Widespread distribution of dissolved uranium (U) from natural and anthropogenic sources poses a challenge to both environmental and human health. Some bacteria are known to reduce highly soluble U(VI) into more insoluble U(IV), limiting the rate it may leach into subsurface environments. Therefore, understanding how this metabolism functions in situ is vital for predicting subsurface U transport. Any thorough understanding of microbial metabolisms must compare different means of energy production (i.e. catabolic reactions). This means the metabolic processes involved in U(VI) reduction must be compared to those where an alternative terminal electron acceptor (TEA) is used. The facultative anaerobic bacterium Shewanella putrefaciens strain CN32 has been the focus of many recent studies on U, but there has yet to be a detailed study of its metabolic efficiency across multiple TEA’s. This work quantitatively examined the metabolic efficiency of Shewanella putrefaciens CN32 by comparing the ratio of cells produced to the total mass of protein produced when growing on three different TEA’s: O2, Fe(III), and U(VI). Furthermore, the overall health of the culture was evaluated by measuring the size of cells grown with each TEA. Initial results indicate that both a larger average cell size and larger ratio of cells to protein mass correspond with potential Gibbs energy of each catabolic reaction (in decreasing order: O2, Fe(III), U(VI) reduction). Gaining a further understanding on bacterial U reduction will allow for hazard mitigation methods to be developed and used in at-risk areas around the world. 

Recurring slope lineae (RSL) observed on Mars appear to be flows of liquid water because they seasonally propagate down sunny slopes in the spring and fade during the winter. Liquid water suggests the potential for life on Mars’ surface and has implications for future exploration; however, recent hypotheses contend that RSL form via dry sand avalanches. To test wet vs. dry flow hypotheses, we analyzed images and topographic data from Garni crater taken by the High Resolution Imaging Science Experiment (HiRISE) during the Martian summer and winter. Our results show that RSL size correlates with areas where we expect high windblown sand deposition, such as on the SE lee side of the crater, or in small gullies below large headwalls. Additionally, RSL do not appear on the wind-scoured NW side of the crater. These surface relationships indicate that RSL in Garni crater form via a dry process in which windblown sand is deposited by prevailing NE winds and seasonally avalanches down steep slopes. To further test our conclusions, we are examining additional confirmed RSL sites on Mars to see if they display the same behavior.

Geothermal flux, the amount of heat from the Earth’s interior that reaches the Earth’s surface, is an important boundary value used when modeling ice sheets in Antarctica and estimating future sea level rise. However, geothermal flux is difficult to measure directly. This research project used a numerical ice and heat flow model to estimate the upper bound for geothermal flux under ice domes in Antarctica. We applied this model to ice domes with identifiable Raymond arches, structures in the internal stratigraphy which form only when the ice is frozen to the bed. We estimated the geothermal flux at which an ice dome’s modeled basal temperature reaches the melting point, thus setting an upper bound, using site-specific values for the accumulation rate, surface temperature, and ice thickness. Where measured basal temperatures are known, we made more precise estimates of geothermal flux. Uncertainty values for the modeled flux values were derived by testing the uncertainty of each input value. Model estimates were compared with Martos et al. (2017) and An et al. (2015) geothermal flux estimates derived from remotely sensed data. Comparisons show that in regions such as the Siple Coast, estimates disagree significantly, while they mostly agree in the Antarctic Peninsula. The results of this project set an upper limit on geothermal flux values that can be used to support past and future geothermal flux estimates at these locations.

During the Last Glacial Maximum (LGM), the Cordilleran Ice Sheet advanced into the northwestern United States and dammed the Clark Fork river in western Montana, forming Glacial Lake Missoula. The ice dam in the valley repeatedly broke, sending at least 100 massive outburst floods known as the Missoula Floods into eastern Washington where they incised deep canyons forming the Channeled Scabland. During the period of flooding, the Okanogan Lobe of the Cordilleran Ice Sheet crossed the Columbia Gorge onto the Waterville Plateau, diverting floodwaters away from the Columbia River into Grand Coulee, before blocking Grand Coulee itself. My research project examines the timing of glaciation of the Waterville Plateau and how it influenced the paths of the successive floods. To determine the timing of glaciation, my advisers and I studied glacially transported boulders that began to accumulate the cosmic ray produced isotope beryllium-10 (10Be) after they were exposed by ice sheet retreat. In the lab, we separated and dissolved quartz from our samples, purified beryllium, and then measured 10Be/⁹Be ratios using Accelerator Mass Spectrometry (AMS). From AMS measurements, we calculated the exposure ages of our samples. We expect the ages to fit within the established sequence of ice advance across the Columbia River, redirection of floodwaters down Grand Coulee, and eventual ice retreat to north of the Columbia River. Following this sequence, we expect our samples from the northern edge of the Waterville Plateau to be younger than the last floods down Grand Coulee (15,300 years) but older than samples from the Omak Plateau north of the Columbia Gorge (13,900 years). Along with dates from previous studies, the new exposure dates from this project explain how the Okanogan Lobe guided Missoula floodwaters and influenced landscape evolution in eastern Washington.

