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,

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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

¹Li, S. ¹Milliken, R. E.
¹Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA

Reliable quantitative mapping of minerals exposed on Vesta’s surface is crucial for understanding the crustal composition, petrologic evolution, and surface modification of the howardite, eucrite, and diogenite (HED) parent body. However, mineral abundance estimates derived from visible–near infrared (VIS–NIR) reflectance spectra are complicated by multiple scattering, particle size, and nonlinear mixing effects. Radiative transfer models can be employed to accommodate these issues, and here we assess the utility of such models to accurately and efficiently determine modal mineralogy for a suite of eucrite and olivine-bearing (harzburgitic) diogenite meteorites. Hapke and Shkuratov radiative transfer models were implemented to simultaneously estimate mineral abundances and particle size from VIS–NIR reflectance spectra of these samples. The models were tested and compared for laboratory-made binary (pyroxene–plagioclase) and ternary mixtures (pyroxene–olivine–plagioclase) as well as eucrite and diogenite meteorite samples. Results for both models show that the derived mineral abundances are commonly within 5–10% of modal values and the estimated particle sizes are within the expected ranges. Results for the Hapke model suggest a lower detection limit for olivine in HEDs when compared with the Shkuratov model (5% versus 15%). Our current implementation yields lower uncertainties in mineral abundance (commonly <5%) for the Hapke model, though both models have an advantage over typically used parameters such as band depth, position, and shape in that they provide quantitative information on mineral abundance and particle size. These results indicate that both the Hapke and Shkuratov models may be applied to Dawn VIR data in a computationally efficient manner to quantify the spatial distribution of pyroxene, plagioclase, and olivine on the surface of Vesta.

Reference
Li S, Milliken RE (2015) Estimating the modal mineralogy of eucrite and diogenite meteorites using visible–near infrared reflectance spectroscopy. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12513]
Published by arrangement with John Wiley & Sons

¹I. Leya, ¹N. Dalcher, ²N. Vogel, ²R. Wieler, ³M. W. Caffee, ⁴K. C. Welten,⁴K. Nishiizumi
¹Space Sciences and Planetology, University of Bern, Bern, Switzerland
²Institute of Geochemistry and Petrology, ETH Zurich, Zurich, Switzerland
³Department of Physics, PRIME Laboratory, Purdue University, West Lafayette, Indiana, USA
⁴Space Sciences Laboratory, University of California, Berkeley, USA

We calibrated the 81Kr-Kr dating system for ordinary chondrites of different sizes using independent shielding-corrected 36Cl-36Ar ages. Krypton concentrations and isotopic compositions were measured in bulk samples from 14 ordinary chondrites of high petrologic type and the cosmogenic Kr component was obtained by subtracting trapped Kr from phase Q. The thus-determined average cosmogenic 78Kr/83Kr, 80Kr/83Kr, 82Kr/83Kr, and 84Kr/83Kr ratiC(Lavielle and Marti 1988; Wieler 2002). The cosmogenic 78Kr/83Kr ratio is correlated with the cosmogenic 22Ne/21Ne ratio, confirming that 78Kr/83Kr is a reliable shielding indicator. Previously, 81Kr-Kr ages have been determined by assuming the cosmogenic production rate of 81Kr, P(81Kr)c, to be 0.95 times the average of the cosmogenic production rates of 80Kr and 82Kr; the factor Y = 0.95 therefore accounts for the unequal production of the various Kr isotopes (Marti 1967a). However, Y should be regarded as an empirical adjustment. For samples whose 80Kr and 82Kr concentrations may be affected by neutron-capture reactions, the shielding-dependent cosmogenic (78Kr/83Kr)c ratio has been used instead to calculate P(81Kr)/P(83Kr), as for some lunar samples, this ratio has been shown to linearly increase with (78Kr/83Kr)c (Marti and Lugmair 1971). However, the 81Kr-Kr ages of our samples calculated with these methods are on average ~30% higher than their 36Cl-36Ar ages, indicating that most if not all the 81Kr-Kr ages determined so far are significantly too high. We therefore re-evaluated both methods to determine P(81Kr)c/P(83Kr)c. Our new Y value of 0.70 ± 0.04 is more than 25% lower than the value of 0.95 used so far. Furthermore, together with literature data, our data indicate that for chondrites, P(81Kr)c/P(83Kr)c is rather constant at 0.43 ± 0.02, at least for the shielding range covered by our samples ([78Kr/83Kr]c = 0.119–0.185; [22Ne/21Ne]c = 1.083–1.144), in contrast to the observations on lunar samples. As expected considering the method used, 81Kr-Kr ages calculated either directly with this new P(81Kr)c/P(83Kr)c value or with our new Y value both agree with the corresponding 36Cl-36Ar ages. However, the average deviation of 2% indicates the accuracy of both new 81Kr-Kr dating methods and the precision of the new dating systems of ~10% is demonstrated by the low scatter in the data. Consequently, this study indicates that the 81Kr-Kr ages published so far are up to 30% too high.

