<p>The <i>Curiosity</i> and <i>Perseverance</i> rovers have both found overwhelming evidence of a long-lived history of complex rock-water interactions on Mars. Understanding how the mineralogy of these deposits is related to depositional and diagenetic environments is critical for evaluating past habitable environments and guiding the search for signs of life with the <i>Curiosity</i> and <i>Perseverance</i> rovers. However, the chemistry and timing of these aqueous environments are poorly constrained. In particular, it is unclear which secondary minerals in the rock record formed in primary lacustrine vs. later diagenetic events. Understanding the origin of alteration minerals is crucial for studying habitability because they provide constraints on the timing and types of environments that existed. The goal of my thesis research is to better constrain the history of diagenetic processes in Gale and Jezero craters using the morphology, sedimentology, and mineralogy of features from rover and orbiter observations and comparisons to Earth analogs to understand their formation mechanisms. This research contributes to building a framework of the history of water in Gale and Jezero craters and will help us better understand past climate, habitability, and sources of water on Mars.</p><p>The <i>Curiosity</i> rover on the Mars Science Laboratory (MSL) mission has found extensive evidence that Gale crater once hosted a habitable lacustrine environment; however, there are remaining questions about the chemistry and duration of the lake and the nature of the climate at the time. In Chapter 2 of this thesis, I use Mastcam multispectral data to investigate the mineralogy of the Sutton Island member of the Murray formation, a part of the basal layers of Mt. Sharp, which consists of heterolithic mudstone and sandstone that are distinct from the finely laminated mudstones that dominate much of the Murray. Sutton Island includes at least one instance of desiccation cracks, indicative of subaerial exposure, and uniquely irregular diagenetic features that may be related to local bedrock permeability. These features suggest that Sutton Island experienced a complex history of deposition and diagenesis which may be crucial for understanding changing water-rock interactions within Gale. I find that most Mastcam bedrock spectra in this region lack the absorptions associated with hematite found throughout the Murray, and instead show deeper absorptions shifted toward longer wavelengths that are more consistent with Fe-smectites such as nontronite. Elemental chemistry from ChemCam supports this interpretation, as SiO, MgO, Li, and the chemical index of alteration are elevated in this region. Combined with observations of bedrock sedimentology, this suggests that Sutton Island was deposited in a nearshore or low stand environment, and we hypothesize that the clay minerals were produced in this region due to sub-aerial exposure and weathering in a semi-arid climate.</p><p>In Chapter 3, I use the Middle Jurassic Carmel Formation from Utah as a terrestrial analog to understand how the history of rock-water interactions is expressed in the rock record on Mars and how we can interpret this history of deposition and diagenesis using visible/near-infrared/short wave-infrared reflectance spectroscopy at rover scales. The Carmel Formation consists of carbonate- and sulfate-rich heterolithic strata deposited in a range of environments from fluvial, aeolian, and coastal sabkha to shallow marine settings. The alteration mineralogy, variable sedimentology, and diagenetic features present makes this formation a good analog for parts of the Murray formation in Gale crater and rocks from the Jezero crater delta front. In this thesis, we find that changes in lake level and climate manifest themselves in diagenetic features and mineralogy in the Carmel Formation with increased carbonate content in marine strata and increased evaporite/clay mineral content in near-shore/playa deposits. These results generally correspond to correlations with sedimentology and bedrock composition observed in Gale and Jezero craters and allows us to better interpret evidence of complex rock-water interactions on Mars using reflectance spectroscopy.