Carbon dioxide concentrations have been on the rise since preindustrial times due to anthropogenic emissions. Understanding how past climates have responded to changes in the atmosphere is important to understand how our current climate will react to changes in our present-day atmosphere. Soil carbonates record the temperature at the time of their formation in their stable isotopic composition (called clumped isotope geochemistry). Ancient soil carbonates can record the temperature and allow us to better understand paleoclimates. Understanding what time of year soil carbonates form allows us to better interpret the temperature being recorded. The timing of changes in soil moisture is likely one of the most important environmental factors to consider. We test whether soil carbonates form during soil drying events using soil moisture and temperature data measured remotely by a satellite called Soil Moisture Active Passive (SMAP). This satellite has been gathering near-surface soil moisture data globally since 2015 at 35-65 km resolution. We compare the air temperature of the month with the greatest net negative soil moisture content month (determined from the satellite data) to the measured growth temperature of soil carbonates (estimated through geochemistry). We first compare the month of drying of three locales in North America, then extend the analysis globally to all locations for which soil carbonate clumped isotope data exist. Preliminary results suggest that the temperature of the month with the most drying agrees with formation temperature we estimated from clumped isotope geochemistry within one degree for a site in Nebraska and within seven degrees for a site in Wyoming. These results suggest that soil drying promotes soil carbonate formation in some environments. By using soil carbonates to explain past climates, we will improve temperature change estimates, which will help improve climate models for the future.

Anatolia, in modern Turkey, is a complex assemblage of micro-continents that collided during the Late Cretaceous and the Paleogene, 80 to 25 million years ago. Despite the large volume of work on the numerous Anatolian terranes and collisions, basic questions regarding the timing of collision, style of post-collisional deformation and development of topography remain enigmatic. In western Anatolia, the timing and mechanisms of these successive collisions are poorly understood and do not conform with current continent-continent collision models. This project reconstructs the evolution of the collision zone in order to reconstruct the tectonic evolution of western Anatolia and refine models of collisional tectonics. Here, we present new data from the 160-40 million year old sedimentary archives preserved in the Central Sakarya Basin, a sedimentary basin that formed adjacent to the collision zone. Two methods for sedimentary analysis are employed in this research: detrital zircon dating and sandstone petrography. Detrital zircon ages attained through Uranium-Lead dating techniques are compared to known ages from surrounding mountain ranges to determine the source of sediment through time and apply age constraints to stratigraphic layers. Sandstone petrographic analysis examines the composition of samples to determine sedimentary provenance. The evolution of sediment sources through time provides a robust timeline of collision, post-collisional deformation and topographic development. The results from zircon dating and sandstone petrography show an evolution of sediment provenance where the oldest, pre-collisional sediments are derived from an adjacent volcanic chain. The onset of collision, around 60 million years ago, is marked by a change in sediment composition as collision creates topography and fault systems exhume older, buried rock. In constructing a progression of sediment source, this research determines a precise chronology for the collision and post-collisional evolution of western Anatolia and contributes to modifying current models on collisional margins.

