<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Primordial and other noble gases in micrometeorites"^^ . "The present study, realized within the framework of the DFG (Deutsche Forschungsgemeinschaft) SPP (Special Priority Program) 1385 \"The First 10 Million\r\nYears of the Solar System - a Planetary Materials Approach\", addresses the\r\nproposition of analyzing micrometeorites (MMs) (sizes of 50μm - 1mm) on their noble\r\ngas content along with their isotopic composition. The experimental studies and the\r\ndissertation was performed at the Max-Planck-Institute for Chemistry in Mainz in\r\ncollaboration with the Heidelberg University since 2010. In particular, the similarities\r\nand differences of MMs to larger meteorites were studied. Also of interest was the\r\nthermal history of MMs along with changes in their noble gas inventory while passing\r\nEarth's atmosphere. In our study we focused on xenon especially in unmelted MMs.\r\nThis required the operation of a special version of a noble gas mass spectrometer\r\n(MS) which in this case was the \"Noblesse\" from Nu Instruments. Continuous care\r\nand optimization of the measurement methods were essential. The specialty of this\r\ndevice is the ion-counting multicollector system for especially high sensitivity and\r\ndetection of small amounts of noble gases. Worldwide there is only one more device\r\nof this type, at Washington University, St. Louis (USA), where, among other things,\r\nthe solar wind noble gases of the Genesis mission have been determined.\r\nTwo different groups of micrometeorites were examined. Firstly MMs collected\r\nfrom a geological trap on top of the Miller Butte ridge, in the area of the\r\nTransantarctic Mountains. These micrometeorites were spotted and collected by\r\nLuigi Folco, Pierre Rochette and colleagues during a PNRA mission (see Rochette et\r\nal. (2008)). The MMs are relatively large (250 - 1000 μm), they sometimes show\r\nweathering and were deposited for probably about 1 Ma. In October 2010, with kind\r\ncooperation of Luigi Folco, Carole Cordier and Matthias van Ginneken, 103 particles\r\nof 51 micrometeorites (MMs) were selected for the noble gas measurements. These\r\nMMs consist of the following three main groups - \"Cosmic spherules - CS \" (more or\r\nless glass spherules caused by complete melting of unmelted MMs), \"scoriaceous\r\nMMs - ScMMs\" (partially molten MMs ) and \"unmelted MMs - UnMMs. The melting\r\nprocesses are caused by the entry and passage of these small extraterrestrial\r\nparticles through the Earth's atmosphere.\r\nThe second group of MMs originated from the snow of the central region of\r\nAntarctica (Dome C (DC) - CONCORDIA Collection (see Duprat et al. (2007)) and\r\nfrom Cap Prudhomme (CP) (Maurette et al. (1991)). These particles were extracted\r\nand collected by melting snow of the Dome C area and are particularly small. The\r\nMMs are deposited only for a short time period (a few decades), thus are \"fresh\" and\r\nrelatively unweathered. In November 2010, samples of these MMs were provided\r\nwith kind support by Jean Duprat, Cécile Engrand and Michel Maurette (University of\r\nSouth-Paris, on the campus in Orsay, France). We were able to acquire a total of 50\r\nMM particles from 28 different MMs. Among them were crystalline (Xtal), fine-grained\r\nunmelted and carbonaceous (FgC) and partially molten (Sc) micrometeorites.\r\nBefore the first MM measurements were carried out, the measuring facility was\r\ntested on reliability and accuracy by using small particles of larger meteorites. We\r\ngradually degassed the MMs by using a 30W CO2-Laser system. For a complete degassing \r\na power of ~1W was sufficient in most cases. After extraction, the inert\r\ngases were partitioned in He + Ne, Ar, Kr and Xe fractions. Furthermore, Ar, Kr and\r\nXe were adsorbed at a cold trap filled with active charcoal. Then the noble gases\r\nsuccessively were analyzed using the \"Noblesse\". The sample measurements were\r\nsupplemented by \"blank\" and calibration measurements.\r\nA total of 29 particles of 25 different TAM MMs and 11 particles of a total of 10\r\ndifferent DC and CP MMs were measured.\r\nFor most of the particles we were able release sufficient noble gas quantities.\r\nHowever, in particular the very strongly melted \"Cosmic spherules \" and some of the\r\nless melted \"scoriaceous MMs\" showed clear signs of pre-degassing, probably\r\nthrough the interaction with the Earth's atmosphere. The MMs of Dome C and Cap\r\nPrudhomme are very small, but, however, the vast majority of these samples shows\r\nhigh noble gas concentrations compared to the TAM MMs.\r\nMeasured 3He/4He ratios were between 0.9 x 10-4 and 149 x 10-4 for the TAM\r\nMMs and between 3 x 10-4 and 50 x 10-4 for the MMs of DC and CP, although\r\nsometimes with accompanied large uncertainties. Part of the TAM UnMMs and the\r\nDC MMs showed a composition in the range between solar wind (SW) and\r\nfractionated solar wind (\"FSW\"). The other (slightly more abundant) part showed -\r\nbeside SW - significant signs of cosmogenic 3He contributions.\r\nAlso in neon, most of the Un- and ScMMs clearly showed signs of solar wind\r\nand spallogenic contributions, the latter especially within the TAM MMs 45c.29,\r\n45b.17 and 45b.08. Here, not surprisingly, in particular the CS and ScMMs show\r\nclear traces of Earth's atmosphere records. The highest measured concentrations for\r\nsolar 20Ne in the TAM MMs were measured in UnMM X1 (~3.5 x 10-6 cc/g), whereas\r\nin the case of MMs from DC and CP this was DC 06_09_149 with ~8.0 x 10-5 cc/g.