Matching Items (33)
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TAM19B-7 is the largest, unmelted fine-grained micrometeorite found to date. It has carbonaceous chondritic origins, but the oxygen isotopic composition does not match any known parent bodies. Additionally, carbon-bearing matter and isotopic composition has been extensively characterized in meteorites, but this work has not been done yet for micrometeorites.

TAM19B-7 is the largest, unmelted fine-grained micrometeorite found to date. It has carbonaceous chondritic origins, but the oxygen isotopic composition does not match any known parent bodies. Additionally, carbon-bearing matter and isotopic composition has been extensively characterized in meteorites, but this work has not been done yet for micrometeorites. Using the NanoSIMS 50 L instrument, the bulk δ13C for TAM19B-7 was found to be 3 + 8‰, and four anomalous spots were identified with δ13C values of 12.9‰, 16.8‰, 32.7‰, and -27.1‰.

ContributorsFroh, Victoria (Author) / Bose, Maitrayee (Thesis director) / Williams, Lynda (Committee member) / School of Earth and Space Exploration (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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We present the isotope yields of two post-explosion, three-dimensional 15 M_sol core-collapse supernova models, 15S and 15A, and compare them to the carbon, nitrogen, silicon, aluminum, sulfur, calcium, titanium, iron, and nickel isotopic compositions of presolar SiC stardust. We find that material from the interior of a core-collapse supernova can

We present the isotope yields of two post-explosion, three-dimensional 15 M_sol core-collapse supernova models, 15S and 15A, and compare them to the carbon, nitrogen, silicon, aluminum, sulfur, calcium, titanium, iron, and nickel isotopic compositions of presolar SiC stardust. We find that material from the interior of a core-collapse supernova can form a rare subset of SiC stardust, called SiC D grains, characterized by enrichments of the isotopes 13C and 15N. The innermost material of these core-collapse supernovae is operating in the neutrino-driven regime and undergoes rapid proton capture early in the explosion, providing these isotopes which are not present in such large abundances in other stardust grains of supernova origin.

ContributorsSchulte, Jack (Author) / Bose, Maitrayee (Thesis director) / Foy, Joseph (Committee member) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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This thesis examines Care Not Cash, a welfare reform measure that replaced traditional cash General Assistance program payments for homeless persons in San Francisco with in-kind social services. Unlike most welfare reform measures, proponents framed Care Not Cash as a progressive policy, aimed at expanding social services and government care

This thesis examines Care Not Cash, a welfare reform measure that replaced traditional cash General Assistance program payments for homeless persons in San Francisco with in-kind social services. Unlike most welfare reform measures, proponents framed Care Not Cash as a progressive policy, aimed at expanding social services and government care for this vulnerable population. Drawing on primary and secondary documents, as well as interviews with homelessness policy experts, this thesis examines the historical and political success of Care Not Cash, and explores the potential need for implementation of a similar program in Phoenix, Arizona.
ContributorsMcCutcheon, Zachary Ryan (Author) / Lucio, Joanna (Thesis director) / Williams, David (Committee member) / Bretts-Jamison, Jake (Committee member) / School of Public Affairs (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
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Subsolidus convection in the mantle of Earth is the driving mechanism behind plate tectonics and provides a central framework linking geophysical, geochemical, petrological, hydrological, and biological processes within the system. Seismic observations have revealed mantle heterogeneities in wide-ranging scales from less than tens of to thousands of kilometers. Understanding the

