¹I.P.Baziotis,¹S.Xydous,¹A.Papoutsa,²J.Hu,²C.Ma,³L.Ferrière,⁴S.Klemme,⁴J.Berndt,²P.D.Asimow
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115326]
¹Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece
²California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA 91125, USA
³Natural History Museum Vienna, Burgring 7, A-1010 Vienna, Austria
⁴Westfälische Wilhelms-Univ. Münster, Correnstrasse 24, 48149 Münster, Germany
Copyright Elsevier

The effects of collisions on the evolution of asteroids, ranging from local fracturing to brecciation or even to catastrophic disruption, depend primarily on the encounter velocities. Here we present a refined view of the mineralogy and texture of the recent fall Viñales, an L6 ordinary chondrite meteorite. It preserves features that require at least one energetic impact, including numerous shock melt veins of variable thickness. We report the identification of two high-pressure phases, majorite and albitic jadeite, limited to just one of these shock melt veins. Viñales is a moderately shocked sample, shock stage S4, that experienced a complex and spatially variable pressure-temperature-time history with a low (but non-zero) probability of preservation of high-pressure phases.

¹Rachel S.Kirby,¹Penelope L.King,¹Marc D.Norman,¹Trevor R.Ireland,¹Margaret Forster,²Arthur D.Pelton,¹Ulrike Troitzsch,³Nobumichi Tamura
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.10.034]
¹Research School of Earth Sciences, The Australian National University, Acton ACT 2601, Australia
²Center for Research in Computational Thermochemistry, Department of Chemical Engineering, Polytechnique Montréal, Montréal QC H3T 1J4 Canada
³Advanced Light Source, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, U.S.A
Copyright Elsevier

Most iron meteorites formed in planetary cores during differentiation, but the IIE iron meteorites have chemical and physical features that are inconsistent with this origin. By combining mineral chemistry, mineral modes and three-dimensional petrography, we reconstruct the bulk chemistry of the felsic silicate-bearing Miles IIE iron meteorite and demonstrate that the silicate inclusion compositions are similar to partial melts produced experimentally from an H chondrite composition. We use the reconstructed bulk composition, mineralogy and thermodynamic modelling to show that melting above ∼1200 °C under reducing conditions formed metal (Fe-Ni alloy) and felsic silicate partial melts. Upon cooling, the melts crystallized Mg-rich pyroxenes, Na- and K-rich feldspars, and tridymite. Importantly, this mechanism enriches cosmochemically volatile elements (i.e., those with a 50% condensation temperature of ∼430-830 °C, like Na and K) to the level found in the felsic silicate inclusions.

The presence of crystallographically disordered srilankite (only stable above 1160 °C) and an absence of Widmanstätten texture require both high peak temperatures and rapid cooling, which cannot be explained by core formation Instead they point to small melt volumes, a transient heat pulse, and small thermal mass, and imply efficient physical segregation of silicate and metallic melts through buoyancy separation followed by rapid cooling that arrested the separation of metal and silicate liquid phases. In situ 207Pb/206Pb ages of 4542 ± 4.0 Ma in Zr-oxide minerals determined here date the melting event that formed the silicate inclusions. This age aligns with the earliest ages found in other IIE iron meteorite silicates and requires a heating event ∼25 million years after the solar system formed. We found 39Ar/40Ar ages of 3495 ± 52 Ma (low-T) and 4303 ± 7 Ma (high-T) in a K-feldspar grain, with the 3495 Ma age aligning with later thermal events recorded in other IIE iron meteorites. Dating reveals the complex petrogenetic and thermal history of Miles and the IIE iron meteorites. This is the first IIE iron meteorite found to record evidence of impact bombardment at 4.5 and 3.5 Ga.

High-velocity impact(s) into an iron-rich, porous chondritic parent body at ∼4.54 Ga produced immiscible metal and silicate melts that cooled rapidly and trapped low density silicate inclusions within high density metal. Other IIE irons that formed at lower peak temperatures (900-1000 °C) contain chondritic silicate inclusions and relict chondrules, supporting this conceptual model. Our model is consistent with thermodynamic modelling, experimental data and the wide range of peak temperatures and cooling rates observed in the IIE iron meteorites.