Reference
Leya I, Dalcher N, Vogel N, Wieler R, Caffee M.W., Welten K.C. Nishiizumi K. (2015) Calibration of cosmogenic noble gas production based on 36Cl-36Ar ages. Part 2. The 81Kr-Kr dating technique. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12515]
Published by arrangement with John Wiley&Sons

¹Sonzogni, Y., ¹Treiman, A. 
¹Lunar and Planetary Institute, Houston, Texas, USA

Melt inclusions in igneous minerals can provide constraints on magma compositions, especially for planetary samples where mass is severely limited. Small inclusions (<15 μm diameter) are more abundant than large ones, but have been used little from concern that they did not entrap average magma, but are rich in melt of a diffusional layer against the host mineral. We compared bulk compositions and calculated original compositions of small and large melt inclusions in the Martian basalt meteorite (shergottite) Tissint. Small and large melt inclusions are consistent with the same line of igneous differentiation, have the same abundance ratios for incompatible elements (P, Ti, Al, K, Na), and are consistent with derivation from the bulk composition of Tissint (inferred to represent its parent melt composition). For Tissint, then, small melt inclusions show no evidence of entrapping diffusional boundary layers, and appear to have entrapped bulk magma. Thus, its small inclusions can be as useful as larger ones; this may be so for other planetary samples, and thus provides an additional tool for investigating planetary Magmas.

Reference
Sonzogni Y., Treiman A.(2015) Small melt inclusions can record bulk magma compositions: A planetary example from the Martian basalt (shergottite) Tissint. Meteoritics & Planetary Science (in Press)
Link to Article [doi: 10.1111/maps.12516]
Published by arrangement with John Wiley & Sons

¹Thomas G. Sharp, ^1,2Zhidong Xie, ³Paul S. de Carli,¹Jinping Hu
¹School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
²State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, China
³SRI International, Menlo Park, California, USA

A large shock-induced melt vein in L6 ordinary chondrite Roosevelt County 106 contains abundant high-pressure minerals, including olivine, enstatite, and plagioclase fragments that have been transformed to polycrystalline ringwoodite, majorite, lingunite, and jadeite. The host chondrite at the melt-vein margins contains olivines that are partially transformed to ringwoodite. The quenched silicate melt in the shock veins consists of majoritic garnets, up to 25 μm in size, magnetite, maghemite, and phyllosilicates. The magnetite, maghemite, and phyllosilicates are the terrestrial alteration products of magnesiowüstite and quenched glass. This assemblage indicates crystallization of the silicate melt at approximately 20–25 GPa and 2000 °C. Coarse majorite garnets in the centers of shock veins grade into increasingly finer grained dendritic garnets toward the vein margins, indicating increasing quench rates toward the margins as a result of thermal conduction to the surrounding chondrite host. Nanocrystalline boundary zones, that contain wadsleyite, ringwoodite, majorite, and magnesiowüstite, occur along shock-vein margins. These zones represent rapid quench of a boundary melt that contains less metal-sulfide than the bulk shock vein. One-dimensional finite element heat-flow calculations were performed to estimate a quench time of 750–1900 ms for a 1.6-mm thick shock vein. Because the vein crystallized as a single high-pressure assemblage, the shock pulse duration was at least as long as the quench time and therefore the sample remained at 20–25 GPa for at least 750 ms. This relatively long shock pulse, combined with a modest shock pressure, implies that this sample came from deep in the L chondrite parent body during a collision with a large impacting body, such as the impact event that disrupted the L chondrite parent body 470 Myr ago.

