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Description
Carbonaceous chondrites (CCs) present a unique opportunity for learning about the earliest organic chemistry that took place in our Solar System. The complex and diverse suite of meteoritic organic material is the result of multiple settings and physicochemical processes, including aqueous and thermal alteration. Though meteorites often inform origin-of-life discussions because they could have seeded early Earth with significant amounts of water and pre-biotic, organic material, their record of abiotic, aqueous, and organic geochemistry is of interest as well.
CC materials previously resided on asteroidal parent bodies, relic planetesimals of Solar System formation which never accreted enough material to develop long-lived, large-scale geological processes. These bodies were large enough, however, to experience some degree of heating due to the decay of radiogenic isotopes, and the meteorite record suggests the existence of 100-150 parent bodies which experienced varying degrees of thermal and aqueous alteration for the first several 10 Myr of Solar System history.
The first chapter of this dissertation reviews literature addressing aqueous alteration as an essential participant in parent body geochemistry, organic synthesis, or both (though papers which address both are rare). The second chapter is a published organic analysis of the soluble organic material of Bells, an unclassified type 2 chondrite. Analytical approaches to assess terrestrial contamination of meteorite samples are also reviewed in the first chapter to allow introduction in chapter 3 of kinetic modeling which rules out certain cases of contamination and constrains the timing of thermal and aqueous alteration. This is the first known application of isoleucine epimerization for either of these purposes. Chapter 4 is a kinetic study of D-allo-isoleucine epimerization to establish its behavior in systems with large, relative abundances of alloisoleucine to isoleucine. Previous epimerization studies for paleontological or geological purposes began with L-isoleucine, the only protein amino acid of the four isoleucine stereoisomers.
Kinetic model calculations using isoleucine stereoisomer abundances from 7 CR chondrites constrain the total duration of the amino acids' residence in the aqueous phase. The comparatively short timescales produced by the presented modeling elicit hypotheses for protection or transport of the amino acids within the CR parent body.
CC materials previously resided on asteroidal parent bodies, relic planetesimals of Solar System formation which never accreted enough material to develop long-lived, large-scale geological processes. These bodies were large enough, however, to experience some degree of heating due to the decay of radiogenic isotopes, and the meteorite record suggests the existence of 100-150 parent bodies which experienced varying degrees of thermal and aqueous alteration for the first several 10 Myr of Solar System history.
The first chapter of this dissertation reviews literature addressing aqueous alteration as an essential participant in parent body geochemistry, organic synthesis, or both (though papers which address both are rare). The second chapter is a published organic analysis of the soluble organic material of Bells, an unclassified type 2 chondrite. Analytical approaches to assess terrestrial contamination of meteorite samples are also reviewed in the first chapter to allow introduction in chapter 3 of kinetic modeling which rules out certain cases of contamination and constrains the timing of thermal and aqueous alteration. This is the first known application of isoleucine epimerization for either of these purposes. Chapter 4 is a kinetic study of D-allo-isoleucine epimerization to establish its behavior in systems with large, relative abundances of alloisoleucine to isoleucine. Previous epimerization studies for paleontological or geological purposes began with L-isoleucine, the only protein amino acid of the four isoleucine stereoisomers.
Kinetic model calculations using isoleucine stereoisomer abundances from 7 CR chondrites constrain the total duration of the amino acids' residence in the aqueous phase. The comparatively short timescales produced by the presented modeling elicit hypotheses for protection or transport of the amino acids within the CR parent body.
ContributorsMonroe, Adam Alexander (Author) / Pizzarello, Sandra (Thesis advisor) / Williams, Peter (Thesis advisor) / Anbar, Ariel D (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2014
Description
The occurrence of exogenic, meteoritic materials on the surface of any world presents opportunities to explore a variety of significant problems in the planetary sciences. In the case of Mars, meteorites found on its surface may help to 1) constrain atmospheric conditions during their time of arrival; 2) provide insights into possible variabilities in meteoroid type sampling between Mars and Earth space environments; 3) aid in our understanding of soil, dust, and sedimentary rock chemistry; 4) assist with the calibration of crater-age dating techniques; and 5) provide witness samples for chemical and mechanical weathering processes. The presence of reduced metallic iron in approximately 88 percent of meteorite falls renders the majority of meteorites particularly sensitive to oxidation by H2O interaction. This makes them excellent markers for H2O occurrence. Several large meteorites have been discovered at Gusev Crater and Meridiani Planum by the Mars Exploration Rovers (MERs). Significant morphologic characteristics interpretable as weathering features in the Meridiani suite of iron meteorites include a 1) large pit lined with delicate iron protrusions suggestive of inclusion removal by corrosive interaction; 2) differentially eroded kamacite and taenite lamellae on three of the meteorites, providing relative timing through cross-cutting relationships with deposition of 3) an iron oxide-rich dark coating; and 4) regmaglypted surfaces testifying to regions of minimal surface modification; with other regions in the same meteorites exhibiting 5) large-scale, cavernous weathering. Iron meteorites found by Mini-TES at both Meridiani Planum and Gusev Crater have prompted laboratory experiments designed to explore elements of reflectivity, dust cover, and potential oxide coatings on their surfaces in the thermal infrared using analog samples. Results show that dust thickness on an iron substrate need be only one tenth as great as that on a silicate rock to obscure its infrared signal. In addition, a database of thermal emission spectra for 46 meteorites was prepared to aid in the on-going detection and interpretation of these valuable rocks on Mars using Mini-TES instruments on both MER spacecraft. Applications to the asteroidal sciences are also relevant and intended for this database.
