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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 323 (1986), S. 138-140 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Nitrogen isotopic measurements performed by Prombo and Clayton7'9 were restricted by sensitivity limitations to a comparison of the total nitrogen extracted from metal and silicate inclusions with that extracted from the parent sample. Interestingly, the bulk meteorite gave higher 515N values (+923 ...
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  • 2
    ISSN: 1751-908X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses.
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  • 3
    Publication Date: 2013-08-31
    Description: Nitrogen is the second most abundant constituent of the Martian atmosphere, after CO2, present at a level of ca. 2.7 percent. Several authors have hypothesized that earlier in the planet's history, nitrogen was more abundant, but has been removed by processes such as exospheric loss from the atmosphere. However, an alternative sink for atmospheric nitrogen is the regolith; model calculations have predicted that, via the formation of NOx, HNO2 and HNO3 in the lower layers of the Martian atmosphere, the regolith might trap nitrite and nitrate anions, leading to the build-up of involatile nitrates. Integrated over 4.5 x 10(exp 9) yr, such a mechanism would contribute the equivalent of a layer of nitrates up to 0.3 cm thick distributed across the Martian surface. Features in thermal emission spectra of the surface of Mars have been interpreted tentatively as emanating from various anions (carbonates, bicarbonates, sulphates, etc.), and the presence of nitrates has also been addressed as a possibility. The identification of carbonates in SCN meteorites has allowed inferences to be drawn concerning the composition and evolution of the Martian atmosphere in terms of its carbon isotope systematics; if nitrites, nitrates, or other nitrogen-bearing salts could be isolated from SNC's, similar conclusions might be possible for an analogous nitrogen cycle. Nitrates are unstable, being readily soluble in water, and decomposed at temperatures between 50 C and 600 C, depending on composition. Any nitrates present in SNC's might be removed during ejection from the planet's surface, passage to Earth, or during the sample's terrestrial history, by weathering etc. The same might have been said for carbonates, but pockets of shock-produced glass (lithology C) from within the EET A79001 shergottite and bulk samples of other SNC contain this mineral, which did apparently survive. Nitrates occurring within the glassy melt pockets of lithology C in EET A79001 might likewise be protected. Lithology C glass was therefore selected for nitrate analysis, first by non-destructive infra red spectroscopy, and then by stepped combustion.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 553-554
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  • 4
    Publication Date: 2019-07-19
    Description: Northwest Africa (NWA) 7034 and its pairings comprise a regolith breccia with a basaltic bulk composition [1] that yields a better match than any other martian meteorite to estimates of Mars' bulk crust composition [1]. Given the similarities between NWA 7034 and the martian crust, NWA 7034 may represent an important sample for constraining the crustal composition of components that cannot be measured directly by remote sensing. In the present study, we seek to constrain the H isotopic composition of the martian crust using Cl-rich apatite in NWA 7034.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-36304 , Goldschmidt 2016; Jun 26, 2016 - Jul 01, 2016; Yokohama; Japan
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  • 5
    Publication Date: 2019-07-19
    Description: It has long been known that certain basaltic achondrites share similarities with eucrites. These eucrite-like achondrites have distinct isotopic compositions and petrologic characteristics indicative of formation on a separate parent body from the howardite-eucrite-diogenite (HED) clan (e.g., Ibitira, Northwest Africa (NWA) 011). Others show smaller isotopic variations but are otherwise petrologically and compositionally indistinguishable from basaltic eucrites (e.g., Pasamonte, Pecora Escarpment (PCA) 91007). The Emmaville eucrite has a delta O-17 value of -0.137 plus or minus 0.024 per mille (1 sigma), which is substantially different from the eucrite mean of -0.246 plus or minus 0.014 per mille (2 sigma), but similar to those of A-881394 and Bunburra Rockhole (BR). Currently little data exist for Emmaville in terms of petrology or bulk composition. Studying anomalous eucrites allows us to more completely understand the numbers of asteroids represented by eucrite- like basalts and thus constrain the heterogeneity of the HED suite. In this study, we present our preliminary petrological and mineral composition results for Emmaville.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-32741 , Lunar and Planetary Science Conference; Mar 16, 2015 - Mar 20, 2015; The Woodlands, TX; United States
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  • 6
    Publication Date: 2019-07-17
    Description: The rate of discovery of new Near Earth Asteroids (NEAs) and the success of D-S 1 and NEAR-Shoemaker, suggest that sample return from NEAs is now technically feasible. Here we present a summary of a recent workshop on the topic. Additional information is contained in the original extended abstract.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXII; LPI-Contrib-1080
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  • 7
    Publication Date: 2019-07-13
    Description: As originally demonstrated by Clayton and co-workers, primitive meteorites and their components commonly display mass-independent oxygen isotopic variation. As a tool to understand this behaviour, a number of reference lines have been defined, with slopes of approximately 1. The Carbonaceous Chondrite Anhydrous Mineral (CCAM) line, derived predominantly from analyses of components in the Allende (CV3) meteorite, is the most widely used reference and has a slope of 0.94 plus or minus 0.01 (2 sigma). However, the fundamental significance of the CCAM line has been questioned. Based on the results of a UV laser ablation study of an Allende CAI (calcium-aluminumrich inclusion), it was suggested that a line of exactly slope 1 (Y&R line - Young and Russell line) was of more fundamental significance. SIMS (Secondary Ion Mass Spectrometry) analysis of chondrules from primitive CRs and related chondrites define a third, distinct slope 1 line, known as the Primitive Chondrule Minerals (PCM) line. Here we discuss the results of bulk oxygen isotope analysis of CO, CV and CR chondrites and various separated components, with the aim of better understanding the origin of slope 1 behaviour in early Solar System materials.