</p><p>Although NASA’s <i>Curiosity</i> rover has found evidence of diagenesis, at a variety of scales, the broader extent of diagenesis in Gale crater is poorly constrained. <i>Curiosity</i> has observed extensive evidence of diagenesis at the unconformity between Mt. Sharp group fluvial/lacustrine mudstones and Siccar Point group (SPg) aeolian sandstones, which is part of the much larger Mound Skirting Unit (MSU) that mantles Mt. Sharp. This diagenetic horizon is visible as a light-toned tan, gray, or blue region in color images from both the ground and orbit. In Chapter 4 of this thesis, I use orbital color images and spectroscopy to look for possible evidence of alteration at the MSU unconformity elsewhere in Gale crater. I find that color variations appear at the MSU unconformity across Mt. Sharp and are co-located with detections of alteration minerals such as hydrated silica and phyllosilicates. This suggests that some of the diagenetic alteration observed by <i>Curiosity </i>below the MSU unconformity was extensive across Mt. Sharp. I hypothesize that this diagenesis was primarily driven by differences in permeability, where the more permeable SPg/MSU sandstones provided a conduit for diagenetic fluids that stagnated within and altered the upper few meters of less permeable clay bearing strata in the Mt. Sharp group below. The extensive diagenesis observed in Gale implies that subsurface fluids were long-lived and widespread in this region on Mars. Gaining a better understanding of what rock properties control and influence diagenetic fluid flow on Mars will help us improve the search for ancient aqueous environments, and possible biosignatures, on Mars.</p><p>The work included herein contributes to our understanding of rock-water interactions on Mars by demonstrating how bedrock properties, such as changes in permeability, can affect the flow of diagenetic fluids. These studies emphasize the importance of reflectance spectroscopy as a useful tool for constraining bedrock mineralogy and how it links to variable depositional and alteration environments. This will help guide current and future missions to search for past habitable environments and biosignatures on Mars.</p>

Poverty Point is a monumental earthwork center dating to the Late Archaic Period (ca. 3700-3100 Cal BP). The site is well known for its diverse collection of foreign lithic materials indicative of a wide-ranging acquisition network. Among the extra-local items recovered from the site are lithic raw materials that were used for bifaces in the form of projectile points and/or knives (PP/Ks). Here, I determined the atomic and molecular composition of 847 bifaces from the Alexander Collection using Visible/Near-Infrared Reflectance (VNIR) and Fourier-Transform Infrared Reflectance (FTIR) spectroscopy. The combined wavelength spectra datasets were compared to a raw material database to determine the location of the parent formations from which the raw materials were obtained. The PP/K raw materials analyzed were sourced to outcrops stretching across the Southeast, Mid-South and Mid-West.

No description available.

<p>Mars’ Polar layered Deposits (PLD) accumulated over the last few millions of years due to seasonal buildup of frost trapping atmospheric gasses and incoming sediments, thereby preserving the history of Mars' recent climate in the form of an ice-rich geologic record. The PLD includes both the North Polar Layered Deposits (NPLD) and the South Polar Layered Deposits (SPLD) which are estimated to be up to 5 Mya and 100 Mya old respectively. Characterizing the contents of these deposits is essential to understand the role of geologic and climatic processes recently active on Mars. The Mars scientific community recommends robotic exploration of these icy NPLD to sample the ice and extract recent climate records; however, linking the geologic record to the climatic history will require quantitative dating of the NPLD. The SPLD is thought to be older than the north polar deposits, so the stratigraphic records of the SPLD are a window to look deeper into the climatic history of Amazonian Mars. Deciphering the paleoenvironment at the PLD requires characterization of the ice-rich deposits, however, the origin, composition, transport histories, and alteration environment of sediments within the deposits are not well constrained.</p> <p>In this study we use orbital reflectance spectroscopy to show for the first time that dateable mafic lithics are present throughout the PLD. We find significant glass as well as diverse crystalline minerals, which suggests that surface processes like impacts and volcanism were active during the late Amazonian and transported sand-sized and finer sediments from across the planet to the poles. In situ investigation of the PLD will thus provide critical quantitative age constraint on both the recent geologic and climatic histories of Mars. Previous studies have confirmed widespread detection of sulfates at the NPLD and here we show that sulfates dominate the alteration mineralogy at the SPLD suggesting acidic, oxidizing, and evaporitic conditions. Based on this more extensive survey, previously reported rare detection of smectites and hydrated silica in the SPLD is likely due to ballistic emplacement by impacts from targets on surrounding smectite-bearing Noachian terrains.