^1,2Kathryn H. McDermott, ¹Richard C. Greenwood, ³Edward R.D. Scott, ¹Ian A. Franchi, ⁴Mahesh Anand
¹Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA
²School of Physical Sciences, University of Kent, Canterbury, CT2 7NH
³Hawaii Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822, USA
⁴Department of Earth Sciences, The Natural History Museum, London, SW7 5BD

The origin of silicate-bearing irons, especially those in groups IAB, IIICD, and IIE, is poorly understood as silicate should have separated rapidly from molten metal. Here we report the results of high precision oxygen isotope analysis of silicate inclusions in eleven group IIE meteorites and a petrological study of silicate inclusions in ten IIE irons including those in Garhi Yasin and Tarahumara, which have not been described in detail before. Oxygen isotopes have also been analysed in 20 H chondrites to investigate their possible relationship with the IIE irons.

Based on petrographic observations and mineral analysis, the silicate-bearing IIE meteorites have been divided into four types according to the nature of their silicate inclusions: 1) primitive chondritic, 2) evolved chondritic, 3) differentiated with >10 vol.% orthopyroxene, and 4) differentiated with

Our data suggest that the IIE meteorites formed on an internally heated H/HH chondrite-like body that experienced the initial stages of differentiation in response to radiogenic heating. However, prior to full differentiation the IIE parent body experienced a major hit-and-run style collision that resulted in silicate-metal mixing. The initial stages of this event involved a phase of rapid cooling that prevented unmixing of metal and silicates. Reassembly of the IIE parent body produced a large regolith blanket that facilitated subsequent slow cooling. The IIE parent body has probably experienced numerous subsequent less catastrophic collisions. The development of alkali glass textures in some differentiated inclusions is probably the result of one of these later events.

Reference
McDermott KH, Greenwood RC, Scott ERD, Franchi IA, Anand M (2015) Oxygen isotope and petrological study of silicate inclusions in IIE iron meteorites and their relationship with H chondrites. Geochimica et Cosmochimica Acta (in Presss)
Link to Article [doi:10.1016/j.gca.2015.10.014]
Copyright Elsevier

¹Ashcroft, H. O.
¹Wood, B. J.
¹Department of Earth Sciences, University of Oxford, Oxford, UK

We have performed an experimental and modeling study of the partial melting behavior of the HED parent body and of the fractional crystallization of liquids derived from its mantle. We estimated the mantle composition by assuming chondritic ratios of refractory lithophile elements, adjusting the Mg# and core size to match the density and moment of inertia of Vesta, and the compositions of Mg-rich olivines found in diogenites. The liquidus of a mantle with Mg# (=100*[Mg/(Mg+Fe)]) 80 is ~1625 °C and, under equilibrium conditions, the melt crystallizes olivine alone until it is joined by orthopyroxene at 1350 °C. We synthesized the melt from our 1350 °C experiment and simulated its fractional crystallization path. Orthopyroxene crystallizes until it is replaced by pigeonite at 1200 °C. Liquids become eucritic and crystal assemblages resemble diogenites below 1250 °C. MELTS correctly predicts the olivine liquidus but overestimates the orthopyroxene liquidus by ~70 °C. Predicted melt compositions are in reasonable agreement with those generated experimentally. We used MELTS to determine that the range of mantle compositions that can produce eucritic liquids and diogenitic solids in a magma ocean model is Mg# 75–80 (with chondritic ratios of refractory elements). A mantle with Mg# ~ 70 can produce eucrites and diogenites through sequential partial melting.

