^1,2Justin Filiberto et al. (>10)*
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12680]
¹Department of Geology, Southern Illinois University, Carbondale, Illinois, USA
²School of Environment, Earth, and Ecosystem Sciences, The Open University, Walton Hall, Milton Keynes, UK
Published by arrangement with John Wiley & Sons
*Find the extensive, full author and affiliation list on the publishers website

Multiple observations from missions to Mars have revealed compelling evidence for a volatile-rich Martian crust. A leading theory contends that eruption of basaltic magmas was the ultimate mechanism of transfer of volatiles from the mantle toward the surface after an initial outgassing related to the crystallization of a magma ocean. However, the concentrations of volatile species in ascending magmas and in their mantle source regions are highly uncertain. This work and this special issue of Meteoritics & Planetary Science summarize the key findings of the workshop on Volatiles in the Martian Interior (Nov. 3–4, 2014), the primary open questions related to volatiles in Martian magmas and their source regions, and the suggestions of the community at the workshop to address these open questions.

^1,2Gordon R. Osinski,¹Richard A. F. Grieve,¹Anna Chanou,¹Haley M. Sapers
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12728]
¹Department of Earth Sciences/Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada
²Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

The term “suevite” has been applied to various impact melt-bearing breccias found in different stratigraphic settings within terrestrial impact craters. Suevite was coined initially for impact glass-bearing breccias from the Ries impact structure, Germany, which is the type locality. Various working hypotheses have been proposed to account for the formation of the Ries suevite deposits over the past several decades, with the most recent being molten-fuel-coolant interaction (MFCI) between an impact melt pool and water. This mechanism is also the working hypothesis for the origin of the bulk of the Onaping Formation at the Sudbury impact structure, Canada. In this study, the key characteristics of the Ries suevite, the Onaping Formation and MFCI deposits from phreatomagmatic volcanic eruptions are compared. The conclusion is that there are clear and significant lithological, stratigraphic, and petrographic observational differences between the Onaping Formation and the Ries suevite. The Onaping Formation, however, shares many key similarities with MFCI deposits, including the presence of layering, their well-sorted and fine-grained nature, and the predominance of vitric particles with similar shapes and lacking included mineral and lithic clasts. These differences argue against the viability of MFCI as a working hypothesis for genesis of the Ries suevite and for a required alternative mechanism for its formation.

^1,2Yang Liu,^2,3Ioannis P. Baziotis,³Paul D. Asimow,⁴Robert J. Bodnar,²Lawrence A. Taylor
Meteoritcs & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12726]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
²Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA
³Department of Natural Resources Management and Agricultural Engineering, Laboratory of Mineralogy and Geology, Agricultural University of Athens, Athens, Greece
³Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
⁴Department of Geosciences, Virginia Tech, Blacksburg, Virginia, USA
Published by arrangement with John Wiley & Sons

The Tissint meteorite is a geochemically depleted, olivine-phyric shergottite. Olivine megacrysts contain 300–600 μm cores with uniform Mg# (~80 ± 1) followed by concentric zones of Fe-enrichment toward the rims. We applied a number of tests to distinguish the relationship of these megacrysts to the host rock. Major and trace element compositions of the Mg-rich core in olivine are in equilibrium with the bulk rock, within uncertainty, and rare earth element abundances of melt inclusions in Mg-rich olivines reported in the literature are similar to those of the bulk rock. Moreover, the P Kα intensity maps of two large olivine grains show no resorption between the uniform core and the rim. Taken together, these lines of evidence suggest the olivine megacrysts are phenocrysts. Among depleted olivine-phyric shergottites, Tissint is the first one that acts mostly as a closed system with olivine megacrysts being the phenocrysts. The texture and mineral chemistry of Tissint indicate a crystallization sequence of: olivine (Mg# 80 ± 1) → olivine (Mg# 76) + chromite → olivine (Mg# 74) + Ti-chromite → olivine (Mg# 74–63) + pyroxene (Mg# 76–65) + Cr-ulvöspinel → olivine (Mg# 63–35) + pyroxene (Mg# 65–60) + plagioclase, followed by late-stage ilmenite and phosphate. The crystallization of the Tissint meteorite likely occurred in two stages: uniform olivine cores likely crystallized under equilibrium conditions; and a fractional crystallization sequence that formed the rest of the rock. The two-stage crystallization without crystal settling is simulated using MELTS and the Tissint bulk composition, and can broadly reproduce the crystallization sequence and mineral chemistry measured in the Tissint samples. The transition between equilibrium and fractional crystallization is associated with a dramatic increase in cooling rate and might have been driven by an acceleration in the ascent rate or by encounter with a steep thermal gradient in the Martian crust.

