Paul A. Giesting^1,†, Susanne P. Schwenzer², Justin Filiberto¹, Natalie A. Starkey², Ian A. Franchi², Allan H. Treiman³, Andy G. Tindle⁴ and Monica M. Grady²

¹Department of Geology, Southern Illinois University Carbondale, Carbondale, Illinois, USA
²Department of Physical Science, Planetary and Space Sciences, The Open University, Milton Keynes, UK
³Lunar and Planetary Science Institute, Houston, Texas, USA
⁴Department of Earth Sciences, The Open University, Milton Keynes, UK
^†Department of Geography and Geology, Illinois State University, Illinois, USA

Amphibole in chassignite melt inclusions provides valuable information about the volatile content of the original interstitial magma, but also shock and postshock processes. We have analyzed amphibole and other phases from NWA 2737 melt inclusions, and we evaluate these data along with published values to constrain the crystallization Cl and H2O content of phases in chassignite melt inclusions and the effects of shock on these amphibole grains. Using a model for the Cl/OH exchange between amphibole and melt, we estimate primary crystallization OH contents of chassignite amphiboles. SIMS analysis shows that amphibole from NWA 2737 currently has 0.15 wt% H2O. It has lost ~0.6 wt% H2O from an initial 0.7–0.8 wt% H2O due to intense shock. Chassigny amphibole had on average 0.3–0.4 wt% H2O and suffered little net loss of H2O due to shock. NWA 2737 amphibole has δD ≈ +3700‰; it absorbed Martian atmosphere-derived heavy H in the aftermath of shock. Chassigny amphibole, with δD ≤ +1900‰, incorporated less heavy H. Low H2O/Cl ratios are inferred for the primitive chassignite magma, which had significant effects on melting and crystallization. Volatiles released by the degassing of Martian magma were more Cl-rich than on Earth, resulting in the high Cl content of Martian surface materials.

Reference
Giesting PA, Schwenzer SP, Filiberto J, Starkey NA, Franchi IA, Treiman AH, Tindle AG and Grady MM (2015) Igneous and shock processes affecting chassignite amphibole evaluated using chlorine/water partitioning and hydrogen isotopes. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12430]

Published by arrangement with John Wiley & Sons

Gulchekhra I. Kokhirova* andPulat B. Babadzhanov

Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan, Dushanbe, Republic of Tajikistan

Three bright fireballs belonging to the August θ-Aquillid (ATA) meteor shower were photographed by the Tajikistan fireball network in 2009. Two of them are classified as the meteorite-dropping fireballs according to the determined parameters of the atmospheric trajectories, velocities, masses, and densities. Detection of the more dense bodies among cometary meteoroids points to a heterogeneous composition of the parent comet, and supports the suggestion that some meteorites might originate in the outer solar system, in the given case from the Jupiter-family comet reservoir. A search for the stream’s parent was undertaken among the near-Earth asteroids (NEAs); as a result, the asteroid 2004MB6 was identified as a possible progenitor of the ATA meteoroid stream. Investigation of the orbital evolution of the 2004MB6 and the fireball-producing meteoroid TN170809A showed that both objects have similar secular variations in the orbital elements during 7 kyr. The comet-like orbit of the 2004MB6 and its association with the ATA shower suppose a cometary origin of the asteroid.

Reference
Kokhirova GI and Babadzhanov PB (2015) The August θ-Aquillid fireballs and possible relationship with the asteroid 2004MB6. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12431]

Published by arrangement with John Wiley & Sons

Patrick N. Peplowski¹, David Bazell¹, Larry G. Evans², John O. Goldsten¹, David J. Lawrence¹ and Larry R. Nittler³

¹The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA
²Computer Sciences Corporation, Lanham-Seabrook, Maryland, USA
³Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA

A reanalysis of NEAR X-ray/gamma-ray spectrometer (XGRS) data provides robust evidence that the elemental composition of the near-Earth asteroid 433 Eros is consistent with the L and LL ordinary chondrites. These results facilitated the use of the gamma-ray measurements to produce the first in situ measurement of hydrogen concentrations on an asteroid. The measured value, inline image ppm, is consistent with hydrogen concentrations measured in L and LL chondrite meteorite falls. Gamma-ray derived abundances of hydrogen and potassium show no evidence for depletion of volatiles relative to ordinary chondrites, suggesting that the sulfur depletion observed in X-ray data is a surficial effect, consistent with a space-weathering origin. The newfound agreement between the X-ray, gamma-ray, and spectral data suggests that the NEAR landing site, a ponded regolith deposit, has an elemental composition that is indistinguishable from the mean surface. This observation argues against a pond formation process that segregates metals from silicates, and instead suggests that the differences observed in reflectance spectra between the ponds and bulk Eros are due to grain size differences resulting from granular sorting of ponded material.

