¹Surjyendu Bhattacharjee,¹John M. Eiler
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.07.013]
¹California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
Copyright Elsevier

We report theoretically calculated equilibrium oxygen isotopic fractionation factors (17O/16O, 18O/16O) between a set of representative O-bearing organic molecules and water, as well as site specific 13C, 15N and 13C-18O equilibrium clumped isotopic anomalies in these compounds, all computed using density functional theory (DFT) methods combined with Urey-Bigeleisen-Mayer (UBM) calculations of reduced partition function ratios. We performed density functional theory (DFT) calculations with the B3LYP exchange correlation functional, and explored different basis sets, and treatments of solvation. After benchmarking results against prior theoretical and empirical studies, we conclude that B3LYP level of theory and aug-cc-pVTZ basis set with cluster solvation provides the most accurate treatment of this problem within the constraints of our approach. A representative set of O bearing organic compounds including aldehyde, ketones, amino acid and aromatic alcohol are predicted to be ∼24–41 ‰ higher in 18O/16O relative to water with θcompound – water varying in the range 0.522 – 0.526; and ∼ 23–41 ‰ lower in 13C/12C and ∼ 11 ‰ higher in 15N/14N relative to CO2 and N2, respectively (all presuming equilibrium partitioning) at 273 K.

This study is motivated by the study of soluble organic molecules found in carbonaceous chondrite meteorites, a significant fraction of which contain oxygen in their structure in the form of functional groups such as carbonyl, carboxylic acid, ester, ethers, and alcohol. These samples also contain oxygen-bearing macromolecular organic matter. We use the fractionation factors presented here to predict the triple oxygen isotope compositions of these organics, assuming equilibration with previously proposed early-solar-system volatile reservoirs and environments of organic synthesis.

¹Devin L. Schrader et al. (>10)
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.07.007]
¹Buseck Center for Meteorite Studies, School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
Copyright Elsevier

We report a comprehensive study of the ungrouped type 2 carbonaceous chondrite, Tarda, which fell in Morocco in 2020. This meteorite exhibits substantial similarities to Tagish Lake, Wisconsin Range 91600, and Meteorite Hills 00432, which are generally considered to have originated from a D-type asteroid(s). We constrain the compositions and petrologies of the materials present in a potential sample of a D-type asteroid by reporting the petrography, bulk chemical compositions, bulk H, C, N, Cr, and Ti isotopic compositions, reflectance spectra, and in situ chemical compositions of metals, sulfides, carbonates, and FeO-poor and FeO-rich chondrule silicates of Tarda. We also present new data for Tagish Lake. We then compare Tarda with the other Tagish Lake-like meteorites.
Tarda and Tagish Lake appear to be from the same parent body, as demonstrated by their similar petrologies (modal abundances, chondrule sizes), mineral compositions, bulk chemical and isotopic compositions, and reflectance spectra. While the two other Tagish Lake-like meteorites, Wisconsin Range 91600 and Meteorite Hills 00432, show some affinities to Tagish Lake and Tarda, they also share similar characteristics to the Mighei-like carbonaceous (CM) chondrites, warranting further study. Similarities in reflectance spectra suggest that P-type asteroids 65 Cybele and 76 Freia are potential parent bodies of Tarda and the Tagish Lake-like meteorites, or at least have similar surface materials. Since upcoming spacecraft missions will spectrally survey D-type, P-type, and C-type Trojan asteroids (NASA’s Lucy) and spectrally study and return samples from Mars’ moon Phobos (JAXA’s Martian Moons eXploration mission), which is spectrally similar to D-type asteroids, these meteorites are of substantial scientific interest. Furthermore, since Tarda closely spectrally matches P-type asteroids (but compositionally matches the D-type asteroid like Tagish Lake meteorite), P-type and D-type asteroids may represent fragments of the same or similar parent bodies.