Reference
Ashcroft HO and Wood BJ (2015) An experimental study of partial melting and fractional crystallization on the HED parent Body. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12556]
Published by arrangement with John Wiley&Sons

¹Lidia Pittarello, ²Julia Roszjar, ³Dieter Mader, ⁴Vinciane Debaille, ¹Philippe Claeys,²Christian Koeberl
¹Analytical, Environmental and Geo-Chemistry (AMGC), Vrije Universiteit Brussel, Brussels, Belgium
²Natural History Museum Vienna, Vienna, Austria
³Department of Lithospheric Research, University of Vienna, Vienna, Austria
⁴Laboratoire G-Time (Géochimie: Traçage isotopique, minéralogique et élémentaire), Université Libre de Bruxelles, Brussels, Belgium

El’gygytgyn (Chukotka, Arctic Russia) is a well-preserved impact structure, mostly excavated in siliceous volcanic rocks. For this reason, the El’gygytgyn structure has been investigated in recent years and drilled in 2009 in the framework of an ICDP (International Continental Scientific Drilling Program) project. The target rocks mostly consist of rhyodacitic ignimbrites and tuffs, which make it difficult to distinguish impact melt clasts from fragments of unshocked target rock within the impact breccia. Several chemical and petrologic attempts, other than dating individual clasts, have been considered to distinguish impact melt from unshocked volcanic rock of the targets, but none has proven reliable. Here, we propose to use cathodoluminescence (imaging and spectrometry), whose intensity is inversely correlated with the degree of shock metamorphism experienced by the investigated lithology, to aid in such a distinction. Specifically, impact melt rocks display low cathodoluminescence intensity, whereas unshocked volcanic rocks from the area typically show high luminescence. This high luminescence decreases with the degree of shock experienced by the individual clasts in the impact breccia, down to almost undetectable when the groundmass is completely molten. This might apply only to El’gygytgyn, because the luminescence in volcanic rocks might be due to devitrification and recrystallization processes of the relatively old (Cretaceous) target rock with respect to the young impactites (3.58 Ma). The alteration that affects most samples from the drill core does not have a significant effect on the cathodoluminescence response. In conclusion, cathodoluminescence imaging and spectra, supported by Raman spectroscopy, potentially provide a useful tool for in situ characterization of siliceous impactites formed in volcanic target.

Reference
Pittarello L, Roszjar J, Mader D, Debaille V, Claeys P, Koeberl C, (2015) Cathodoluminescence as a tool to discriminate impact melt, shocked and unshocked volcanics: A case study of samples from the El’gygytgyn impact structure. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12559]
Published by arangement with John Wiley & Sons

¹Thomas Kenkmann, ²Abdulkader M. Afifi, ²Simon A. Stewart, ¹Michael H. Poelchau, ²Douglas J. Cook,²Allen S. Neville2
¹Institute of Earth and Environmental Sciences, Geology, Albert-Ludwigs University Freiburg, Freiburg, Germany
²Area Exploration Department, Saudi Aramco, Dhahran, Saudi Arabia

Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al. 2014), with an apparent diameter of 34 km, centered at 29°35′N, 38°42′E. The structure is formed in Cambrian–Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2-D reflection seismic profiles and six drilled wells. First-order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring-like low, respectively. The wells were drilled within the central uplift, the deepest among them exceeded 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {10inline image3}, and less frequently along {10inline image1} and {10inline image4}. Planar fractures (PFs) predominantly occur along (0001) and {10inline image1}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1–2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.

Reference
Kenkmann T, Afifi AM, Stewart SA, Poelchau MH, Douglas J. Cook DJ, Neville AS (2015)
Saqqar: A 34 km diameter impact structure in Saudi Arabia. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12555]
Published by arrangement with John Wiley & Sons

Maike Becker^a,b, Dominik C. Hezel^a,c, Toni Schulz^d, Bo-Magnus Elfers^a, Carsten Münker^a
aInstitut für Geologie und Mineralogie, Universität zu Köln, Zülpicherstrasse 49b, D-50674 Köln, Germany
^bInstitut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), 51147 Köln, Germany
^cDepartment of Mineralogy, Natural History Museum, Cromwell Road, SW7 5BD London, UK
^dDepartment of Lithospheric Research, University of Vienna, Althanstraße 14, 1090 Vienna, Austria

