles; however, little work has been done on apatite F, Cl, and OH abundances of apatite from primitive achondrite meteorites. There are broad differences between apatite X-site chemistry in chondrite parent bodies (typically F-poor) compared to apatite from basaltic rocks from many achondrite parent bodies (Cl-poor, apart from Mars). These differences could indicate that planetary differentiation processes, namely melting, play an important role in the evolution of apatite X-site chemistry. In fact, some ordinary chondrite meteorites that exhibit evidence of minor impact melting have apatite with X-site compositions that are much more F-rich than typical chondrite apatite. McCubbin et al., hypothesized that the F-rich compositions of the apatite in ordinary chondrites affected by impact melting could be the result of apatite partially melting, driving the residual apatite to more F-rich compositions; however, they also indicated that degassing of the more volatile Cl and H may also contribute to the F-enrichment. To further test the partial melting hypothesis, we investigate the F, Cl, and OH (by difference) abundances of apatite from primitive achondrite parent bodies given that they are thought to come from partially differentiated parent bodies that represent residues after partial melting. Consequently, their apatites could provide valuable insights into the effects of melting on apatite X-site chemistry. In this study, we report F and Cl abundances of apatite from a broad array of primitive achondrite meteorites, and we develop a model for apatite fractional melting using known apatite-melt partitioning relationships. Together, we use these results to further elucidate the role of melting on apatite X-site compositions. more...

The ‘Civet Cat Norite’ is a ~ 2.5 cm clast within the Apollo impact melt breccia sample 72255 collected during Apollo 17 EVA 2 at Boulder 1. The norite is primarily composed of plagioclase and orthopyroxene with fine-scale exsolution lamellae of augite. The plagioclase and orthopyroxene (OPX) coexist with minor quartz and augitic clinopyroxene (CPX), and accessory apatite, baddeleyite, chromite, ilmenite, loveringite, merrillite, rutile and zircon. The major minerals range from 1 to 4 mm in size and show a cataclastic texture indicated by banding of the light and dark phases]. The chemical composition of the orthopyroxene, augitic exsolution lamellae, and exsolved oxides suggest the norite crystallized in the lower crust of the Moon (10 – 70 km depth) and was subsequently excavated by impact(s). Shock pressure estimates for the norite range from 15 – 35 GPa based on maskeleynite formation within the plagioclase, kink banding in pyroxenes, and granular recrystallization in the accessory phosphates. Previous Rb-Sr and 40Ar/39Ar analyses recalculated with modern decay constants yield relatively young ages of 4.16 ± 0.05 Ga and 3.99 ± 0.03 Ga, respectively. However, recent U-Pb analyses of some zircon grains from within the Civet Cat yield an age of 4.45 ± 0.03 Ga. While this is the oldest age for any rock recovered from the Moon, the full age spread of zircon from the Civet Cat range from ca. 4.46 to 4.02 Ga, indicating variable Pb-loss and complicating interpretation of the primary age. Recent atom probe analyses indicate minimal Pb mobilization within the oldest zircon grain from Civet Cat, supporting the interpretation that these ancient zircon ages reflect the age of the norite, rather than an apparent antiquity caused by reverse discordance. To investigate the potential antiquity and deep crustal origin of the Civet Cat norite, we have undertaken high resolution microstructural analyses of the major, minor, and accessory minerals to characterize the primary igneous textures and secondary overprinting by impact and metamorphism. The employed analytical techniques include scanning electron microscope-based electron backscatter diffraction (EBSD) analyses, electron probe microanalyzer (EPMA) chemical analyses, and transmission electron microscopy (TEM) of pyroxene, plagioclase, quartz, zircon, and phosphates. more...

