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- All Subjects: supernovae
- All Subjects: mantle
- Creators: Bose, Maitrayee
- Creators: Chen, Huawei
Description
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
Description
Recent measurements of silicate and oxide stardust grains have revealed large Mg-isotope anomalies in silicate stardust belonging to group 1, which has challenged the low-mass origins of these grains, among others. In this work, stardust searches were performed in a thin section of the CO3.0 carbonaceous chondrite meteorite Allan Hills (ALHA) 77307 with the NanoSIMS 50L. Several group 1 silicate and oxide grains were subsequently measured for their silicon and magnesium isotopes. Although several group 1 silicate grains were found to fall on the Galactic Chemical Evolution line for both Si and Mg isotopes, a significant fraction do not. These grains are therefore incompatible with their proposed low-mass Red Giant or Asymptotic Giant Branch stellar origins. These observations corroborate recent work and suggest that group 1 grains may have multiple stellar sources which might include pre-supernovae massive stars and supernovae. The silicate stardust abundance calculated from this study is 168 ppm, while the oxide abundance is 18 ppm in ALHA 77307, which is in good agreement with published literature. Additionally, three large silicate stardust grains were found which range in size from 0.8 x 0.6 µm2 to 1.6 x 0.6 µm2 and exhibit unusual “bi-lobed” or “ameboid” shapes. Several C-anomalous presolar grains were also identified in ALHA 77307, many of which were subsequently measured for their N and Si isotopes. These grains are important because in-situ measurements of N and Si isotopes in SiC stardust are rare and N in chemically isolated SiC grains is likely affected by the sample preparation procedure and/or contamination. A majority of SiC grains from this study belong to the “mainstream” group proposed to form in the circumstellar envelopes of low-intermediate mass AGB stars, while two rare SiC AB grains were found with possible origins in J-type carbon stars and/or supernovae. The calculated SiC abundance in ALHA 77307 ranged from 57-148 ppm, the upper limit of which would be the highest presolar SiC abundance so far reported for this meteorite.
ContributorsMares-Manton, Elliot Aaron (Author) / Bose, Maitrayee (Thesis advisor) / Nittler, Larry (Committee member) / Schrader, Devin (Committee member) / Arizona State University (Publisher)
Created2024
Description
The transport of hydrogen to the Earth’s deep interior remains uncertain. The upper mantle minerals have very low hydrogen solubilities (hundreds of ppm). The hydrogen storage capability in the transition zone minerals (2 wt%) is high compared to those of the upper mantle. The hydrogen storage in the lower mantle is not well known. The main minerals in the lower mantle bridgmanite and ferropericlase have very low hydrogen storage capacities (less than 20 ppm). In order to further understand the hydrogen storage in the lower mantle, a series of experiments had been conducted to simulate the environment similar to the Earth’s mantle. The experiments with hydrous Mg2SiO4 ringwoodite (Rw) show that it converts to crystalline dense hydrous silica, stishovite (Stv) or CaCl2-type SiO2(mStv), containing ∼1 wt% H2O together with bridgmanite (Brd) and MgO at the pressure-temperature conditions expected for lower mantle depths between approximately 660 to 1600 km. Brd would break down partially to dense hydrous silica (6–25 mol%) and(Mg,Fe)O in mid-mantle regions with 0.05–0.27 wt% H2O. The hydrous stishovite has a CaCl2 structure, which is common among hydrous minerals in the lower mantle. Based on this observation, I hypothesize the existence of hydrous phases in the lower mantle. The experiments found a new hexagonal iron hydroxide (η-Fe12O18+x/2Hx) between the stability fields of the epsilon and pyrite-type FeOOH at 60–80 GPa and high temperature. The new phase contains less H2O, limiting the H2O transport from the shallow to the deep mantle in the Fe–O–H system. Possible hydrogen storage in Ca-perovskite was studied. CaPv could contain 0.5–1 wt% water and the water in CaPv could distort the crystal structure of CaPv from cubic to tetragonal structure. In conclusion, hydrogen can be stored in hydrous stishovite in the shallower depth of the lower mantle. At greater depth, the new η phase and pyrite-type phase would take over the hydrogen storage. The role of CaPv in deep water storage needs to be considered in future studies.
ContributorsChen, Huawei (Author) / Shim, Sang-Heon (Thesis advisor) / Garnero, Edward (Committee member) / Bose, Maitrayee (Committee member) / Li, Mingming (Committee member) / Leinenweber, Kurt (Committee member) / Arizona State University (Publisher)
Created2019