This study uses high precision silicon isotopic measurements to understand events that occurred during the earliest stages of formation of the terrestrial planets. The isotopic compositions of diverse materials such as chondrites, lunar rocks and asteroidal basalts can shed light on the homogeneity of the solar nebula, metal-silicate differentiation on planetary bodies, and terrestrial moon formation.
Where there is water, there can be life. Improving our understanding of how life, as we know it, arose uniquely in our solar system on Earth depends critically on our understanding of the history of water in the solar system. Better characterizing the sources of water to the Earth-Moon system is crucial in constraining this history and motivated the experiments described in this dissertation. The oxygen isotopic composition of water in lunar samples in addition to meteorites from Mars and several asteroids, which have delivered significant material to the Earth-Moon system, were characterized. The ordinary chondrite (OC) samples, Bjurböle matrix, Bjurböle chondrules, and ALHA77216, contain 17O-enriched water with, [delta]17O up to 1.5%, released by high temperature heating. Water liberated from the carbonaceous chondrite (CC), Murchison, by heating to high temperatures (≤1000°C) possess [delta]17O approaching -1.5%. Low-temperature fractions of water from these OC and CC samples is mass-dependently fractionated ([delta]17O [approximately equal to]0%). The eucrite, PCA 91006 releases water upon heating to 50-350°C with [delta]17O [approximately equal to]1% and 600-1000°C with as low as -11%. The martian meteorite, NWA 7034, contains water with an average [delta]17O = 0.32%. The lunar samples analyzed (10049, 10057, 10060, 12021, 12039, 14163, 14305, 79035) possess water with average [delta]17O = 0.18%. The oxygen isotopic composition of a whole rock sample of a carbonaceous chondrite (CC) meteorite, Sutter's Mill, was also measured, and possesses [delta]17O = -1.8%. The 1[sigma] error on these [delta]17O values is 0.011%. These results reveal that delivery of water by OCs and CCs could account for almost all of the lunar water isotopic compositions measured. Complementary studies measuring the isotopic composition of ozone (O3), an important precursor to water, formed in experiments performed under analogous conditions to those that existed early in the formation of the solar system were also conducted. Additionally, experiments characterizing the isotopic composition of O2 involved in ion-molecule reactions which dominate molecule-formation processes occurring in cold regions of interstellar molecular clouds were also conducted. These complementary studies help define and explain the isotopic composition of oxygen-bearing reservoirs, especially water, in the present-day inner solar system.
The book starts with an introduction on silicon isotopes and related analytical methods, and explains the mechanisms of silicon isotope fractionation. Silicon isotope distributions in lithosphere, hydrosphere and biosphere are shown based on results from field studies, and silicon isotope relevance for applications are presented.
Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope abundance variations potentially are large enough to result in future expansion of their atomic weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope-abundance variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic weight uncertainties.
A comprehensive guide to carbon inside Earth - its quantities, movements, forms, origins, changes over time and impact on planetary processes. This title is also available as Open Access on Cambridge Core.
This volume of the EMU Notes in Mineralogy is one of the outcomes of a school in planetary mineralogy that was held in Glasgow, Scotland, in 2014. The school was inspired by the recent advances in our understanding of the nature and evolution of our Solar System that have come from the missions to study and sample asteroids and comets, and the very successful Mars orbiters and landers. At the same time our horizons have expanded greatly with the discovery of extrasolar protoplanetary disks, planets and planetary systems by space telescopes. The continued success of such telescopic and robotic exploration requires a supply of highly skilled people and so one of the goals of the Glasgow school was to help build a community of early-career planetary scientists and space engineers.
Chondrules are spherical silicate grains which formed from protoplanetary disk material, and as such provide an important record of the conditions of the Solar System in pre-planetary times. Chondrules are a major constituent in chondritic meteorites, however despite being recognised for over 200 years, their origins remain enigmatic. This comprehensive review describes state-of-the-art research into chondrules, bringing together leading cosmochemists and astrophysicists to review the properties of chondrules and their possible formation mechanisms based on careful observations of their chemistry, mineralogy, petrology and isotopic composition. Current and upcoming space missions returning material from chondritic asteroids and cometary bodies has invigorated research in this field, leading to new models and observations, and providing new insight into the conditions and timescales of the solar protoplanetary disk. Presenting the most recent advances, this book is an invaluable reference for researchers and graduate students interested in meteorites, asteroids, planetary accretion and solar system dynamics.
Using isotopes as a tool for understanding Earth processes From establishing the absolute age of the Earth to providing a stronger understanding of the nexus between geology and life, the careful measurement and quantitative interpretation of minor variations in the isotopic composition of Earth’s materials has provided profound insight into the origins and workings of our planet. Isotopic Constraints on Earth System Processes presents examples of the application of numerous different isotope systems to address a wide range of topical problems in Earth system science. Volume highlights include: examination of the natural fractionation of non-traditional stable isotopes utilizing isotopes to understand the origin of magmas and evolution of volcanic systems application of isotopes to interrogate and understand Earth’s Carbon and Oxygen cycles examination of the geochemical and hydrologic processes that lead to isotopic fractionation application of isotopic reactive transport models to decipher hydrologic and biogeochemical processes The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.