Reference
Sharp TG, Xie Z, de Carli PS, Hu J (2015) A large shock vein in L chondrite Roosevelt County 106: Evidence for a long-duration shock pulse on the L chondrite parent Body. Meteoritics & Planetary Sciences (in Press)
Link to Article [DOI: 10.1111/maps.12557]
Published by arrangement with John Wiley & Sons

¹Joseph A. Nuth III, ²Natasha M. Johnson, ^2,3Frank T. Ferguson, ⁴Frans J.M. Rietmeijer, ⁵Hugh G.M. Hill
¹Solar System Exploration Division, Code 690, NASA’s Goddard Space Flight Center, Greenbelt, MD 20771 USA
²Astrochemistry Laboratory, Code 691, NASA’s Goddard Space Flight Center, Greenbelt, MD 20771 USA
³Chemistry Department, Catholic University of America, Washington, DC, USA
⁴Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, USA
⁵International Space University (ISU), Strasbourg Central Campus, France

Experimental data and observations, whether telescopic or analytical, are never wrong, though data derived from such sources can be misinterpreted or applied inappropriately to derive conclusions that are incorrect. Given that nature always behaves according to the laws of physics and chemistry, rather than according to currently popular models and theories, experimental results should always be considered correct even when the results are far from those that one might initially expect. We discuss a number of cases where the results of experiments, even one carried out as a simple calibration measure, produced wildly different results that generally required many years of effort or contemplation to understand. On the positive side, exploration of the circumstances that produced the “errant” results often led to new and interesting insights concerning processes that might occur in natural environments and that were well worth the effort involved.

Specifically, we show how an experiment that “failed” due to a broken conductor led to experiments that made the first refractory oxide solids containing mass independently fractionated oxygen isotopes and to 1998 predictions of the oxygen isotopic composition of the sun that were confirmed by the analysis of Genesis samples in 2011. We describe a calibration experiment that unexpectedly produced single magnetic domain iron particles. We discuss how tracking down a persistent source of “contamination” in experiments intended to produce amorphous iron and magnesium silicate smokes led to a series of studies on the synthesis of carbonaceous grain coatings that turn out to be very efficient Fischer–Tropsch catalysts and have great potential for trapping the planetary noble gases found in meteorites. We describe how models predicting the instability of silicate grains in circumstellar environments spurred new measurements of the vapor pressure of SiO partially based on previous experiments showing unexpected but systematic non-equilibrium behavior instead of the anticipated equilibrium products resembling meteoritic minerals. We trace the process that led from observations of the presence of crystalline minerals detected in the comae of some comets to the 1999 prediction of large-scale circulation of materials from the hot, innermost regions of the solar nebula out to the cold dark nebular environments where comets form. This large-scale circulation was ultimately confirmed by analyses of highly refractory Stardust samples collected from the Kuiper Belt Comet Wild 2. Finally we discuss a modern and still unresolved conflict between the assumptions built into three well known processes: the CO Self Shielding Model for mass independent isotopic fractionation of oxygen in solar system solids, rapid and thorough mixing within the solar nebula, and the efficient conversion of CO into organic coatings and volatiles on the surfaces of nebular grains via Fischer–Tropsch-type processes.

Reference
Nuth III JA, Johnson NM, Ferguson FT, Rietmeijer FJM, Hill HGM (2015) Great new insights from failed experiments, unanticipated results and embracing controversial observations. Chemie der Erde (in Press)
Link to Article [doi:10.1016/j.chemer.2015.09.002]
Copyright Elsevier

¹Luca Bindi et al. (>10)*
¹Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Florence, Italy
*Find the extensive, full author and affiliation list on the publishers website

