T. Kohout1,2,¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Department of Physics, University of Helsinki, Helsinki, Finland
²Institute of Geology, Academy of Sciences of the Czech Republic, Prague, Czech Republic

X-ray microtomography (XMT), X-ray diffraction (XRD), and magnetic hysteresis measurements were used to determine micrometeorite internal structure, mineralogy, crystallography, and physical properties at μm resolution. The study samples include unmelted, partially melted (scoriaceous), and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types but also reveals changes in meteoroid properties during atmospheric entry at various velocities. At low entry velocities, meteoroids do not melt and their physical properties do not change. The porosity of unmelted micrometeorites varies considerably (0–12%) with one friable example having porosity around 50%. At higher velocities, the range of meteoroid porosity narrows, but average porosity increases (to 16–27%) due to volatile evaporation and partial melting (scoriaceous phase). Metal distribution seems to be mostly unaffected at this stage. At even higher entry velocities, complete melting follows the scoriaceous phase. Complete melting is accompanied by metal oxidation and redistribution, loss of porosity (1 ± 1%), and narrowing of the bulk (3.2 ± 0.5 g cm⁻³) and grain (3.3 ± 0.5 g cm⁻³) density range. Melted cosmic spherules with a barred olivine structure show an oriented crystallographic structure, whereas other subtypes do not.

Reference
Kohout et al. (in press) Density, porosity, mineralogy, and internal structure of cosmic dust and alteration of its properties during high-velocity atmospheric entry. Meteoritics & Planetary Science
[doi:10.1111/maps.12325]
Published by arrangement with John Wiley & Sons

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Weiming Cheng, Jiao Wang, Cong Wan

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

Reference
Cheng W, Wang J and Wan C (2014) Morphometric Characterization and Reconstruction Effect Among Lunar Impact Craters. Earth, Moon, and Planets 111:139.

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N. Biver¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France

A spectral survey in the 1 mm wavelength range was undertaken in the long-period comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy) using the 30 m telescope of the Institut de radioastronomie millimétrique (IRAM) in April and November−December 2013. We report the detection of ethylene glycol (CH₂OH)₂ (aGg’ conformer) and formamide (NH₂CHO) in the two comets. The abundances relative to water of ethylene glycol and formamide are 0.2–0.3% and 0.02% in the two comets, similar to the values measured in comet C/1995 O1 (Hale-Bopp). We also report the detection of HCOOH and CH₃CHO in comet C/2013 R1 (Lovejoy), and a search for other complex species (methyl formate, glycolaldehyde).

Reference
Biver et al. (2014) Complex organic molecules in comets C/2012 F6 (Lemmon) and C/2013 R1 (Lovejoy): detection of ethylene glycol and formamide. Astronomy & Astrophysics 566:L50.
[doi:10.1051/0004-6361/201423890]
Reproduced with permission © ESO

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Justin Filiberto^a, Allan H. Treiman^b, Paul A. Giesting^a,c, Cyrena A. Goodrich^d, Juliane Gross^e

^aSouthern Illinois University, Geology Department, Carbondale, IL 62901, USA
^bLunar and Planetary Institute, Houston, TX 77058, USA
^cIllinois State University, Department of Geography–Geology, Normal, IL 61790-4400, USA
^dPlanetary Science Institute, Tucson, AZ 85719, USA
^eAmerican Museum of Natural History, New York, NY 10024, USA

We report scapolite in a melt inclusion in olivine in Nakhla, which is the first occurrence of Cl-scapolite found in a martian meteorite. Using terrestrial metamorphic experiments and modeling we constrain its origin. Cl-rich scapolite in Nakhla is consistent with formation from either a late stage Cl-rich, water-poor magma or magmatic Cl-rich hydrothermal brine at a minimum temperature of 700 °C. The temperature of hydrothermal activity recorded by the Cl-scapolite is significantly higher than the temperatures recorded by alteration minerals in Nakhla, and the fluid was Cl-rich, not CO₂-rich. Our results demonstrate that high-temperature Cl-rich fluids were present within the martian crust, and any potential biologic activity would have to survive in these high temperatures and saline fluids. Halophiles can thrive in NaCl-rich systems but at significantly lower temperatures than those recorded by the scapolite. During cooling of the fluid, the system could have reached a habitable state for halophiles. Importantly, halophiles can survive the conditions of space if they are encased in salt crystals, and therefore chlorine-rich phases present an opportunity to investigate for extant life both on the surface of Mars and in martian meteorites.