Reference
Peplowski PN, Bazell D, Evans LG, Goldsten JO, Lawrence DJ and Nittler LR (2015) Hydrogen and major element concentrations on 433 Eros: Evidence for an L- or LL-chondrite-like surface composition. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12434]

Published by arrangement with John Wiley & Sons

Aaron S. Burton^1,†, Hannah McLain³, Daniel P. Glavin¹, Jamie E. Elsila¹, Jemma Davidson⁴, Kelly E. Miller⁵, Alexander V. Andronikov⁵, Dante Lauretta⁵ and Jason P. Dworkin¹

¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
³Catholic University of America, Washington, District of Columbia, USA
⁴Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, District of Columbia, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
^†Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA

Exogenous delivery of amino acids and other organic molecules to planetary surfaces may have played an important role in the origins of life on Earth and other solar system bodies. Previous studies have revealed the presence of indigenous amino acids in a wide range of carbon-rich meteorites, with the abundances and structural distributions differing significantly depending on parent body mineralogy and alteration conditions. Here we report on the amino acid abundances of seven type 3–6 CK chondrites and two Rumuruti (R) chondrites. Amino acid measurements were made on hot water extracts from these meteorites by ultrahigh-performance liquid chromatography with fluorescence detection and time-of-flight mass spectrometry. Of the nine meteorites analyzed, four were depleted in amino acids, and one had experienced significant amino acid contamination by terrestrial biology. The remaining four, comprised of two R and two CK chondrites, contained low levels of amino acids that were predominantly the straight chain, amino-terminal (n-ω-amino) acids β-alanine, and γ-amino-n-butyric acid. This amino acid distribution is similar to what we reported previously for thermally altered ureilites and CV and CO chondrites, and these n-ω-amino acids appear to be indigenous to the meteorites and not the result of terrestrial contamination. The amino acids may have been formed by Fischer–Tropsch-type reactions, although this hypothesis needs further testing.

Reference
Burton AS, McLain H, Glavin DP, Elsila JE, Davidson J, Miller KE, Andronikov AV, Lauretta D and Dworkin JP
(2015) Amino acid analyses of R and CK chondrites. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12433]

Published by arrangement with John Wiley & Sons

William K. Hartmann

Planetary Science Institute, Tucson, Arizona, USA

The well-recorded Chelyabinsk event, the Tunguska event, and the re-entry of the Zond IV vehicle offer opportunities to compare reactions of modern eyewitnesses to eyewitness accounts of possible ancient fireball events. The first-century book, Acts of the Apostles, gives three separate descriptions of a bright light “from heaven,” which occurred probably in the 30s (C.E.) near Damascus, Syria. The details offer a strikingly good match to a Chelyabinsk-class or Tunguska-class fireball. Among the most impressive, unexpected consistencies with modern knowledge is the first-century description of symptoms of temporary blindness caused by exposure to intense radiation, matching a condition now known as photokeratitis. An analysis of the re-entry of debris from the Russian Zond IV over the eastern United States in 1968 shows how actual perceived phenomena in an unfamiliar natural celestial apparition are often conceived by the observer in terms of current cultural conceptions, and it is suggested that this happened also in the first-century case.

Reference
Hartmann WK (2015) Chelyabinsk, Zond IV, and a possible first-century fireball of historical importance. Meteoritics & Planetary Sciences (in Press)
Link to Article [doi:10.1111/maps.12428]

Published by arrangement with John Wiley & Sons

Moe Matsuoka^a, Tomoki Nakamura^a, Yuki Kimura^b, Takahiro Hiroi^c, Ryosuke Nakamura^d, Satoshi Okumura^a, Sho Sasaki^e
aDivision of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Aoba, Sendai, Miyagi 980-8578, Japan
^bInstitute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819, Japan
^cDepartment of Geological Sciences, Brown University, Providence, RI 02912, USA
^dNational Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
^eDepartment of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan

We performed pulse-laser irradiation experiments of a primitive meteorite to simulate space weathering by micrometeorite bombardments on C-type asteroids. Pellets of powdered Murchison CM2 chondrite were set in vacuum and exposed to pulse laser with a diameter of 0.5 mm and delivered energies of 5, 10 and 15 mJ. We measured reflectance spectra of unirradiated and irradiated surfaces of the pellets. During analysis the pellet was heated to approximately 100°C and purged in N2 gas in order to reduce absorption of ambient water. The spectra become darker and bluer with increasing laser energies. Their UV reflectance increases and 0.7- and 3-μm band depths decrease from 0 to 15 mJ. The spectral bluing observed in our experiments reproduces the bluing occurred during space weathering of C-type asteroids. High-resolution observation by a transmission electron microscope showed that the laser heating causes preferential melting and evaporation in FeS-rich fine-grained portions, which results in dispersion and deposition of numerous FeS-rich amorphous silicate particles 20-1000 nm in size on the surface of the pellet. In addition, at the laser-irradiated but unmelted areas, heat-induced amorphization and decomposition of serpentine occur. These mineralogical changes make the reflectance spectra of the Murchison CM chondrite darker and bluer.

