The Arpu Kuilpu meteorite: In-depth characterization of an H5 chondrite delivered from a Jupiter Family Comet orbit

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1Seamus L. Anderson et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14268]
1Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

Over the Nullarbor Plain in South Australia, the Desert Fireball Network detected a fireball on the night of June 1, 2019 (7:30 pm local time), and 6 weeks later recovered a single meteorite (42 g) named Arpu Kuilpu. This meteorite was then distributed to a consortium of collaborating institutions to be measured and analyzed by a number of methodologies including SEM-EDS, EPMA, ICP-MS, gamma-ray spectrometry, ideal gas pycnometry, magnetic susceptibility measurement, μCT, optical microscopy, and accelerator and noble gas mass spectrometry techniques. These analyses revealed that Arpu Kuilpu is an unbrecciated H5 ordinary chondrite, with minimal weathering (W0-1) and minimal shock (S2). The olivine and pyroxene mineral compositions (in mole%) are Fa: 19.2 ± 0.2 and Fs: 16.8 ± 0.2, further supporting the H5 type and class. The measured oxygen isotopes are also consistent with an H chondrite (δ17O‰ = 2.904 ± 0.177; δ18O‰ = 4.163 ± 0.336; Δ17O‰ = 0.740 ± 0.002). Ideal gas pycnometry measured bulk and grain densities of 3.66 ± 0.02 and 3.77 ± 0.02 g cm−3, respectively, yielding a porosity of 3.0% ± 0.7. The magnetic susceptibility of this meteorite is log χ = 5.16 ± 0.08. The most recent impact-related heating event experienced by Arpu Kuilpu was measured by 40Ar/39Ar chronology to be 4467 ± 16 Ma, while the cosmic ray exposure age is estimated to be between 6 and 8 Ma. The noble gas isotopes, radionuclides, and fireball observations all indicate that Arpu Kuilpu’s meteoroid was quite small (maximum radius of 10 cm, though more likely between 1 and 5 cm). Although this meteorite is a rather ordinary ordinary chondrite, its prior orbit resembled that of a Jupiter Family Comet (JFC) further lending support to the assertion that many cm- to m-sized objects on JFC orbits are asteroidal rather than cometary in origin.

Ferric Iron Evolution During Crystallization of the Earth and Mars

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1Laura Schaefer,2Kaveh Pahlevan,3Linda T. Elkins-Tanton
Journal of Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2023JE008262]
1Department of Earth and Planetary Sciences, Stanford University, Stanford, CA, USA
2Carl Sagan Center, SETI Institute, Mountain View, CA, USA
3School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
Published by arrangement with John Wiley & Sons

Magma ocean crystallization models that track fO2 evolution can reproduce the D/H ratios of both the Earth and Mars without the need for exogenous processes. Fractional crystallization leads to compositional evolution of the bulk oxide components. Recent work suggests that metal-saturated magma oceans may contain near-present-day Fe3+ concentrations. We model the fractional crystallization of Earth and Mars, including Fe2+ and Fe3+ as separate components. We calculate Fe3+ partition coefficients for lower mantle minerals and compare the results of fractional crystallization for both Earth and Mars. We calculate oxygen fugacity (fO2) at the surface as the systems evolve and compare them to constraints on the fO2 of the last magma ocean atmosphere from D/H ratios, both with and without metal saturation. For Earth, we find that Fe3+ likely behaves incompatibly in the lower mantle in order to match the D/H constraint for whole mantle models, but shallow magma ocean models also provide reasonable matches. Disproportionation in whole mantle magma oceans likely overpredicts the amount of Fe3+ and metal that form or require subsequent reduction to return to present-day values. For Mars, we cannot match the D/H constraints on last fO2 unless the magma ocean begins with <50% of the predicted Fe3+, but better match the present day mantle redox. We show that Fe3+ partitioning has a measurable effect on magma ocean redox, and that it evolves throughout the magma ocean’s lifetime. We highlight the need for additional experimental constraints on ferric iron mineral/melt partitioning and more thermodynamic data for the Fe-disproportionation reaction.

Consus Crater on Ceres: Ammonium-Enriched Brines in Exchange With Phyllosilicates?

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1A. Nathues,1M. Hoffmann,1R. Sarkar,1P. Singh,1J. Hernandez,2J. H. Pasckert,2N. Schmedemann,3G. Thangjam,4E. Cloutis,1K. Mengel,1M. Coutelier
Journal og Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008150]
1Max Planck Institute for Solar System Research, Goettingen, Germany
2Institut für Planetologie, Universität Münster, Münster, Germany
3School of Earth and Planetary Sciences, National Institute of Science Education and Research, NISER, HBNI, Khurda, Odisha, India
4University of Winnipeg, Winnipeg, MB, Canada
Published by arrangement with John Wiley & Sons