^1,2Jörg Fritz,³Roald Tagle,⁴Luisa Ashworth,²Ralf Thomas Schmitt,⁵Axel Hofmann,⁶Béatrice Luais,⁴Phillip D. Harris,^2,7Desirée Hoehnel,⁸Seda Özdemir,^2,9Tanja Mohr-Westheide,^9,10Christian Koeberl
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12736]
¹Saalbau Weltraum Projekt, Heppenheim, Germany
²Museum für Naturkunde—Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
³Bruker-Nano GmbH, Berlin, Germany
⁴GeoSpectral Imaging, Johannesburg, South Africa
⁵Department of Geology, University of Johannesburg, Johannesburg, South Africa
⁶Centre de Recherches Pétrographiques et Géochimiques, CRPG UMR 7358 CNRS-UL, France
⁷Institut für Erd und Umweltwissenschaften, Universität Potsdam, Potsdam-Golm, Germany
⁸Department of Lithospheric Research, University of Vienna, Vienna, Austria
⁹Institut für Geologische Wissenschaften, Freie Universität Berlin (FU Berlin), Berlin, Germany
¹⁰Natural History Museum, Vienna, Austria
Published by arrangement with John Wiley & Sons

A Paleoarchean impact spherule-bearing interval of the 763 m long International Continental Scientific Drilling Program (ICDP) drill core BARB5 from the lower Mapepe Formation of the Fig Tree Group, Barberton Mountain Land (South Africa) was investigated using nondestructive analytical techniques. The results of visual observation, infrared (IR) spectroscopic imaging, and micro-X-ray fluorescence (μXRF) of drill cores are presented. Petrographic and sedimentary features, as well as major and trace element compositions of lithologies from the micrometer to kilometer-scale, assisted in the localization and characterization of eight spherule-bearing intervals between 512.6 and 510.5 m depth. The spherule layers occur in a strongly deformed section between 517 and 503 m, and the rocks in the core above and below are clearly less disturbed. The μXRF element maps show that spherule layers have similar petrographic and geochemical characteristics but differences in (1) sorting of two types of spherules and (2) occurrence of primary minerals (Ni-Cr spinel and zircon). We favor a single impact scenario followed by postimpact reworking, and subsequent alteration. The spherule layers are Al2O3-rich and can be distinguished from the Al2O3-poor marine sediments by distinct Al-OH absorption features in the short wave infrared (SWIR) region of the electromagnetic spectrum. Infrared images can cover tens to hundreds of square meters of lithologies and, thus, may be used to search for Al-OH-rich spherule layers in Al2O3-poor sediments, such as Eoarchean metasediments, where the textural characteristics of the spherule layers are obscured by metamorphism.

^1,2Gregory A. Brennecka, ²Lars E. Borg, ³Stephen J. Romaniello, ^3,4Amanda K. Souders, ^1,2Quinn R. Shollenberger, ²Naomi E. Marks, ³Meenakshi Wadhwa
Geochimica et Cosmochimica Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.10.003]
¹Institut für Planetologie, Westfälische Wilhelms-Universität, Münster, Germany
²Nuclear & Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA 94550 USA
³School of Earth and Space Exploration, Arizona State University, PO Box 871404, Tempe, AZ 85287-1404 USA
⁴Department of Geosciences, Texas Tech University, Lubbock, TX 79409, USA
Copyright Elsevier