\r\nThe DC values are in the range of what has been found for Dome Fuji MMs\r\nmeasured by Osawa and Nagao (2002). The values for the TAM MMs are\r\nsignificantly lower.\r\nThe fact that for most TAM and DC/CP MMs the 40Ar/36Ar ratios are\r\nconsiderable lower than in air (40Ar/36Ar = 298.56; Lee et al. (2006)) suggests that\r\nthese samples include extraterrestrial primordial Ar. Air contamination was indeed\r\ndetectable, but except for 40Ar usually negligible. The lowest 40Ar/36Ar of 2.0 ± 1.8\r\nwas found for TAM UnMM 45c.33(1). The next lowest value, with a much smaller\r\nuncertainty is that of TAM MM 45c.35(3), with 4.1 ± 0.1. In the same context the low\r\n38Ar/36Ar ratio of 0.185 ± 0.002 indicates a high proportion of the planetary\r\ncomponent \"Q(P1)\". This component is detected in higher concentrations in\r\ncarbonaceous chondrites. The same is true for the crystalline Dome C MM DC\r\n06_09_149 which shows 40Ar/36Ar = 5.62 and 38Ar/36Ar = 0.186.\r\nKrypton in extraterrestrial samples typically shows only small variations in its\r\nisotopic composition and pure Kr evaluations are challenging. Nevertheless, for most\r\nof the MMs sufficient Kr-amounts were detected and particularly in association with\r\nthe results for Ar and Xe interpretations are conceivable. It seems that especially\r\nisotopic fractionation processes are explainable by using combined elemental and\r\nisotopic plots of Ar, Kr and Xe. Here, isotopic fractionation processes are clearly\r\npresent and often occur due to Earth atmosphere transitions of MMs, extraterrestrial\r\nradiation as well as terrestrial weathering. An example is 36Ar/132Xe versus 84Kr/132Xe, \r\nwhich shows for most of the ScMMs and CS a clear indication of fractionated air. The\r\nunmelted UnMMs, however, show noble gas compositions similar to Q (P1). A few\r\nMMs indicate a solar influence not only in He and Ne, but also in Ar - especially in the\r\ncase of TAM UnMM X1 as well as a number of DC MMs .\r\nThe main focus of the measurements was on xenon. On the one hand, the MS\r\n\"Noblesse\" gave us the opportunity to measure Xe in small quantities along with high\r\nsensitivities. On the other hand, so far, Xe has not been adequately measured within\r\nMMs. The results in this work represent a significant improvement compared to\r\nprevious measurements of Osawa and Nagao (2002). Of the overall 29 TAM MMs we\r\nwere able to analyze Xe for 24 particles, however, partially and in particular for the\r\nlight Xe isotopes with large uncertainties. Here, UnMM 45c.35(3) shows the highest\r\nconcentration of 132Xe with ~1.1 x 10-8 cc STP/g. The highest concentration for DC\r\nand CP MMs was found in DC 06_09_189, with ~1.7 x 10-7 cc STP/g. Overall,\r\nhowever, the Xe concentration was for both, the TAM MMs as well as the DC and CP\r\nMMs, at a similar level.\r\nTwo distinct groupings are present. One group shows Xe with an isotopic\r\ncomposition similar to that of the Q(P1) component. This is usually true for the\r\nUnMMs. The other group shows Xe ratios similar to isotopically fractionated air Xe. A\r\nsingle MM sample is particularly and distinctly different of all others - 45c.29. The two\r\nmeasured particles of this MM show within all noble gas ratios increased, however,\r\nvariable spallogenic contributions. Also, this MM contains 244Pu fission Xe. The\r\nprobable origin (parent body) of this MM has so far not been revealed by both the\r\nnoble gas and by petrological and mineralogical studies and requires further\r\nresearch.\r\nUsing the detected spallogenic 21Ne concentrations for the two MMs of 45c.29\r\nand for 45b.17, we were able to calculate rather large CRE-ages of ~9-71 Ma.\r\nCosmogenic 38Ar, on the other hand, revealed a range of ~5-186 Ma. However, the\r\nmajority of TAM MMs show CRE-ages of less than 1 Ma. The cosmogenic contents\r\nin MMs of DC and CP were negligible due to the high levels of solar neon and solar /\r\nprimordial Ar. In addition, one must consider that the specimens may have lost a\r\nlarge proportion of their original trapped inventory during passage through the Earth's\r\natmosphere, especially concerning the lighter noble gases He and Ne.\r\nOn Earth, micrometeorites are explored in large numbers, located in a variety\r\nof mineralogical compositions as well as sizes and in different climatic regions -\r\ncertainly the best region would be those of ice and snow. Many MMs show alteration\r\nand weathering effects along with signs for interaction with the Earth's atmosphere.\r\nHowever, there exist some specimens, which are virtually unchanged and show the\r\ncomplete spectrum of extraterrestrial components. The results obtained in this work\r\nshow that the investigation of these particles may contribute to the understanding of\r\nthe origin of Earth's atmosphere - and thus also of other planetary atmospheres.\r\nFurthermore micrometeorites may also help to understand how tiny particles behave\r\nand evolve in the solar system.\r\n"^^ . "2014" . . . . . . . "Bastian"^^ . "Baecker"^^ . "Bastian Baecker"^^ . . . . . . "Primordial and other noble gases in micrometeorites (PDF)"^^ . . . "PrimordialAndOtherNobleGasesInMicrometeorites_Dissertation_BastianBaecker.pdf"^^ . . . "Primordial and other noble gases in micrometeorites (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Primordial and other noble gases in micrometeorites (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Primordial and other noble gases in micrometeorites (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Primordial and other noble gases in micrometeorites (Other)"^^ . . . . . . "medium.jpg"^^ . . . 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