Isotopic and Elemental Compositions of Stardust and Protosolar Dust Grains in Primitive Meteorites PDF Download
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Author: Maitrayee Bose
Publisher:
ISBN:
Category :
Languages : en
Pages : 251
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Author: Maitrayee Bose
Publisher:
ISBN:
Category :
Languages : en
Pages : 251
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Author: Maria Lugaro
Publisher: World Scientific
ISBN: 9812703489
Category : Body, Mind & Spirit
Languages : en
Pages : 226
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Book Description
The study of presolar meteoritic grains is a new inter-disciplinary field that brings together topics from nuclear physics to astronomy and chemistry. Traditionally, most of the information about the cosmos has been gathered by observing light through telescopes. However, with the recent discovery that some dust grains extracted from primitive meteorites were produced in stellar environments, we now have the opportunity to gather information about stars and our Galaxy from the laboratory analysis of tiny pieces of stardust. Stellar grains represent a unique and fascinating subject of study. Their analysis is a breakthrough in research on stellar nucleosynthesis and the origin of the elements. While a number of specialized reviews exist on the topic, this book is the first work that brings together in a unified and accessible manner the background knowledge necessary for the study of presolar grains together with up-to-date discoveries in the field. The book includes exercise questions and answers, an extensive glossary for easy reference, and more than 40 figures and tables OCo from schematic diagrams to electron microscope images and graphs of results from stellar grain measurements and theoretical stellar models."
Author: Andrew M. Davis
Publisher:
ISBN: 9780080443362
Category : Comets
Languages : en
Pages : 737
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Book Description
/inca/publications/misc/622551sample1.pdf Sample chapter Volume 1 provides a broad overview of the chemistry of the solar system. It includes chapters on the origin of the elements and solar system abundances, the solar nebula and planet formation, meteorite classification, the major types of meteorites, important processes in early solar system history, geochemistry of the terrestrial planets, the giant planets and their satellite, comets, and the formation and early differentiation of the Earth. This volume is intended to be the first reference work one would consult to learn about the chemistry of the solar system.
Author: Janaina Avila
Publisher:
ISBN:
Category : Cosmic grains
Languages : en
Pages : 346
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Isotopic and elemental abundance signatures of heavy elements determined in presolar stardust grains have provided important constraints on nucleosynthetic processes in individual stars. The present study reports on new analytical protocols developed to measure the isotopic compositions of heavy elements in large (> 4 urn) individual presolar stardust SiC grains by Sensitive High-Resolution Ion Microprobe (SHRIMP). Isotopic analyses of Ba, Eu, W, Pb, U and Th in stardust SiC grains extracted from the Murchison meteorite are presented. Most of the studied grains show Si-, C-, and N-isotopic compositions in the range displayed by the socalled "mainstream grains" and, therefore, likely condensed in the outflows oflow mass carbonrich asymptotic giant branch (AGB) stars with close-to-solar metallicity. A detailed investigation by SHRIMP of the mass regIOn around Ba and Eu using a suite of carbide and silicate reference materials revealed several significant molecular interferences. Importantly, the interferences observed in carbide matrices, including stardust SiC grains, were not identified in silicate matrices. We found that employing an energy offset to select secondary ions from the high range of energies, in combination with high-mass resolution, was sufficient to suppress the unwanted interferences. These findings emphasize the importance of matrixmatching standards to obtain accurate ion microprobe isotopic data. The Ba-isotopic compositions determined in large stardust SiC grains employing such an approach were found to be mostly normal, which could suggest that the conditions for growth of large SiC grains are more favourable in the early C-rich stages of AGB evolution before much dredge-up episodes have happened. One of the main goals of the present study was to measure the isotopic compositions of heavy elements affected by branching points, such as Eu and W, in individual mainstream SiC grains and investigate their potential as proxies for temperature and neutron density during s-process nucleosynthesis. The Eu-isotopic compositions determined in large stardust SiC grains were found to be in agreement with observations in carbon-enhanced metal-poor stars enriched in 5process elements, despite differences in metallicity. Unfortunately, given the low Eu abundances in the SiC grains, the 151Eu isotope fractions [fr(151Eu) = 151Eu/(151Eu+153Eu)] derived from our measurements show large uncertainties and, in most cases, cannot be distinguished from the solar value. On the other hand, thefi(15IEu) value derived for a SiC-enriched bulk sample was very well constrained, matching those of carbon-enhanced metal-poor stars, but approximately 12% higher than current s-process predictions. The W-isotopic compositions determined in large stardust SiC grains were found to be anomalous in comparison with solar system materials. They are also in disagreement with current s-process predictions, unless the 183W and 185W neutron capture cross sections are increased. The results of this study provide an alternative explanation for the problem of the overproduction of s-process 1860s, since the higher observed 186W/ 184W ratios could eventually lead to lower 1860s as a consequence of the activation of the branching point at 185W during thermal pulse phases, when the neutron density is sufficiently high to modify the 186W abundance. Also investigated was utility of the U-Th-Pb system to obtain insights into the timescale of stardust grains and their parent stars. The Ph-isotopic compositions determined in large stardust SiC grains were found to be highly anomalous with respect to both modern terrestrial and primordial lead, showing enrichment in the non-radiogenic s-only 204Pb. It is speculated that the Pb-isotopic compositions of stardust grains may result from mixing of three components: common Pb, s-process Pb, and radiogenic Pb. The application of conventional radiometric dating using the U-Th-Pb decay system in stardust SiC grains was found not to be viable, given the large observed Pb isotopic anomalies. A rough correlation exists between Th and U concentrations and 829Si/ 28Si, which likely reflects the average Galactic Chemical Evolution trends of these elements. It is suggested that 238U/232Th ratios may be used as a relative chronometer of star formation, provided that unfractionated Th and U were incorporated into SiC grains. If assumed that the 238U/232Th ratios are initially unfractionated, then the results indicate that 29,30Si/28Si ratios decrease with time in the interstellar medium for close-to-solar metallicities. These results, therefore, would confirm that the placement of the Solar System Si isotopes near the bottom of the mainstream line is indeed what one would expect for its age and current location.