Carbonaceous chondrites are an important meteorite group that closely resembles the bulk composition of the solar system. We report the first elemental and isotope dataset for Hf–W in carbonaceous chondrites that includes chondrules, matrix, magnetic fractions as well as bulk compositions. Our study focuses on the three CV3 chondrites, Allende, Vigarano and Bali. Compared to bulk chondrites, matrix splits have low Hf/W ratios and ε¹⁸²W compositions, whereas chondrule splits are characterized by high, but more variable, Hf/W ratios and ε¹⁸²W compositions. Thus, Hf/W ratios behave complementary between chondrules and matrix in the analysed CV chondrites, supporting the view that both components formed from the same parental reservoir. Strong nucleosynthetic effects were observed in most of the analysed CV3 components, especially in matrices and chondrule splits that were found to have large ε¹⁸³W anomalies of several ε-units. All separates define a rough correlation between initial ¹⁸²W/¹⁸⁴W and ¹⁸³W/¹⁸⁴W ratios, in agreement with theoretical model trends based on calculations for stellar nucleosynthesis. Our results, therefore, indicate a heterogeneous distribution of s- and r-process W isotopes among the different CV3 chondrite components, arguing for selective thermal processing of early solar system matter during chondrule formation. After correcting for nucleosynthetic anomalies, chondrules and matrix splits of reduced (Vigarano) as well as oxidised (Allende) CV3 chondrites define a linear correlation in ε¹⁸²W vs. ¹⁸⁰Hf/¹⁸⁴W space, which is interpreted as an isochron, covering an age interval within the first ~2.6 Ma after solar system formation. As peak metamorphic temperatures for CV3 chondrites were well below the ¹⁸²Hf–¹⁸²W closure temperature, the resulting isochron within its error most likely defines a common formation interval for all components. The calculated age interval is for the first time based on a combined chondrule-matrix isochron, a marked difference compared to previous studies where only chondrules were analysed. Notably, our formation age interval covers previously reported chondrule formation ages determined using ²⁶Al and Pb–Pb chronometry, illustrating that chondrule and matrix formation started contemporaneously with CAI formation and lasted over a time interval of about 2–3 Ma. Our results also corroborate previous models from ordinary chondrites, in that chondrite parent bodies were not the first planetesimals to have formed in the early solar system.

Reference
Becker M, Hezel DC, Schulz T, Elfers B-M, Münker C (2015) Formation timescales of CV chondrites from component specific Hf–W systematics. Earth and Planetary Science Letters (in Press)
Link to Article [doi:10.1016/j.epsl.2015.09.049]
Copyright Elsevier

¹Patricia M. Doyle, ²Kaori Jogoa, ¹Kazuhide Nagashima, ^1,2Gary R. Huss,²Alexander N. Krot
¹Hawai‘i Institute for Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, HI, 96822, USA
²University of Hawai‘i NASA Astrobiology Institute, Honolulu, HI, 96822, USA

The short-lived radionuclide 53Mn, which decays to 53Cr with a half-life of ∼3.7 Myr, is useful for sequencing objects that formed within the first 20 Myr of Solar System evolution. 53Mn-53Cr relative chronology enables aqueously formed secondary minerals such as fayalite and various carbonates in ordinary and carbonaceous chondrites to be dated, thereby providing chronological constraints on aqueous alteration processes. In situ measurements of Mn-Cr isotope systematics in fayalite by secondary ion mass spectrometry (SIMS) require consideration of the relative sensitivities of the 55Mn+ and 52Cr+ ions, for which a relative sensitivity factor [RSF = (55Mn+/52Cr+)SIMS/(55Mn/52Cr)true] is defined using appropriate standards. In the past, San Carlos olivine (Fa∼10) was commonly used for this purpose, but a growing body of evidence suggests that it is an unsuitable standard for meteoritic fayalite (Fa>90). Natural fayalite also cannot be used as a standard because it contains only trace amounts of chromium, which makes determining a true 55Mn/52Cr ratio and its degree of heterogeneity very difficult.

