The most popular papers on Cosmochemistry Papers this year were:

1-Shearer CK, Elardo SM, Petro NE, Borg LE, McCubbin FM (2015) Origin of the lunar highlands Mg-suite: An integrated petrology, geochemistry, chronology, and remote sensing perspective. American Mineralogist, 100,294-325
Link to Article [doi: 10.2138/am-2015-4817]

2-Martín-Torres FJ et al. (2015) Transient liquid water and water activity at Gale crater on Mars. Nature Geoscience 8, 357-361
Link to Article [doi:10.1038/ngeo2412]

3-Santos AR, Agee CB, McCubbin FM, Shearer CK, Burger PV, Tartèse R, Anand M (2015) Petrology of igneous clasts in Northwest Africa 7034: Implications for the petrologic diversity of the martian crust. Geochimica et Cosmochimica Acta 157, 56-85
Link to Article [doi:10.1016/j.gca.2015.02.023]

4-Touboul M, Puchtel IS, Walker RJ (2015) Tungsten isotopic evidence for disproportional late accretion to the Earth and Moon. Nature 520, 530-533
Link to Article [doi:10.1038/nature14355]

5-Changela HG, Cody GD, Alexander CMOD, Peeters Z, Nittler LR, Stroud RM (2015) Morphological Study of Insoluble Organic Matter from Carbonaceous Chondrites: Correlation with Petrologic Grade. Geochimica et Cosmochimica Acta 159, 285-297
Link to Article [doi:10.1016/j.gca.2015.02.007]

6-Renne PR, Sprain CJ, Richards MA, Self S, Vanderkluysen L, Pande K (2015) State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact. Science 6256:76-78
Link to Article [doi:10.1126/science.aac7549]

7-Németh P, Garvie LAJ, Aoki T, Dubrovinskaia N, Dubrovinsky L, Buseck PR (2014) Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material. Nature Communications 5, 5447
Link to Article [doi:10.1038/ncomms6447]

8-Svetsov VV, Shuvalov VV (2015) Water delivery to the Moon by asteroidal and cometary Impacts. Planetary and Space Science 117, 444-452
Link to Article [doi:10.1016/j.pss.2015.09.011]

8-Hallis LJ, Huss GR, Nagashima K, Taylor GJ, Halldórsson SA, Hilton DR, Mottl MJ, Meech KJ (2015) Evidence for primordial water in Earth’s deep mantle. Science 350, 795-797
Link to Article [DOI: 10.1126/science.aac4834]

9-Holst JC, Paton C, Wielandt D., Bizzarro M. (2015) Tungsten isotopes in bulk meteorites and their inclusions—Implications for processing of presolar components in the solar protoplanetary disk. Meteoritics&Planetary Science 50, 1643-1660
Link to Article [DOI: 10.1111/maps.12488]

10-Young ED, Manning CE, Schauble EA, Shahar A, Macris CA, Lazar C, Jordan M (2015) High-temperature equilibrium isotope fractionation of non-traditional stable isotopes: Experiments, theory, and applications. Chemical Geology 395, 176-195
Link to Article [DOI: 10.1016/j.chemgeo.2014.12.013]

During the last days of this year, Cosmochemistry Papers will be on Christmas break (more or less). Normal service will commence on January, 4nd, after we have recovered.

Merry Christmas& Happy New Year to everyone and see you in 2016 !

¹Jun-ichi Matsuda, ¹Kazuhiko Morishita, ²Masayuki Nara,³Sachiko Amari
¹Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
²Laboratory of Chemistry, College of Liberal Arts and Sciences, Tokyo Medical and Dental University, Chiba, Japan
³McDonnell Center for the Space Sciences and the Physics Department, Washington University, St. Louis, Missouri, USA

We analyzed noble gases in an oxidized residue prepared from a HF-HCl residue of the Saratov L4 chondrite. The Ar, Kr, and Xe concentrations in the oxidized residue are two orders of magnitude lower than those in the HF-HCl residue, and they are close to concentrations in the bulk. The He and Ne concentrations are similar in the three samples. The Ne isotopic ratios are almost purely cosmogenic, indicating absence of presolar diamonds (the carrier of the HL component). Thus, Saratov contains phase Q without presolar diamond. A study of the Raman spectroscopic parameters for the HF-HCl residue and the oxidized residue shows large changes due to oxidation. The directions of these changes are the same as observed in Allende, except oxidation increased the ID/IG (intensity ratio of the D band to the G band) in Saratov but decreased in Allende. This difference may be attributed to the different crystalline stages of carbon in both meteorites. The shifts in the Raman parameters to a discrete and/or more expanded region suggest that (1) oxidation changes the crystalline condition of graphitic carbon, (2) phase Q is not a dissolved site, and (3) the release of Q-gas is simply related to the rearrangement of the carbon structure during oxidation.