^1,2Antonin Wargnier et al. (>10)
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116216]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, Université Paris Cité, Sorbonne Université, 5 place Jules Janssen, Meudon, 92195, France
²LATMOS, CNRS, Université Versailles St-Quentin, Université Paris-Saclay, Sorbonne Université, 11 Bvd d’Alembert, Guyancourt, F-78280, France
Copyright Elsevier

Previous Mars Reconnaissance Orbiter and Mars Express observations of Phobos and Deimos, the moons of Mars, have improved our understanding of these small bodies. However, their formation and composition remain poorly constrained. Physical and spectral properties suggest that Phobos may be a weakly thermal-altered captured asteroid but the dynamical properties of the martian system suggest a formation by giant collision similar to the Earth moon. In 2027, the JAXA’s MMX mission aims to address these outstanding questions.

We undertook measurements with a new simulant called OPPS (Observatory of Paris Phobos Simulant) which closely matches Phobos reflectance spectra from the visible to the mid-infrared wavelength range. The simulant was synthesized using a mixture of olivine, saponite, anthracite, and coal.

Since observation geometry strongly influences the photometry and spectra of the light reflected from planetary surfaces, we evaluated the parameters obtained by modeling the phase curves – obtained through laboratory measurements – of two different Phobos simulants (UTPS-TB and OPPS) using Hapke IMSA model. Our results show that the photometric properties of Phobos simulants are not fully consistent with those of carbonaceous chondrites and martian meteorites. We also investigated the detection of volatiles/organic compounds and hydrated minerals, as the presence of such components is expected on Phobos in the hypothesis of a captured primitive asteroid. To investigate their detectability, we examined the variability of the 3.28μm and 3.42μm absorption bands related to aliphatic/aromatic carbon (as a proxy of organic material), as well as the 2.7μm O-H feature in a Phobos laboratory spectroscopic simulant. The results indicate that a significant amount of organic compounds is required for the detection of C-H bands at 3.4μm. The bands at 3.28 and 3.42μm are faint (less than 2%) when ∼3 wt% of organic compounds are present in the simulant and are likely undetectable by the MIRS spectrometer onboard the MMX mission. When the concentration of aliphatic and aromatic compounds is increased to 6 wt%, a positive detection starts to become more plausible using remote sensing infrared spectroscopy. In contrast, the 2.7μm absorption band, due to hydrated minerals, is much deeper and easier to detect than C-H organic features at the same concentration levels. The feature is still clearly detectable even when the simulant contains only 3 vol.% of phyllosilicates, corresponding to 0.7 wt% OH groups.

Posing limits on detectability of some possible key components of Phobos surface will be pivotal to prepare and interpret future observations of the MIRS spectrometer as well as TENGOO and OROCHI cameras onboard MMX mission.

¹Shuying Yang,¹Munir Humayun,²Kevin Righter
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14235]
¹National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, USA
²Astromaterials Research and Exploration Sciences, NASA Johnson Space Center, Houston, Texas, USA
Copyright Elsevier

Understanding the mineralogy of the Martian mantle is essential for constructing geochemical and geophysical models of Mars. This study employs the pMELTS program to determine the mineralogy at the solidus from 11 published bulk silicate Mars (BSM) compositions, within a pressure range of 2–5 GPa. The pMELTS results align with experimental data and calculations from another thermodynamic program (Perple_X/stx11). Mineral modes from compositional models based on Martian meteorite geochemistry show relatively consistent abundances modes (olivine: 48–56 wt%, orthopyroxene: 20–25 wt%, clinopyroxene: 15–17 wt%, garnet: 6–9 wt%). In contrast, mineral modes from compositional models that are not based on Martian meteorite geochemistry exhibit a wider range of olivine and garnet abundances. Additionally, we constrained the mineral modes of the Martian mantle using trace element partitioning and partial melting models. Our calculations indicate that melts derived from mantle sources with a hypothesized garnet content of 5–10 wt% closely match the analyzed compositions of shergottites, validating the garnet mode (6–9 wt%) constrained in our pMELTS calculations. Extracting low-degree (<4 wt%) melts from a BSM to form depleted Martian mantle (DMM) does not significantly alter the mineralogical modes of solid residues, but it does lead to substantial trace elemental depletion in the DMM. Therefore, enriched, intermediate, and depleted shergottite sources are likely characterized by similar mineral modes yet differ in incompatible element abundances.

