Marc Fries¹, Lucille Le Corre², Mike Hankey³, Jeff Fries⁴, Robert Matson⁵, Jake Schaefer⁶, Vishnu Reddy⁷

¹NASA Astromaterials Research and Exploration Science (ARES), Mail Code KT, Johnson Space Center, Houston, Texas, USA
²Planetary Science Institute, Tucson, Arizona, USA
³American Meteor Society, Monkton, Maryland, USA
⁴First Weather Group, Air Force Weather Agency, Offutt AFB, Nebraska, USA
⁵Science Applications International Corp., Seal Beach, California, USA
⁶NASA Dryden, Edwards, California, USA
⁷Planetary Science Institute, Tucson, Arizona, USA

The Sutter’s Mill C-type meteorite fall occurred on 22 April 2012 in and around the town of Coloma, California. The exact location of the meteorite fall was determined within hours of the event using a combination of eyewitness reports, weather radar imagery, and seismometry data. Recovery of the first meteorites occurred within 2 days and continued for months afterward. The recovery effort included local citizens, scientists, and meteorite hunters, and featured coordination efforts by local scientific institutions. Scientific analysis of the collected meteorites revealed characteristics that were available for study only because the rapid collection of samples had minimized terrestrial contamination/alteration. This combination of factors—rapid and accurate location of the event, participation in the meteorite search by the public, and coordinated scientific investigation of recovered samples—is a model that was widely beneficial and should be emulated in future meteorite falls. The tools necessary to recreate the Sutter’s Mill recovery are available, but are currently underutilized in much of the world. Weather radar networks, scientific institutions with interest in meteoritics, and the interested public are available globally. Therefore, it is possible to repeat the Sutter’s Mill recovery model for future meteorite falls around the world, each for relatively little cost with a dedicated researcher. Doing so will significantly increase the number of fresh meteorite falls available for study, provide meteorite material that can serve as the nuclei of new meteorite collections, and will improve the public visibility of meteoritics research.

Reference
Fries M, Le Corre L, Hankey M, Fries J, Matson R, Schaefer J and Reddy V (in press) Detection and rapid recovery of the Sutter’s Mill meteorite fall as a model for future recoveries worldwide. Meteoritics & Planetary Science
[doi:10.1111/maps.12249]
Published by arrangement with John Wiley & Sons

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J. Ormö¹, E. Sturkell², J. Nõlvak³, I. Melero-Asensio¹, Å. Frisk^4,†, T. Wikström⁵

¹Centro de Astrobiologia (INTA-CSIC), Madrid, Spain
²Department of Earth Sciences, University of Gothenburg, Sweden, Gothenburg, Sweden
³Institute of Geology, Tallinn University of Technology, Tallinn, Estonia
⁴Paläontologisches Institut und Museum, Universität Zürich, Zürich, Switzerland
⁵Stockholm, Sweden
^†Palaeobiology, Department of Earth Sciences, Uppsala University, Uppsala, Sweden

The Målingen structure is an approximately 700 m wide, rimmed, sediment-filled, circular depression in Precambrian crystalline basement approximately 16.2 km from the concentric, marine-target Lockne crater (inner, basement crater diameter approximately 7.5 km, total diameter in sedimentary strata approximately 13.5 km). We present here results from geologic mapping, a 148.8 m deep core drilling from the center of the structure, detailed biostratigraphic dating of the structure’s formation and its age correlation with Lockne, chemostratigraphy of the sedimentary infill, and indication for shock metamorphism in quartz from breccias below the crater infill. The drill core reveals, from bottom to the top, approximately 33 m of basement rocks with increased fracturing upward, approximately 10 m of polymict crystalline breccia with shock features, approximately 97 m of slumped Cambrian mudstone, approximately 4.7 m of a normally graded, polymict sedimentary breccia that in its uppermost part grades into sandstone and siltstone (cf. resurge deposits), and approximately 1.6 m of secular sediments. The combined data set shows that the Målingen structure formed in conjunction with the Lockne crater in the same marine setting. The shape and depth of the basement crater and the cored sequence of crystalline breccias with shocked quartz, slumped sediments, and resurge deposits support an impact origin. The stratigraphic and geographic relationship with Lockne suggests the Lockne and Målingen craters to be the first described doublet impact structure by a binary asteroid into a marine-target setting.