¹M.Angrisani,¹E.Palomba,¹A.Longobardo,¹A.Raponi,¹F.DirriC.Gisellu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115320]
¹INAF-IAPS Rome, Via Fosso del Cavaliere,100 Rome, Italy
Copyright Elsevier

Among main belt asteroids, some have a spectrum similar to Vesta so they are taxonomically classified as V-type asteroids. Probably they were removed from Vesta and migrated to their current positions via some still unknown dynamical mechanisms. Several issues on the relationship between V-type asteroids, Howardite -Eucrite -Diogenite (HED) meteorites and Vesta are still unresolved. Although some of them can be directly linked to (4) Vesta, forming its dynamical family, others do not appear to have a clear dynamical link, thus suggesting the existence of other basaltic parent bodies. In this work we present a new approach of analysis to investigate 76 VNIR V-type asteroids spectra downloaded from PDS. The composition of the regolith and particle size of V-type asteroid have been investigated with a combination of spectroscopic analysis and Hapke radiative transfer model. Retrieved particle sizes are very small, with a mean value of 20 μm.

Therefore, we look for statistically significant differences among the modal mineralogy of V-type asteroids belonging to different dynamical subclasses. It seems there is a possible chronologic link between impact events on Vesta and the V-type families. The most ancient V-type family, e.g. Low -I asteroids, seems to have a eucritic composition compatible with an ejection of the outermost layer of Vesta. The Fugitive V-type were probably ejected in an older cratering event that produced the Veneneia basin while the Vestoids family, whose dynamical parameters are still more similar to Vesta and which seems to be the youngest family among them, could be associated to Rheasilvia basin. The last two families seem to have a diogenitic composition compatible with that of the south of Vesta, where the two huge craters are located.

Spartacus asteroid is also analysed and it was found to have a modal mineralogy consistent with the presence of olivine as noted before (Moskovitz et al.,2010; Burbine et al., 2001).

¹C.J.Renggli,^2,3J.L.Hellmann,^2,4C.Burkhardt,¹S.Klemme,¹J.Berndt,¹P.Pangritz,^2,4T.Kleine
Geochimica et Cosmochimica acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.10.032]
¹Institut für Mineralogie, University of Münster, Münster, 48149, Deutschland
²Institut für Planetologie, University of Münster, Wilhelm-Klemm Straße 10, 48149 Münster, Deutschland
³Department of Geology, University of Maryland, 8000 Regents Drive, College Park, Maryland 20742, USA
⁴Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
Copyright Elsevier

As a moderately volatile, redox-sensitive chalcophile and siderophile element, Te and its isotopic composition can inform on a multitude of geochemical and cosmochemical processes. However, the interpretation of Te data from natural settings is often hindered by an insufficient understanding of the behavior of Te in high-temperature conditions. Here, we present the results of Te evaporation and isotopic fractionation in silicate melting experiments. The starting material was boron-bearing anorthite-diopside glass with 1 wt.% TeO2. The experiments were conducted over the temperature range of 868-1459 °C for 15 minutes each, and at oxygen fugacities (logfO2) relative to the fayalite-magnetite-quartz buffer (FMQ) of FMQ−6 to FMQ+1.5, and in air. Evaporation of Te decreases with decreasing fO2. For high-temperature experiments performed at >1200 °C Te loss is accompanied by Te isotope fractionation towards heavier compositions in the residual glasses. By contrast, Te loss in experiments performed at temperatures <1200 °C typically resulted in lighter Te isotopic compositions in the residues relative to the starting material. In air, Te evaporates as TeO2, whereas at lower oxygen fugacities we predict the evaporation of Te2, using Gibbs free energy minimization calculations. In air, the experimentally determined kinetic isotopic fractionation factor for δ128/126Te at T > 1200 °C is αK = 0.99993. At reducing conditions, Te likely substitutes as Te2- for O2- in the melt structure and becomes increasingly soluble at highly reducing conditions. Consequently, Te evaporation is not predicted for volcanic processes on reduced planetary bodies such as the Moon or Mercury.

^1,2Laura Noel García,¹María Eugenia Varela,³Shyh-Lung Hwang,⁴Pouyan Shen,⁵Raúl Bolmaro,⁵Martina Ávalos
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13911]
¹Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE), Universidad Nacional de San Juan, CONICET, J5402DSP San Juan, Argentina
²Instituto de Mecánica Aplicada, Universidad Nacional de San Juan, J5400ARL San Juan, Argentina
³Department of Materials Science and Engineering, National Dong Hwa University, 974 Hualien, Taiwan, ROC
⁴Department of Materials and Optoelectronic Science, National Sun Yat-sen University, 804 Kaohsiung, Taiwan, ROC
⁵Instituto de Física Rosario (IFIR), Universidad Nacional de Rosario, CONICET, S2000EKF Rosario, Argentina
Published by arrangement with John Wiley & Sons