Reference
Filiberto J, Treiman AH, Giesting PA, Goodrich CA and Gross J (2014) High-temperature chlorine-rich fluid in the martian crust: A precursor to habitability.  Earth and Planetary Science Letters 401:110.
[doi:10.1016/j.epsl.2014.06.003]
Copyright Elsevier
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Bridges¹ et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.

¹Applied Physics Laboratory, Laurel, Maryland, USA

Ventifacts, rocks abraded by wind-borne particles, are found in Gale Crater, Mars. In the eastward drive from “Bradbury Landing” to “Rocknest,” they account for about half of the float and outcrop seen by Curiosity’s cameras. Many are faceted and exhibit abrasion textures found at a range of scales, from submillimeter lineations to centimeter-scale facets, scallops, flutes, and grooves. The drive path geometry in the first 100 sols of the mission emphasized the identification of abrasion facets and textures formed by westerly flow. This upwind direction is inconsistent with predictions based on models and the orientation of regional dunes, suggesting that these ventifact features formed from very rare high-speed winds. The absence of active sand and evidence for deflation in the area indicates that most of the ventifacts are fossil features experiencing little abrasion today.

Reference
Bridges et al. (in press) The rock abrasion record at Gale Crater: Mars Science Laboratory results from Bradbury Landing to Rocknest.  Journal of Geophysical Research: Planets
[doi:10.1002/2013JE004579]
Published by arrangement with John Wiley & Sons
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Marissa J. F. Rosenberg¹, Olivier Berné^2,3 and Christiaan Boersma⁴

¹Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
²Université de Toulouse, UPS-OMP, IRAP, Toulouse, France
³CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁴NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-0001, USA

The mid-infrared (mid-IR; 5–15 μm) spectrum of a wide variety of astronomical objects exhibits a set of broad emission features at 6.2, 7.7, 8.6, 11.3, and 12.7 μm. About 30 years ago it was proposed that these signatures are due to emission from a family of UV heated nanometer-sized carbonaceous molecules known as polycyclic aromatic hydrocarbons (PAHs), causing them to be referred to as aromatic IR bands (AIBs). Today, the acceptance of the PAH model is far from settled, as the identification of a single PAH in space has not yet been successful, and physically relevant theoretical models involving true PAH cross sections do not reproduce the AIBs in detail. In this paper, we use the NASA Ames PAH IR Spectroscopic Database, which contains over 500 quantum-computed spectra, in conjunction with a simple emission model, to show that the spectrum produced by any random mixture of at least 30 PAHs converges to the same kernel-spectrum. This kernel-spectrum captures the essence of the PAH emission spectrum and is highly correlated with observations of AIBs, strongly supporting PAHs as their source. Furthermore, the fact that a large number of molecules are required implies that spectroscopic signatures of the individual PAHs contributing to the AIBs spanning the visible, near-IR, and far-IR spectral regions are weak, explaining why they have not yet been detected. An improved effort, joining laboratory, theoretical, and observational studies of the PAH emission process, will support the use of PAH features as a probe of physical and chemical conditions in the near and distant Universe.