When seeking to better understand specific bedrock river erosional processes due to flooding, numerical modeling can help answer many questions, specifically the extent to which floods contribute to setting the landscape. The eastern Himalaya experiences multiple flooding events of different magnitude: annual monsoon floods (10³m³/s) and centennial outburst floods (10⁵ m³/s). This region also experienced at least two ancient megafloods during the Holocene (10⁶ m³/s). Previous studies of flooding in the region have assessed the potential geomorphic role of the outburst floods and megafloods; however, the relative geomorphic impact of annual monsoon flooding remains unknown. To fully understand the relative erosive power of these eastern Himalayan floods, it is necessary to compare the hydraulics of outburst dam-break floods to the hydraulics of seasonal monsoon flow. To do this, we use the program GeoClaw to numerically simulate monsoon flood flow in this region. GeoClaw, which uses the 2D shallow water equations, has accurately been used to model outburst flooding events, including the centennial outburst floods and the ancient megafloods. By modifying the program to simulate constant monsoon discharge, we can analyze patterns of flow velocity and depth (GeoClaw outputs) to understand the spatial pattern of shear stress during monsoon floods. We expect to find that monsoon flow will yield lower magnitudes of shear stress and more homogeneous patterns of potential erosion compared to those observed for the outburst floods and megafloods. Understanding these erosional spatial patterns will help us better recognize the relative contributions of various magnitude floods and the extent to which each can set the landscape.

The rocks that comprise the San Juan Islands were transported thousands of kilometers along the coast of North America, and then stacked together during 50 million years of subduction off the coast of northern Washington. Unravelling the origins of these rock packages is critical to understanding the tectonic history of the Pacific Northwest. Pillow basalts (pillow shaped structures formed during submarine eruption of basaltic lava) at two locations on Lopez Island are examples of two unrelated units. While the basalt units are only 2 km apart and similar in texture and mineralogy, they differ in age and possibly magmatic origin. The radiogenic isotopic compositions of Nd, Sr and Pb in magmas provide information on their source. Since Earth’s mantle has a heterogeneous isotopic composition, it is possible to infer the volcanic setting in which the basalts formed. Little chemical and no isotopic data exist for these rocks. We analyze the Sm-Nd, Rb-Sr, and U-Pb isotopic systems of samples from both pillow basalt exposures, and compare the measured isotopic ratios to known variations in magmatic sources. During microscopic examination of the sample mineralogy, we identified strong metamorphic alteration to the pillows, which would alter their chemical composition. To obtain the original isotopic composition of the samples we developed a procedure to remove altered minerals and added elements using successively stronger acid leaches. We are testing this on subsamples of a single “pillow” with different extents of alteration to test if we can obtain original compositions. With these ratios we can determine the volcanic setting of these units and gain a better understanding of complex structural geology of Lopez Island. If we can see through alteration to original isotopic compositions, it will open a new way to investigate the origin of the complex geologic history of the San Juan Islands.

The Bonneville Landslide dam, also known as the Bridge of the Gods, blocked the Columbia River about 550 years ago at the site of the modern Bonneville Dam, on the Washington-Oregon border. According to Klickitat lore, the Bridge of the Gods was created by the chief of all gods to join the lands north and south of the river. The dam’s failure, thought to be a result of the violent dispute between the chief’s sons, led to an outburst flood that drowned a forest and carved the Cascade Rapids. Sedimentary deposits from this dam break flood have been observed downstream, but the flood behavior and inundation pattern remains unknown. In this study, we created a paleo-digital elevation model (DEM) of the Columbia Valley Gorge landscape before the flood, which will serve as the basemap for numerical models of the flood. The paleo-DEM combines three data sets: 1) topographic data derived from the 1868 and 1901 U.S. Coast and Geodetic Survey historic topographic survey maps and bathymetric depth values from hydrographic sheets; 2) bathymetry of the Lower Columbia River with removed modern structures in Portland, validated by tide records from 1853 to 1876; and 3) bathymetry upstream from the Bonneville Dam, merged with adjacent topography and derived from NOAA data. In ArcGIS, we filled in data holes and modern channels and subtracted modern structures in an attempt to accurately represent the paleo-environment. Because the Columbia estuary is heavily influenced by tides, we used historic tide observations to create a low and high tide paleo-DEM to make preliminary analyses of how the tide might have influenced this flood. Once we know the paleo-topography of the Columbia Gorge, Portland basin, and Columbia Estuary, we can begin to numerically model this flood and explore its geomorphic impact.