To investigate the dependence of the Mn-Cr RSF on ferromagnesian olivine compositions, we synthesized a suite of compositionally homogeneous Mn,Cr-bearing liquidus-phase ferromagnesian olivines (Fa31-99). Manganese-chromium isotopic measurements of San Carlos olivine and synthesized ferromagnesian olivines using the University of Hawai‘i Cameca ims-1280 SIMS show that the RSF for Fa10 is ∼0.9; it increases rapidly between Fa10 and Fa31 and reaches a plateau value of ∼1.5±0.1 for Fa>34. The RSF is time-dependent: it increases during the measurements of olivines with fayalite content 50. The RSF measured on ferroan olivine (Fa>90) is influenced by pit shape, whereas the RSF measured on magnesian olivine (Fa10) is less sensitive to changes in pit shape. For these reasons, 53Mn-53Cr systematics of chondritic fayalite (Fa>90) should be determined using standards of similar composition that are measured under the same analytical conditions as the “unknown”.

The 53Mn-53Cr ages of secondary fayalites (Fa90-100) in the Elephant Moraine (EET) 90161 (L3.05), Vicencia (LL3.2), Asuka 881317 (CV3) and MacAlpine Hills (MAC) 88107 (C3) chondrites (View the MathML source2.4-1.3+1.8, View the MathML source4.0-1.1+1.4, View the MathML source4.2-0.7+0.8 and View the MathML source5.1-0.4+0.5 Myrs after CV CAIs, respectively) are ∼3 Myr older when using an RSF measured on a matrix-matched (Fa99) standard, rather than on a San Carlos olivine. The inferred 53Mn-53Cr ages of fayalite formation are consistent with the ages reported for calcites in CM chondrites measured with similarly matrix-matched standards (Fujiya et al., 2012), suggesting an early onset of aqueous alteration on the ordinary and carbonaceous chondrite parent bodies heated by decay of 26Al.

Reference
Doyle PM, Jogo K, Nagashima K, Huss GR, Krot AN (2015) Mn-Cr relative sensitivity factor in ferromagnesian olivines defined for SIMS measurements with a Cameca ims-1280 ion microprobe: Implications for dating secondary fayalite. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.10.010]
Copyright Elsevier

¹Andreas Morlok, ¹Aleksandra Stojic, ²Isabelle Dittmar, ¹Harald Hiesinger, ¹Manuel Ahmedi, ²Martin Sohn, ¹Iris Weber, ³Joern Helbert 
¹Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
²Hochschule Emden/Leer, Constantiaplatz 4, 26723 Emden, Germany
³Institute for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany

This study is part of an effort to build a mid-infrared database (7-14μm) of spectra for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo space probe to be launched to Mercury in 2017.

Mercury was exposed to abundant impacts throughout its history. This study of terrestrial impactites can provide estimates of the effects of shock metamorphism on the mid-infrared spectral properties of planetary materials.

In this study, we focus on the Nördlinger Ries crater in Southern Germany, a well preserved and easily accessible impact crater with abundant suevite impactites. Suevite and melt glass bulk samples from Otting and Aumühle, as well as red suevite from Polsingen were characterized and their reflectance spectra in mid-infrared range obtained. In addition, in-situ mid-infrared spectra were made from glasses and matrix areas in thin sections. The results show similar, but distinguishable spectra for both bulk suevite and melt glass samples, as well as in-situ measurements.