¹Cassandra Seltzer,¹Hoagy O’Ghaffari,¹Matěj Peč
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008296]
¹Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
Published by arrangement with John Wiley & Sons

Icy moons in the outer Solar System likely contain rocky, chondritic interiors, but this material is rarely studied under confining pressure. The contribution of rocky interiors to deformation and heat generation is therefore poorly constrained. We deformed LL6 chondrites at confining pressures ≤100 MPa and quasistatic strain rates. We defined a failure envelope, recorded acoustic emissions (AEs), measured ultrasonic velocities, and retrieved static and dynamic elastic moduli for the experimental conditions. The Young’s modulus, which quantifies stiffness, of the chondritic material increased with increasing confining pressure. The material reached its peak strength, which is the maximum supported differential stress (σ1 − σ3), between 40 and 50 MPa confining pressure. Above this 40–50 MPa range of confining pressure, the stiffness increased significantly, while the peak strength dropped. Acoustic emission events associated with brittle deformation mechanisms occurred both during isotropic pressurization (σ1 = σ2 = σ3) as well as at low differential stresses during triaxial deformation (σ1 > σ2 = σ3), during nominally “elastic” deformation, indicating that dissipative processes are likely possible in the rocky interiors of icy moons. These events also occurred less frequently at higher confining pressures. We therefore suggest that the chondritic interiors of icy moons could become less compliant, and possibly less dissipative, as a function of the moons’ pressure and size.

¹Konstantin M. Ryazantsev,²Alexander N. Krot,³Chi Ma,¹Marina A. Ivanova,¹Cyril A. Lorenz,⁴Vasiliy D. Shcherbakov
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14238]
¹Vernadsky Institute of Geochemistry of the Russian Academy of Sciences, Moscow, Russia
²Hawai’i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai’i at Mānoa, Honolulu, Hawai’i, USA
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Lomonosov Moscow State University, Moscow, Russia
Published by arrangement with John Wiley & Sons

Isolated corundum grains and corundum ± Mg-deltalumite [(Al,Mg)(Al,◻)2O4] ± hibonite assemblages were investigated in the CH3.0 metal-rich carbonaceous chondrite Sayh al Uhaymir (SaU) 290. Although very refractory inclusions containing abundant Zr- and Sc-rich oxides and silicates, hibonite, grossite, or perovskite have been previously described in CH chondrites, this is the first discovery of corundum and Mg-deltalumite in CHs and the first discovery of Mg-deltalumite in nature. Magnesium-deltalumite can be indexed by the Fd3m spinel-type structure and gives a perfect fit to the synthetic Al-rich spinel cells. Corundum-Mg-deltalumite grains, 5–20 μm in size, are occasionally rimmed by a thin layer of hibonite replacing corundum. Some corundum grains contain tiny inclusions of ultrarefractory Zr,Sc-rich minerals and platinum-group element (PGE) nuggets. All corundum, hibonite, and Mg-deltalumite grains studied have 16O-rich compositions (average Δ17O ± 2SD = −22 ± 3‰). Two corundum grains show evidence for significant mass-dependent fractionation of oxygen isotopes: Δ18O ~ +34‰ and ~ +19‰. We suggest that the SaU 290 corundum-rich objects were formed by evaporation and/or condensation in a hot nebular region close to the proto-sun where the ambient temperature was close to the condensation temperature of corundum. A corundum grain with tiny inclusions of Zr- and Sc-rich phases and PGE metal nuggets recorded formation temperatures higher than the condensation temperature of corundum. Two corundum-rich objects with highly fractionated oxygen isotopes must have crystallized from a melt that experienced evaporation. Corundum grains corroded by hibonite recorded gas–solid interaction in this region during its cooling. The Mg-deltalumite ± corundum ± hibonite objects were formed by rapid crystallization of high-temperature (>2000°C) refractory melts. The lack of minerals with condensation temperatures below those of corundum and hibonite in the SaU 290 corundum-rich objects suggests that after formation, these objects were rapidly removed from the hot nebular region by disk wind and/or by turbulent diffusion and disk spreading.

