Download or read book An Astrobiological Exploration of Mass Dependent and Mass Independent Sulphur Isotope Fractionation written by Kristyn Rodzinyak and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis, I examined multiple sulfur isotopes in two different systems: mass dependent fractionation and mass independent fractionation. Mass dependent sulfur isotopes elucidate low-temperature oxidative processes from pyrite nodules within Miocene lake sediments found in the Haughton impact structure on Devon Island, Nunavut. Mass independent samples are investigated for lithological and geographical controls on the pattern of 33S and 36S anomalies in Mesoarchaean samples from Northwestern Ontario. In mass dependent systems, the distribution of isotopes can be predicted based on the differences in mass of the various isotopes. Published studies of abiotic and biotic sulfur oxidation show negligible fractionation between starting sulfide and resulting sulfates. Pyrite nodules are being oxidized in a polar desert environment to a variety of sulfates including gypsum, jarosite, and schwertmannite. Within individual nodules, fractionation between sulfate and sulfide range from -10.1 to +17.9 [per mille]. In addition, a two-component mixing between pyrite and bedrock sulfates divides the nodules into three types. The first two are explained by conventional oxidation and mixing; however, most samples cannot be described solely through mixing or oxidation. Measuring large fractionations in sulfide oxidation has implications for the study of 'biosignatures' such that an oxidizing environment, for example the surface of Mars, would be incompatible with the preservation of 'biosignatures'. In samples older than approximately 2.45 billion years, mass independent fractionation is observed in rock samples. These anomalous enrichments or depletions in 33S cannot be predicted solely on mass differences; rather they are attributed to photochemical reactions of SO2 in an oxygen poor atmosphere. Within the Mesoarchaean the magnitude of these anomalous 33S measurements are considerably diminished compared to contiguous time periods. Previous work has focused on changes in atmospheric chemistry to explain these minimum values. By looking at samples from Northwestern Ontario, the effect of lithology and geography are tested. In addition, a sulfur isotope database compiles the literature data. The range of multiple sulfur isotope data is extended as compared to the data from South Africa and Australia; however, the magnitude remains small when compared to adjacent time periods. Nevertheless, the isotope systematics of the Mesoarchaean, with this added dataset, follow the Archaean reference array which has previously not been used for the Mesoarchaean samples. Regarding lithology, chemically and biologically precipitated samples show large variation in anomalous 33S whereas clastic rocks remain close to zero. " --
Download or read book Mass independent Sulfur Isotope Fractionation During Photochemistry of Sulfur Dioxide written by Andrew Richard Whitehill and published by . This book was released on 2015 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mass-independent sulfur isotope signatures are observed in Archean and early Paleoproterozoic sedimentary sulfate and sulfide minerals, and provide the most robust constraints on early atmospheric oxygen levels. Smaller mass-independent sulfur isotope anomalies are observed in ice cores and interpreted as a tracer of stratospheric volcanic loading. Photochemistry of sulfur dioxide (SO2) has been implicated as a possible source of the mass-independent sulfur isotope signatures in both the modern stratosphere and on the early earth. However, the mechanisms responsible for the production of mass-independent sulfur isotope fractionation remain poorly constrained. This thesis investigates the multiple sulfur isotope systematics during photochemical reactions of sulfur dioxide as a function of a variety of experimental conditions. Two absorption regions of SO2 are tested - photolysis in the 190 to 220 nm region and photoexcitation in the 250 to 350 nm region. Experimental conditions modified include temperature, SO2 pressure, bath gas pressure, and addition of reactive gases (C2 H2, 02 and CH4). Results of photochemical experiments are compared with isotope systematics predicted from isotopologue-specific absorption cross-sections to identify potential mechanisms for the production of mass-independent fractionation during photochemical reactions. Strong similarity between the isotope systematics of SO2 photolysis and ice core data suggest that SO2 photolysis is responsible for the production of mass-independent sulfur isotope effects in the modern stratosphere. In contrast, significant discrepancies between the isotope signatures from SO2 photochemistry and those in the Archean record suggest that, although SO2 photolysis was likely an important process in the Archean atmosphere, an additional reaction likely contributes to the mass-independent sulfur isotope signatures preserved in the Archean rock record.