Impact melt glass from Aumühle and Otting have spectra dominated by a Reststrahlen band at 9.3-9.6 μm. Bulk melt rock from Polsingen and bulk suevite and fine-grained matrix have their strongest band between 9.4 to 9.6 μm. There are also features between 8.5 and 9 μm, and 12.5 – 12.8 μm associated with crystalline phases. There is evidence of weathering products in the fine-grained matrix, such as smectites. Mercury endured many impacts with impactors of all sizes over its history. So spectral characteristics observed for impactites formed only in a single impact like in the Ries impact event can be expected to be very common on planetary bodies exposed to many more impacts in their past. We conclude that in mid-infrared remote sensing data the surface of Mercury can be expected to be dominated by features of amorphous materials.

Reference
Morlok A, Stojic A, Dittmar I, Hiesinger H, Ahmedi M, Sohn M, Weber I, Helbert J (2015) Mid-Infrared spectroscopy of impactites from the Nördlinger Ries impact crater. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.10.003]
Copyright Elsevier

¹Jamie E. Elsila, ¹Michael P. Callahan, ¹Jason P. Dworkin, ¹Daniel P. Glavin, ^1,2Hannah L. McLain, ^1,2Sarah K. Noble, ³Everett K. Gibson Jr.
¹NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
²Catholic University of America, Washington, DC 20064
³NASA Johnson Space Center, Houston, TX 77058

We analyzed the amino acid content of seven lunar regolith samples returned by the Apollo 16 and Apollo 17 missions and stored under NASA curation since collection using ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Consistent with results from initial analyses shortly after collection in the 1970s, we observed amino acids at low concentrations in all of the curated samples, ranging from 0.2 parts-per-billion (ppb) to 42.7 ppb in hot-water extracts and 14.5 ppb to 651.1 ppb in 6M HCl acid-vapor-hydrolyzed, hot-water extracts. Amino acids identified in the Apollo soil extracts include glycine, d- and l-alanine, d- and l-aspartic acid, d- and l-glutamic acid, d- and l-serine, l-threonine, and l-valine, all of which had previously been detected in lunar samples, as well as several compounds not previously identified in lunar regoliths: α-aminoisobutyric acid (AIB), d- and l-β-amino-n-butyric acid (β-ABA), dl-α-amino-n-butyric acid, γ-amino-n-butyric acid, β-alanine, and ε-amino-n -caproic acid. We observed an excess of the l enantiomer in most of the detected proteinogenic amino acids, but racemic alanine and racemic β-ABA were present in some samples.

We also examined seven samples from Apollo 15, 16, and 17 that had been previously allocated to a non-curation laboratory, as well as two samples of terrestrial dunite from studies of lunar module engine exhaust that had been stored in the same laboratory. The amino acid content of these samples suggested that contamination had occurred during non-curatorial storage.

We measured the compound-specific carbon isotopic ratios of glycine, β-alanine, and l-alanine in Apollo regolith sample 70011 and found values of -21‰ to -33‰. These values are consistent with those seen in terrestrial biology and, together with the enantiomeric compositions of the proteinogenic amino acids, suggest that terrestrial biological contamination is a primary source of the amino acids in these samples. However, the presence of the non-proteinogenic amino acids such as AIB and β-ABA suggests the possibility of some contribution from exogenous sources.

We did not observe a correlation of amino acid content with proximity to the Apollo 17 lunar module, implying that lunar module exhaust was not a primary source of amino acid precursors. Solar-wind-implanted precursors such as HCN also appear to be at most a minor contributor, given a lack of correlation between amino acid content and soil maturity (as measured by Is/FeO ratio) and the differences between the δ13C values of the amino acids and the solar wind.