Ceres is a partially differentiated dwarf planet located in the main asteroid belt. Consus crater (diameter ∼64 km) is one of the oldest impact features (∼450 Ma) on the Cerean surface that surprisingly still shows a large variety of color lithologies, including exposures of bright material, which are thought to be brine residues. Here, we present new results that help in understanding the structure and composition of the Cerean crust. These results were deduced by using newly processed Dawn Framing Camera (FC) color imagery and FC clear filter images combined with infrared spectral data of Dawn’s Visible and Infrared Spectrometer (VIR). Consus exhibits a variety of color lithologies, which we describe in detail. Interestingly, we found three spectrally different types of bright material exposed by a large old crater on Consus’ floor. One of these, the yellowish bright material (Nathues et al., 2023, https://www.hou.usra.edu/meetings/lpsc2023/pdf/1073.pdf) and its modification, shows spectral signatures consistent with ammonium-enriched smectites. We hypothesize that the ammonium in these smectites stems from contact with ascending brines, originating from a low-lying former brine ocean that has been enriched in ammonium during the differentiation and freezing process of the Cerean crust. This enrichment is mainly due to ammonium uptake by sheet silicates. If such an ammonium enrichment occurred over long-time scales on a global scale, this process may explain the vast presence of ammonium on the Cerean surface. Therefore, an outer solar system origin of Ceres is possibly not needed to explain the global presence of ammonium.

Microscopic slickenside as a record of weak shock metamorphism in the surface layer of asteroid Ryugu

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1Masaaki Miyahara et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14271]
1Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Japan
Published by arrangement with John Wiley & Sons

The surface morphology of regolith grains from the C-type asteroid Ryugu was studied in search of evidence of impact events on the asteroid. Scanning electron microscopy revealed that ~8% of C0105-042 Ryugu grains have a smooth surface on one side of the grains. One of these grains has striated linear grooves (striations) on its smooth surface. Transmission electron microscopy of the grain showed that a porous fine-grained Mg-Fe phyllosilicate assemblage, which is the main component of Ryugu grains, is compacted near the smooth surface. The smooth surface with striations closely resembles a slickenside, a characteristic texture found in terrestrial fault rocks formed by shear deformation. There is no evidence of melting/decomposition in the Mg-Fe phyllosilicates near the smooth surface, indicating that the shear heating temperature is less than ~1100 K. Assuming that the average length of the striations corresponds to the minimum displacement of the micro-fault, the shock pressure recorded in the C0105-042 Ryugu grain is estimated to be <~4.5 GPa by a fault mechanics calculation. The shock pressures of C0105-042, together with those of C0014 (~2 GPa) and C0055 (>~3.9 GPa) in previous studies suggest that the impact velocities recorded in these grains are < ~0.89–1.63 km s−1. Based on the impact velocities, these grains may record an impact event that occurred when asteroid Ryugu was in the orbit in Main Belt.

Effects of hot desert weathering on highly siderophile elements in ordinary chondrites

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1Kiran Shahood Almas,1Richard D. Ash,1Richard J. Walker
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14267]
1Department of Geology, University of Maryland, College Park, Maryland, USA
Published by arrangenent with John Wiley & Sons

Over 20,000 meteorites have been recovered from hot deserts. The effects of hot desert weathering upon highly siderophile elements (HSE) have been little studied. We have investigated the effects of neutral to mildly acidic leaching of three L6-type ordinary chondrites of different weathering grades on HSE concentrations and Re-Os isotopic systematics. We have characterized the bulk sample HSE patterns of these meteorites and conducted leaching experiments with progressively longer leaching times to determine the possible effects of long-term residence in a desert. The most weathered sample (NWA 14239) displayed greater HSE concentration homogeneity than the other samples and released lower quantities of HSEs during leaching. Water leaching was milder than acetic acid and did not significantly modify the Re-Os isotopic systematics of the residue relative to the bulk sample of NWA 869. Short-term leachates of the less weathered samples (Viñales and NWA 869) were characterized by low 187Os/188Os ratios, indicating the preferential dissolution of early solar system–formed phases such as non-magnetic chondrules and matrix with low Re/Os that are no longer intact in the most weathered sample. Of the HSE, Pd is most resistant to both water and acetic acid leaching, with a maximum removal of ~5% Pd, while Re, Os, and Ir are most mobile with up to 40% removal.

NWA 11562: A Unique Ureilite with Extreme Mg-rich Constituents

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1,2Mingbao Li,3,4Ke Zhu,1,5Yan Fan,6P. M. Ranjith,7Chao Wang,1Wen Yu, 1,8,9Shijie Li
The Planetary Science Journal 5, 178 Open Access Link to Article [DOI 10.3847/PSJ/ad6154]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 55021, People’s Republic of China
2State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Macau 999078, People’s Republic of China
3Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, Berlin 12249, Germany
4Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, UK
5State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, People’s Republic of China
6Graduate School of Advanced Science and Technology, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan
7School of Earth and Space Sciences, Peking University, Beijing 100871, People’s Republic of China
8CAS Center for Excellence in Comparative Planetology, Hefei, 230022, People’s Republic of China

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Low temperature phase transitions in the visible and near-infrared (VNIR) reflectance spectra of (NH4)2HPO4 and (NH4)HSO4 salts