Although there is limited direct evidence for supernova input into the nascent Solar System, many models suggest it formed by the gravitational collapse of a molecular cloud that was triggered by a nearby supernova. Existing lines of evidence, mostly in the form of short-lived radionuclides present in the early Solar System, are potentially consistent with this hypothesis, but still allow for alternative explanations. Since the natural production of ¹²⁶Sn is thought to occur only in supernovae and this isotope has a short half-life (¹²⁶Sn→¹²⁶Te, t_1/2=235 ky), the discovery of extant ¹²⁶Sn would provide unequivocal proof of supernova input to the early Solar System. Previous attempts to quantify the initial abundance of ¹²⁶Sn by examining Sn-Te systematics in early solids have been hampered by difficulties in precisely measuring Te isotope ratios in these materials. Thus, here we describe a novel technique that uses hydride generation to dramatically increase the ionization efficiency of Te—an approximately 30-fold increase over previous work. This introduction system, when coupled to a MC-ICPMS, enables high-precision Te isotopic analyses on samples with 126Sn. This sample set shows no evidence of live ¹²⁶Sn, implying at most minor input of supernova material during the time at which the CAIs formed. However, based on the petrology of this sample set combined with the higher than expected concentrations of Sn and Te, as well as the lack of nucleosynthetic anomalies in other isotopes of Te suggest that the bulk of the Sn and Te recovered from these particular refractory inclusions is not of primary origin and thus does not represent a primary signature of Sn-Te systematics of the protosolar nebula during condensation of CAIs or their precursors. Although no evidence of supernova input was found based on Sn-Te systematics in this sample set, hydride generation represents a powerful tool that can now be used to further explore Te isotope systematics in less altered materials.

^1,2Changkun Park, ¹Kazuhide Nagashima, ¹Alexander N. Krot, ¹Gary R. Huss, ³Andrew M. Davis, ⁴Martin Bizzarro
Geochimica et Cosmochimica Acta (in Press) Link to Article [http://dx.doi.org/10.1016/j.gca.2016.10.002]
¹Hawai‘i Institute of Geophysics and Planetology, School of Ocean, Earth Science and Technology, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
²Division of Earth-System Sciences, Korea Polar Research Institute, Incheon 21990, South Korea
³Department of the Geophysical Sciences, Enrico Fermi Institute, and Chicago Center for Cosmochemistry, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637-1433, USA
⁴Centre for Star and Planet Formation, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Denmark
Copyright Elsevier

Calcium-aluminum-rich inclusions with isotopic mass fractionation effects and unidentified nuclear isotopic anomalies (FUN CAIs) have been studied for more than 40 years, but their origins remain enigmatic. Here we report in situ high precision measurements of aluminum-magnesium isotope systematics of FUN CAIs by secondary ion mass spectrometry (SIMS). Individual minerals were analyzed in six FUN CAIs from the oxidized CV3 carbonaceous chondrites Axtell (compact Type A CAI Axtell 2271) and Allende (Type B CAIs C1 and EK1-4-1, and forsterite-bearing Type B CAIs BG82DH8, CG-14, and TE). Most of these CAIs show evidence for excess 26Mg due to the decay of 26Al. The inferred initial 26Al/27Al ratios [(26Al/27Al)0] and the initial magnesium isotopic compositions (δ26Mg0) calculated using an exponential law with an exponent β of 0.5128 are (3.1±1.6)×10−6 and 0.60±0.10‰ (Axtell 2271), (3.7±1.5)×10−6 and −0.20±0.05‰ (BG82DH8), (2.2±1.1)×10−6 and −0.18±0.05‰ (C1), (2.3±2.4)×10−5 and −2.23±0.37‰ (EK1-4-1), (1.5±1.1)×10−5 and −0.42±0.18‰ (CG-14), and (5.3±0.9)×10−5 and −0.05±0.08‰ (TE) with 2σ uncertainties. We infer that FUN CAIs recorded 26Al and magnesium isotopic heterogeneity in the CAI-forming region(s). Comparison of 26Al-26Mg systematics, stable isotope (oxygen, magnesium, calcium, and titanium) and trace element studies of FUN and non-FUN igneous CAIs indicates that there is a continuum among these CAI types. Based on these observations and evaporation experiments on CAI-like melts, we propose a generic scenario for the origin of igneous (FUN and non-FUN) CAIs: (i) condensation of isotopically normal solids in an 16O-rich gas of approximately solar composition; (ii) formation of CAI precursors by aggregation of these solids together with variable abundances of isotopically anomalous grains—possible carriers of unidentified nuclear (UN) effects; and (iii) melt evaporation of these precursors accompanied by crystallization under different temperatures and gas pressures, leading to the observed variations in mass-dependent isotopic fractionation (F) effects.