Reference
Ormö J, Sturkell E, Nõlvak J, Melero-Asensio I, Frisk Å and Wikström T (in press) The geology of the Målingen structure: A probable doublet to the Lockne marine-target impact crater, central Sweden. Meteoritics & Planetary Science
[doi:10.1111/maps.12251]
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M. Kimura^1,5, J. A. Barrat², M. K. Weisberg^3,4, N. Imae⁵, A. Yamaguchi⁵, H. Kojima⁵

¹Faculty of Science, Ibaraki University, Mito, Japan
²Université Européenne de Bretagne, 2CNRS UMR 6538 (Domaines Océaniques), U.B.O.-I.U.E.M., Plouzané Cedex, France
³Department of Physical Sciences, Kingsborough College and Graduate School of the City University of New York, Brooklyn, New York, USA
⁴Department of Earth and Planetary Sciences, American Museum of Natural History, New York, New York, USA
⁵National Institute of Polar Research, Tokyo, Japan

Carbonaceous chondrites are classified into several groups. However, some are ungrouped. We studied one such ungrouped chondrite, Y-82094, previously classified as a CO. In this chondrite, chondrules occupy 78 vol%, and the matrix is distinctly poor in abundance (11 vol%), compared with CO and other C chondrites. The average chondrule size is 0.33 mm, different from that in C chondrites. Although these features are similar to those in ordinary chondrites, Y-82094 contains 3 vol% Ca-Al-rich inclusions and 5% amoeboid olivine aggregates (AOAs). Also, the bulk composition resembles that of CO chondrites, except for the volatile elements, which are highly depleted. The oxygen isotopic composition of Y-82094 is within the range of CO and CV chondrites. Therefore, Y-82094 is an ungrouped C chondrite, not similar to any other C chondrite previously reported. Thin FeO-rich rims on AOA olivine and the mode of occurrence of Ni-rich metal in the chondrules indicate that Y-82094 is petrologic type 3.2. The extremely low abundance of type II chondrules and high abundance of Fe-Ni metal in the chondrules suggest reducing condition during chondrule formation. The depletion of volatile elements indicates that the components formed under high-temperature conditions, and accreted to the parent body of Y-82094. Our study suggests a wider range of formation conditions than currently recorded by the major C chondrite groups. Additionally, Y-82094 may represent a new, previously unsampled, asteroidal body.

Reference
Kimura M, Barrat JA, Weisberg MK, Imae N, Yamaguchi A and Kojima H (in press) Petrology and bulk chemistry of Yamato-82094, a new type of carbonaceous chondrite. Meteoritics & Planetary Science
[doi:10.1111/maps.12254]
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Philipp R. Heck^1,2 et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Robert A. Pritzker Center for Meteoritics and Polar Studies, The Field Museum, Chicago, Illinois, USA
²Chicago Center for Cosmochemistry, The University of Chicago, Chicago, Illinois, USA

Atom-probe tomography (APT) is currently the only analytical technique that, due to its spatial resolution and detection efficiency, has the potential to measure the carbon isotope ratios of individual nanodiamonds. We describe three different sample preparation protocols that we developed for the APT analysis of meteoritic nanodiamonds at sub-nm resolution and present carbon isotope peak ratios of meteoritic and synthetic nanodiamonds. The results demonstrate an instrumental bias associated with APT that needs to be quantified and corrected to obtain accurate isotope ratios. After this correction is applied, this technique should allow determination of the distribution of ¹²C/¹³C ratios in individual diamond grains, solving the decades-old question of the origin of meteoritic nanodiamonds: what fraction, if any, formed in the solar system and in presolar environments? Furthermore, APT could help us identify the stellar sources of any presolar nanodiamonds that are detected.