¹Haiyang Luo,¹Lidunka Vočadlo,^1,2John Brodholt
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2024.07.002]
¹Department of Earth Sciences, University College London, London, UK
²Center for Planetary Habitability, University of Oslo, Oslo, Norway
Copyright Elsevier

Fe isotope variations in rocky bodies reveal fundamental information about planetary evolution. However, experimental results have come to contradictory conclusions on the equilibrium Fe isotope fractionation between metal and silicate during core-mantle differentiation. Many different processes, including evaporation, core formation, partial melting and disproportion of mantle silicate, have been consequently proposed to explain the observed Fe isotope variations in rocky solar system bodies. Here we perform ab initio molecular dynamics simulations and find that the anharmonicity in iron strongly decreases the force constant of Fe at low pressures (<∼50 GPa), which even reverses the equilibrium Fe isotope fractionation between metal and silicate. We conclude that pyrolitic melt is always enriched in heavy Fe isotopes relative to liquid Fe-alloys, no matter what pressure. Therefore core-mantle differentiation will play a significant role in explaining the heavy Fe isotope compositions of the mantles of some rocky bodies (e.g., Earth, the ureilite parent body, and possibly the asteroid Vesta). As all previously proposed processes for Fe isotope fractionation can only enrich the mantle-derived rocks in heavy Fe isotopes, the near/sub-chondritic Fe isotope signatures of Mars and the aubrite parent body thus imply that iron sulfide enriched in light Fe isotopes may significantly contribute to the iron components of those meteoritic samples.

¹Brendan J. Orenstein,^2,3,4Michael W.M. Jones,¹David T. Flannery,⁵Austin P. Wright,⁶Scott Davidoff,⁷Michael M. Tice,¹Luke Nothdurft,¹Abigail C. Allwood
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2024.116202]
¹School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, QLD 4000, Australia
²Central Analytical Research Facility, Queensland University of Technology, Brisbane, QLD 4000, Australia
³School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia
⁴Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
⁵School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
⁶Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
⁷Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA
Coypright Elsevier

Elemental quantification instruments for planetary missions provide a capability for in-situ identification of mineral phases via stoichiometry, an essential step in petrological investigations. X-ray fluorescence (XRF) has been employed for this purpose by multiple generations of Mars rovers (i.e., Pathfinder, Spirit and Opportunity, Curiosity and Perseverance). The Planetary Instrument for X-ray Lithochemistry (PIXL) aboard Perseverance rasters a micro-focused X-ray beam to generate micron-mm-sized maps illustrating variations in elemental composition and allowing mission scientists to identify rock components (i.e., sedimentary grains, veins and igneous crystals). Energy-dispersive X-ray diffraction can also be detected with PIXL and can be used as an additional constraint on component boundaries, providing PIXL with the capability to map monocrystalline regions in-situ. Here we introduce and apply a new method where each diffraction peak is partitioned independently according to its energy, using the instrument geometry to inform consistent partitioning. Applying this method to datasets acquired from the Dourbes abrasion patch in the Séítah formation of Jezero crater, Mars, reveals monocrystalline regions that were hidden using previous methods. This application of the technique allows faster and more accurate visualization of petrographic textures in future PIXL datasets, in particular those with rock components that are not easily separable using stoichiometry alone.