Reference
Rosenberg MJF, Berné O and Boersma C (2014) Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission.  Astronomy & Astrophysics 566:L4.
[doi:10.1051/0004-6361/201423953]
Reproduced with permission © ESO
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P. Koten^a, J. Vaubaillon^b, D. Čapek^a, V. Vojáček^a, P. Spurný^a, R. Štork^a, F. Colas^b

^aAstronomical Institute of the Academy of Sciences, Ondřejov Observatory, Fričova 298, 25165 Ondřejov, Czech Republic
^bInstitut de Mécanique Céleste et de Calcul des Éphémérides – Observatoire de Paris, 77 avenue Denfert-Rochereau, 75014, Paris, France

The very next year following the fall of Neuschwanstein meteorites and discovery of their orbital similarity with the Příbram meteorite, dedicated observational campaigns aiming for the detection of faint meteors on similar orbits were started. The goal of this paper is to process all the data collected within 7 years, to analyse their atmospheric trajectories and heliocentric orbits and to investigate the possibility that they belong to the stream.

The trajectories and orbits of the detected meteors were used to determine whether those meteors are members of the same shower. An orbital evolution model was applied on a certain number of cloned particles to investigate their possible connection with the meteorite stream. Statistical tests were conducted to determine if such small sample of the orbits is similar by chance or if the stream is real. It was found that from the observational as well as the theoretical point of view it is impossible to prove the existence of faint meteor shower connected with the Příbram and Neuschwanstein meteorite stream.

Reference
Koten P, Vaubaillon J, Čapek D, Vojáček V, Spurný P, Štork R and Colas F (in press) Search for faint meteors on the orbits of Příbram and Neuschwanstein meteorites.  Icarus
[doi:10.1016/j.icarus.2014.06.014]
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Paul H. Warrena, Alan E. Rubina, Junko Isaa, Nicholas Gesslerb, Insu Ahnc, Byeon-Gak Choic

^aInstitute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, USA
^bInformation Science & Information Studies Program, Duke University, Durham, NC 27708 USA
^cEarth Science Education, Seoul National University, Seoul 151-748, Korea

The Northwest Africa 5738 eucrite contains a record of unprecedented geochemical complexity for a sample from the HED asteroid. It originated with a uniquely evolved (Stannern Trend) primary igneous composition, combining ultra-high bulk incompatible element and Na₂O concentrations with a relatively low mg. Its bulk oxygen-isotopic composition (Δ’¹⁷O = – 0.27 ‰), as well as its trace element composition (e.g., Ga/Al), confirm other evidence for classification as a eucrite. Pyroxene mg equilibration, exsolution and “cloudy” inclusions, all reflect a typical eucritic degree of thermal metamorphism. The rock contains an unprecedented array of microscopic fluid-metasomatic vein deposits. Most common are curvy microveins within pyroxene, which consist dominantly of Ca-plagioclase (typically An₉₅, in stark contrast with the rock’s An_68-78 primary-igneous plagioclase), with Fe-olivine (Fo₁₄) and Cr-spinel as additional major constituents. Likely related to these microveins are small masses of intergrown Ca-plagioclase (again roughly An₉₅) and silica (or high-Si glass). Analyses of the microvein Cr-spinels show stoichiometry implying a significant Fe³⁺ content (Fe₂O₃0.7-2.3 wt%), and fO₂ up to roughly IW+3; clearly elevated in comparison to the normal HED fO₂ of about IW-1. The fO₂ results show an anticorrelation with equilibration T (and with Mg/Fe), which suggests the parent fluid system became more oxidizing as it cooled. NWA 5738 also contains apparent secondary iron metal. The Fe-metals are very pure, with Ni consistently below an EPMA detection limit of ∼0.01 wt%. The vein-like shapes of roughly 1/3 of the largest Fe-metals suggest origin by deposition from a fluid. The role of pyroxene exsolution as template for a denticular (sawtooth) Fe-metal edge shape, and the survival of Fo₁₄ olivine in a rock with abundant silica and a far higher bulk mg, suggest that the most intense thermal metamorphism occurred no later than the secondary alteration. Near-complete lack of spatial association suggests that the Fe-metals formed during a distinct time period from the curvy microveins. The immediate cause of Fe-metal deposition was most plausibly (or anyway, least implausibly) an abrupt downshift in the fluid fO₂. Considering the extremely evolved bulk composition, the fluid(s) may have been largely deuteric. However, more likely the main source of fluid was a nearby buried mass of volatile-rich impactor matter, such as carbonaceous chondrite, that hit the asteroid at low enough velocity to remain mostly intact. We further speculate that the abrupt drop in fluid fO₂ may have been caused by a process of carbon-fueled “smelting” (cf. ureilites), triggered by an impact-effected shift of the carbonaceous material to a changed environment, with higher Tand/or lower P. These and other recent eucrite results point to a need for greater scrutiny regarding the absence of comparable alteration-veining in rocks from the lunar highland crust, a mysterious lack in view of recent evidence for abundant lunar water.