^1,2Zuzana Rodovská,¹Tomáš Magna,³Karel Žák,³Roman Skála,⁴Tomasz Brachaniec,^5,6Channon Visscher
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12733]
¹Czech Geological Survey, Prague 1, Czech Republic
²Faculty of Science, Charles University in Prague, Prague 2, Czech Republic
³Institute of Geology, The Czech Academy of Sciences, Prague 6, Czech Republic
⁴Department of Geochemistry, Mineralogy, and Petrology, Faculty of Earth Sciences, University of Silesia, Sosnowiec, Poland
⁵Chemistry and Planetary Sciences, Dordt College, Sioux Center, Iowa, USA
⁶Space Science Institute, Boulder, Colorado, USA
Published by arrangement with John Wiley & Sons

Lithium abundances and isotope compositions are presented for a suite of sediments from the surroundings of the Ries Impact structure, paralleled by new Li data for central European tektites (moldavites) from several substrewn fields (South Bohemia, Moravia, Cheb Basin, Lusatia), including a specimen from the newly discovered substrewn field in Poland. The data set was supplemented by three clay fractions isolated from sedimentary samples. Moldavites measured in this study show a very narrow range in δ7Li values (−0.6 to 0.3‰ relative to L-SVEC) and Li contents (23.9–48.1 ppm). This contrasts with sediments from the Ries area which show remarkable range in Li isotope compositions (from −6.9 to 13.4‰) and Li contents (0.6–256 ppm). The OSM sediments which, based on chemical similarity, formed the major part of moldavites, show a range in δ7Li values from −2.0 to 7.9‰ and Li contents from 5.8 to 78.9 ppm. Therefore, the formation of moldavites was apparently accompanied by large-scale mixing, paralleled by chemical and isotope homogenization of their parent matter. The proposed Li mixing model indicates that sands, clayey sediments, and low volumes of carbonates are the major components for tektite formation whereas residual paleokarst sediments could have been a minor but important component for a subset of moldavites. Striking homogenization of Li in tektites, combined with limited Li loss during impacts, may suggest that moderately volatile elements are not scavenged and isotopically fractionated during large-scale collisions, which is consistent with recent models. In general, whether homogenization of bodies with distinct Li isotope systematics takes place, or collision of bodies with similar Li systematics operates cannot be resolved at present stage but Li isotope homogeneity of solar system planets and asteroidal bodies tentatively implies the latter.

¹Gerrit Budde, ¹Christoph Burkhardt, ¹Gregory A. Brennecka, ¹Mario Fischer-Gödde, ¹Thomas S. Kruijer, ¹Thorsten Kleine
Earth and Planetary Science Letters (in Press) Link to Article [http://dx.doi.org/10.1016/j.epsl.2016.09.020]
¹Institut für Planetologie, University of Münster, Wilhelm-Klemm-Straße 10, 48149 Münster, Germany
Copyright Elsevier

Nucleosynthetic isotope anomalies are powerful tracers to determine the provenance of meteorites and their components, and to identify genetic links between these materials. Here we show that chondrules and matrix separated from the Allende CV3 chondrite have complementary nucleosynthetic Mo isotope anomalies. These anomalies result from the enrichment of a presolar carrier enriched in s-process Mo into the matrix, and the corresponding depletion of this carrier in the chondrules. This carrier most likely is a metal and so the uneven distribution of presolar material probably results from metal–silicate fractionation during chondrule formation. The Mo isotope anomalies correlate with those reported for W isotopes on the same samples in an earlier study, suggesting that the isotope variations for both Mo and W are caused by the heterogeneous distribution of the same carrier. The isotopic complementary of chondrules and matrix indicates that both components are genetically linked and formed together from one common reservoir of solar nebula dust. As such, the isotopic data require that most chondrules formed in the solar nebula and are not a product of protoplanetary impacts.

Allende chondrules and matrix together with bulk carbonaceous chondrites and some iron meteorites (groups IID, IIIF, and IVB) show uniform excesses in 92Mo, 95Mo, and 97Mo that result from the addition of supernova material to the solar nebula region in which these carbonaceous meteorites formed. Non-carbonaceous meteorites (enstatite and ordinary chondrites as well as most iron meteorites) do not contain this material, demonstrating that two distinct Mo isotope reservoirs co-existed in the early solar nebula that remained spatially separated for several million years. This separation was most likely achieved through the formation of the gas giants, which cleared the disk between the inner and outer solar system regions parental to the non-carbonaceous and carbonaceous meteorites. The Mo isotope dichotomy of meteorites provides a new means to determine the provenance of meteoritic and planetary materials, and to assess genetic links between chondrites and differentiated meteorites.