Reference
Heck PR et al. (in press) Atom-probe analyses of nanodiamonds from Allende. Meteoritics & Planetary Science. Meteoritics & Planetary Science
[doi:10.1111/maps.12265]
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J. Gattacceca^1,2, C. Suavet¹, P. Rochette², B. P. Weiss¹, M. Winklhofer³, M. Uehara², Jon M. Friedrich^4,5

¹Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
²CNRS, Aix-Marseille Université, Aix en Provence, France
³Department of Earth and Environmental Sciences, Ludwig-Maximilians-University Munich, Munich, Germany
⁴Department of Chemistry, Fordham University, Bronx, New York, USA
⁵Department of Earth and Planetary Sciences, American Museum of Natural History, New York City, New York, USA

Magnetic properties are sensitive proxies to characterize FeNi metal phases in meteorites. We present a data set of magnetic hysteresis properties of 91 ordinary chondrite falls. We show that hysteresis properties are distinctive of individual meteorites while homogeneous among meteorite subsamples. Except for the most primitive chondrites, these properties can be explained by a mixture of multidomain kamacite that dominates the induced magnetism and tetrataenite (both in the cloudy zone as single-domain grains, and as larger multidomain grains in plessite and in the rim of zoned taenite) dominates the remanent magnetism, in agreement with previous microscopic magnetic observations. The bulk metal contents derived from magnetic measurements are in agreement with those estimated previously from chemical analyses. We evidence a decreasing metal content with increasing petrologic type in ordinary chondrites, compatible with oxidation of metal during thermal metamorphism. Types 5 and 6 ordinary chondrites have higher tetrataenite content than type 4 chondrites. This is compatible with lower cooling rates in the 650–450 °C interval for higher petrographic types (consistent with an onion-shell model), but is more likely the result of the oxidation of ordinary chondrites with increasing metamorphism. In equilibrated chondrites, shock-related transient heating events above approximately 500 °C result in the disordering of tetrataenite and associated drastic change in magnetic properties. As a good indicator of the amount of tetrataenite, hysteresis properties are a very sensitive proxy of the thermal history of ordinary chondrites, revealing low cooling rates during thermal metamorphism and high cooling rates (e.g., following shock reheating or excavation after thermal metamorphism). Our data strengthen the view that the poor magnetic recording properties of multidomain kamacite and the secondary origin of tetrataenite make equilibrated ordinary chondrites challenging targets for paleomagnetic study.

Reference
Beck P et al. (in press) Metal phases in ordinary chondrites: Magnetic hysteresis properties and implications for thermal history. Meteoritics & Planetary Science
[doi:10.1111/maps.12268]
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G. A. Brennecka¹, L. E. Borg¹, M. Wadhwa²

¹Lawrence Livermore National Laboratory, Livermore, California, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA

The recent witnessed fall of the meteorite Tissint represents the delivery of a pristine new sample from the surface of Mars. This meteorite provides an unprecedented opportunity to study a variety of aspects about the planet’s evolution. Using the Rb–Sr and Sm–Nd isotopic systems, we determined that Tissint, a depleted shergottite, has a crystallization age of 574 ± 20 Ma, an initial ε¹⁴³Nd = +42.2 ± 0.5, and an initial ⁸⁷Sr/⁸⁶Sr = 0.700760 ± 11. These initial Nd and Sr isotopic compositions suggest that Tissint originated from a mantle source on Mars that is distinct from the source reservoirs of the other Martian meteorites. The known crystallization ages, geochemical characteristics, ejection ages, and ejection dynamics of Tissint and other similarly grouped Martian meteorites suggest that they are likely derived from a source crater up to approximately 90 km in diameter with an age of approximately 1 Ma that is located on terrain that is approximately 600 million years old.

Reference
Beck P et al. (in press) Insights into the Martian mantle: The age and isotopics of the meteorite fall Tissint. Meteoritics & Planetary Science
[doi:10.1111/maps.12258]
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P. Beck¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, France