Carbonaceous asteroids allow us to study the original materials that formed the planets in the protoplanetary disk. They contain organic matter and (sub-)micrometer-size dust grains, called presolar grains, that condensed in the circumstellar envelopes of evolved stars and the ejecta of stellar explosions, such as novae and supernovae, before the formation of our Solar System. The isotopically anomalous organics are thought to have formed in the interstellar medium and the early Solar System. Whereas presolar grains provide insight into the building blocks of our Solar System, studying organics can help us understand the origin of life on Earth. These organics might have contributed to ingredients that helped life emerge. The return of samples from asteroid 101955 Bennu by NASA’s Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission gives us a new opportunity to elucidate the formation mechanism(s) and evolution of organics, as well as the abundance and distribution presolar grains in carbonaceous asteroids. Here, we report on our ongoing work to characterize the isotopic and chemical compositions, microstructure, distribution, and abundance of insoluble organic matter (IOM) and presolar grains in Bennu samples. This work supports hypotheses 2 and 3 of the OSIRIS-REx Sample Analysis Plan. more...

On September 24, 2023, NASA’s OSIRIS-REx mission returned a capsule to Earth carrying material from asteroid Bennu. This event was the first time a U.S. mission delivered pristine samples from an asteroid and is the largest asteroid sample return to date. As these samples represent some of the oldest, most primitive, and pristine materials available to us, and which originate from a known and well-studied asteroid, they allow us a rare opportunity to gain a better understanding of the formation and evolution of our solar system. Key to understanding the material returned from asteroid Bennu is establishing its bulk chemical composition. Previous studies have shown that each chondrite group has a distinct elemental composition. For the carbonaceous chondrites specifically, each group exhibits a distinct pattern of moderately and highly volatile elemental depletions, relative to CI chondrites. CI chondrites are considered the most primitive chondrite group and broadly represent the solar photosphere composition. The two most striking features of these depletion patterns is that the moderately volatile element depletions increase with decreasing 50% condensation temperature and then plateau out at abundances that roughly correlate with matrix abundance. Due to these distinctive patterns, bulk elemental composition has become an important classification tool for establishing the different chondrite groups and the connections between them. As such, determining the bulk chemical composition of the Bennu aggregates will help to test two mission hypothesis: “Bennu’s bulk elemental composition reflects that of its main parent asteroid and is similar to the composition of the Sun, with depletions in moderately to highly volatile elements” and “Bennu’s dominant lithologies are comparable in bulk mineralogy, petrology, and composition to the most aqueously altered carbonaceous chondrites”. Furthermore as the carbonaceous and non-carbonaceous chondrites are thought to have likely formed in the inner and outer protoplanetary disk, respectively (e.g., [8]), determining the bulk chemical compositions of the Bennu aggregates will also help test the major mission hypothesis that “Bennu's parent body formed beyond the snow line by accretion of material in the pro-toplanetary disk”. Regarding chondrite formation, observed elemental patterns have been successfully used to model how the mixing of volatile-rich and volatile-poor chondritic components can produce the observed carbonaceous chondrites groups. They have also been significant in investigating how volatilization processes influenced chondrite formation. As such, establishing bulk chemical compositions of the pristine Bennu samples is vital for understanding the asteroid, and solar system formation. To begin this processes, we analyzed the bulk major and trace elemental compositions of Bennu aggregates. more...

The highly volatile elements (e.g. H, C, S, Cl) released during lunar volcanism provide important insights into the bulk volatile composition of the Moon. Once erupted, some fraction of the species containing these elements may have migrated to the poles where they could have become sequestered in shadowed cold traps such as those found near the lunar South pole. The volatiles trapped in the lunar South pole are of great interest to the upcoming Artemis missions, which will be operating nearby and could sample some of those materials. Volcanic vapor deposits in the polar regions might also be supplemented by volatiles from other sources both exogenous (i.e. comets) and endogenous (i.e. remobilization of lunar volatiles by impact). Characterizing these endogenous sources is challenging because the highly volatile elements often leave little trace behind in the rocks themselves, which are inherently refractory by nature. Minerals are found on vug, vesicle, or fracture surfaces that have characteristics consistent with phases formed via direct deposition of a vapor, as opposed to crystallization from a liquid or via solid state decomposition. One common vapor-deposited species is metallic Fe, typically observed as subhedral to euhedral crystals found on vug or vesicle walls in mare basalts and on select breccia clast surfaces in regolith soil samples returned from the Moon. A particularly striking example is seen below in Fig. 1, where numerous Fe crystals are deposited onto the wall of a vug in Apollo 17 basalt sample 71036. Euhedral Fe crystals are not very common in Apollo breccia samples, though this may be from the limited number of systematic searches that have been performed. However, when Fe crystals are found, they can occur in extremely high abundance(e.g., sample 15402 which was specifically selected because of its numerous Fe crystals, was found to have a clast with 477 euhedral Fe crystals in a 570 x 570 μm area). What struck us as interesting about this was not only that it takes a large amount of Fe to make these crystal-rich deposits, but also that these crystal-rich deposits are not ubiquitous, and therefore they must be controlled by some aspect of their depositional conditions that varies. Since those conditions are inherently difficult to investigate and are critically interesting, we used thermochemical modeling as a tool to investigate the relationship between vapor-deposited Fe and various intensive and extensive parameters. We assumed that a high abundance of Fe in the vapor is required to form these crystals, thus the mass of Fe in the vapor was used to determine the plausibility of the vapor-deposited, euhedral Fe crystals observed in Apollo samples. more...