Download or read book Assessment of the NASA Astrobiology Institute written by National Research Council and published by National Academies Press. This book was released on 2008-04-20 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astrobiology is a scientific discipline devoted to the study of life in the universe - its origin, evolution, distribution, and future. In 1997, NASA established an Astrobiology program (the NASA Astrobiology Institute - NAI) as a result of a series of new results from solar system exploration and astronomical research in the mid-1990s together with advances in the biological sciences. To help evaluate the NAI, NASA asked the NRC to review progress made by the Institute in developing the field of astrobiology. This book presents an evaluation of NAI's success in meeting its goals for fostering interdisciplinary research, training future astrobiology researchers, providing scientific and technical leadership, exploring new research approaches with information technology, and supporting outreach to K-12 education programs.
Download or read book Mass Independent Isotopic Fractionation in Solid Phase written by Xianping Xu and published by . This book was released on 1998 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Collisional Transfer Between Excited Electronic States as a Mechanism for Sulfur Mass independent Fractionation written by Alexander William Hull and published by . This book was released on 2020 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Great Oxygenation Event, the introduction of O2 into the Earth’s atmosphere approximately 2.5 billion years ago, is a critical milestone in the development of life on Earth. The exact timing of this event is thought to be correlated with the disappearance of Archean sulfur isotopic anomalies, called Sulfur Mass -Independent Fractionation (S-MIF), in the rock record. This anomalous fractionation pattern can be described, generally, as an enrichment in the three rare isotopes: S-33 (0.75%), S-34 (4.25%) S-36 (0.01%), relative to the most abundant isotopologue S-32 (0.75%), However, the mechanism for the generation of S-MIF in a reducing atmosphere is still unknown. I use the B-X UV transition (~31,000−36,000 cm−1) in S2 as a proxy for study of excited state collisional transfer as a possible mechanism for S-MIF. The short-lifetime B state (natural lifetime: 32 ns) state-mixes extensively with a longer-lifetime B” state (4200 ns). Furthermore, the most abundant isotopologue of S2, 32S-32S has only half the number of rotational states compared to its asymmetric counterparts. In this work, I replicated Green and Western’s effective Hamiltonian for the X, B, and B” states with additional considerations for mass-dependent vibrational level shifts and nuclear permutation effects. I hypothesize that the collisional transfer between the B and B" states occurs differently for different isotopologues. This difference results in a different average excited state lifetimes, which, in turn, affects the relative rate at which they undergo chemical reactions and enter the rock record. Here, spectroscopic B/B” perturbations act as doorways through which population can exchange between the B and B” states. My model incorporates absorption, fluorescence, and predissociation, as described by Green and Western. It also includes the Gelbart-Freed model for electronically inelastic collisions and Brunner and Pritchard model for rotationally inelastic collisions. I calculate the amount of each isotopologue that enters the rock record by time-dependently solving a master equation kinetic model. Results show that, generally, each region where a B vibronic state crosses a B" vibronic state behaves differently. However, the interactions display some systematic behavior. Because of the energy level patterns, lighter isotopologues are generally favored over the heavier ones (i.e. 32-36
Download or read book Encyclopedia of Astrobiology written by Muriel Gargaud and published by Springer Nature. This book was released on 2023-07-27 with total page 3376 pages. Available in PDF, EPUB and Kindle. Book excerpt: Now in its third edition the Encyclopedia of Astrobiology serves as the key to a common understanding in the extremely interdisciplinary community of astrobiologists. Each new or experienced researcher and graduate student in adjacent fields of astrobiology will appreciate this reference work in the quest to understand the big picture. The carefully selected group of active researchers contributing to this work are aiming to give a comprehensive international perspective on and to accelerate the interdisciplinary advance of astrobiology. The interdisciplinary field of astrobiology constitutes a joint arena where provocative discoveries are coalescing concerning, e.g. the prevalence of exoplanets, the diversity and hardiness of life, and its chances for emergence. Biologists, astrophysicists, (bio)-chemists, geoscientists and space scientists share this exciting mission of revealing the origin and commonality of life in the Universe. With its overview articles and its definitions the Encyclopedia of Astrobiology not only provides a common language and understanding for the members of the different disciplines but also serves for educating a new generation of young astrobiologists who are no longer separated by the jargon of individual scientific disciplines. This new edition offers ~170 new entries. More than half of the existing entries were updated, expanded or supplemented with figures supporting the understanding of the text. Especially in the fields of astrochemistry and terrestrial extremophiles but also in exoplanets and space sciences in general there is a huge body of new results that have been taken into account in this new edition. Because the entries in the Encyclopedia are in alphabetical order without regard for scientific field, this edition includes a section “Astrobiology by Discipline” which lists the entries by scientific field and subfield. This should be particularly helpful to those enquiring about astrobiology, as it illustrates the broad and detailed nature of the field.