ContributorsAshley, James Warren (Author) / Christensen, Philip R. (Thesis advisor) / Sharp, Thomas G (Committee member) / Shock, Everett L (Committee member) / Hervig, Richard L (Committee member) / Zolotov, Mikhail Y (Committee member) / Arizona State University (Publisher)
Created2011
Description
The San Andreas Fault (SAF) is the primary structure within a system of faults accommodating motion between the North American and Pacific plates. Physical models of faulting and characterizations of seismic hazard are informed by investigations of paleoseismology, slip distribution, and slip rate. The impact of earthquakes on people is due in large part to social vulnerability. This dissertation contributes an analysis about the relationships between earthquake hazard and social vulnerability in Los Angeles, CA and investigations of paleoseismology and fault scarp array complexity on the central SAF. Analysis of fault scarp array geometry and morphology using 0.5 m digital elevation models along 122 km of the central SAF reveals significant variation in the complexity of SAF structure. Scarp trace complexity is measured by scarp separation, changes in strike, fault trace gaps, and scarp length per SAF kilometer. Geometrical complexity in fault scarp arrays indicates that the central SAF can be grouped into seven segments. Segment boundaries are controlled by interactions with subsidiary faults. Investigation of an offset channel at Parkfield, CA yields a late Holocene slip rate of 26.2 +6.4/- 4.3 mm/yr. This rate is lower than geologic measurements on the Carrizo section of the SAF and rates implied by far-field geodesy. However, it is consistent with historical observations of slip at Parkfield. Paleoseismology at Parkfield indicates that large earthquakes are absent from the stratigraphic record for at least a millennia. Together these observations imply that the amount of plate boundary slip accommodated by the main SAF varies along strike. Contrary to most environmental justice analyses showing that vulnerable populations are spatially-tied to environmental hazards, geospatial analyses relating social vulnerability and earthquake hazard in southern California show that these groups are not disproportionately exposed to the areas of greatest hazard. Instead, park and green space is linked to earthquake hazard through fault zone regulation. In Los Angeles, a parks poor city, the distribution of social vulnerability is strongly tied to a lack of park space. Thus, people with access to financial and political resources strive to live in neighborhoods with parks, even in the face of forewarned risk.
ContributorsToké, Nathan A (Author) / Arrowsmith, J R (Thesis advisor) / Boone, Christopher G (Committee member) / Heimsath, Arjun M (Committee member) / Shock, Everett L (Committee member) / Whipple, Kelin X (Committee member) / Arizona State University (Publisher)
Created2011
Description
Volcanic eruptions are serious geological hazards; the aftermath of the explosive eruptions produced at high-silica volcanic systems often results in long-term threats to climate, travel, farming, and human life. To construct models for eruption forecasting, the timescales of events leading up to eruption must be accurately quantified. In the field of igneous petrology, the timing of these events (e.g. periods of magma formation, duration of recharge events) and their influence on eruptive timescales are still poorly constrained.
In this dissertation, I discuss how the new tools and methods I have developed are helping to improve our understanding of these magmatic events. I have developed a method to calculate more accurate timescales for these events from the diffusive relaxation of chemical zoning in individual mineral crystals (i.e., diffusion chronometry), and I use this technique to compare the times recorded by different minerals from the same Yellowstone lava flow, the Scaup Lake rhyolite.
