Matching Items (33)
Description
The temperature of a planet's surface depends on numerous physical factors, including thermal inertia, albedo and the degree of insolation. Mars is a good target for thermal measurements because the low atmospheric pressure combined with the extreme dryness results in a surface dominated by large differences in thermal inertia, minimizing the effect of other physical properties. Since heat is propagated into the surface during the day and re-radiated at night, surface temperatures are affected by sub-surface properties down to several thermal skin depths. Because of this, orbital surface temperature measurements combined with a computational thermal model can be used to determine sub-surface structure. This technique has previously been applied to estimate the thickness and thermal inertia of soil layers on Mars on a regional scale, but the Mars Odyssey Thermal Emission Imaging System "THEMIS" instrument allows much higher-resolution thermal imagery to be obtained. Using archived THEMIS data and the KRC thermal model, a process has been developed for creating high-resolution maps of Martian soil layer thickness and thermal inertia, allowing investigation of the distribution of dust and sand at a scale of 100 m/pixel.
ContributorsHeath, Simon (Author) / Christensen, Philip R. (Philip Russel) (Thesis advisor) / Bel, James (Thesis advisor) / Hervig, Richard (Committee member) / Arizona State University (Publisher)
Created2013
Description
In this thesis I model the thermal and structural evolution of Kuiper Belt Objects (KBOs) and explore their ability to retain undifferentiated crusts of rock and ice over geologic timescales. Previous calculations by Desch et al. (2009) predicted that initially homogenous KBOs comparable in size to Charon (R ~ 600 km) have surfaces too cold to permit the separation of rock and ice, and should always retain thick (~ 85 km) crusts, despite the partial differentiation of rock and ice inside the body. The retention of a thermally insulating, undifferentiated crust is favorable to the maintenance of subsurface liquid and potentially cryovolcanism on the KBO surface. A potential objection to these models is that the dense crust of rock and ice overlying an ice mantle represents a gravitationally unstable configuration that should overturn by Rayleigh-Taylor (RT) instabilities. I have calculated the growth rate of RT instabilities at the ice-crust interface, including the effect of rock on the viscosity. I have identified a critical ice viscosity for the instability to grow significantly over the age of the solar system. I have calculated the viscosity as a function of temperature for conditions relevant to marginal instability. I find that RT instabilities on a Charon-sized KBO require temperatures T > 143 K. Including this effect in thermal evolution models of KBOs, I find that the undifferentiated crust on KBOs is thinner than previously calculated, only ~ 50 km. While thinner, this crustal thickness is still significant, representing ~ 25% of the KBO mass, and helps to maintain subsurface liquid throughout most of the KBO's history.
ContributorsRubin, Mark (Author) / Desch, Steven J (Thesis advisor) / Sharp, Thomas (Committee member) / Christensen, Philip R. (Philip Russel) (Committee member) / Arizona State University (Publisher)
Created2013
Description
The implications of a changing climate have a profound impact on human life, society, and policy making. The need for accurate climate prediction becomes increasingly important as we better understand these implications. Currently, the most widely used climate prediction relies on the synthesis of climate model simulations organized by the Coupled Model Intercomparison Project (CMIP); these simulations are ensemble-averaged to construct projections for the 21st century climate. However, a significant degree of bias and variability in the model simulations for the 20th century climate is well-known at both global and regional scales. Based on that insight, this study provides an alternative approach for constructing climate projections that incorporates knowledge of model bias. This approach is demonstrated to be a viable alternative which can be easily implemented by water resource managers for potentially more accurate projections. Tests of the new approach are provided on a global scale with an emphasis on semiarid regional studies for their particular vulnerability to water resource changes, using both the former CMIP Phase 3 (CMIP3) and current Phase 5 (CMIP5) model archives. This investigation is accompanied by a detailed analysis of the dynamical processes and water budget to understand the behaviors and sources of model biases. Sensitivity studies of selected CMIP5 models are also performed with an atmospheric component model by testing the relationship between climate change forcings and model simulated response. The information derived from each study is used to determine the progressive quality of coupled climate models in simulating the global water cycle by rigorously investigating sources of model bias related to the moisture budget. As such, the conclusions of this project are highly relevant to model development and potentially may be used to further improve climate projections.
