Glasses in coarse-grained micrometeorites

Micrometeorites (MMs, interplanetary dust particles with 25 - 500 μm diameters) carry the main mass of extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed. Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere), which caused a range from very little chemical modification of the glass to total melting of the precursor object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical modification, e.g., metasomatic enrichments in Na and Fe2+ presumably in the solar nebula. Glasses of MMs heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild 2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents samples from comets. © 2009 Elsevier B.V. All rights reserved.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, G.. Universidad de Viena; Austri

Characterization of the noble gases and CRE age of the D'Orbigny angrite

Introduction: The D’Orbigny angrite, a 16.55 kg stone, was found 1979 in Argentina [1]. Mineralogy and chemistry of this meteorite were characterized in detail [2-6]. A Pb-U-Th age of 4.559 Ga was obtained for pyroxenes by Jagoutz et al. [7]. Here we report results on the noble gas isotopic composition and, in particular, on the cosmic-ray exposure (CRE) age of D’Orbigny

Glasses in meteorites and the Primary Liquid Condensation Model

Meteoritic glasses are quenched samples of the silicate liquid that was involved in the formation of chondritic constituents and achondritic rocks. Conventional genetic models see them as residual liquids from which the associated minerals crystallized – as demonstrated by terrestrial igneous rocks – or as locally produced impact melts. These models are all closely related to our experiences with terrestrial geology and petrology and, consequently,make planetary processes, such asmixing andmelting of solid precursors and planetary differentiation primarily responsible for the formation of the large variety of meteoritic rocks. However, different types of glasses (e.g., glass inclusions in minerals, mesostasis glasses, glass pockets, glass veins) in a variety of meteorites (chondrites and achondrites) have particular chemical features that cannot be reconciled with these models: 1)Glasses do not showthe chemical signature of crystallization of theminerals they are associated with – a geochemical impossibility; 2) All types of glasses in all types of meteorites reported here show very similar trace element abundance pattern with the refractory lithophile element abundances at ~ 10–20 x CI chondrite abundances. 3) All refractory element abundance patterns in primitive glasses have unfractionated solar relative abundances (they are flat) and medium refractory and volatile elements are depleted relative to the refractory elements. 4) Medium volatile and volatile elements, when present, display chaotic abundance patterns. The ubiquitous pattern for refractory elements signals vapor fractionation rather than geochemical (“igneous”) fractionation or stochasticmixing of precursorminerals (as in shockmelts). It indicates that the same process must have been involved in the origin of all glasses in chondritic constituents aswell as achondritic rocks and, consequently, in the formation of allmeteorite types investigated. The chaotic abundances of volatile elements signal that chaotic processes were involved during condensation. 279 Herewe present a newmodel - the Primary Liquid Condensation (PLC)model – as an alternative to the currently acceptedmodels for the formation ofmeteoritic rocks. The PLCmodel is capable of accommodating all observational and chemical data accumulated so far on meteorites – with the exception of enstatite and SNC meteorites, which record physico-chemical conditions that were different fromthose of themajority ofmeteoritic rocks (the processes, however, could have been the same). The new model identifies a new role for silicate liquids in cosmochemistry as being an essential phase for the formation of early crystalline condensates from the hot solar nebula. Liquids are identified to have been the first major phase to condense from the solar nebula. In order to be capable to produce early liquid condensates, the nebula must have been either enriched in condensable elements over solar abundances (> 500 times) or was at total pressuresmuch higher than the canonically predicted ones (> 500 times, > 0.5 bar ). Our data require that this liquid – we named it “universal liquid” (UL) - had a refractory composition (Ca-Mg-Al-silicate or CMAS) and facilitated condensation of the major minerals for chondritic constituents as well as for achondritic rocks. The process possibly was a variant of the vapor-liquid-solid (VLS) condensation process, which is utilized in industrial crystal growth. Thereby, the liquid condenses first, then nucleates a crystal of the species that is oversaturated in the vapor – in the case of the solar nebula usually olivine. As this olivine grows from the liquid, it depletes the liquid in Mg and Si. The liquid tries to maintain equilibrium with the solar nebula. Thereby, Mg and Si are replenished by condensation from the gas phase and all incompatible elements are kept at an equilibrium concentration by condensation-evaporation equilibrium. Thus, the contents of incompatible refractory elements are kept at an approximately constant level throughout crystallization of the major minerals olivine and pyroxene. This way not only the abundances of incompatible refractory elements are kept at a constant level but also their relative abundances remain unfractionated solar. The UL also represents the long sought for refractory component of chondritic constituents and appears also to be the source of achondritic “igneous” rocks. Variations in the amount of liquid available, the liquid condensation and crystal nucleation rates, as well as different crystal-liquid mixing proportion will allow the formation of objects of highly variable composition. The final composition (chemical and isotopic) of any chondritic object or achondrite, as well as that of the associated glasses, will be determined by different degrees of post-formational metasomatic elemental exchange processes taking place between solids and the cooling nebular gas. These processes add medium volatile and volatile elements to the products of high temperature condensation. As these processes usually don’t run to completion, an infinite number of chaotic compositional variations are produced – and this is exactly what we observe in meteorites.Fil: Varela, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Kurat, G.. Vienna University of Technology; Austri