I have also derived a new geothermometer to calculate magma temperature from the compositions of the mineral clinopyroxene and the surrounding liquid. This empirically-derived geothermometer is calibrated for the high FeOtot (Mg# = 56) and low Al2O3 (0.53–0.73 wt%) clinopyroxene found in the Scaup Lake rhyolite and other high-silica igneous systems. A determination of accurate mineral temperatures is crucial to calculate magmatic heat budgets and to use methods such as diffusion chronometry. Together, these tools allow me to paint a more accurate picture of the conditions and tempo of events inside a magma body in the millennia to months leading up to eruption.
Additionally, I conducted petrological experiments to determine the composition of hypothetical exoplanet partial mantle melts, which could become these planets’ new crust, and therefore new surface. Understanding the composition of an exoplanet’s crust is the first step to understanding chemical weathering, surface-atmosphere chemical interactions, the volcanic contribution to any atmosphere present, and biological processes, as life depends on these surfaces for nutrients. The data I have produced can be used to predict differences in crust compositions of exoplanets with similar bulk compositions to those explored herein, as well as to calibrate future exoplanet petrologic models.
In this dissertation, I discuss how the new tools and methods I have developed are helping to improve our understanding of these magmatic events. I have developed a method to calculate more accurate timescales for these events from the diffusive relaxation of chemical zoning in individual mineral crystals (i.e., diffusion chronometry), and I use this technique to compare the times recorded by different minerals from the same Yellowstone lava flow, the Scaup Lake rhyolite.
I have also derived a new geothermometer to calculate magma temperature from the compositions of the mineral clinopyroxene and the surrounding liquid. This empirically-derived geothermometer is calibrated for the high FeOtot (Mg# = 56) and low Al2O3 (0.53–0.73 wt%) clinopyroxene found in the Scaup Lake rhyolite and other high-silica igneous systems. A determination of accurate mineral temperatures is crucial to calculate magmatic heat budgets and to use methods such as diffusion chronometry. Together, these tools allow me to paint a more accurate picture of the conditions and tempo of events inside a magma body in the millennia to months leading up to eruption.
Additionally, I conducted petrological experiments to determine the composition of hypothetical exoplanet partial mantle melts, which could become these planets’ new crust, and therefore new surface. Understanding the composition of an exoplanet’s crust is the first step to understanding chemical weathering, surface-atmosphere chemical interactions, the volcanic contribution to any atmosphere present, and biological processes, as life depends on these surfaces for nutrients. The data I have produced can be used to predict differences in crust compositions of exoplanets with similar bulk compositions to those explored herein, as well as to calibrate future exoplanet petrologic models.
ContributorsBrugman, Karalee (Author) / Till, Christy B. (Thesis advisor) / Bose, Maitrayee (Committee member) / Desch, Steven J (Committee member) / Hervig, Richard L (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2020
Description
With the development and successful landing of the NASA Perseverance rover, there has been growing interest in identifying how evidence of ancient life may be preserved and recognized in the geologic record. Environments that enable fossilization of biological remains are termed, “taphonomic windows”, wherein signatures of past life may be detected. In this dissertation, I have sought to identify taphonomic windows in planetary-analog environments with an eye towards the exploration of Mars. In the first chapter, I describe how evidence of past microbial life may be preserved within serpentinizing systems. Owing to energetic rock-water reactions, these systems are known to host lithotrophic and organotrophic microbial communities. By investigating drill cores from the Samail Ophiolite in Oman, I report morphological and associated chemical biosignatures preserved in these systems as a result of subsurface carbonation. As serpentinites are known to occur on Mars and potentially other planetary bodies, these deposits potentially represent high-priority targets in the exploration for past microbial life. Next, I investigated samples from Atacama Desert, Chile, to understand how evidence of life may be preserved in ancient sediments formed originally in evaporative playa lakes. Here, I describe organic geochemical and morphological evidence of life preserved within sulfate-dominated evaporite rocks from the Jurassic-Cretaceous Tonel Formation and Oligocene San Pedro Formation. Because evaporative lakes are considered to have been potentially widespread on Mars, these deposits may represent additional key targets to search for evidence of past life. In the final chapter, I describe the fossilization potential of surficial carbonates by investigating Crystal Geyser, an active cold spring environment. Here, carbonate minerals precipitate rapidly in the presence of photosynthetic microbial mat communities. I describe how potential biosignatures are initially captured by mineralization, including cell-like structures and microdigitate stromatolites. However, these morphological signatures quickly degrade owing to diagenetic dissolution and recrystallization reactions, as well as textural coarsening that homogenizes the carbonate fabric. Overall, my dissertation underscores the complexity of microbial fossilization and highlights chemically-precipitating environments that may serve as high-priority targets for astrobiological exploration.
ContributorsZaloumis, Jonathan (Author) / Farmer, Jack D (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Ruff, Steven W (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2021