Meteorites carry information about the most common processes that have been active in the early solar system. In particular, mesosiderites are meteorites with a structure considered to be composed of equal parts of iron–nickel metal and silicates. A natural delimitation in the study of such complex systems is the discrimination of the iron–nickel metallic and silicate domains. In this work, we focus on the metallic phases of the Mincy mesosiderite, a specimen available at the Instituto de Ciencias Astronómicas, de la Tierray y del Espacio repository. In Mincy, the metallic phases are iron–nickel–carbon alloys that are distributed forming metallic lumps or pebbles (referred to as metallic nodules in the article) in which kamacite and taenite are present, and taenite is found both at the kamacite/silicate interface and surrounded by kamacite, that is, isolated from the silicates. We made use of the electron backscattered diffraction technique to determine the crystallographic orientation relationships along the taenite/kamacite boundaries as well as for characterizing the (hkl)-specific grain boundaries regarding the underlying tilt, twist, or twinning mechanism to assist the interpretation of the phase transformations and mechanisms that could explain the formation of these metallic nodules. From the results, each of the metallic nodules has a unique temperature–pressure history and kinetics to undergo phase transformations (mainly partial melting, heterogeneous nucleation-controlled solidification, and possible evaporation–condensation) as well as liquid-phase sintering and recrystallization in its own way.

¹Aryavart Anand,¹Pascal M. Kruttasch,¹Klaus Mezger
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13916]
¹Institut für Geologie, Universität Bern, Baltzerstrasse 1+3, 3012 Bern, Switzerland
Published by arrangement with John Wiley & Sons

The meteorite Erg Chech (EC) 002 is the oldest felsic igneous rock from the solar system analyzed to date and provides a unique opportunity to study the formation of felsic crusts on differentiated protoplanets immediately after metal–silicate equilibration or core formation. The extinct ⁵³Mn-⁵³Cr chronometer provides chronological constraints on the formation of EC 002 by applying the isochron approach using chromite, metal–silicate–sulfide, and whole-rock fractions as well as “leachates” obtained by sequential digestion of a bulk sample. Assuming a chondritic evolution of its parent body, a ⁵³Cr/⁵²Cr model age is also obtained from the chromite fraction. The ⁵³Mn-⁵³Cr isochron age of 1.73 ± 0.96 Ma (anchored to D’Orbigny angrite) and the chromite model age constrained between $$ {1.46}_{-0.68}^{+0.78} $$ and $$ {2.18}_{-1.06}^{+1.32} $$ Ma after the formation of calcium-aluminium-rich inclusions (CAIs) agree with the ²⁶Al-²⁶Mg ages (anchored to CAIs) reported in previous studies. This indicates rapid cooling of EC 002 that allowed near-contemporaneous closure of multiple isotope systems. Additionally, excess in the neutron-rich ⁵⁴Cr (nucleosynthetic anomalies) combined with mass-independent isotope variations of ¹⁷O provides genealogical constraints on the accretion region of the EC 002 parent body. The ⁵⁴Cr and ¹⁷O isotope compositions of EC 002 confirm its origin in the “noncarbonaceous” reservoir and overlap with the vestoid material Northwest Africa 12217 and anomalous eucrite Elephant Moraine 92023. This indicates a common feeding zone during accretion in the protoplanetary disk between the source of EC 002 and vestoids. The enigmatic origin of iron meteorites remains still unresolved as EC 002, which is more like a differentiated crust, has an isotope composition that does not match known iron meteorite groups that were once planetesimal cores.

¹Takaaki Noguchi et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13919]
¹Division of Earth and Planetary Sciences, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
Published by arrangement with John Wiley & Sons

Asteroids and comets are thought to form in the inner and outer solar systems, respectively. Chondritic porous and smooth interplanetary dust particles (CP IDPs and CS IDPs, respectively) in the stratosphere are regarded as dust grains from comets and hydrated asteroids, respectively. Here, we describe an Antarctic micrometeorite (AMM) composed of lithologies of both CP and CS IDPs. In addition to the CS IDP-like compact lithology that experienced severe aqueous alteration, the CP IDP-like porous lithology shows evidence of very weak aqueous alteration. The structure of the organic matter in the porous lithology varies from that in the CP IDPs to aromatic-rich organic matter. In contrast, the structure of the organic matter in the compact lithology is homogenous, which is consistent with higher degrees of aqueous alteration. Its structure is more similar to that of CP IDPs and Wild 2 samples than that of meteoritic insoluble organic matter, suggesting that the compact lithology formed from the porous lithology. Some CP IDPs are related to cometary dust streams, such as those originating from 26P/Grigg-Skjellerup. In addition, the presence of this AMM indicates an additional origin of the CP IDPs and their equivalent AMMs. The mineralogy and organic chemistry of this AMM suggest that its parent body was composed of the same building blocks as those of the comets, and later experienced incomplete aqueous alteration. The AMM probably formed as microbreccia in the regolith layer composed of materials from a CP IDP-like crust and a hydrated interior.