Subsolidus convection in the mantle of Earth is the driving mechanism behind plate tectonics and provides a central framework linking geophysical, geochemical, petrological, hydrological, and biological processes within the system. Seismic observations have revealed mantle heterogeneities in wide-ranging scales from less than tens of to thousands of kilometers. Understanding the origins and dynamics of these anomalies is critical to advance our knowledge on how mantle convection operates and coevolves with the surface system. This dissertation attempts to constrain the past, present and future of mantle dynamics with lines of evidence from seismology, geodynamics, petrology, geochemistry, and astrophysics. Above Earth’s core, two continent-sized large low shear velocity provinces (LLSVPs) beneath Africa and the Pacific Ocean were seismically detected decades ago. Yet their origin, composition, detailed morphology and influence over mantle convection remain elusive. First, I propose the two LLSVPs may represent the mantle remnants of the Moon-forming impactor Theia. I show that the mantle of Theia is intrinsically denser than Earth’s mantle and would have sunk and accumulated into LLSVP-like structures in the deepest mantle after 4.5 billion years. Second, I examined the maximum height of the two LLSVPs and determined that the African LLSVP is ~1,000 km higher than the Pacific counterpart. Using geodynamic simulations, I find the height of a stable LLSVP is mainly controlled by its density and the ambient mantle viscosity. With ~1,000 numerical experiments, I conclude that the origin of the great height difference between the LLSVPs is that the African LLSVP is less dense, and thus less stable than the Pacific LLSVP. Next, I numerically identified another dynamic scenario accounting for the vastly different height of the two LLSVPs, which is caused by catastrophic sinking of accumulated subducted slabs at the 660-km boundary. Last, targeting one ancient carbonatite above the African LLSVP, I show that lithium isotopes in humite measured by nanoscale secondary ion mass spectrometry was able to uncover the signature of a subducted oceanic crust in its magma source, which may return from the interior to the surface by mantle plumes.
ContributorsYuan, Qian (Author) / Li, Mingming (Thesis advisor) / Garnero, Edward (Committee member) / Shim, Sang-Heon (Committee member) / Hervig, Richard (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2022
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Space weathering of planetary surfaces is a complex process involving many mechanisms that work independently over different timescales. This research aims to address outstanding questions related to solar wind rim formation on space weathered regolith and tests a new hypothesis that dielectric breakdown plays an important role in the optical

Space weathering of planetary surfaces is a complex process involving many mechanisms that work independently over different timescales. This research aims to address outstanding questions related to solar wind rim formation on space weathered regolith and tests a new hypothesis that dielectric breakdown plays an important role in the optical maturation of lunar regolith. The purpose of this work is to highlight the limitations imposed by laboratory equipment to accurately simulate the solar wind’s effects on regolith and to provide physical context for the possible contributions of dielectric breakdown to space weathering. Terrestrial and lunar samples were experimentally irradiated and damage was characterized using electron microscopy techniques. Low-fluence proton irradiation produced differential weathering in a lunar mare basalt, with radiation damage on some phases being inconsistent with that found in the natural lunar environment. Dielectric breakdown of silicates revealed two electrical processes that produce characteristic surface and subsurface damage, in addition to amorphous rims. The results of this research highlight experimental parameters that if ignored, can significantly affect the results and interpretations of simulated solar wind weathering, and provides a framework for advancing space weathering research through experimental studies.
ContributorsShusterman, Morgan (Author) / Robinson, Mark S (Thesis advisor) / Sharp, Thomas G (Thesis advisor) / Hibbits, Charles (Committee member) / Bose, Maitrayee (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2023
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Description
Brown dwarfs are a unique class of object which span the range between the lowest mass stars, and highest mass planets. New insights into the physics and chemistry of brown dwarfs comes from the comparison between spectroscopic observations, and theoretical atmospheric models. In this thesis, I present a uniform atmospheric

Brown dwarfs are a unique class of object which span the range between the lowest mass stars, and highest mass planets. New insights into the physics and chemistry of brown dwarfs comes from the comparison between spectroscopic observations, and theoretical atmospheric models. In this thesis, I present a uniform atmospheric retrieval analysis of the coolest Y, and late-T spectral type brown dwarfs using the CaltecH Inverse ModEling and Retrieval Algorithms (CHIMERA). In doing so, I develop a foundational dataset of retrieved atmospheric parameters including: molecular abundances, thermal structures, evolutionary parameters, and cloud properties for 61 different brown dwarfs. Comparisons to other modeling techniques and theoretical expectations from the James Webb Space Telescope (JWST) are made. Finally, I describe the techniques used to improve CHIMERA to run on Graphical Processing Units (GPUs), which directly enabled the creation of this large dataset.
ContributorsZalesky, Joseph (Author) / Line, Michael R (Thesis advisor) / Patience, Jennifer (Committee member) / Groppi, Christopher (Committee member) / Young, Patrick (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2022
Description