Scheme for preparation of W state via cavity QED

In this paper, we presented a physical scheme to generate the multi-cavity maximally entangled W state via cavity QED. All the operations needed in this scheme are to modulate the interaction time only once.Comment: 8 pages, 1 figur

STONE 6: Artificial Sedimentary Meteorites in Space

The STONE 6 experiment demonstrated the survivability of carbonaceous and microfossiliferous martian analogue sediments during atmospheric re-entry. Doped endoliths died but their carbonised cells remained

Flexibility of a Eukaryotic Lipidome – Insights from Yeast Lipidomics

Mass spectrometry-based shotgun lipidomics has enabled the quantitative and comprehensive assessment of cellular lipid compositions. The yeast Saccharomyces cerevisiae has proven to be a particularly valuable experimental system for studying lipid-related cellular processes. Here, by applying our shotgun lipidomics platform, we investigated the influence of a variety of commonly used growth conditions on the yeast lipidome, including glycerophospholipids, triglycerides, ergosterol as well as complex sphingolipids. This extensive dataset allowed for a quantitative description of the intrinsic flexibility of a eukaryotic lipidome, thereby providing new insights into the adjustments of lipid biosynthetic pathways. In addition, we established a baseline for future lipidomic experiments in yeast. Finally, flexibility of lipidomic features is proposed as a new parameter for the description of the physiological state of an organism

Dual Lipolytic Control of Body Fat Storage and Mobilization in Drosophila

Energy homeostasis is a fundamental property of animal life, providing a genetically fixed balance between fat storage and mobilization. The importance of body fat regulation is emphasized by dysfunctions resulting in obesity and lipodystrophy in humans. Packaging of storage fat in intracellular lipid droplets, and the various molecules and mechanisms guiding storage-fat mobilization, are conserved between mammals and insects. We generated a Drosophila mutant lacking the receptor (AKHR) of the adipokinetic hormone signaling pathway, an insect lipolytic pathway related to ß-adrenergic signaling in mammals. Combined genetic, physiological, and biochemical analyses provide in vivo evidence that AKHR is as important for chronic accumulation and acute mobilization of storage fat as is the Brummer lipase, the homolog of mammalian adipose triglyceride lipase (ATGL). Simultaneous loss of Brummer and AKHR causes extreme obesity and blocks acute storage-fat mobilization in flies. Our data demonstrate that storage-fat mobilization in the fly is coordinated by two lipocatabolic systems, which are essential to adjust normal body fat content and ensure lifelong fat-storage homeostasis

Diamondites: evidence for a distinct tectono-thermal diamond-forming event beneath the Kaapvaal craton

The petrogenesis and relationship of diamondite to well-studied monocrystalline and fibrous diamonds are poorly understood yet would potentially reveal new aspects of how diamond-forming fluids are transported through the lithosphere and equilibrate with surrounding silicates. Of 22 silicate- and oxide-bearing diamondites investigated, most yielded garnet intergrowths (n = 15) with major element geochemistry (i.e. Ca–Cr) classifying these samples as low-Ca websteritic or eclogitic. The garnet REE patterns fit an equilibrium model suggesting the diamond-forming fluid shares an affinity with high-density fluids (HDF) observed in fibrous diamonds, specifically on the join between the saline–carbonate end-members. The δ13C values for the diamonds range from − 5.27 to − 22.48‰ (V-PDB) with δ18O values for websteritic garnets ranging from + 7.6 to + 5.9‰ (V-SMOW). The combined C–O stable isotope data support a model for a hydrothermally altered and organic carbon-bearing subducted crustal source(s) for the diamond- and garnet-forming media. The nitrogen aggregation states of the diamonds require that diamondite-formation event(s) pre-dates fibrous diamond-formation and post-dates most of the gem monocrystalline diamond-formation events at Orapa. The modelled fluid compositions responsible for the precipitation of diamondites match the fluid-poor and fluid-rich (fibrous) monocrystalline diamonds, where all grow from HDFs within the saline-silicic-carbonatitic ternary system. However, while the nature of the parental fluid(s) share a common lithophile element geochemical affinity, the origin(s) of the saline, silicic, and/or carbonatitic components of these HDFs do not always share a common origin. Therefore, it is wholly conceivable that the diamondites are evidence of a distinct and temporally unconstrained tectono-thermal diamond-forming event beneath the Kaapvaal craton