    Keywords: Astrophysics
    Type: JSC-E-DAA-TN56757 , Annual Meeting of the Meteoritical Society 2018; Jul 22, 2018 - Jul 27, 2018; Moscow; Russia
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  • 8
    Publication Date: 2019-01-25
    Description: Nitrogen is one of the enigmatic elements in lunar soils and breccias. The large range in (delta)N-15 values found within lunar soils was initially attributed to a secular increase in the N-15/N-14 ratio of 50 percent within the solar corona, and hence in the implanted nitrogen within the lunar regolith. However, more recent explanations have proposed a two (or many) component mixing model of solar wind nitrogen with some hypothetical non-solar components. Such components could include indigenous lunar nitrogen, nitrogen contained in interstellar grains in primitive meteorites, and magnetospheric nitrogen from the terrestrial atmosphere. To understand the makeup of multi-component mixtures it is advantageous to have carbon and noble gas data measured simultaneously, particularly in the case of lunar soils, where the solar wind is a likely fundamental contributor of nitrogen. To this end, a new nitrogen instrument was adapted to give some of the desired data in parallel. Conjoint measurements of N abundance and (delta)N-15 together with N/Ar-36 and Ar-36/Ar-38 ratios obtained during a stepped combustion of lunar soil 12023. The results are preliminary to a much more comprehensive investigation of well characterized fractions of the sample which we still have available from a previous study. Stepped combustion of a sample of 12023,7 yielded 94 ppm nitrogen with a (delta)N-15 = +22.2 percent, as well as the characteristic heavy-light-heavy pattern observed for lunar samples. The low temperature maximum was +75.1 percent at 550 C, the minimum at 800 C with (delta)N-15 = -16.7 percent and the high temperature (delta)N-15 peak is +90.6 percent at 1250 C. The major releases of nitrogen occurred between 650 C - 800 C in the form of a double peak; a third, substantial release occurred at 1150 C yielding 14.2 ppm of nitrogen coinciding with a small but recognizable drop in (delta)N-15 against a regularly increasing trend.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F; p 191-192
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  • 9
    Publication Date: 2019-01-25
    Description: The ureilite meteorite group is known to be rich in carbon in the form of graphite/diamond veins that are associated with planetary type noble gases. This paper reports preliminary data from a systematic study of the carbon and nitrogen isotopic composition of this carbonaceous vein material. A previous study focused on the whole rock signatures and reported that the carbon inventory appeared to be dominated by the graphitic/diamond intergrowths, whereas the nitrogen was clearly composed of several distinct components including one that was isotopically light, possibly associated with the carbonaceous material. Recent studies have demonstrated that diamonds in the solar system formed in many different environments. C and N measurements from ureilitic diamond made in a similar way would be a useful addition to this overall study. The methods used for isolating diamonds of possible presolar origin from primitive meteorites are equally applicable to the processing of carbon bearing components in the ureilite group so that their stable isotopic composition can be determined. Herein we discuss conjoint C and N stepped combustion measurements made on crushed whole rock ureilite samples that have been treated with 1M HCl/9M HF to dissolve silicate and free metal. In addition, two samples have been further treated with oxidizing acids to leave a diamond rich residue.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1221-1222
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  • 10
    Publication Date: 2019-07-10
    Description: The CR clan of meteorites has been established and a detailed review of these meteorites is presented. There are several kinds of carbonaceous chondrites included in this clan: Carbonaceous Renazzo-like (CR), Carbonaceous with High metal (CH), Carbonaceous Bencubbin-like (CB), and LEW 85332, a unique-metal rich meteorite. The CB chondrites are further divided into two subgroups: CB(sub a) and CB(sub b). Here we describe a new member of the CR chondrite clan, Fountain Hills, a recent find with a total mass of approximately 60 g.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXV: Carbonaceous Chondrites; LPI-Contrib-1197
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