</p> <p>Detrital ice-rich sediments within the PLD are a complex mixture of mafic minerals and weathering products from multiple sources and are continuously reworked. In order to investigate the material and grain-size dependent effects of chemical and physical weathering in a cold and wet basaltic environment, a rover-based Mars analog study is conducted in the glacio-fluvial-aeolian landscapes of Iceland. A DCS-based color analysis technique is employed in tandem with VNIR spectroscopy and XRF analysis to develop a strategy for conducting sediment provenance. We observe that DCS-based color analysis is a powerful tool for identifying spectral diversity, and that it has the capability to differentiate primary minerals from alteration minerals. Because color analysis can aid in identifying diverse targets for sampling within the rover’s workspace, tactically, DCS colors can be used during operations to link detrital sediments within the rover’s vicinity to surrounding bedrock sources. DCS images enhance our ability to correlate observation of surface features from orbit, extend local mineralogical interpretation to surrounding regions, optimize rover’s traverse and select science targets. </p>

Postmortem interval (PMI) estimation is a necessary but often difficult task that must completed during a death investigation. The level of difficulty rises as time since death increases, especially with the case of skeletonized remains (long PMI). While challenging, a reliable PMI estimate may be of great importance for investigative direction and cost-savings (e.g. suspect identification, tailoring missing persons searches, non-forensic remains exclusion). Long PMI can be estimated by assessing changes in the organic content of bone (i.e. collagen), which degrades and is lost as the PMI lengthens. Visible-near infrared (VNIR) spectroscopy is one method that can be used for analyzing organic constituents, including proteins, in solid specimens. A 2013 preliminary investigation using a limited number of human cortical bone samples suggested that VNIR spectroscopy could provide a fast, reliable technique for assessing PMI in human skeletal remains. Clear separation was noted between "forensic" and "archaeological" specimen spectra within the near-infrared (NIR) bands. The goal of this research was to develop reliable multivariate classification models that could assign skeletal remains to appropriate PMI classes (e.g. "forensic" and "non-forensic"), based on NIR spectra collected from human cortical bone. Working with a large set of cortical samples (n=341), absorbance spectra were collected with an ASD/PANalytical LabSpec® 4 full range spectrometer. Sample spectra were then randomly assigned to training and test sets, where training set spectra were used to build internally cross-validated models in Camo Unscrambler® X 10.4; external validations of the models were then performed on test set spectra. Selected model algorithms included soft independent modeling of class analogy (SIMCA), linear discriminant analysis on principal components (LDA-PCA), and partial least squares discriminant analysis (PLSDA); an application of support vector machines on principal components (SVM-PCA) was attempted as well. Multivariate classification models were built using both raw and transformed spectra (standard normal variate, Savitzky-Golay) that were collected from the longitudinally cut cortical surfaces (Set A models) and the superficial cortical surface following light grinding (Set B models). SIMCA models were consistently the poorest performers, as were many of the SVM-PCA models; LDA-PCA models were generally the best performers for these data. Transformed-spectra model classification accuracies were generally the same or lower than corresponding raw spectral models. Set A models out-performed Set B counterparts in most cases; Set B models often yielded lower classification accuracy for older forensic and non-forensic spectra. A limited number of Set B transformed-spectra models out-performed the raw model counterparts, suggesting that these transformations may be removing scattering-related noise, leading to improvements in model accuracy. This study suggests that NIR spectroscopy may represent a reliable technique for assessing the PMI of unknown human skeletal remains. Future work will require identifying new sources of remains with established extended PMI values. Broadening the number of spectra collected from older forensic samples would allow for the determination of how many narrower potential PMI classes can be discriminated within the forensic time-frame.