¹Jean-Pierre Lorand,¹Sylvain Pont,¹Roger H. Hewins,¹Brigitte Zanda
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14233]
¹Institut de Minéralogie, Physique de la matière et Cosmochimie, et Muséum National d’Histoire Naturelle, UMR CNRS 7590, Sorbonne Université, Paris, France
Copyright Elsevier

Northwest Africa (NWA) 14672, the most highly shocked Martian meteorite so far, has experienced >50% melting, compatible with peak pressure >~65 Gpa, at a transition stage 6/7. Despite these extreme shock conditions, the meteorite still preserves a population of “large” Fe sulfide blebs from the pre-shock igneous assemblage. These primary blebs preserve characteristics of basaltic shergottites in term of modal abundance, preferential occurrence in interstitial pores along with late-crystallized phases (ilmenite, merrillite), and Ni-free pyrrhotite compositions. Primary sulfides underwent widespread shock-induced remelting, as indicated by perfect spherical morphologies when embedded in fine-grained silicate melt zones and a wealth of mineral/glass/vesicle inclusions. Extensive melting of Fe-sulfides is consistent with the decompression path experienced by NWA 14672 after the peak shock pressure at ~70 GPa. Primary sulfides acted as preferential sites for nucleation of vesicles of all sizes which helped sulfur degassing during decompression, leading to partial resorption of Fe-sulfide blebs and reequilibration of pyrrhotite metal/sulfur ratios (0.96–0.98) toward the low oxygen fugacity conditions indicated by Fe-Ti oxides hosted in fine-grained materials. The extreme shock intensity also provided suitable conditions for widespread in situ redistribution of igneous sulfur as micrometric globules concentrated in glassy portions of fine-grained lithologies. These globules exsolved early on quenching, allowing dendritic skeletal Fe-Ti oxide overgrowths to nucleate on sulfides.

^1,2,3Zhan Zhou,¹Jiawei Zhao,^1,4Long Xiao,^1,5Jiahuai Sun
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116205]
¹State Key Laboratory of Geological Processes and Mineral Resources, Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
²Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴State Key Laboratory of Lunar and Planetary Sciences, Space Science Institute, Macau University of Science and Technology, Macau, China
⁵CAS Key Laboratory of Crust–Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
Copyright Elsevier

High-pressure minerals formed during asteroid impact events are critical for unraveling the details of impact processes. Reidite, a high-pressure polymorph of zircon (ZiSiO₄), forms at ~20–50 GPa in shock-recovery experiments. However, high-contents of reidite in natural zircon (30–100%), which indicate a exceeding 40 GPa formation pressure, are rare in terrestrial and extraterrestrial materials. It is potentially associated with the extreme formation conditions, limiting the potential to use a shock thermobarometer in zircon. Here we report one outcrop of typical microstructures (reidite, granular zircon, and zirconia) in shocked zircon extracted from the outer suevite at the Ries impact crater, Germany. We describe a variety of complex habits of reidite with different proportions (0 − ~90%) of shocked zircon. As supported by previous shock-recovery experiments, these habits of reidite indicate a formation pressure of ~20–50 GPa, further constraining the application range of shock thermobarometer in natural zircon. The presence of diverse ZrSiO₄ phases at the centimeter or micrometer scale, as well as the co-occurrence of reidite, granular zircon, and zirconia at the grain scale reveal highly heterogeneous P-T conditions in outer suevite. We suggest that these thoroughly mixed materials have two types of origins: (1) The excavation flow (or cross-flow) fields mix materials with different shock levels from various positions within the crater. (2) The heterogeneous heating of impact melt result in the diversification of high-temperature phases in zircon. Furthermore, the extensive preservation of shock features of zircon such as reidite reveals that the outer suevite experienced rapid cooling during emplacement and was not exposed to a long-term overheated environment. This supports the radial flow hypothesis of emplacement rather than the FCI (fuel-coolant interaction) model. In general, this study indicates that zircon is a robust shock thermobarometer (0 − ~50 GPa) to help in understanding the formation history of parent rocks and unraveling the P-T conditions of the impact events.