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1M. Fastelli, 2B. Schmitt, 2P. Beck, 2O. Poch, 1A. Zucchini, 1P. Comodi
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116321]
1Department of Physics and Geology, University of Perugia, I-06123 Perugia, Italy
2Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
Copyright Elsevier

The detection of ammonium bearing crystalline solids in salt-water systems on icy bodies and solar system bodies could provide information about the ascent of these salts from a deep reservoir within the hydrosphere. Due to their chemical-physical properties, NH4+ compounds play a key role both in the internal dynamics of celestial bodies and in the potential habitability of ocean worlds.. In this work we analysed the reflectance spectra of two synthetic NH4+ salts: ammonium hydrogen phosphate (NH4)2HPO4 and ammonium hydrogen sulphate (NH4)HSO4 in the 1–4.2 μm spectral range at low temperature, between 110 and 290 K. For (NH4)2HPO4 we also examined the effect of three different grain sizes (150–125 μm; 125–80 μm; 80–32 μm). The collected reflectance spectra show absorption features related to NH4+ group overtone and combination modes in the 1–2.5 μm range. In particular, the bands located at ~1.09 μm (3ν3), ~1.30 μm (2ν3 + ν4), ~1.58 μm (2ν3), ~2.02 μm (ν2 + v3) and ~ 2.2 μm (v3 + v4) could be useful to discriminate these salts. The low temperature spectra, compared to those at ambient temperature, reveal finer structures, displaying sharper and narrower absorption bands. The selected NH4+-bearing salts are subjected to reversible low temperature phase transitions, which are revealed in the spectra by a progressive growth and shift of the bands toward shorter wavelengths with a drastic change of their depth. We performed laboratory measurements ammonium (NH4+) compounds to address the limited data available expanding the existing database. The collected cryogenic spectra can be directly compared with remote sensing data from planetary missions of the upcoming decade such as NASA’s Europa Clipper, and ESA’s JUICE and the newly launched James Webb Space Telescope expanding the existing database of ammonium compounds at cryogenic temperature.

Fe, Zn, and Mg stable isotope systematics of acapulcoite lodranite clan meteorites

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1,2Stepan M. Chernonozhkin,3Lidia Pittarello,4Genevieve Hublet,5Philippe Claeys,4Vinciane Debaille,1Frank Vanhaecke,5Steven Goderis
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14258]
1Atomic & Mass Spectrometry—A&MS Research Unit, Department of Chemistry, Ghent University, Ghent, Belgium
2Isotope Ratio Analysis Research Group, Chair of General and Analytical Chemistry, Montanuniversität Leoben, Leoben, Austria
3Naturhistorisches Museum Wien – NHMW, Vienna, Austria
4Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium
5Archaeology, Environmental Changes, and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, Brussels, Belgium
Published by arrangement with John Wiley & Sons

The processes of planetary accretion and differentiation, whereby an unsorted mass of primitive solar system material evolves into a body composed of a silicate mantle and metallic core, remain poorly understood. Mass-dependent variations of the isotope ratios of non-traditional stable isotope systems in meteorites are known to record events in the nebula and planetary evolution processes. Partial melting and melt separation, evaporation and condensation, diffusion, and thermal equilibration between minerals at the parent body (PB) scale can be recorded in the isotopic signatures of meteorites. In this context, the acapulcoite–lodranite meteorite clan (ALC), which represents the products of thermal metamorphism and low-degree partial melting of a primitive asteroid, is an attractive target to study the processes of early planetary differentiation. Here, we present a comprehensive data set of mass-dependent Fe, Zn, and Mg isotope ratio variations in bulk ALC species, their separated silicate and metal phases, and in handpicked mineral fractions. These non-traditional stable isotope ratios are governed by mass-dependent isotope fractionation and provide a state-of-the-art perspective on the evolution of the ALC PB, which is complementary to interpretations based on the petrology, trace element composition, and isotope geochemistry of the ALC. None of the isotopic signatures of ALC species show convincing co-variation with the oxygen isotope ratios, which are considered to record nebular processes occurring prior to the PB formation. Iron isotopic compositions of ALC metal and silicate phases broadly fall on the isotherms within the temperature ranges predicted by pyroxene thermometry. The isotope ratios of Mg in ALC meteorites and their silicate minerals are within the range of chondritic meteorites, with only accessory spinel group minerals having significantly different compositions. Overall, the Mg and Fe isotopic signatures of the ALC species analyzed are in line with their formation as products of high-degree thermal metamorphism and low-degree partial melting of primitive precursors. The δ66/64Zn values of the ALC meteorites demonstrate a range of ~3.5‰ and the Zn is overall isotopically heavier than in chondrites. The superchondritic Zn isotopic signatures have possibly resulted from evaporative Zn losses, as observed for other meteorite parent bodies. This is unlikely to be the result of PB differentiation processes, as the Zn isotope ratio data show no covariation with the proxies of partial melting, such as the mass fractions of the platinum group and rare earth elements.