Reference
Warren PH, Rubin AE, Isa J, Gessler N, Ahn I and Choi B-G (in press) Northwest Africa 5738: Multistage fluid-driven secondary alteration in an extraordinarily evolved eucrite. Geochimica et Cosmochimica Acta
[doi:10.1016/j.gca.2014.06.008]
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Derek W. G. Sears

NASA Ames Research Center/Bay Area Environmental Research Institute, Space Science and Astrobiology Division, Mountain View, California, USA

Vagn Buchwald (Fig. 1) was born in Copenhagen where he attended school and college. Then after 18 months of military service, he assumed a position at the Technical University of Copenhagen. A few years later, he was presented with a piece of the Cape York meteorite, which led to an interest in iron meteorites. Through a campaign of informed searching, Vagn found the 20 ton Agpalilik meteorite (part of the Cape York shower) on 31st July 1963 and by September 1967 had arranged its transport to Copenhagen. After sorting and describing the Danish collection, which included application of the Fe-Ni-P phase diagram to iron meteorite mineralogy, Vagn was invited to sort and describe other iron meteorite collections. This led to a 7 yr project to write his monumental Handbook of Iron Meteorites. Vagn spent 3 yr in the United States and visited most of the world’s museums, the visit to Berlin being especially important since the war had left their iron meteorites in bad condition and without labels. During a further decade or more of iron meteorite research, he documented natural and anthropomorphic alterations experienced by iron meteorites, discovered five new minerals (roaldite, carlsbergite, akaganeite, hibbingite, and arupite); had a mineral (buchwaldite, NaCaPO₄) and asteroid (3209 Buchwald 1982 BL1) named after him; and led expeditions to Chile, Namibia, and South Africa in search of iron meteorites and information on them. Vagn then turned his attention to archeological metal artifacts. This work resulted in many papers and culminated in two major books on the subject published in 2005 and 2008, after his retirement in 1998. Vagn Buchwald has received numerous Scandinavian awards and honors, and served as president of the Meteoritical Society in 1981–1982.

Reference
Sears DWG (in press) Oral histories in meteoritics and planetary science—XXV: Vagn F. Buchwald. Meteoritics & Planetary Science
[doi:10.1111/maps.12332]
Published by arrangement with John Wiley & Sons

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Danielle Piskorz and David J. Stevenson

Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125

The giant impact hypothesis for the origin of the Moon points to the creation of a hot, young moon, likely with a global magma ocean. Such a magma ocean would produce a flotation crust of plagioclase crystals, or an anorthositic crust. Early calculations of the expected anorthosite content of the lunar highlands crust did not match initial measurements of Apollo samples, and more recently have not matched Clementine measurements or SELENE measurements, because they assumed interstitial melt would freeze. We consider a physical model of a magma ocean with an accumulating flotation lid, and find that significant escape of melt can take place for reasonable physical parameters and timescales of melt migration, even allowing for the inhibiting effect of plausible compaction viscosities. This model permits more nearly pure lunar anorthosites, consistent with observations. The model encounters some difficulty in explaining the expulsion of melt for the near-surface crust (up to five-kilometers’ depth) that presumably dominates the Apollo samples, suggesting that impact mixing and tidal heating are needed to explain the discrepancy.

Reference
Piskorz D and Stevenson DJ (in press) The Formation of Pure Anorthosite on the Moon. Icarus
[doi:10.1016/j.icarus.2014.06.015]
Copyright Elsevier

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