Author: John F. Kerridge
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1304
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Although the Earth was formed, together with the other planets, at the birth of the solar system, geological activity has since erased all but a hint of the processes that accompanied its formation. If we wish to explore the processes that occurred in the earliest solar system, and the nature of the environment in which they took place, we must turn to the record contained in more primitive material. Many meteorites appear to satisfy that criterion, and much effort has been applied during the past twenty years or so in identifying those meteorites, or their constituents, that have retained a reliable record of the early solar system. This book provides a synthesis of what has been learned so far about the earliest stages of solar system history through the study of meteorites, and what, given our current level of understanding, remains to be learned. Contents 1. Introduction 2. Source Regions 3. Secondary Processing 4. Irradiation Effects 5. Solar System Chronology 6. Chondrites and the Early Solar System 7. Elemental Composition of Chondrites 8. Magnetic Fields in the Early Solar System 9. Chondrules10. Primitive Material Surviving in chondrites11. Micrometeorites12. Inhomogencity of the Nebula13. Survival of Presolar Material in Meteorites14. Nucleosynthesis15. Nucleocosmochronology16. Summary
Author: L. Wanat
Publisher:
ISBN:
Category : Meteorites
Languages : en
Pages : 142
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Author: Andrea Longobardo
Publisher: Elsevier
ISBN: 0128183314
Category : Science
Languages : en
Pages : 398
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Sample Return Missions: The Last Frontier of Solar System Exploration examines the discoveries and results obtained from sample return missions of the past, present, and future. It analyses the results in the context of the current state of knowledge and their relation to the formation and evolution of planetary bodies, as well as to the available technologies and techniques. It provides detailed descriptions of experimental procedures applied to returned samples. Beginning with an overview of previous missions, Sample Return Missions then goes on to provide an overview of facilities throughout the world used to analyze the returned samples. Finally, it addresses techniques for collection, transport, and analysis of the samples, with an additional focus on lessons learned and future perspectives. Providing an in-depth examination of a variety of missions, with both scientific and engineering implications, this book is an important resource for the planetary science community, as well as the experimentalist and engineering communities. - Presents sample return results obtained so far in relation to remote sensing measurements, methods and techniques for laboratory analysis, and technology - Provides an overview of a variety of sample return missions, from Apollo, to Hayabusa-2, to future missions - Examines technological and methodological advances in analyzing returned samples, as well as the resources available globally
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 74
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We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O, S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in 15N, including the largest 15N enrichments ((almost equal to)1300 {per_thousand}) observed in IDPs to date. A number of the IDPs also contain larger regions with more modest enrichments in 15N, leading to average bulk N isotopic compositions that are 15N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two 15N-rich N-hotspots have correlated 13C anomalies. CN−/C− ratios suggest that most of the 15N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct very D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in the IDPs. The O isotopic compositions of the grains are similar to those found in presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the 17O and 18O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being ''isotopically primitive'' and consists of those IDPs that have anomalous bulk N isotopic compositions. These particles typically also contain numerous 15N-rich N-hotspots, occasional C isotopic anomalies, and abundant presolar silicate grains. In contrast, the other ''isotopically normal'' IDPs have normal bulk N isotopic compositions and, although some contain 15N-rich hotspots, none exhibit C isotopic anomalies and none contain presolar silicate or oxide grains. Thus, isotopically interesting IDPs can be identified and selected on the basis of their N isotopic compositions for further study. However, this distinction does not extend to H isotopic compositions. Although both H and N anomalies are frequently attributed to the survival of molecular cloud material in IDPs and, thus, should be more common in IDPs with anomalous bulk N compositions, D anomalies are as common in normal IDPs as they are in those characterized as isotopically primitive, based on their N isotopes. This may be due to different effects of secondary processing on the isotopic systems involved.
Author: J. Kielbasiński
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: J. Kielbasinski
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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