NASA’s OSIRIS-REx mission re-turned material from asteroid Bennu on September 24, 2023, marking the first time a U.S. mission has delivered asteroid samples to Earth, and the largest asteroid sample return to date. Due to the pristine nature of these primitive carbonaceous-rich samples, they allow us a rare opportunity to study our solar system’s formation to a degree not previously possible. Isotopes of moderately volatile elements (MVEs) have been recently developed as robust tracers for tracking different volatilization events within our Solar System. Of the MVEs, K has gained significant interest in recent years due to its ideal chemical and physical properties combined with technique improvements. Due to this, several recent studies have investigated the K isotope systematics within bulk chondrites and found an isotopic dichotomy be-tween the carbonaceous and non-carbonaceous chondrites (Figure 1), likely reflecting their different reservoirs which formed in the inner and outer protoplanetary disk respectively. Furthermore, systematic K isotope variations across the different carbonaceous chondrite groups and correlations with mass independent isotope systems such as Cr, Ti, and Ni, have also been observed. As a result, establishing the K isotope composition of bulk Bennu can be used to test the mission hypothesis that “Bennu’s parent asteroid accreted in the outer protoplanetary disk, beyond Jupiter, as recorded by distinct isotopic anomalies in a variety of elements”. In addition to early solar system processes, K isotopes can also be fractionated by space weathering as shown by comparisons between mature and immature lunar regolith. The degree of K isotope fractionation caused by space weathering correlates with the regolith maturity index and is an order of magnitude larger than what is observed in bulk meteorite samples which have not undergone strong space weathering processes. As such, the K isotope systematics of Bennu samples could provide an independent assessment of regolith maturity of the asteroid surface, helping to directly test the mission hypothesis that “Space weathering changed the chemistry and mineralogy of optically active surfaces”. In order to test both this hypothesis, and the hypothesis relating to Bennu’s accretion location, we aim to conduct high-precision K isotope analysis on bulk Bennu aggregates. more...

Material from the B-type carbonaceous asteroid (101955) Bennu was returned on September 24, 2023, by NASA’s OSIRIS-REx mission. The mission brought back the largest sample of pristine primordial asteroidal material, largely free from the challenges of terrestrial contamination that are common in meteorite studies. The Bennu sample thus provides a unique source of material to investigate the abundance and isotopic signatures of C and N. The specific hypotheses tested by these analyses are whether Bennu contains macromolecular material and/or presolar grains similar to the populations found in CI and CM chondrites and recently returned samples from Ryugu. more...