The Seattle Fault Zone (SFZ) is a region of complex, east-west striking thrust faults in the Puget Sound area in Washington. Radiocarbon dating of landslides has determined that the SFZ most recently ruptured ~1100 years ago. At this time, non-glacial sedimentary rocks from the Blakeley Formation (26-37 Mya) were uplifted up to 7 meters along the hanging wall of the fault. In this study, we use low temperature (U-Th)/He thermochronology to constrain the timing of slip on the main thrust of the Seattle Fault Zone. The dating technique is used on apatite crystals obtained from samples of the Blakeley sandstone to develop a time-temperature cooling history as the rocks were uplifted and subsequently exhumed. The apatite (U-Th)/He thermochronometer records the date that the mineral passed through the approximately 70°C closure temperature. Based on a 25°C/km geothermal gradient, this closure temperature represents the upper 2-3 km of the crust. The samples were collected from a transect along the hanging wall of the fault, from Alki Point, Seattle in the west to East Lake Sammamish, Issaquah in the east. All samples were collected between 0.5 and 1 m from the surface, and at similar elevations in order to account for different exhumation rates. The rate of exhumation along the fault will be determined from plots of the apatite time-temperature cooling history, where younger dates indicate more rapid exhumation rates. From this data, we will back out erosion rates in order to constrain the total fault uplift.

Grasslands cover approximately 20% of Earth’s land today and spread gradually worldwide in subtropical areas during the last 40 million years. Pollen data from sedimentary rocks in Myanmar suggest that grasslands might have existed there as early as 25 million years ago but did not spread to other Asian regions until much later, 10-6 million years ago. To fully understand the ecology of these early Asian grasslands, I reconstructed the paleoenvironments of Myanmar during the late Oligocene and early Miocene, 25 to 18 million years ago. I used two paleoenvironmental proxies on paleosol samples from Burmese sedimentary rocks: carbon isotopic composition of bulk sediment and phytolith analysis. The bulk carbon isotopic composition in paleosol is an indirect insight into the local aridity and can help reconstructing soil productivity; phytoliths–silica bodies deposited inside living plant tissue that remain in the soil after the tissue decays, forming fossils—when extracted, can help identify the grass types and their relative abundance in the ecosystem. Documenting the characteristics and paleoenvironmental setting of these early grasslands will help us understanding why they did not spread until millions of years later in Asia –and if this timing of ecological expansion is linked to the regional evolution of monsoonal intensity.

As anthropogenic climate change progresses and alters our marine ecosystems, it is important to monitor the changes it creates in order to inform plans for mitigation or management. This project, completed as part of the Puget Sound Foraminifera Research Project at The Burke Museum, uses sediment samples collected by the Washington State Department of Ecology and extracts benthic foraminifera from those samples to learn vital information about the health of the Puget Sound. Benthic foraminifera are single-celled organisms that live on or in marine sediment and form shells of calcium carbonate or agglutinated sand grains. This research looks at the dissolution of shells of a species of calcareous foraminifera called Elphidiella hannai in order to establish whether different populations across Puget Sound are affected differently and if dissolution primarily happens before or after the death of individuals. For this research, samples collected from a variety of Puget Sound embayments over four years starting in 2015 were processed and stained with Rose Bengal to ascertain whether the foraminifera were alive at the time they were collected. Following this, foraminifera were sorted and species were grouped. Finally Elphidiella hannai were assessed for dissolution on a 0-3 scale, 0 meaning pristine and 3 heavily damaged. Preliminary results show higher levels of damage in stained individuals and vastly differing amounts of damage in different Puget Sound embayments, suggesting most damage happened while foraminifera were still alive and that changes in acidity of water are impacting populations at different rates.

The Irrawaddy River is Myanmar’s biggest river system and the world’s third largest river in terms of sediment load. It drains the eastern edge of the Himalayas and flows through the Central Myanmar Basin into the Andaman Sea. Its geological history remains yet poorly documented, and when its modern drainage basin was established is unknown. For my research, I reconstructed the history of the Irrawaddy drainage system by using sedimentary provenance methods. Sediments in the Central Myanmar Basin can be traced back to their source rock by using different geochemical and petrographic proxies; by using these proxies on dated sedimentary rocks in the basin, I aimed at determining when the modern sediment sources were established. My research focused on two proxies: zircon geochronology and petrographic analysis of sandstones. Zircon geochronology is a method of dating zircon minerals from sandstones. The zircon age distribution obtained from a particular sediment sample is a direct insight into the age of the sediment source rock. Sandstone petrographic analysis involves analyzing at least 300 individual sediment grains and classifying them according to their mineralogy to compare them with the known rock characteristics in the potential sediment source areas. Both proxies were applied on sedimentary rocks of different ages previously collected in the field. I compared the results from both analyses with the modern sediments collected from the Irrawaddy river mouth and modern sediment source areas. I looked for consistency in the zircon age distributions and petrography signatures between the modern and older deposits to deduce the maximum age of the river. My preliminary results suggest that the Irrawaddy River was established around Middle Eocene (40Ma), which would make the Irrawaddy one of the oldest drainage systems of Asia.