Reference
Matsuok M, Tomoki Nakamura T, Kimura Y, Hiroi T, Nakamura R, Okumura S, Sho Sasaki S (2015) Pulse-laser irradiation experiments of Murchison CM2 chondrite for reproducing space weathering on C-type asteroids. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.02.029]

Copyright Elsevier

Kelsey D. Hargrove^a, Josh Emery^b, Humberto Campins^a, Michael S.P. Kelley^c
a Physics Department, University of Central Florida, Orlando, FL 32816
^b Earth and Planetary Science Dept. and Planetary Geosciences Institute, University of Tennessee, Knoxville, TN 37996
^c Department of Astronomy, University of Maryland, College Park, MD 20742-2421

Many members of the Themis family show evidence of hydration in the form of oxidized iron in phyllosilicates (Florczak et al. 1999), and OH-bearing minerals (Takir and Emery 2012). The largest member, (24) Themis, has H2O ice covering its surface (Campins et al., 2010 and Rivkin and Emery, 2010). We have investigated the second largest Themis-family asteroid, (90) Antiope, which Castillo-Rogez and Schmidt (2010) predict to have a composition that includes water ice and organics. We obtained 2-4-μm spectroscopy of (90) Antiope in 2006 and 2008, and we find an absorption in the 3-μm region clearly present in our 2008 spectrum and likely in our 2006 spectrum. Both spectra have rounded, bowl-shaped absorptions consistent with those due to water ice as in the spectrum of (24) Themis, but do not uniquely identify water ice. We also present and compare Spitzer 8-12-μm mid-infrared spectra of (24) Themis and (90) Antiope. We find that (90) Antiope is lacking a “fairy castle” dusty surface, which is in contrast to (24) Themis, other Themis family members (Licandro et al. 2012), and Jupiter Trojans (e.g. Emery et al. 2006). We conclude that the surface structure of (90) Antiope is most similar to Cybele asteroid (121) Hermione (Hargrove et al. 2012).

Reference
Hargrove KD, Emery J, Michael HC, Kelley SP (2015) Asteroid (90) Antiope: Another Icy Member of the Themis Family? Icarus (in Press)
Link to Article [doi:10.1016/j.gca.2015.03.007]

Copyright Elsevier

¹Agnès Elmaleh,^1,2Franck Bourdelle,¹Florent Caste,¹Karim Benzerara,³Hugues Leroux,
⁴Bertrand Devouard
¹Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Université Pierre et Marie Curie, Sorbonne Universités, CNRS UMR 7590, MNHN, IRD UR 206, Campus Jussieu, 4 Place Jussieu, Boîte Courrier 115, 75252 Paris Cedex 05, France Paris, France
²GeoRessources, Université de Lorraine, CNRS UMR 7359, FST, rue Jacques Callot, BP 70239, 54506 Vandoeuvre-lès-Nancy, France
³Unité Matériaux et Transformations, Université Lille 1, CNRS UMR 8207, 59655 Villeneuve d’Ascq, France
⁴CEREGE UM34, Aix-Marseille Université, CNRS UMR 7330, Europôle Méditerranéen de l’Arbois – Avenue Louis Philibert, BP 80, 13545 Aix en Provence cedex 04, France

