Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 28 for “"Early Earth"”.
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Late accretion to the early Earth and rocky exoplanets
The final stages of Earth's formation were characterised by the violent collisions of planetesimals, asteroids and comets -- by-products of the primary stage of planet formation -- with the nascent planet. It is thought these impacts, delivering vast sums of energy, may have transformed surface …
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Determining the physico-chemical conditions on the early earth : Barberton scientific drilling project, South Africa
… oceanic regimes, as well as potential early life-sustaining environments. Over the past four decades, widely varying interpretations have been reported for the origin of these silica-rich fuchsitic alteration zones in the BGB, ranging from very low temperature (less than 60oC) …
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The Archean origin of assimilatory sulfate metabolisms provides novel insight into redox conditions of early Earth environments
Dissimilatory sulfur metabolisms recording differing biological isotopic fractionation are well studied, important components of sulfur cycling (Mateos et al., 2023). Assimilatory sulfur metabolisms and genes across life provide a complementary window into sulfur biogeochemistry with individual …
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SYNTHESIS, CHARACTERIZATION, AND THERMAL INVESTIGATION OF METAL PHOSPHITES AND POTENTIAL IMPLICATIONS FOR ASTROBIOLOGY
… route by which phosphorus was incorporated into early biomolecules on the prebiotic Earth is uncertain. Phosphate, the most prevalent species of phosphorus found in Earth’s geological record, is insoluble and unreactive with organics in aqueous environments. While the most abundant biogenic …
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Phosphorus Pathways In Deep Time
… in natural science ask about the nature of early Earth. The conditions under which Earth formed and life emerged on its surface are especially uncertain. However, we are left with precious little evidence to study: most sufficiently ancient terrestrial rocks have long since been destroyed, …
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Cyanobacterial evolution and interactions with the Proterozoic world
… ancient biosphere and how it interacted with the early Earth. Cyanobacteria are thought to have evolved early in Earth history and played a large part in shaping the ancient biosphere and geosphere, but questions remain about their evolution and the ways in which cyanobacterial communities …
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Near-Infrared Spectroscopy of Near-Earth Asteroids: 3122 Florence, (357439) 2004 BL86, 1036 Ganymed, and 4055 Magellan
The near-infrared spectra of four near-Earth asteroids, 3122 Florence, (357439) 2004 BL86, 1036 Ganymed, and 4055 Magellan, were analyzed for traces of surface water. NEAs are widely thought to be the source of water and organics delivered to early Earth. Additionally, some NEAs are considered …
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Characterization of a Novel Dynamic Combinatorial Depsipeptide System with Implications for the Origin of Biopolymers
… are thought to have been present on the ancient Earth—long before biology inhabited the planet. However, the orderly association of these monomers to form functional covalent biopolymers under simulated early Earth conditions has proven difficult, if not impossible. A further complication is that …
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A thermotectonic framework for the growth and stabilization of the eastern Kaapvaal craton, southern Africa
… -4 Gyr and are therefore our best record of the early Earth. Exposures of rocks -3.0-3.7 Ga cover -20,000 km2 of eastern S. Africa and Swaziland, and provide a record of the continental assembly and subsequent stabilization of the eastern Kaapvaal craton. This thesis uses structural, …
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Bridging the gap between microbial and metazoan evolutionary history
While microbial life originated early in Earth history and continues to underpin most modern ecosystems, its evolutionary trajectory remains murky. This is predominantly due to the dearth of diagnostic microbial fossils and biomarkers. Conversely, metazoans (animals) emerged relatively recently and …
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Layered Double Hydroxides: Morphology, Interlayer Anion, and the Origins of Life
… concentrations similar to that expected on the early earth, hydrolysis to formamide rather than self-addition occurs. One theory to alleviate this side reaction is the use of minerals or clays that are thought to concentrate and catalyze prebiotics of interest. Layered double hydroxides have …
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Inside-out diversity of rocky planets
… revealed to us that no one could have predicted Earth. Many stars host planets which appear to be made of rock and iron like Earth, but sit at several times its mass—we have no visible analogues nearby to show us what these massive rocky planets look like, and how differ from our own. Further, …
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Activity of methanogenic archaea under simulated Mars analog conditions
Assumed comparable environmental conditions of early Mars and early Earth in 3.7 Ga ago – at a time when first fossil records of life on Earth could be found – suggest the possibility of life emerging on both planets in parallel. As conditions changed, the hypothetical life on Mars either became …
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Lateral Transfer of DNA in Protocell-like Synthetic Cells
… events such as those generated by lightning on early earth Earth could have promoted the horizontal movement of genetic material among protocells. Additionally, this work highlights key experimental challenges in modeling prebiotic genetic exchange, while also contributing to the development of …
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Mineral-Surface Chemistry of Hydroxyapatite and Urea-Rich Solutions
… plausible phosphate mineral source on the early Earth, with urea-rich solvents (urea, ammonium formate, and water, UAFW) and magnesium sulfate. Time-dependent infrared studies were conducted via polarization modulated – infrared reflection-absorption spectroscopy (PM-IRRAS) to monitor …
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Mass-independent sulfur isotope fractionation during photochemistry of sulfur dioxide
… 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 …
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Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems
… direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH4) formation under hydrothermal conditions. The overall reduction of carbon …
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Laboratory and field-based investigations of subsurface geochemical processes in seafloor hydrothermal systems
… direct implications for the emergence of life in early Earth settings and sustainment of present day microbial populations in hydrothermal environments. Chapter 2 represents an experimental investigation of methane (CH4) formation under hydrothermal conditions. The overall reduction of carbon …
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Making oceanic plagiogranite bodies by thermal migration: evidence from the Agros transect, Troodos ophiolite, Cyprus
… silicic crust from a mafic magma setting in the early earth.
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Tellurium, antimony, and selenium isotopes as indicators of elemental mobility
… resource extraction, or the oxygenation of early Earth. Stable isotopic fractionation of redox-sensitive elements can be used as a means to identify redox reactions taking place. For example, selenium (Se) isotopes track reductive immobilization of the contaminant Se in groundwater or …
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