The Olympic Mountains on the west coast of Washington State are an impressive topographic feature, the emergence timing of which remains poorly documented. The Olympic Peninsula comprises 52 million year old (52 Ma) igneous rocks, and marine sedimentary rocks deposited from 52Ma to present. Here, we use a proxy to model sourcing of sediment called detrital zircon provenance (DZP). We use DZP of sedimentary rocks from the Olympic peninsula and from the Seattle Basin further east to model ancient drainage systems in order to place age constraints on the uplift of the Olympic Mountains. Our data from both areas show that 52 Ma through 23 Ma sandstones display DZP patterns and sediment type in agreement with a direct supply from central Washington. Samples of 13 to 11 Ma sandstones and modern river sands from the west of the Olympic Peninsula display a youngest zircon age population at 17 Ma. These data indicate that this area was still fed by central Washington at that time. 11 Ma sandstones from the eastern part of the Seattle Basin display DZP patterns still in agreement with supply from central Washington. By contrast, contemporary river sandstones from the western part of the basin mostly consist of reworked older sediment. This change in sediment source shows that by 11 Ma, the Olympics had already emerged and reached sufficient topographic prominence to support eastward draining rivers that deposited the 11 Ma river sandstone units of the Seattle Basin. These data allow us to constrain the initial uplift of the Olympic Mountains sometime after 17 Ma but before 11 Ma. The data are in close agreement with previously published ages that establish the exhumation of the Olympic Mountains beginning at 18 Ma, and show that the Olympic Peninsula became an emerged topographic high in less than 6 million years.

This research focuses on using advanced surveying techniques as well as hand mapping to analyze force distribution during laboratory impacts of man-made projectiles into ice. This is done in the hopes of characterizing substrate damage surrounding an impact crater created by a proposed hard landing system. Knowing where these different deformation zones occur is useful in determining where the lander could sample. The landing system, the Subsurface Ice Plume Sampler (SIPS) utilizes ejecta (broken up debris thrown from the crater) to create a transient atmosphere - decelerating a secondary instrument package through momentum transfer. Small-scale experiments were done on one-ton buckets of ice using scale-sized projectiles. Between two hundred and five hundred images used to 3D models of the ice craters using the structure from motion imaging technique. Hand mapping of the deformation zones (areas of different types of fractures) was conducted to compare to the 3D model to help show the directionality of force distributions through the crater. Using both the 3D models and a hand mapping analysis of the craters, we were able to determine that the crater shapes were atypical. In a typical crater, the force disperses radially outward from the impactor; however, we determined that the majority of the force was focalized directly below the impactor. Future work includes using Rhinoceros 3D computer software to quantitatively analyze each crater’s individual morphology, curvature, and volume and compare them to traditional impact craters.

Marine terraces are geomorphic features created by wave erosion of the land, which is modulated by crustal uplift or past sea level changes. In this study, I consider possible driving mechanisms that could have generated the marine terraces on the archipelago of Haida Gwaii, Canada. Southwest of the island, there is a young subduction zone that was only initiated ~6 Ma. This subduction has generated a M_w 7.8 earthquake in 2012. From this study, we can find out more information about the plate boundary, including uplift and deformation histories. The island has also experienced ice coverage during the last glacial maximum. Since then, the ice has melted. As a result, the island may have uplifted in response to the ice melting during the Holocene. To obtain the data needed, I am using newly released LIDAR data which contain high resolution elevation topography to map the landforms digitally. The purpose of this project is to provide a resource for locations of the terraces and also to find patterns in distribution and in elevation of marine terraces in Haida Gwaii.