NASA’s OSIRIS-REx spacecraft delivered a sample from the carbonaceous asteroid (101955) Bennu to Earth on September 24, 2023. Since Bennu presumably accreted in the outer protoplanetary disk, beyond Jupiter’s orbit, the collected material is expected to be rich in highly volatile elements such as H, C, N, and noble gases—similar to Ivuna-type (CI) carbonaceous chondrites and material from asteroid (162173) Ryugu returned by JAXA’s Hayabusa2 spacecraft. This type of material may have contributed to the volatile inventory of Earth and the other terrestrial planets. Bulk CI chondrites record a narrow range of δ15N values (i.e., the permil difference from the atmospheric 15N/14N ratio), averaging between +42 and 49‰. In contrast, recent analyses at CRPG’s noble gas facility revealed that two pelletized Ryugu samples have lower δ15N values of +18.1 ± 0.9‰ and +19.5 ± 0.9‰. Together with the low measured N abundances, this observation suggests that Ryugu has lost a 15N-rich, labile organic phase due to pervasive aqueous alteration. Subsequent high-resolution step-heating analyses of an additional Ryugu particle demonstrated that the δ15N value varies significantly during successive extraction steps (between +1.0 ± 1.0‰ and 65.8 ± 1.1‰); the variable N isotopic composition points to the presence of several isotopically distinct N-carrier phases in CI-type material. Here, we report preliminary N-Ne-Ar results obtained for individual particles from an aggregate Bennu sample using the Noblesse-HR (Nu Instruments) noble gas mass spectrometer at CRPG’s noble gas facility. In a companion abstract, we will present the noble gas (He, Ne, Ar, Kr, Xe) characteristics of other aggregate particles determined with a HELIX MC Plus. Whereas the abundance and isotopic composition of noble gases permit detection of various presolar phases and the so-called phase Q, as well as quantification of solar wind–derived and cosmogenic components, the abundance and isotopic composition of N are expected to provide further insights into the origin and evolution of N-bearing phases in carbonaceous asteroids. more...

Observations by NASA’s OSIRIS-REx spacecraft of asteroid Bennu revealed evidence that this small rubble-pile asteroid experiences several active surface processes that likely control its recent surface exposure history. In October 2020, the spacecraft collected a surface sample from a relatively young ~20 m diameter crater (Hokioi) on asteroid Bennu, and the sample was successfully delivered to Earth on September 24, 2023. Based on the population of craters >50 m diameter, Bennu’s surface is 0.1–1 Ga old, but the old surface is affected by recent processes including smaller meteoroid impacts, mass movement, and particle ejections. The sampling location within Hokioi crater was selected based on its relatively flat surface devoid of large boulders, but the crater floor is also believed to be one of the youngest surfaces on asteroid Bennu, with an age of <100 kyr. As the crater is ~2 m deep, the samples that were collected by OSIRIS-REx may have been relatively shielded from cosmic rays during most of its recent history. This scenario is different from the samples that were collected by Hayabusa2 from asteroid Ryugu, where cosmogenic noble gas and radionuclides indicate cosmic-ray exposure (CRE) ages of ~5 Myr near the surface. Our goal is to understand the recent exposure history of surface samples of asteroid Bennu utilizing radionuclides (10Be, 26Al, 36Cl, 41Ca) produced by both galactic (GCR) and solar (SCR) cosmic rays. With half- lives ranging from 0.1 to 1.36 million years (Myr), the concentrations of these cosmogenic nuclides provide information on the duration and exposure conditions (irradiation depth) of these samples on a timescale of a few Myr. This work will test one of the OSIRIS-REx mission’s driving hypotheses about asteroid Bennu’s recent evolution: that Hokioi crater is part of a population of small (25 m) spectrally red craters on Bennu that are less than 0.1 Myr old. more...

Asteroid (101955) Bennu is a B-type asteroid and a prime candidate for investigating the remnants of planet formation and enhancing our understanding of potential sources of crucial bio-essential elements for the early Earth. Remote observations of the surface of Bennu unveiled a terrain of boulders primarily composed of hydrated phyllosilicates, organic molecules, and carbonates. The hydrated nature of Bennu, the abundance of carbonates, and the presence of cm-scale carbonate veins provide clues to the nature of the building blocks of Bennu’s parent body and to its complex geological history. Here we present the first mineralogical, chemical, and isotopic results of analysis of phosphates in samples returned from Bennu by NASA’s OSIRIS-REx mission. We seek to test the hypothesis that heating of Bennu’s parent asteroid resulted in hydrothermal alteration in which melted ice reacted with the initial constituents. more...