Sutter’s Mill is a regolith breccia composed of both heavily altered clasts and more reduced xenoliths. Here, we present a detailed investigation of fragments of SM18 and SM51. We have characterized the water content and the mineralogy by infrared (IR) and thermogravimetric analysis (TGA) and the structure of the organic compounds by Raman spectroscopy, to characterize the secondary history of the clasts, including aqueous alteration and thermal metamorphism. The three methods used in this study suggest that SM18 was significantly heated. The amount of water contained in phyllosilicates derived by TGA is estimated to be approximately 3.2 wt%. This value is quite low compared with other CM chondrites that typically range from 6 to 12 wt%. The infrared transmission spectra of SM18 show that the mineralogy of the sample is dominated by a mixture of phyllosilicate and olivine. SM18 shows an intense peak at 11.2 μm indicative of olivine (Fig. ). If we compare SM18 with other CM and metamorphosed CM chondrites, it shows one of the most intense olivine signatures, and therefore a lower proportion of phyllosilicate minerals. The Raman results tend to support a short-duration heating hypothesis. In the I_D/I_Gversus FWHM-D diagram, SM18 appears to be unusual compared to most CM samples, and close to the metamorphosed CM chondrites Pecora Escarpment (PCA) 91008 and PCA 02012. In the case of SM51, infrared spectroscopy reveals that olivine is less abundant than in SM18 and the 10 μm silicate feature is more similar to that of moderately altered CM chondrites (like Murchison or Queen Alexandra Range [QUE] 97990). Raman spectroscopy does not clearly point to a heating event for SM51 in the I_D/I_G versus FWHM-D diagram. However, TGA analysis suggests that SM51 was slightly dehydrated as the amount of water contained in phyllosilicates is approximately 3.7 wt%, which is higher than SM18, but still lower than phyllosilicate water contents in weakly altered CM chondrites. Altogether, these results confirm that fragments with different secondary histories are present within the Sutter’s Mill fall. The dehydration that is clearly observed for SM18 is attributed to a short-duration heating based on the similarity of its Raman spectra to that of PCA 91008. Because of the brecciated nature of Sutter’s Mill and the presence of adjacent clasts with different thermal histories, impacts that can efficiently fragment and heat porous materials are the preferred heat source.

Reference
Beck P et al. (in press) The secondary history of Sutter’s Mill CM carbonaceous chondrite based on water abundance and the structure of its organic matter from two clasts. Meteoritics & Planetary Science
[doi:10.1111/maps.12273]
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A. Rotundi^1,2 et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Dip. Scienze e Tecnologie, Università degli Studi di Napoli “Parthenope”, Napoli, Italy
²INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy

We present the analyses results of two bulk Terminal Particles, C2112,7,171,0,0 and C2112,9,171,0,0, derived from the Jupiter-family comet 81P/Wild 2 returned by the Stardust mission. Each particle embedded in a slab of silica aerogel was pressed in a diamond cell. This preparation, as expected, made it difficult to identify the minerals and organic materials present in these particles. This problem was overcome using a combination of three different analytical techniques, viz. FE-SEM/EDS, IR, and Raman microspectroscopy that allowed identifying the minerals and small amounts of amorphous carbon present in both particles. TP2 and TP3 were dominated by Ca-free and low-Ca, Mg-rich, Mg,Fe-olivine. The presence of melilite in both particles is supported by IR microspectroscopy, but is not confirmed by Raman microspectroscopy, possibly because the amounts are too small to be detected. TP2 and TP3 show similar silicate mineral compositions, but Ni-free and low-Ni, subsulfur (Fe,Ni)S grains are present in TP2 only. TP2 contains indigenous amorphous carbon hot spots; no indigenous carbon was identified in TP3. These nonchondritic particles probably originated in a differentiated body. This work found an unanticipated carbon contamination following the FE-SEM/EDS analyses. It is suggested that organic materials in the embedding silica aerogel are irradiated during FE-SEM/EDS analyses creating a carbon gas that develops a strong fluorescence continuum. The combination of the selected analytical techniques can be used to characterize bulk Wild 2 particles without the need of extraction and removal of the encapsulating aerogel. This approach offers a relatively fast sample preparation procedure, but compressing the samples can cause spurious artifacts, viz. silica contamination. Because of the combination of techniques, we account for these artifacts.