ContributorsBaker, Noel C (Author) / Huang, Huei-Ping (Thesis advisor) / Trimble, Steve (Committee member) / Anderson, James (Committee member) / Clarke, Amanda (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2013
Description
The present understanding of the formation and evolution of the earliest bodies in the Solar System is based in large part on geochemical and isotopic evidences contained within meteorites. The differentiated meteorites (meteorites originating from bodies that have experienced partial to complete melting) are particularly useful for deciphering magmatic processes occurring in the early Solar System. A rare group of differentiated meteorites, the angrites, are uniquely suited for such work. The angrites have ancient crystallization ages, lack secondary processing, and have been minimally affected by shock metamorphism, thus allowing them to retain their initial geochemical and isotopic characteristics at the time of formation. The scarcity of angrite samples made it difficult to conduct comprehensive investigations into the formation history of this unique meteorite group. However, a dramatic increase in the number of angrites recovered in recent years presents the opportunity to expand our understanding of their petrogenesis, as well as further refine our knowledge of the initial isotopic abundances in the early Solar System as recorded by their isotopic systematics. Using a combination of geochemical tools (radiogenic isotope chronometers and trace element chemistry), I have investigated the petrogenetic history of a group of four angrites that sample a range of formation conditions (cooling histories) and crystallization ages. Through isotope ratio measurements, I have examined a comprehensive set of long- and short-lived radiogenic isotope systems (26Al-26Mg, 87Rb-87Sr, 146Sm-142Nd, 147Sm-143Nd, and 176Lu-176Hf) within these four angrites. The results of these measurements provide information regarding crystallization ages, as well as revised estimates for the initial isotopic abundances of several key elements in the early Solar System. The determination of trace element concentrations in individual mineral phases, as well as bulk rock samples, provides important constraints on magmatic processes occurring on the angrite parent body. The measured trace element abundances are used to estimate the composition of the parent melts of individual angrites, examine crystallization conditions, and investigate possible geochemical affinities between various angrites. The new geochemical and isotopic measurements presented here significantly expand our understanding of the geochemical conditions found on the angrite parent body and the environment in which these meteorites formed.
ContributorsSanborn, Matthew E (Author) / Wadhwa, Meenakshi (Thesis advisor) / Hervig, Richard (Committee member) / Sharp, Thomas (Committee member) / Clarke, Amanda (Committee member) / Williams, Lynda (Committee member) / Carlson, Richard (Committee member) / Arizona State University (Publisher)
Created2012
Description
Seismic observations have revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath Pacific and Africa. One hypothesis for the origin of LLSVPs is that they are caused by accumulation of subducted oceanic crust on the core-mantle boundary (CMB). Here, I perform high resolution geodynamical calculations to test this hypothesis. The result shows that it is difficult for a thin (~ 6 km) subducted oceanic crust to accumulate on the CMB, and the major part of it is viscously stirred into the surrounding mantle. Another hypothesis for the origin of LLSVPs is that they are caused by thermochemical piles of more-primitive material which is remnant of Earth's early differentiation. In such case, a significant part of the subducted oceanic crust would enter the more-primitive reservoir, while other parts are either directly entrained into mantle plumes forming on top of the more-primitive reservoir or stirred into the background mantle. As a result, mantle plumes entrain a variable combination of compositional components including more-primitive material, old oceanic crust which first enters the more-primitive reservoir and is later entrained into mantle plumes with the more-primitive material, young oceanic crust which is directly entrained into mantle plumes without contacting the more-primitive reservoir, and depleted background mantle material. The result reconciles geochemical observation of multiple compositional components and varying ages of oceanic crust in the source of ocean-island basalts. Seismic studies have detected ultra-low velocity zones (ULVZs) in some localized regions on the CMB. Here, I present 3D thermochemical calculations to show that the distribution of ULVZs provides important information about their origin. ULVZs with a distinct composition tend to be located at the edges of LLSVPs, while ULVZs solely caused by partial melting tend to be located inboard from the edges of LLSVPs. This indicates that ULVZs at the edges of LLSVPs are best explained by distinct compositional heterogeneity, while ULVZs located insider of LLSVPs are better explained by partial melting. The results provide additional constraints for the origin of ULVZs.