The OSIRIS-REx mission sampled material from the B-type asteroid Bennu and delivered the sample to Earth on 24 September 2023. Here we present initial xenon isotopic analysis of individual intermediate particles of Bennu material collected by the OSIRIS-REx mission. Noble gases are key tracers of Solar System evolution. Xenon is particularly useful among the noble gases because its nine isotopes allow multiple contributing sources to be unambiguously identified. The sun, asteroids (as measured in meteorites), and comets (measured in the coma of comet 67P) have distinct xenon isotopic signatures reflecting different mixtures of nucleosynthetic components. In addition, 129I, 238U, and 244Pu decay with different half-lives, producing characteristic xenon signatures. Exposure of samples containing light rare earth elements and barium to cosmic rays produces xenon from spallation and secondary neutron capture reaction. Noble gas analyses help address several of the driving hypotheses of the mission [9]. Particle-by-particle analysis can elucidate the diversity of material present and reveal distinct noble gas compositions, including the potential to detect presolar or cometary noble gas signatures on a small scale. The isotopic signature provides a fingerprint that can be used to constrain the sources of volatiles in planetary reservoirs and combined with other information (e.g. mineralogy and petrology of the material analyses) contributes to our understanding of the initial constituents, formation, and history of Bennu and its parent asteroid. more...

On 24 September 2023, the OSIRIS-REx spacecraft delivered to Earth material collected from the surface of the B-type asteroid Bennu. During its ~2.5-year encounter with the asteroid, OSIRIS-REx made many important discoveries, including establishing its extremely primitive chemical composition, the presence of at least two lithologies, and evidence of fluid flow on its parent asteroid. One of the driving hypotheses of the Sample Analysis Plan is that Bennu’s dominant lithologies are comparable to the most aqueously altered carbonaceous chondrites. Oxygen three-isotope analysis is a powerful tool for defining the relationship between different meteorite groups and can be used to understand the nature of the returned Bennu samples. The O isotope signatures reflect the materials that parent asteroids accreted from and the geological processes that operated during asteroidal evolution. Aggregate samples of particles (typically <500 μm) likely sampled many different larger stones and boulders, and their composition may therefore represent the average composition of Bennu. Fractionation of the sample, e.g. comparison of aliquots of finer material with coarser particles within the aggregate samples, offers the opportunity to identify different isotopic reservoirs within the returned material. The average O isotope composition will also provide a baseline from which to identify and characterize any exogenous clasts present in the sample. more...

The abundance and distribution of magmatic volatiles (i.e., H, C, N, F, S, and Cl) within the silicate portion of a differentiated planetary body has important consequences on its thermochemical evolution. However, the abundances of magmatic volatiles within differentiated bodies are difficult to quantify, and they are often depleted by varying degrees relative to CI chondrites. The mechanisms of depletion are not well constrained and could relate to intrinsic volatile depletion of the building blocks that formed the bodies, high temperature processes that result from accretion, post-accretion loss through parent body geological processes and large-scale impacts, and/or redistribution within a parent body through processes like core formation [1–4]. In the present study, we aim to constrain the abundances of F, Cl, and H2O in eucrites to better understand the magnitude of volatile depletion on 4Vesta. To accomplish this objective, we report electron microprobe analyses of apatite from seven unbrecciated, non-cumulate eucrites (i.e., CMS 04049,GRA 98098, LEW 88010, MAC 02522, MAC 041169,QUE 94484, and QUE 97053) and two monomict, non-cumulate eucrites (i.e., Berthoud and Stannern). In combination with previously published data on eucrite-hosted apatite, we determine Cl/F and H2O/F ratios in bulk rock eucrites through the application of apatite-based melt hygrometry and chlorometry [e.g., 5–7].Additionally, we estimate the bulk rock abundances of F in six non-cumulate eucrites (i.e., GRA 98098, MAC041169, PCA 91078, QUE 97053, Stannern, and Berthoud), which we combine with previously published bulk rock F data on non-cumulate eucrites[8] to constrain the abundances of F, Cl, and H2O in 4Vesta using appropriately paired volatile/refractory element ratios for F, followed by Cl/F and H2O/F ratios for Cl and H2O, respectively. more...