Electric propulsion is becoming an increasingly important field due to the rise of microsatellites in education, research, and industry. Because chemical propulsion is impractical for these small-scale satellites, the need for an efficient, long-term electric propulsion solution has become apparent. In response to this, the Dielectric Barrier Discharge (DBD) Thruster was developed. The DBD is a novel electric propulsion system that uses a low power input to ionize Argon gas and accelerate ions to produce thrust. For initial characterization, thrust values and plasma characterization parameters were collected in the far field of the plasma using electric propulsion diagnosics. The experiment was repeated for multiple operational spaces, and data was collected, compiled, and analyzed. Preliminary results indicate thrust values and plasma characteristics comparable to those of other propulsion systems at similar electrical power levels. Further testing with different high voltage parameters as well as implementing additional diagnostic equipment will help fully characterize the DBD system and assess its potential usefulness in a satellite architecture. To increase the versatility of the DBD system, research will be done on developing multi-DBD arrays and incorporating a nanoparticle injection system for demonstrating future space resource utilization.

Asteroid sample return has potential to impact research and how humans collect resources, but sample return missions remain prohibitively expensive and complex. We propose a device to retrieve a preexisting sample container from the surface of an asteroid or other extraterrestrial body, focusing on simplicity, repeatability, and reliability. Taking inspiration from a classical design, the bear trap, we created a functional 3D printed prototype, which is mechanical and capable of capturing a 1.5x15 in cylinder resting on a flat surface. Consideration was given to potential rocky terrain or an awkwardly positioned return container, and to sealing the sample container to prevent contamination upon return to earth. Future prototypes will be constructed from stronger, lighter weight materials and will be further developed during active field tests on debris at a penetrator impact site in Eastern Washington.

Our current research with the Kinematics and Impacts Lab at the University of Washington entails the design, buildup, and field testing of an asteroid sampling system. These field tests include the buildup of two stage closer rockets, which are highlighted in this presentation. This asteroid sampler field testing helps characterize the sampling process of impacting an asteroid at high speeds- necessitating our rocket system be capable of stable, high speed flight, even at an inverted trajectory. The booster stage, or primary stage, of the system consists of a single large motor to allow the system to reach between 3000-4000 feet above the ground. The sustainer, or second stage, consists of eight smaller motors clustered around a central body tube, allowing the second stage to be hollow. Finally, a hollow point steel nose cone caps the sustainer. Inside the nose come assembly a sample dive is attached, designed to eject during impact. Field testing of this system occurred in December 2018, with preliminary results being compiled.

The study of firn is integral to determining past climate from ice cores and calculating present and future melt runoff from ice sheets. The Herron and Langway model is a semi-emperical firn densification model. While the model's simplicity makes it easy to use, it assumes constant temperatures and accumulation rates, but Earth's climate is changing. The goal was to recalibrate the model by adding data from new ice cores to a gap in the model's dataset to create more accurate depth-density curves. Preliminary results show the recalibration is a better fit for 57 percent of depth-density profiles. The recalibration could help determine melt runoff, informing sea level rise forecasts. The recalibration could also increase the precision of timing between past CO2 and air temperature changes.

This purpose of this project was to investigate the impact of a rocket penetrator for sample-return missions focused on Jupiter’s icy moon, Europa. In particular, primary analysis used the kinetic energy from the ejecta plume of the impact crater to halt the momentum of the primary payload to model the impact. To do so, steel alloy projectile impacts in a material with properties of ice (so as to simulate the surface of Europa) were simulated using ANSYS Autodyn computational dynamics software. ANSYS Autodyn makes use of both Lagrangian and Hamiltonian meshes, as well as smooth particle hydrodynamic mesh-less modeling with cross-coupling so as to best represent the impact of the projectile, the material deformation, and the projectile deformation. This analysis of elastic and plastic behavior, as well as bulk failure and separation, resulted in accurate depictions of deformation in both the projectile and target material, validating it as a model with the potential to simulate the impact of a Europa sample-return rocket penetrator. This analysis serves as a basis for future progress, and will soon be enhanced via further simulation in conjunction with ISAIL simulations so as to accurately depict the material deformation and ejecta plume. The data from these computer simulations can eventually be compared to physical experiments and field tests that are to be conducted under the University of Washington’s Kinematics and Impacts Laboratory (KILa).