ContributorsLi, Mingming (Author) / McNamara, Allen K (Thesis advisor) / Garnero, Edward J (Committee member) / Shim, Sang-Heon (Committee member) / Tyburczy, James (Committee member) / Clarke, Amanda (Committee member) / Arizona State University (Publisher)
Created2015
Description
Much of Mars' surface is mantled by bright dust, which masks the spectral features used to interpret the mineralogy of the underlying bedrock. Despite the wealth of near-infrared (NIR) and thermal infrared data returned from orbiting spacecraft in recent decades, the detailed bedrock composition of approximately half of the martian surface remains relatively unknown due to dust cover. To address this issue, and to help gain a better understanding of the bedrock mineralogy in dusty regions, data from the Thermal Emission Spectrometer (TES) Dust Cover Index (DCI) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) were used to identify 63 small localized areas within the classical bright dusty regions of Arabia Terra, Elysium Planitia, and Tharsis as potential "windows" through the dust; that is, areas where the dust cover is thin enough to permit infrared remote sensing of the underlying bedrock. The bedrock mineralogy of each candidate "window" was inferred using processed spectra from the Mars Express (MEx) Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) NIR spectrometer and, where possible, TES. 12 areas of interest returned spectra that are consistent with mineral species expected to be present at the regional scale, such as high- and low-calcium pyroxene, olivine, and iron-bearing glass. Distribution maps were created using previously defined index parameters for each species present within an area. High-quality TES spectra, if present within an area of interest, were deconvolved to estimate modal mineralogy and support NIR results. OMEGA data from Arabia Terra and Elysium Planitia are largely similar and indicate the presence of high-calcium pyroxene with significant contributions of glass and olivine, while TES data suggest an intermediate between the established southern highlands and Syrtis Major compositions. Limited data from Tharsis indicate low-calcium pyroxene mixed with lesser amounts of high-calcium pyroxene and perhaps glass. TES data from southern Tharsis correlate well with the previously inferred compositions of the Aonium and Mare Sirenum highlands immediately to the south.
ContributorsLai, Jason Chi-Shun (Author) / Bell, James (Thesis advisor) / Christensen, Philip R. (Philip Russel) (Committee member) / Hervig, Richard (Committee member) / Arizona State University (Publisher)
Created2014
Description
Dust devils have proven to be commonplace on Mars, although their occurrence is unevenly distributed across the surface. They were imaged or inferred by all six successful landed spacecraft: the Viking 1 and 2 Landers (VL-1 and VL-2), Mars Pathfinder Lander, the Mars Exploration Rovers Spirit and Opportunity, and the Phoenix Mars Lander. Comparisons of dust devil parameters were based on results from optical and meteorological (MET) detection campaigns. Spatial variations were determined based on comparisons of their frequency, morphology, and behavior. The Spirit data spanning three consecutive martian years is used as the basis of comparison because it is the most extensive on this topic. Average diameters were between 8 and 115 m for all observed or detected dust devils. The average horizontal speed for all of the studies was roughly 5 m/s. At each site dust devil densities peaked between 09:00 and 17:00 LTST during the spring and summer seasons supporting insolation-driven convection as the primary formation mechanism. Seasonal number frequency averaged ~1 dust devils/ km2/sol and spanned a total of three orders of magnitude. Extrapolated number frequencies determined for optical campaigns at the Pathfinder and Spirit sites accounted for temporal and spatial inconsistencies and averaged ~19 dust devils/km2/sol. Dust fluxes calculated from Pathfinder data (5x10-4 kg/m2/s and 7x10-5 kg/m2/s) were well with in the ranges calculated from Spirit data (4.0x10-9 to 4.6x10-4 kg/m2/s for Season One, 5.2x10-7 to 6.2x10-5 kg/m2/s during Season Two, and 1.5x10-7 to 1.6x10-4 kg/m2/s during Season Three). Based on the results a campaign is written for improvements in dust devil detection at the Mars Science Laboratory's (MSL) site. Of the four remaining candidate MSL sites, the dusty plains of Gale crater may potentially be the site with the highest probability of dust devil activity.