Most asteroids originated in larger parent bodies that underwent accretion and heating during the first few million years of the solar system. We investigated the parent body of S-type asteroid 25143 Itokawa by developing a computational model which can approximate the thermal evolution of an early solar system body. We

Most asteroids originated in larger parent bodies that underwent accretion and heating during the first few million years of the solar system. We investigated the parent body of S-type asteroid 25143 Itokawa by developing a computational model which can approximate the thermal evolution of an early solar system body. We compared known constraints on Itokawa’s thermal history to simulations of its parent body and constrained its time of formation to between 1.6 and 2.5 million years after the beginning of the solar system, though certain details could allow for even earlier or later formation. These results stress the importance of precise data required of the material properties of asteroids and meteorites to place better constraints on the histories of their parent bodies. Additional mathematical and computational details are discussed, and the full code and data is made available online.

ContributorsHallstrom, Jonas (Author) / Bose, Maitrayee (Thesis director) / Beckstein, Oliver (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / Materials Science and Engineering Program (Contributor)
Created2023-05
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Characterizing the surface mineralogy of asteroids is critical to constraining their formation history and provides insight into the processes of planetary formation. One method of determining the surface mineralogy of asteroids is comparison of their visible to near-infrared reflectance (VNIR) spectra with laboratory spectra from meteorites and minerals. Subsequent in-situ

Characterizing the surface mineralogy of asteroids is critical to constraining their formation history and provides insight into the processes of planetary formation. One method of determining the surface mineralogy of asteroids is comparison of their visible to near-infrared reflectance (VNIR) spectra with laboratory spectra from meteorites and minerals. Subsequent in-situ investigation of these asteroids by spacecraft can supplement or supersede interpretations derived from Earth-based observations.I investigated a suite of aubrites, sulfide minerals, and metal-rich chondrites in a variety of forms (hand samples, powders, and slabs) to identify similarities with ‘spectrally featureless’ asteroids. I collected VNIR spectra and powder X-ray diffraction patterns of these samples and compared their overall reflectance and spectral slope with X-complex and T-, L-, and D-type asteroid spectra. The Psyche Mission will orbit asteroid (16) Psyche beginning in 2026. I provide a pre-flight assessment of the surface composition of Psyche by comparing spectra of Psyche to a large spectral library of possible surface analog materials (e.g., iron meteorites, mesosiderites, pallasites, sulfides, enstatite, ordinary, and metal-rich chondrites, endmember silicates, and mixtures of silicates, metal, and sulfides). Spectra of Psyche are generally consistent with iron meteorite powder, mixtures of iron meteorite powder and low-Fe, low-Ca pyroxene, sulfide minerals, and the CH/CBb chondrite Isheyevo. Next, I demonstrate some anticipated capabilities of the Psyche Multispectral Imager by comparing spectral parameters derived from Imager-convolved data to those from high resolution laboratory spectra. I offer preliminary strategies for classifying surface composition based on Imager filter ratios and overall reflectance. Last, I present an assessment of a benchtop, commercial-off-the-shelf (COTS) version of the Psyche Imager. The COTS Imager uses the same model CCD and a similar f-number commercial camera lens. I measured the gain, full well, linearity, read noise, quantum efficiency, and modulation transfer function to compare with eventual calibration data from the flight Imager. I validate the results of a radiometric model developed for the flight Imager with signal measurements from the COTS Imager. This work demonstrates that the COTS Imager is an effective testbed for validating Imager requirements and developing software and procedures for eventual calibration of the flight instrument.
ContributorsDibb, Steven (Author) / Bell, James (Thesis advisor) / Hardgrove, Craig (Committee member) / Garvie, Laurence (Committee member) / Elkins-Tanton, Linda (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2021
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Description
Lithium (Li) is a trace element in kerogen, but the content and isotopic distribution (δ7Li) in kerogen has not previously been quantified. Furthermore, kerogen has been overlooked as a potential source of Li to sedimentary porefluids and buried sediments. Thus, knowing the content and isotopic composition of Li derived from