Reference
Elsila JE, Callahan MP, Dworkin JP, Glavin DP, McLain HL, Noble SK, Gibson Jr. EK (2015) The origin of amino acids in lunar regolith samples. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.10.008]
Copyright Elsevier

¹Boris Laurent, ¹Mathieu Roskosz, ²Laurent Remusat, ²François Robert, ¹Hugues Leroux,³Hervé Vezin, ¹Christophe Depecker, ⁴Nicolas Nuns, ¹Jean-Marc Lefebvre
¹UMET, Université Lille 1, CNRS UMR 8207, Villeneuve d’Ascq F-59655, France
²IMPMC, CNRS UMR 7590, Sorbonne Universités, Université Pierre et Marie Curie, IRD, Muséum National d’Histoire Naturelle, CP 52, 57 rue Cuvier, Paris 75231
³LASIR, Université de Lille 1, CNRS UMR 8516, Villeneuve d’Ascq F-59655,
⁴Institut M.E. Chevreul, Université de Lille 1, CNRS, FR 2638, Villeneuve d’Ascq F-59655,

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

Reference
Laurent B, Roskosz M, Remusat L, Robert F, Leroux H, Vezin H, Depecker C, Nuns N, Lefebvre J-M (2015) The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing Irradiation. Nature Communications 6, 8567
Link to Article [doi:10.1038/ncomms9567]

^1,2C. Defouilloy, ¹P. Cartigny, ¹N. Assayag, ^3,4F. Moynier, ⁵J.-A. Barrat
¹Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154 CNRS, 1 rue Jussieu, 75238 Paris, France
²Laboratoire de Minéralogie et Cosmochimie du Muséum, Muséum National d’Histoire Naturelle, Paris, UMR 7202, 61 rue Buffon, 75005 Paris, France
³Cosmochimie, Astrophysique et Géophysique Expérimentale, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154 CNRS, 1 rue Jussieu, 75238 Paris, France
⁴Institut Universitaire de France, Paris, France
⁵U.B.O.-I.U.E.M., CNRS UMR 66538 (Domaines Océaniques), Place Nicolas Copernic, 29280 Plouzané Cedex, France

In order to better understand the formation and evolution of their parent bodies, the three isotope ratios of sulfur were analyzed in 33 enstatite meteorites (24 enstatite chondrites and 9 aubrites). The results show that on average all enstatite chondrite groups are enriched in the lightest isotopes compared to other chondrite groups, with means of δ34S of -0.28 ± 0.22 ‰ for EH3/4, -0.16 ± 0.16 ‰ for EH5, -0.32 ± 0.15 ‰ for EL3, -0.67 ± 0.16 ‰ for EL6 and -0.64 ± 0.00 ‰ for EL7 (all 1σ). Aubrites show a larger isotope variability in their composition, with a δ34S varying from -1.350‰ to +0.154 ‰. Contrary to previously published results, our data show a distinct composition for EL6 compared to other enstatite chondrites. This could be related to an impact-induced loss of isotopically heavy oldhamite (δ34S = by 3.62 ± 3.02 ‰ (1σ)) on the EL parent body. Although the bulk sulfur in both enstatite meteorites and aubrites does not show any significant Δ33S and Δ36S, the oldhamite fraction shows clear evidence of mass independent fractionation on the 36S/32S ratio (in 3 out of 9 analyzes, Δ36S up to +2.2‰), a signal that is not correlated to any 33S/32S anomaly (in 1 out of 9 analyzes, Δ33S down to -0.085‰). Though a nebular or photochemical origin cannot be ruled out, the most plausible mechanism to produce such isolated non-mass dependent 36S/32S anomalies would be a contribution of FeCl2 containing excesses of 36S due to the decay of 36Cl to the leached oldhamite fraction. Even though the sulfur isotopic composition measured in enstatite meteorites is distinct from the Bulk Silicate Earth (BSE), the isotopically lightest samples of EL6, EL7 and aubrites are approaching the isotopic composition of the BSE and enstatite meteorites remain the meteorites with the sulfur isotopic composition the closest to the terrestrial one.

Reference
Defouilloy C, Cartigny P, Assayag N, Moynier F, Barrat J-A (2015) High-precision sulfur isotope composition of enstatite meteorites and implications of the formation and evolution of their parent bodies. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.10.009]
Copyright Elsevier