During the Cambrian Period, 541 Ma to 485.4 Ma, the radiation of animals generated substantial diversity and produced most extant phyla. However, there remains a poor understanding of nutrient cycling during this exciting evolutionary interval. Furthermore, the point at which Earth’s oceans became fully oxygenated – and widely amenable to animal life – is unknown. It thus remains unclear whether oxygen exerted the primary control on the distribution of animals during their early evolution in the Cambrian. In order to elucidate the dynamic between oxygen and early animal ecosystems, we examined the Mt. Isa drill core from the Georgina Basin, Australia, which intersects the exceptionally well-preserved ~510 Ma Currant Bush Limestone. We used measurements of organic carbon (δ¹³C_org) and nitrogen (δ¹⁵N) isotope ratios as proxies for oxygen and nutrient cycling in ancient marine environments. The preliminary data suggest that at ~510 Ma, the Georgina Basin water column was predominantly anoxic. Nitrogen isotope ratios (δ¹⁵N from 0 to -1%) are indicative of anaerobic N₂-fixation-dominated ecosystems. Ratios of total organic carbon to total nitrogen (25 to 30) also suggest anaerobic organic matter remineralization, as smaller ratios would be expected in well-oxygenated waters. Both of these signals are consistent with low ocean oxygen levels. The organic carbon isotope ratios (δ¹³C_org) range from -30% to -31%, consistent with carbon fixation by oxygenic photosynthesis, suggesting that oxygen production was insufficient to fully oxygenate seawater. Future work will explore whether these signs of anoxia correlate with organic biomarker proxies for eukaryotes, indicating animal abundance, from work done by our collaborators at Australian National University. Together, these data will clarify the ecology of this mid-Cambrian animal ecosystem.

In this research, we looked at the possible use of an Air Breathing Pulsed Plasma Thruster (AB-PPT) for propelling an aircraft that could potentially act as an atmospheric satellite at atmospheric altitudes > 25 km. One of the advantages of operating at such altitudes is that the aircraft is not subject to highly variable weather conditions. An atmospheric satellite is an aircraft that can perpetually fly around the same area, and can be launched at significantly reduced cost when compared to conventional satellites while providing similar services such as communication and imaging. At the desired altitude, conventional blade-based propellers are too inefficient due to low background pressure, but it is still too low of an altitude for conventional space propulsion, prompting the use of AB-PPT. The AB-PPT is an adaptation of the conventional PPT which is a pulsed device that uses an electric discharge to ionize and expel the solid propellant such as PTFE at high speeds. For the AB-PPT, a large amount of voltage discharge generated across the two coaxial electrodes ionizes and expels the background air instead. In order to identify the most efficient AB-PPT design, three different configurations were tested using a pendulum-based thrust stand to measure the thrust efficiency, a Rogowski coil to measure the current per discharge, and high-speed video. One configuration has been identified, and we are currently investigating an alternative electric connection to further increase the amount of thrust per discharge. Future work includes plasma diagnostics of the AB-PPT such as Langmuir probe, and B-dot probe, in addition to the development of more robust electronics capable of delivering higher power, and the development of the final version of the AB-PPT for patenting purposes.

My research is a case study of coseismic landslides triggered by the M6.9 earthquake in Loma Prieta, California on 17 October 1989. Coseismic landslides bring deadly consequences, often resulting in more casualties and infrastructure damage than from the earthquake directly. In addition, coseismic landslides are understudied geomorphic features and are difficult to predict, resulting in a high safety hazard. My study area, located in the Forest of Nisene Marks State Park, California, a regional park in the Santa Cruz Mountains where the earthquake shaking was strongest, includes over a hundred coseismic landslides triggered from the 1989 earthquake. I am using geographic information systems (GIS) software to map and analyze the landslides on a high-resolution LiDAR Digital Elevation Model (DEM) and using data from the United States Geological Survey to create an inventory of the Loma Prieta coseismic landslides. This dataset will be compared against seismic shaking strength estimates and local lithology to look for spatial patterns in sliding. I am also using this dataset, an event of known age, to test a recently developed landslides Surface Roughness - Age model. I expect to find that the zones with greatest seismic shaking produced the most or biggest landslides, certain lithologies are prones to greatest failure, and that the 1989 coseismic landslides currently have approximately equal surface roughness. Learning how certain lithologies respond to seismic shaking will help predict future coseismic landslides, and evaluating the current surface roughness will help validate, or invalidate, the Surface Roughness - Age model.