Lithium (Li) is a trace element in kerogen, but the content and isotopic distribution (δ7Li) in kerogen has not previously been quantified. Furthermore, kerogen has been overlooked as a potential source of Li to sedimentary porefluids and buried sediments. Thus, knowing the content and isotopic composition of Li derived from kerogen may have implications for research focused on the Li-isotopes of buried sediments (e.g., evaluating paleoclimate variations using marine carbonates).The objective of this work is to better understand the role of kerogen in the Li geochemical cycle. The research approach consisted of 1) developing reference materials and methodologies to measure the Li-contents and δ7Li of kerogen in-situ by Secondary Ion Mass Spectrometry, 2) surveying the Li-contents and δ7Li of kerogen bearing rocks from different depositional and diagenetic environments and 3) quantifying the Li-content and δ7Li variations in kerogen empirically in a field study and 4) experimentally through hydrous pyrolysis. A survey of δ7Li of coals from depositional basins across the USA showed that thermally immature coals have light δ7Li values (–20 to – 10‰) compared to typical terrestrial materials (> –10‰) and the δ7Li of coal increases with burial temperature suggesting that 6Li is preferentially released from kerogen to porefluids during hydrocarbon generation. A field study was conducted on two Cretaceous coal seams in Colorado (USA) intruded by dikes (mafic and felsic) creating a temperature gradient from the intrusives into the country rock. Results showed that δ7Li values of the unmetamorphosed vitrinite macerals were up to 37‰ lighter than vitrinite macerals and coke within the contact metamorphosed coal. To understand the significance of Li derived from kerogen during burial diagenesis, hydrous pyrolysis experiments of three coals were conducted. Results showed that Li is released from kerogen during hydrocarbon generation and could increase sedimentary porefluid Li-contents up to ~100 mg/L. The δ7Li of coals becomes heavier with increased temperature except where authigenic silicates may compete for the released Li. These results indicate that kerogen is a significant source of isotopically light Li to diagenetic fluids and is an important contributor to the global geochemical cycle.
ContributorsTeichert, Zebadiah (Author) / Williams, Lynda B. (Thesis advisor) / Bose, Maitrayee (Thesis advisor) / Hervig, Richard (Committee member) / Semken, Steven (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2022
Description

During the Dawn mission, bright spots were discovered on the surface of the dwarf planet Ceres, which were determined to be evaporite deposits of sodium carbonate, ammonium carbonate, and hydrohalite. These deposits are significant because they indicate the presence of subsurface water and potential geologic activity on Ceres. These evaporites

During the Dawn mission, bright spots were discovered on the surface of the dwarf planet Ceres, which were determined to be evaporite deposits of sodium carbonate, ammonium carbonate, and hydrohalite. These deposits are significant because they indicate the presence of subsurface water and potential geologic activity on Ceres. These evaporites form from the brine-water mixture in the deep Ceres reservoir, which likely possesses the conditions ideal for forming complex organics. Here, we report the results of a suite of laboratory techniques (CHN Elemental Analyzer, Secondary Ion Mass Spectrometry, Fourier-Transform Infrared Spectroscopy, Gas Chromatography, and Brunauer-Emmett-Teller Analysis) for quantifying the likelihood of primordial carbon survival and distribution in analog materials found on Ceres, particularly in salt evaporates. We are specifically looking at if the amino acid glycine can be preserved in sodium chloride crystals. Our results conclude that if the Ceres brine reservoir is saturated with organics, and with the lower limits that we have for our instrumentation thus far, these techniques should be more than sufficient to measure glycine content should we ever receive samples from Ceres.

ContributorsReynoso, Lucas (Author) / Bose, Maitrayee (Thesis director) / Castillo-Rogez, Julie (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / School of Earth and Space Exploration (Contributor)
Created2023-05