ContributorsWaller, Devin (Author) / Greeley, Ronald (Thesis advisor) / Christensen, Philip R. (Philip Russel) (Committee member) / Cerveny, Randall (Committee member) / Arizona State University (Publisher)
Created2011
Description
Understanding the evolution of the Himalayan-Tibetan orogen is important because of its purported effects on global geodynamics, geochemistry and climate. It is surprising that the timing of initiation of this canonical collisional orogen is poorly constrained, with estimates ranging from Late Cretaceous to Early Oligocene. This study focuses on the Ladakh region in the northwestern Indian Himalaya, where early workers suggested that sedimentary deposits of the Indus Basin molasse sequence, located in the suture zone, preserve a record of the early evolution of orogenesis, including initial collision between India and Eurasia. Recent studies have challenged this interpretation, but resolution of the issue has been hampered by poor accessibility, paucity of robust depositional age constraints, and disputed provenance of many units in the succession. To achieve a better understanding of the stratigraphy of the Indus Basin, multispectral remote sensing image analysis resulted in a new geologic map that is consistent with field observations and previously published datasets, but suggests a substantial revision and simplification of the commonly assumed stratigraphic architecture of the basin. This stratigraphic framework guided a series of new provenance studies, wherein detrital U-Pb geochronology, 40Ar/39Ar and (U-Th)/He thermochronology, and trace-element geochemistry not only discount the hypothesis that collision began in the Early Oligocene, but also demonstrate that both Indian and Eurasian detritus arrived in the basin prior to deposition of the last marine limestone, constraining the age of collision to older than Early Eocene. Detrital (U-Th)/He thermochronology further elucidates the thermal history of the basin. Thus, we constrain backthrusting, thought to be an important mechanism by which Miocene convergence was accommodated, to between 11-7 Ma. Finally, an unprecedented conventional (U-Th)/He thermochronologic dataset was generated from a modern river sand to assess steady state assumptions of the source region. Using these data, the question of the minimum number of dates required for robust interpretation was critically evaluated. The application of a newly developed (U-Th)/He UV-laser-microprobe thermochronologic technique confirmed the results of the conventional dataset. This technique improves the practical utility of detrital mineral (U-Th)/He thermochronology, and will facilitate future studies of this type.
ContributorsTripathy, Alka (Author) / Hodges, Kip V (Thesis advisor) / Semken, Steven (Committee member) / Van Soest, Matthijs C (Committee member) / Whipple, Kelin X (Committee member) / Christensen, Philip R. (Philip Russel) (Committee member) / Arizona State University (Publisher)
Created2011
Description
Impact cratering and volcanism are two fundamental processes that alter the surfaces of the terrestrial planets. Though well studied through laboratory experiments and terrestrial analogs, many questions remain regarding how these processes operate across the Solar System. Little is known about the formation of large impact basins (>300 km in diameter) and the degree to which they modify planetary surfaces. On the Moon, large impact basins dominate the terrain and are relatively well preserved. Because the lunar geologic timescale is largely derived from basin stratigraphic relations, it is crucial that we are able to identify and characterize materials emplaced as a result of the formation of the basins, such as light plains. Using high-resolution images under consistent illumination conditions and topography from the Lunar Reconnaissance Orbiter Camera (LROC), a new global map of light plains is presented at an unprecedented scale, revealing critical details of lunar stratigraphy and providing insight into the erosive power of large impacts. This work demonstrates that large basins significantly alter the lunar surface out to at least 4 radii from the rim, two times farther than previously thought. Further, the effect of pre-existing topography on the degradation of impact craters is unclear, despite their use in the age dating of surfaces. Crater measurements made over large regions of consistent coverage using LROC images and slopes derived from LROC topography show that pre-existing topography affects crater abundances and absolute model ages for craters up to at least 4 km in diameter.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
On Mars, small volcanic edifices can provide valuable insight into the evolution of the crust and interior, but a lack of superposed craters and heavy mantling by dust make them difficult to age date. On Earth, morphometry can be used to determine the ages of cinder cone volcanoes in the absence of dated samples. Comparisons of high-resolution topography from the Context Imager (CTX) and a two-dimensional nonlinear diffusion model show that the forms observed on Mars could have been created through Earth-like processes, and with future work, it may be possible to derive an age estimate for these features in the absence of superposed craters or samples.
ContributorsMeyer, Heather (Author) / Robinson, Mark S (Thesis advisor) / Bell, Jim (Thesis advisor) / Denevi, Brett (Committee member) / Clarke, Amanda (Committee member) / Asphaug, Erik (Committee member) / Arizona State University (Publisher)
Created2018
Description
The dynamic Earth involves feedbacks between the solid crust and both natural and anthropogenic fluid flows. Fluid-rock interactions drive many Earth phenomena, including volcanic unrest, seismic activities, and hydrological responses. Mitigating the hazards associated with these activities requires fundamental understanding of the underlying physical processes. Therefore, geophysical monitoring in combination with modeling provides valuable tools, suitable for hazard mitigation and risk management efforts. Magmatic activities and induced seismicity linked to fluid injection are two natural and anthropogenic processes discussed in this dissertation.