Reference
Rotundi A et al. (in press) Two refractory Wild 2 terminal particles from a carrot-shaped track characterized combining MIR/FIR/Raman microspectroscopy and FE-SEM/EDS analyses. Meteoritics & Planetary Science
[doi:10.1111/maps.12274]
Published by arrangement with John Wiley & Sons

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Maria Gritsevich^1,2,3, Vladimir Vinnikov², Tomáš Kohout^4,5, Juraj Tóth⁶, Jouni Peltoniemi^1,4, Leonid Turchak², Jenni Virtanen¹

¹Finnish Geodetic Institute, Masala, Finland
²Department of Computational Physics, Dorodnicyn Computing Centre, Russian Academy of Sciences, Moscow, Russia
³Institute of Mechanics, Lomonosov Moscow State University, Moscow, Russia
⁴Department of Physics, University of Helsinki, Helsinki, Finland
⁵Institute of Geology, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
⁶Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia

In this study, we conduct a detailed analysis of the Košice meteorite fall (February 28, 2010), to derive a reliable law describing the mass distribution among the recovered fragments. In total, 218 fragments of the Košice meteorite, with a total mass of 11.285 kg, were analyzed. Bimodal Weibull, bimodal Grady, and bimodal lognormal distributions are found to be the most appropriate for describing the Košice fragmentation process. Based on the assumption of bimodal lognormal, bimodal Grady, bimodal sequential, and bimodal Weibull fragmentation distributions, we suggest that, prior to further extensive fragmentation in the lower atmosphere, the Košice meteoroid was initially represented by two independent pieces with cumulative residual masses of approximately 2 and 9 kg, respectively. The smaller piece produced about 2 kg of multiple lightweight meteorite fragments with the mean around 12 g. The larger one resulted in 9 kg of meteorite fragments, recovered on the ground, including the two heaviest pieces of 2.374 kg and 2.167 kg with the mean around 140 g. Based on our investigations, we conclude that two to three larger fragments of 500–1000 g each should exist, but were either not recovered or not reported by illegal meteorite hunters.

Reference
Gritsevich M, Vinnikov V, Kohout T, Tóth J, Peltoniemi J, Turchak L and Virtanen J (in press) A comprehensive study of distribution laws for the fragments of Košice meteorite. Meteoritics & Planetary Science
[doi:10.1111/maps.12252]
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Deon van Niekerk¹, Klaus Keil¹, Munir Humayun²

¹Hawai‘i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai‘i at Manoa, Honolulu, Hawai‘i, USA
²National High Magnetic Field Laboratory, Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, USA

Queen Alexandra Range (QUE) meteorite 94204 is an anomalous enstatite meteorite whose petrogenesis has been ascribed to either partial melting or impact melting. We studied the meteorite pairs QUE 94204, 97289/97348, 99059/99122/99157/99158/99387, and Yamato (Y)-793225; these were previously suggested to represent a new grouplet. We present new data for mineral abundances, mineral chemistries, and siderophile trace element compositions (of Fe,Ni metal) in these meteorites. We find that the texture and composition of Y-793225 are related to EL6, and that this meteorite is unrelated to the QUEs. The mineralogy and siderophile element compositions of the QUEs are consistent with petrogenesis from an enstatite chondrite precursor. We caution that potential re-equilibration during melting and recrystallization of enstatite chondrite melt-rocks make it unreliable to use mineral chemistries to assign a specific parent body affinity (i.e., EH or EL). The QUEs have similar mineral chemistries among themselves, while slight variations in texture and modal abundances exist between them. They are dominated by inclusion-bearing millimeter-sized enstatite (average En_99.1–99.5) with interstitial spaces filled predominantly by oligoclase feldspar (sometimes zoned), kamacite (Si approximately 2.4 wt%), troilite (≤2.4 wt% Ti), and cristobalite. Siderophile elements that partition compatibly between solid metal and liquid metal are not enriched like in partial melt residues Itqiy and Northwest Africa (NWA) 2526. We find that the modal compositions of the QUEs are broadly unfractionated with respect to enstatite chondrites. We conclude that a petrogenesis by impact melting, not partial melting, is most consistent with our observations.

Reference
van Niekerk D, Keil K and Humayun M (in press) Petrogenesis of anomalous Queen Alexandra Range enstatite meteorites and their relation to enstatite chondrites, primitive enstatite achondrites, and aubrites. Meteoritics & Planetary Science
[doi:10.1111/maps.12248]
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