Fe-rich serpentines are an abundant product of the early aqueous alteration events that affected the parent bodies of CM carbonaceous chondrites. Alteration assemblages in these meteorites show a large chemical variability and although water-rock interactions occurred under anoxic conditions, serpentines contain high amounts of ferric iron. To date very few studies have documented Fe valence variations in alteration assemblages of carbonaceous chondrites, limiting the understanding of the oxidation mechanisms. Here, we report results from a nanoscale study of a calcium-aluminum-rich inclusion (CAI) from the Murray chondrite, in which alteration resulted in Fe import and Ca export by the fluid phase and in massive Fe-rich serpentines formation. We combined scanning and transmission electron microscopies and scanning transmission X-ray microscopy for characterizing the crystal chemistry of Fe-serpentines. We used reference minerals with known crystallographic orientations to quantify the Fe valence state in Fe-rich serpentines using X-ray absorption spectroscopy at the Fe L2,3-edges, yielding a robust methodology that would prove valuable for studying oxidation processes in other terrestrial or extra-terrestrial cases of serpentinization. We suggest that aqueous Fe2+ was transported to the initially Fe-depleted CAI, where local changes in pH conditions, and possibly mineral catalysis by spinel promoted the partial oxidation of Fe2+ into Fe3+ by water and the formation of Fe-rich serpentines close to the cronstedtite endmember. Such mechanisms produce H2, which opens interesting perspectives as hydrogen may have reacted with carbon species, or escaped and yield increasingly oxidizing conditions in the parent asteroid. From the results of this nanoscale study, we also propose transformations of the initial cronstedtite, destabilized by later input of Al- and Mg-rich solutions, leading to Fe2+ leaching from serpentines, as well as to random serpentine-chlorite interstratifications. Such transformations towards polysomatic assemblages that are un-equilibrated from the structural, chemical and redox point of views are probably controlled by the various rates of alteration of primary minerals, but also by porosity gradients, as in terrestrial hydrothermal systems. We suggest that the proposed mechanisms may have played a role in the early formation of (Fe2+,Fe3+)-rich serpentines documented in CM chondrites, as well as in their transformation with on-going alteration towards Fe-poorer compositions inferred from previous petrologic, mineralogical and magnetic studies of CM chondrites.

Reference
Elmaleh A, Bourdelle F, Caste F, Benzerara K, Leroux H, Devouard B (2015) Formation and transformations of Fe-rich serpentines by asteroidal aqueous alteration processes: A nanoscale study of the Murray chondrite. Geochimica et Cosmochimica Acta (in Press)
Link to Article [doi:10.1016/j.gca.2015.03.007]

Copyright Elsevier

^1,4M. D. Hopkins,^1,2,3S. J. Mojzsis
¹Department of Geological Sciences, NASA Lunar Science Institute Center for Lunar Origin and Evolution (CLOE), University of Colorado, UCB 399, 2200 Colorado Avenue, Boulder, CO, 80309-0399, USA
²Laboratoire de Géologie de Lyon, École Normale Supérieure de Lyon, CNRS UMR 5276, Université Claude Bernard Lyon 1, 46 Allée d’Italie, 69007, Lyon, France
³Research Center for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Hungarian Academy of Sciences, 45 Budaörsi Street, Budapest, 1112, Hungary
⁴Department of Earth Science, Santa Monica College, 1900 Pico Boulevard, Santa Monica, CA, 90405, USA

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

Reference
Hopkins MD, Mojzsis SJ (2015) A protracted timeline for lunar bombardment from mineral chemistry, Ti thermometry and U–Pb geochronology of Apollo 14 melt breccia zircons. Contributions to Mineralogy and Petrology 169:30
Link to Article [DOI 10.1007/s00410-015-1123-x]

¹Donald S. Burnett et al. (>10)*
¹California Institute of Technology, Pasadena, CA, USA
*Find the extensive, full author and affiliation list on the publishers Website

Ion microprobe elemental and isotopic determinations can be precise but difficult to quantify. Error is introduced when the reference material and the sample to be analysed have different compositions. Mitigation of such ‘matrix effects’ is possible using ion implants. If a compositionally homogeneous reference material is available which is ‘matrix-appropriate’ (i.e., close in major element composition to the sample to be analysed, but having an unknown concentration of the element, E, to be determined) then ion implantation can be used to introduce a known amount of an E isotope, calibrating the E concentration and producing a matrix-appropriate calibrator. Nominal implant fluences (ions cm−2) are inaccurate by amounts up to approximately 30%. However, ion implantation gives uniform fluences over large areas; thus, it is possible to ‘co-implant’ an additional reference material of any bulk composition having known amounts of E, independently calibrating the implant fluence. Isotope ratio measurement standards can be produced by implanting two different isotopes, but permil level precision requires postimplant calibration of the implant isotopic ratio. Examples discussed include (a) standardising Li in melilite; (b) calibrating a 25Mg implant fluence using NIST SRM 617 glass and (c) using Si co-implanted with 25Mg alongside NIST SRM 617 to produce a calibrated measurement of Mg in Si.

Reference
Burnett DS et al. (2015) Ion Implants as Matrix-Appropriate Calibrators for Geochemical Ion Probe Analyses. Geostandards and Geoanalytical Research (in Press)
Link to Article [DOI: 10.1111/j.1751-908X.2014.00318.x]

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