Successful forecasting of the timing, style, and intensity of a volcanic eruption is made possible by improved understanding of the volcano life cycle as well as building quantitative models incorporating the processes that govern rock melting, melt ascending, magma storage, eruption initiation, and interaction between magma and surrounding host rocks at different spatial extent and time scale. One key part of such models is the shallow magma chamber, which is generally directly linked to volcano’s eruptive behaviors. However, its actual shape, size, and temporal evolution are often not entirely known. To address this issue, I use space-based geodetic data with high spatiotemporal resolution to measure surface deformation at Kilauea volcano. The obtained maps of InSAR (Interferometric Synthetic Aperture Radar) deformation time series are exploited with two novel modeling schemes to investigate Kilauea’s shallow magmatic system. Both models can explain the same observation, leading to a new compartment model of magma chamber. Such models significantly advance the understanding of the physical processes associated with Kilauea’s summit plumbing system with potential applications for volcanoes around the world.
The unprecedented increase in the number of earthquakes in the Central and Eastern United States since 2008 is attributed to massive deep subsurface injection of saltwater. The elevated chance of moderate-large damaging earthquakes stemming from increased seismicity rate causes broad societal concerns among industry, regulators, and the public. Thus, quantifying the time-dependent seismic hazard associated with the fluid injection is of great importance. To this end, I investigate the large-scale seismic, hydrogeologic, and injection data in northern Texas for period of 2007-2015 and in northern-central Oklahoma for period of 1995-2017. An effective induced earthquake forecasting model is developed, considering a complex relationship between injection operations and consequent seismicity. I find that the timing and magnitude of regional induced earthquakes are fully controlled by the process of fluid diffusion in a poroelastic medium and thus can be successfully forecasted. The obtained time-dependent seismic hazard model is spatiotemporally heterogeneous and decreasing injection rates does not immediately reduce the probability of an earthquake. The presented framework can be used for operational induced earthquake forecasting. Information about the associated fundamental processes, inducing conditions, and probabilistic seismic hazards has broad benefits to the society.
Successful forecasting of the timing, style, and intensity of a volcanic eruption is made possible by improved understanding of the volcano life cycle as well as building quantitative models incorporating the processes that govern rock melting, melt ascending, magma storage, eruption initiation, and interaction between magma and surrounding host rocks at different spatial extent and time scale. One key part of such models is the shallow magma chamber, which is generally directly linked to volcano’s eruptive behaviors. However, its actual shape, size, and temporal evolution are often not entirely known. To address this issue, I use space-based geodetic data with high spatiotemporal resolution to measure surface deformation at Kilauea volcano. The obtained maps of InSAR (Interferometric Synthetic Aperture Radar) deformation time series are exploited with two novel modeling schemes to investigate Kilauea’s shallow magmatic system. Both models can explain the same observation, leading to a new compartment model of magma chamber. Such models significantly advance the understanding of the physical processes associated with Kilauea’s summit plumbing system with potential applications for volcanoes around the world.
The unprecedented increase in the number of earthquakes in the Central and Eastern United States since 2008 is attributed to massive deep subsurface injection of saltwater. The elevated chance of moderate-large damaging earthquakes stemming from increased seismicity rate causes broad societal concerns among industry, regulators, and the public. Thus, quantifying the time-dependent seismic hazard associated with the fluid injection is of great importance. To this end, I investigate the large-scale seismic, hydrogeologic, and injection data in northern Texas for period of 2007-2015 and in northern-central Oklahoma for period of 1995-2017. An effective induced earthquake forecasting model is developed, considering a complex relationship between injection operations and consequent seismicity. I find that the timing and magnitude of regional induced earthquakes are fully controlled by the process of fluid diffusion in a poroelastic medium and thus can be successfully forecasted. The obtained time-dependent seismic hazard model is spatiotemporally heterogeneous and decreasing injection rates does not immediately reduce the probability of an earthquake. The presented framework can be used for operational induced earthquake forecasting. Information about the associated fundamental processes, inducing conditions, and probabilistic seismic hazards has broad benefits to the society.
ContributorsZhai, Guang (Author) / Shirzaei, Manoochehr (Thesis advisor) / Garnero, Edward (Committee member) / Clarke, Amanda (Committee member) / Tyburczy, James (Committee member) / Li, Mingming (Committee member) / Arizona State University (Publisher)
Created2018