Download or read book Non mass Dependent Isotope Fractionation written by Tao Sun and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stable Isotope Behaviour During Planetary Differentiation written by Remco Christiaan Hin and published by . This book was released on 2012 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Astrobiology written by and published by . This book was released on 2002 with total page 722 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mass Dependent Isotopic Fractionation of Molybdenum in the Solar System written by Yu-Hsuan Liang and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Non traditional Stable Isotope Constraints on Earth s Mantle Composition and Mass dependent Isotopic Fractionation at High Temperature written by Yi-Jen Lai and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photochemistry of Small Molecules written by Hideo Okabe and published by John Wiley & Sons. This book was released on 1978 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Chemical Evolution of the Atmosphere and Oceans written by Heinrich D. Holland and published by Princeton University Press. This book was released on 1984-07-21 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this first full-scale attempt to reconstruct the chemical evolution of the Earth's atmosphere and oceans, Heinrich Holland assembles data from a wide spectrum of fields to trace the history of the ocean-atmosphere system. A pioneer in an increasingly important area of scholarship, he presents a comprehensive treatment of knowledge on this subject, provides an extensive bibliography, and outlines problems and approaches for further research. The first four chapters deal with the turbulent first half billion years of Earth history. The next four chapters, devoted largely to the Earth from 3.9 to 0.6 b.y.b.p., demonstrate that changes in the atmosphere and oceans during this period were not dramatic. The last chapter of the book deals with the Phanerozoic Eon; although the isotopic composition of sulfur and strontium in seawater varied greatly during this period of Earth history, the chemical composition of seawater did not.
Download or read book Photochemistry of Planetary Atmospheres written by Yuk Ling Yung and published by Oxford University Press, USA. This book was released on 1999 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: This valuable reference presents detailed studies of eleven planetary atmospheres: four for the giant planets (Jupiter, Saturn, Uranus, and Neptune), four for the small bodies (Io, Titan, Triton, and Pluto), and three for the terrestrial planets (Mars, Venus, and Earth). Also, using the database provided by recent space missions supplemented by Earth-based observations, the authors offer an extensive survey of the principal chemical cycles that control the present composition and past history of planetary atmospheres.
Download or read book Stable Isotope Geochemistry written by John W. Valley and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-12-17 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 43 of Reviews in Mineralogy and Geochemistry follows the 1986 Reviews in Mineralogy (Vol. 16) in approach but reflects significant changes in the field of Stable Isotope Geochemistry. In terms of new technology, new sub-disciplines, and numbers of researchers, the field has changed more in the past decade than in any other since that of its birth. Unlike the 1986 volume, which was restricted to high temperature fields, this book covers a wider range of disciplines. However, it would not be possible to fit a comprehensive review into a single volume. Our goal is to provide state-of-the-art reviews in chosen subjects that have emerged or advanced greatly since 1986. This volume was prepared for Short Course on Stable Isotope Geochemistry presented November 2-4, 2001 in conjunction with the annual meetings of the Geological Society of America in Boston, Massachusetts.
Download or read book Calculation of Equilibrium Constants for Isotopic Exchange Reactions written by Jacob Bigeleisen and published by . This book was released on 1947 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Atmospheric Evolution on Inhabited and Lifeless Worlds written by David C. Catling and published by Cambridge University Press. This book was released on 2017-04-13 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and authoritative text on the formation and evolution of planetary atmospheres, for graduate-level students and researchers.