Decagonite is the second natural quasicrystal, after icosahedrite (Al63Cu24Fe13), and the first to exhibit the crystallographically forbidden decagonal symmetry. It was found as rare fragments up to ~60 μm across in one of the grains (labeled number 126) of the Khatyrka meteorite, a CV3 carbonaceous chondrite. The meteoritic grain contains evidence of a heterogeneous distribution of pressures and temperatures that occurred during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200 °C. Decagonite is associated with Al-bearing trevorite, diopside, forsterite, ahrensite, clinoenstatite, nepheline, coesite, pentlandite, Cu-bearing troilite, icosahedrite, khatyrkite, taenite, Al-bearing taenite, and steinhardtite. Given the exceedingly small size of decagonite, it was not possible to determine most of the physical properties for the mineral. A mean of seven electron microprobe analyses (obtained from three different fragments) gave the formula Al70.2(3)Ni24.5(4)Fe5.3(2), on the basis of 100 atoms. A combined TEM and single-crystal X-ray diffraction study revealed the unmistakable signature of a decagonal quasicrystal: a pattern of sharp peaks arranged in straight lines with 10-fold symmetry together with periodic patterns taken perpendicular to the 10-fold direction. For quasicrystals, by definition, the structure is not reducible to a single three-dimensional unit cell, so neither cell parameters nor Z can be given. The likely space group is P105/mmc, as is the case for synthetic Al71Ni24Fe5. The five strongest powder-diffraction lines [d in Å (I/I0)] are: 2.024 (100), 3.765 (50), 2.051 (45), 3.405 (40), 1.9799 (40). The new mineral has been approved by the IMA-NMNC Commission (IMA2015-017) and named decagonite for the 10-fold symmetry of its structure. The finding of a second natural quasicrystal informs the longstanding debate about the stability and robustness of quasicrystals among condensed matter physicists and demonstrates that mineralogy can continue to surprise us and have a strong impact on other disciplines.

Reference
Bindi L. et al. (2015) Decagonite, Al71Ni24Fe5, a quasicrystal with decagonal symmetry from the Khatyrka CV3 carbonaceous chondrite. American Mineralogist 100, 2340-2343
Link to Article [doi:10.2138/am-2015-5423]
Copyright: The Mineralogical Society of America

¹T. Michikami, ²A. Hagermann, ³T. Kadokawa, ¹A. Yoshida, ³A. Shimada, ⁴S. Hasegawa, ³A.Tsuchiyama
¹Faculty of Engineering, Kinki University, Hiroshima Campus, 1 Takaya Umenobe, Higashi-Hiroshima, Hiroshima 739-2116, Japan
²Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
³Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University, Kiashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8052, Japan
⁴Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-8510, Japan

Laboratory impact experiments have found that impact fragments tend to be elongated. Their shapes, as defined by axes a, b and c, these being the maximum dimensions of the fragment in three mutually orthogonal planes (a ⩾ b ⩾ c), are distributed around mean values of the axial ratios b/a ∼0.7 and c/a ∼0.5. This corresponds to a: b: c in the simple proportion 2: √2: 1. The shape distributions of some boulders on asteroid Eros, the small- and fast-rotating asteroids (diameter < 200 m and rotation period < 1 h), and asteroids in young families, are similar to those of laboratory fragments created in catastrophic disruptions. Catastrophic disruption is, however, a process that is different from impact cratering. In order to systematically investigate the shapes of fragments in the range from impact cratering to catastrophic disruption, impact experiments for basalt targets 5 to 15 cm in size were performed. A total of 28 impact experiments were carried out by firing a spherical nylon projectile (diameter 7.14 mm) perpendicularly into the target surface at velocities of 1.60 to 7.13 km/s. More than 12,700 fragments with b ⩾ 4 mm generated in the impact experiments were measured. We found that the mean value of c/a in each impact decreases with decreasing impact energy per unit target mass. For instance, the mean value of c/a in an impact cratering event is nearly 0.2, which is considerably smaller than c/a in a catastrophic disruption (∼0.5). The data presented here can provide important evidence to interpret the shapes of asteroids and boulders on asteroid surfaces, and can constrain current interpretations of asteroid formation. As an example, by applying our experimental results to the boulder shapes on asteroid Itokawa’s surface, we can infer that Itokawa’s parent body must have experienced a catastrophic disruption.

Reference
Michikami T, Hagermann A, Kadokawa T, Yoshida A, Shimada A, Hasegawa S, Tsuchiyama A (2015) Fragment shapes in impact experiments ranging from cratering to catastrophic disruption. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.09.038]

Copyright Elsevier