¹R. Brasser, ^2,3S.J. Mojzsis, ⁴S.C. Werner, ⁵S. Matsumura, ¹S. Ida
Earth and Planetary Science Letters (in Press) Link to Article [http://dx.doi.org/10.1016/j.epsl.2016.09.013]
¹Earth Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan
²Department of Geological Sciences, University of Colorado, UCB 399, 2200 Colorado Avenue, Boulder, CO 80309-0399, USA
³Institute for Geological and Geochemical Research, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, 45 Budaörsi Street, H-1112 Budapest, Hungary
⁴The Centre for Earth Evolution and Dynamics, University of Oslo, Sem Saelandsvei 24, 0371 Oslo, Norway
⁵School of Science and Engineering, Division of Physics, Fulton Building, University of Dundee, Dundee DD1 4HN, UK
Copyright Elsevier

It is generally accepted that silicate-metal (‘rocky’) planet formation relies on coagulation from a mixture of sub-Mars sized planetary embryos and (smaller) planetesimals that dynamically emerge from the evolving circum-solar disc in the first few million years of our Solar System. Once the planets have, for the most part, assembled after a giant impact phase, they continue to be bombarded by a multitude of planetesimals left over from accretion. Here we place limits on the mass and evolution of these planetesimals based on constraints from the highly siderophile element (HSE) budget of the Moon. Outcomes from a combination of N-body and Monte Carlo simulations of planet formation lead us to four key conclusions about the nature of this early epoch. First, matching the terrestrial to lunar HSE ratio requires either that the late veneer on Earth consisted of a single lunar-size impactor striking the Earth before 4.45 Ga, or that it originated from the impact that created the Moon. An added complication is that analysis of lunar samples indicates the Moon does not preserve convincing evidence for a late veneer like Earth. Second, the expected chondritic veneer component on Mars is 0.06 weight percent. Third, the flux of terrestrial impactors must have been low (≲10−6 M⊕ Myr−1≲10−6 M⊕ Myr−1) to avoid wholesale melting of Earth’s crust after 4.4 Ga, and to simultaneously match the number of observed lunar basins. This conclusion leads to an Hadean eon which is more clement than assumed previously. Last, after the terrestrial planets had fully formed, the mass in remnant planetesimals was ∼10−3 M⊕∼10−3 M⊕, lower by at least an order of magnitude than most previous models suggest. Our dynamically and geochemically self-consistent scenario requires that future N-body simulations of rocky planet formation either directly incorporate collisional grinding or rely on pebble accretion.

^1,2Jérôme Gattacceca, ²Benjamin P. Weiss, ^3,4Matthieu Gounelle
Earth and Planetary Science Letters (in Press) Link to Article [http://dx.doi.org/10.1016/j.epsl.2016.09.008]
¹CNRS, Aix Marseille Univ, IRD, Coll France, CEREGE, Aix-en-Provence, France
²Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
³Institut de Mineralogie de Physique des Materiaux et de Cosmochimie, CNRS & Museum National d’Histoire Naturelle, UMR 7202, 75005 Paris, France
⁴Institut Universitaire de France, 103 Boulevard Saint Michel, 75005 Paris, France
Copyright Elsevier

Recent paleomagnetic studies of Allende CV chondrite as well as thermal modeling suggest the existence of partially differentiated asteroids with outer unmelted and variably metamorphosed crusts overlying differentiated interiors. To further constrain the magnetic history of the CV parent body, we report here paleomagnetic results on Kaba CV chondrite. This meteorite contains 11 wt% pseudo-single domain magnetite, making it a rock with an excellent paleomagnetic recording capacity. Kaba appears to carry a stable natural remanent magnetization acquired on its parent body upon cooling in an internally generated magnetic field of about 3 μT3 μT from temperatures below 150 °C during thermal metamorphism about 10 to several tens of Myr after solar system formation. This strengthens the case for the existence of a molten advecting core in the CV parent body. Furthermore, we show that no significant magnetic field (i.e. lower than ∼0.3 μT∼0.3 μT) was present when aqueous alteration took place on the Kaba parent body around 4 to 6 Myr after solar system formation, suggesting a delay in the onset of the dynamo in the CV parent body and confirming that nebular fields had already decayed at that time.