Reference
Matsuda J-I, Morishita K, Nara M, Amari S (2015) Noble gases in oxidized residue prepared from the Saratov L4 chondrite and Raman spectroscopic study of residues to characterize phase Q. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12587]
Published by arrangement with John Wiley & Sons

¹Wei Wang, ²Yongli Song, ²Xianjie Wang, ²Yanqiang Yang, ³Xiaoyang Liu
¹Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin, China.
²Department of Physics, Harbin Institute of Technology, Harbin, China.
³State Key Lab of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun, China.

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Wang W, Song Y, Wang X, Yang Y, Liu X (2015) Alpha-Oxo Acids Assisted Transformation of FeS to Fe3S4 at Low Temperature: Implications for Abiotic, Biotic, and Prebiotic Mineralization. Astrobiology 15 1043-1051.
Link to Article [doi:10.1089/ast.2015.1373]

¹C. Tubiana, ^1,2C. Snodgrass, ³R. Michelsen, ³H. Haack, ¹H. Böhnhardt, ⁴A. Fitzsimmons, ⁵I. P. Williams
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 33077 Göttingen, Germany
e-mail: tubiana@mps.mpg.de
²Planetary and Space Sciences, Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
³Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, 1350 Copenhagen, Denmark
⁴Astrophysics Research Centre, Department of Physics and Astronomy, Queen’s University Belfast, Belfast BT7 1NN, UK
⁵School of Physics and Astronomy, Queen Mary, University of London, London E1 4NS, UK

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Tubiana C, Snodgrass C, Michelsen R, Haack H, Böhnhardt H, Fitzsimmons A, Williams IP (2015) 2P/Encke, the Taurid complex NEOs and the Maribo and Sutter’s Mill meteorites. Astronomy & Astrophysics 584, A97
Link to Article [http://dx.doi.org/10.1051/0004-6361/201425512]

¹Matthew Markley, ^1,2,3Gunther Kletetschka
¹Charles University in Prague, Faculty of Science, Albertov 6, 128 00 Prague, Czech Republic
²Academy of Sciences of the Czech Republic, Institute of Geology, Prague, Czech Republic
³Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Airless bodies are constantly exposed to space weathering. The Moon and other similar S-type asteroids physically change through comminution, melting, and agglutinate formation, while spectrally they are darkening, steepening (or reddening) the spectral slope towards longer wavelengths, and reducing silicate mineral absorption bands. In these S-type bodies the production of submicroscopic metallic iron, or nanophase iron (SMFe, npFe0) is a major contributor in these spectral changes. We made a qualitative estimate of both quantity and size distribution of produced metallic iron by space weathered analog, olivine irradiated by laser. Through SEM observation we confirmed that nanoparticles of metallic iron formed in the nm range. Spectroscopic and magnetic susceptibility (MS) through temperature analyses reveal an increasing trend of npFe0 formation, darkening, reddening, and shallowing of the 1 μm olivine absorption band. Olivine that produced the larger end of the size range of npFe0 produced similar effects, except for increased reddening. The magnetic data suggests that with laser irradiation there is both a linear increase of nanoparticles and a logarithmic increase in spectral change with SW time.

Reference
Markley M, Kletetschka G (2015) Nanophase Iron Production through Laser Irradiation and Magnetic Detection of Space Weathering Analogs. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.12.022]
Copyright Elsevier

^1,2Ai-Cheng Zhang, ³Shoichi Itoh, ³Hisayoshi Yurimoto, ⁴Wei-Biao Hsu, ¹Ru-Cheng Wang, ⁵Lawrence A. Taylor
¹State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
²Lunar and Planetary Science Institute, Nanjing University, Nanjing, China
³Department of Natural History Sciences, Hokkaido University, Sapporo, Japan
⁴Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
⁵Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA

CM chondrites are a group of primitive meteorites that have recorded the alteration history of the early solar system. We report the occurrence, chemistry, and oxygen isotopic compositions of P-O-rich sulfide phase in two CM chondrites (Grove Mountains [GRV] 021536 and Murchison). This P-O-rich sulfide is a polycrystalline aggregate of nanometer-size grains. It occurs as isolated particles or aggregates in both CM chondrites. These grains, in the matrix and in type-I chondrules from Murchison, were partially altered into tochilinite; however, grains enclosed by Ca-carbonate are much less altered. This P-O-rich sulfide in Murchison is closely associated with magnetite, FeNi phosphide, brezinaite (Cr3S4), and eskolaite (Cr2O3). In addition to sulfur as the major component, this sulfide contains ~6.3 wt% O, ~5.4 wt% P, and minor amounts of hydrogen. Analyses of oxygen isotopes by SIMS resulted in an average δ18O value of −22.5 ‰ and an average Δ17O value of 0.2 ± 9.2 ‰ (2σ). Limited variations in both chemical compositions and electron-diffraction patterns imply that the P-O-rich sulfide may be a single phase rather than a polyphase mixture. Several features indicate that this P-O-rich sulfide phase formed at low temperature on the parent body, most likely through the alteration of FeNi metal (a) close association with other low-temperature alteration products, (b) the presence of hydrogen, (c) high Δ17O values and the presence in altered mesostasis of type-I chondrules and absence in type-II chondrules. The textural relations of the P-O-rich sulfide and other low-temperature minerals reveal at least three episodic-alteration events on the parent body of CM chondrites (1) formation of P-O-rich sulfide during sulfur-rich aqueous alteration of P-rich FeNi metal, (2) formation of Ca-carbonate during local carbonation, and (3) alteration of P-O-rich sulfide and formation of tochilinite during a period of late-stage intensive aqueous alteration

Reference
Zhang A-C, Itoh S, Yurimoto H, Hsu W-B, Wang R-C, Taylor LA (2015)
P-O-rich sulfide phase in CM chondrites: Constraints on its origin on the CM parent body. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12583]
Published by arrangement with John Wiley & Sons

^1,2Xiande Xie, ³Xiangping Gu,²Ming Chen
¹Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
²Guangdong Key Laboratory of Mineral Physics and Materials, Guangzhou, China
³School of Geosciences and Info-Physics, Central South University, Changsha, Hunan, China

Tuite is a high-pressure γ-form of Ca3(PO4)2. An occurrence of tuite partly transformed from merrillite and chlorapatite was observed in the chondritic area adjacent to the shock veins in the Suizhou meteorite. Tuite grains are found in contact with both merrillite and chlorapatite, indicating two different transformation pathways. Tuite isochemically transformed from merrillite contains much higher contents of Na2O and MgO than those transformed from chlorapatite. Tuite transformed from merrillite does not contain Cl, but tuite transformed from chlorapatite contains 1.90–3.91 wt% of Cl, hence indicating an incomplete phase transformation from chlorapatite to tuite. P-T conditions of above 12 GPa and 1100 °C are probably required for the transformation from merrillite and chlorapatite to tuite. A temperature gradient from the hot vein at 2000 °C to the surrounding chondritic area at 1000 °C corresponds to the partial phase transitions in the Suizhou phosphates. Fast cooling of the thin shock veins plays a key role in the preservation of phosphates that suffered partial high-pressure phase transformation.

Reference
Xie X, Gu X, Chen M (2015) An occurrence of tuite, γ-Ca3(PO4)2, partly transformed from Ca-phosphates in the Suizhou meteorite. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12577]
Published by arrangement with John Wiley & Sons

^1,2Nicole G. Lunning, ³Kees C. Welten, ²Harry Y. McSween Jr, ⁴Marc W. Caffee,⁵Andrew W. Beck
¹Department of Mineral Sciences, Smithsonian Institution, National Museum of Natural History, Washington, District of Columbia, USA
²Department of Earth and Planetary Sciences and Planetary Geosciences Institute, University of Tennessee, Knoxville, Tennessee, USA
³Space Science Laboratory, University of California, Berkeley, California, USA
⁴Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana, USA
⁵The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA

Regolithic howardites are analogs for the surface materials of asteroid 4 Vesta, recently mapped by the Dawn spacecraft. Rigorously evaluating pairing of howardites recovered in 1995 in the Grosvenor Mountains (GRO 95), Antarctica, enables an examination of a larger, more representative regolith sample. Previous work on two of the howardites studied here concluded that GRO 95602 and GRO 95535 are solar wind-rich surface regolith samples and that they are not paired with each other, leading to uncertainty regarding pairing relationships between the other GRO 95 howardites. Based on petrology, cosmic-ray exposure history, and terrestrial age, four GRO 95 howardites are paired. The paired howardites (GRO 95534, 95535, 95574, 95581) were from a meteoroid with radius of 10–15 cm, a preatmospheric size comparable to that of Kapoeta, the largest known regolithic howardite. The paired GRO 95 howardites contain clasts of at least 18 separate HED lithologies, providing evidence they were assembled from diverse source materials. The total eucrite:diogenite mixing ratio (ratio of all eucrite lithologies to all diogenite lithologies) in the paired GRO 95 howardites is ~2:1. Petrographically determined basaltic eucrite:cumulate eucrite ratios in regolithic howardites, studied here and previously, vary more widely than total eucrite:diogenite ratios. Relative to eucritic pyroxene, plagioclase is depleted in these howardites, which provides evidence that plagioclase is preferentially comminuted in the vestan regolith. The extent of plagioclase depletion could be an indicator of regolith maturity.

Reference
Lunning NG, Welten KC, McSween Jr HY, Caffee MC, Beck AW (2015)
Grosvenor Mountains 95 howardite pairing group: Insights into the surface regolith of asteroid 4 Vesta. Meteoritics & Planetary Sciences (in Press)
Link to Article [DOI: 10.1111/maps.12580]
Published by arrangement with John Wiley & Sons

¹I. Weber, ¹A. Morlok, ¹A. Bischoff,¹H. Hiesinger1 ¹D. Ward, ²K. H. Joy, ²S. A. Crowther, ²N. D. Jastrzebski, ²J. D. Gilmour, ²P. L. Clay, ²R. A. Wogelius, ³R. C. Greenwood, ³I. A. Franchi,⁴C. Münker
¹Institut für Planetologie, Münster, Germany
²School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester, UK
³Planetary and Space Sciences, The Open University, Milton Keynes, UK
⁴Institut für Geologie und Mineralogie, Universität zu Köln, Köln, Germany

This work is part of a project to build an infrared database in order to link IR data of planetary materials (and therefore possible Mercury material) with remote sensing observations of Mercury, which will probably be obtained by the MERTIS instrument on the forthcoming BepiColombo mission.
The unique achondrite Northwest Africa (NWA) 7325, which has previously been suggested to represent the first sample from Mercury, was investigated by optical and electron microscopy, and infrared and Raman spectroscopy. In addition, the oxygen, strontium, xenon, and argon isotopes were measured and the abundance of selected trace elements determined. The meteorite is a cumulate rock with subchondritic abundances of HFSE and REE and elevated Sr contents, which underwent a second heating and partial remelting process. Oxygen isotope measurements show that NWA 7325 plots in the ureilite field, close to the ALM-A trachyandesitic fragment found in the unique Almahata Sitta meteorite breccia. On the other hand, mineralogical investigations of the pyroxenes in NWA 7325 provide evidence for similarities to the lodranites and acapulcoites. Furthermore, the rock is weakly shocked and argon isotope data record ancient (~4.5 Ga) plateau ages that have not been reset. The sample records a cosmogenic exposure age of ~19 Ma. Systematics of Rb-Sr indicate an extreme early volatile depletion of the precursor material, similar to many other achondrite groups. However, despite its compositional similarities to other meteorite groups, our results suggest that this meteorite is unique and unrelated to any other known achondrite group. An origin for NWA 7325 as a sample from the planet Mercury is not supported by the results of our investigation. In particular, the evidence from infrared spectroscopy indicates that a direct relationship between NWA 7325 and the planet Mercury can be ruled out: no acceptable spectral match between laboratory analyses and remote sensing observations from Mercury has been obtained. However, we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions.

Reference
Weber I, Morlok A, Bischoff A, Hiesinger H, Ward D, Joy KH, Crowther SA, Jastrzebski ND, Gilmour JD, Clay PL, Wogelius RA, Greenwood RC, Franchi IA, Münker C (2015) Cosmochemical and spectroscopic properties of Northwest Africa 7325—A consortium study. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12586]
Published by arrangement with John Wiley & Sons