¹Jüri Plado,^2,3Ania Losiak,¹Argo Jõeleht,⁴Jens Ormö,⁵Helena Alexanderson,⁵Carl Alwmark,⁶Eva Maria Wild,⁶Peter Steier,²Marek Awdankiewicz,³Claire Belcher
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13914]
¹Department of Geology, University of Tartu, Ravila 14A, EE 50411 Tartu, Estonia
²Institute of Geological Sciences, Polish Academy of Sciences, Podwale 75, PL 50-449 Wrocław, Poland
³WildFIRE Lab, University of Exeter, Exeter, EX4 4PS UK
⁴Centro de Astrobiología CSIC-INTA, Instituto Nacional de Técnica Aeroespacial, 28850 Torrejon de Ardoz, Spain
⁵Department of Geology, Lund University, SE-22362 Lund, Sweden
⁶VERA Laboratory, Faculty of Physics, Isotope Physics, University of Vienna, Währinger Straße 17, A-1090 Vienna, Austria
Published by arrangement with Johne Wiley & Sons

Compared to intensive research on km-sized meteorite impact craters, fewer studies focus on smaller craters. The small craters are often hard or impossible to recognize using “classical” criteria like the presence of shatter cones, shocked quartz, and geochemical indicators. Therefore, a long list of candidate structures awaiting approval/disapproval of their origin has been formed over the last decades. One of them is the Tor structure in central Sweden. To test a hypothesis of an impact origin of this structure, we have performed topographical analysis, geophysical studies, 10Be exposure dating of boulders, and 14C dating of Tor-associated charcoal. None of the methods gave us a reason to claim the Tor structure is of impact origin. Thus, we support a recently suggested idea of Tor being formed by a grounded iceberg within a glacial lake.

¹Victoria Froh,¹Maitrayee Bose,^2,3Martin D.Suttle,⁴Jacopo Nava,^2,5Luigi Folco,¹Lynda B.Williams,⁶JulieCastillo-Rogez
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2022.115300]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
²School of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
³Dipartimento di Scienze della Terra, Università di Pisa, 56126 Pisa, Italy
⁴University of Padova, Department of Geosciences, Via G.Gradenigo 6, 35131 Padova, Italy
⁵CISUP, Centro per l’Integrazione della Strumentazione dell’Università di Pisa, Lungarno Pacinotti 43, 56126 Pisa, Italy
⁶Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Copyright: Elsevier

Micrometeorites represent a major potential source of volatiles for the early Earth, although often overlooked due to their small sizes and the effects of atmospheric entry. In this study we explore an unusual ~2000 μm, fine-grained unmelted micrometeorite TAM19B-7 derived from a water-rich C-type asteroid. Previous analysis revealed a unique O-isotope composition and intensely aqueously altered geological history. We investigated its carbon isotopic composition using the NanoSIMS and characterized the carbon-bearing carriers using Raman and Near-Infrared spectroscopy. We found that TAM19B-7 has a 13C enriched bulk composition (δ13C = +3 ± 8 ‰), including a domain with 13C depletion (δ13C = −27.1 ‰). Furthermore, a few micro-scale domains show 13C enrichments (δ13C from +12.9 ‰ to +32.7 ‰) suggesting much of the particle’s carbon content was reprocessed into fine-grained carbonates, likely calcite. The heavy bulk C-isotope composition of TAM19B-7 indicates either open system gas loss during aqueous alteration or carbonate formation from isotopically heavy soluble organics. Carbonates have been detected on small body surfaces, including across dwarf planet Ceres, and on the C-type asteroids Bennu and Ryugu. The preservation of both carbonates with 13C enrichments and organic carbon with 13C depletion in TAM19B-7, despite having been flash heated to high temperatures (<1000 °C), demonstrates the importance of cosmic dust as a volatile reservoir.

^1,2Allison Pease,²Jie Li
Earth and Planetary Science Letters 599, 117865 Link to Article [https://doi.org/10.1016/j.epsl.2022.117865]
¹Department of Earth and Environmental Sciences, Michigan State University, East Lansing, MI, 48824, USA
²Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA
Copyright Elsevier

Mercury has fascinated researchers for decades due to its sizable metallic core and weak magnetic field. The behavior of Fe-S and (Fe, Ni)-S systems provides constraints on core conditions and regimes of solidification to predict magnetic field strength. In this study, we investigate the melting behavior of the (Fe, Ni)-S system, a candidate composition to model the Mercurian core. We observe that the Fe-S liquidus has an inflection point at ∼10 wt.% S at 14 GPa and ∼11.5 wt.% S at 24 GPa, while (Fe, Ni)-S does not. At 24 GPa, Ni may lower the melting point of the Fe-S system by as much as 300 °C, indicating that solidification models and adiabatic calculations must account for the presence of Ni.