ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
Displaying 1 - 3 of 3
Filtering by
- All Subjects: geology
Description
Understanding the history of water on Mars is one of the highest priority goals of the international Mars exploration community. Water would have played a key role in any potential abiogenesis in the past and will play a key role in the future human exploration of the planet. Chloride salts are an indicator of past hydrologic activity in the Martian geologic record and have the potential to preserve fluid inclusions and organic material within their crystal structure over geologic timescales. This dissertation will describe an innovative method for identifying chloride salts on the Martian surface, explore the implication of their distribution within Early Noachian terrains, and document important opportunistic discoveries made in the process. Decorrelation stretched Thermal Emission Imaging System (THEMIS) infrared images have long been used to identify chloride salts on Mars, but the process has been time-consuming, subjective, and qualitative. By analyzing the entire THEMIS dataset, acquired over more than twenty years at Mars, a globally-applicable covariance matrix was calculated that describes the geologic diversity of the Martian surface. This covariance matrix allows all THEMIS daytime infrared images to be translated into globally-consistent decorrelation stretch and principal component images, enabling an automatic, objective, and quantitative method for identifying chloride salts. A new global survey located 1,605 chloride salt deposits across the Martian surface, a significant increase over previous surveys. In particular, the 257 deposits in Early Noachian terrains have characteristics that indicate they formed contemporaneously with the surrounding terrain. In addition, a chloride salt formation was identified on the floor of Ares Vallis with a unique three-dimensional structure that has been interpreted as an exposed chloride salt diapir, which would indicate the presence of a significant subsurface chloride salt layer. By improving our understanding of the distribution and diversity of chloride salts on the Martian surface, this work has provided future investigators with new tools and avenues of research to explore the history of water on Mars.
ContributorsHill, Jonathon Ryan (Author) / Christensen, Philip R. (Thesis advisor) / Sharp, Thomas G (Committee member) / Ruff, Steven W (Committee member) / Simon, Molly N (Committee member) / O'Rourke, Joseph G (Committee member) / Arizona State University (Publisher)
Created2022
Description
With the development and successful landing of the NASA Perseverance rover, there has been growing interest in identifying how evidence of ancient life may be preserved and recognized in the geologic record. Environments that enable fossilization of biological remains are termed, “taphonomic windows”, wherein signatures of past life may be detected. In this dissertation, I have sought to identify taphonomic windows in planetary-analog environments with an eye towards the exploration of Mars. In the first chapter, I describe how evidence of past microbial life may be preserved within serpentinizing systems. Owing to energetic rock-water reactions, these systems are known to host lithotrophic and organotrophic microbial communities. By investigating drill cores from the Samail Ophiolite in Oman, I report morphological and associated chemical biosignatures preserved in these systems as a result of subsurface carbonation. As serpentinites are known to occur on Mars and potentially other planetary bodies, these deposits potentially represent high-priority targets in the exploration for past microbial life. Next, I investigated samples from Atacama Desert, Chile, to understand how evidence of life may be preserved in ancient sediments formed originally in evaporative playa lakes. Here, I describe organic geochemical and morphological evidence of life preserved within sulfate-dominated evaporite rocks from the Jurassic-Cretaceous Tonel Formation and Oligocene San Pedro Formation. Because evaporative lakes are considered to have been potentially widespread on Mars, these deposits may represent additional key targets to search for evidence of past life. In the final chapter, I describe the fossilization potential of surficial carbonates by investigating Crystal Geyser, an active cold spring environment. Here, carbonate minerals precipitate rapidly in the presence of photosynthetic microbial mat communities. I describe how potential biosignatures are initially captured by mineralization, including cell-like structures and microdigitate stromatolites. However, these morphological signatures quickly degrade owing to diagenetic dissolution and recrystallization reactions, as well as textural coarsening that homogenizes the carbonate fabric. Overall, my dissertation underscores the complexity of microbial fossilization and highlights chemically-precipitating environments that may serve as high-priority targets for astrobiological exploration.
ContributorsZaloumis, Jonathan (Author) / Farmer, Jack D (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Trembath-Reichert, Elizabeth (Committee member) / Ruff, Steven W (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2021
Description
The presence of ices (H2O and CO2) and liquid water is key to the evolution ofmartian geology, with implications for the potential for past or extant life, and the future
of robotic and human exploration on Mars.
In this dissertation, I present the first direct evidence that the smooth deposits
covering mid-latitude, martian pole-facing slopes are composed of shallow dusty H2O ice
covered by desiccated material. To analyze this H2O ice, I developed the first validated
radiative transfer model for dusty martian snow and glacier ice. I found that these ice
exposures have < 1% dust in them, and discovered the lowest latitude detection of H2O
ice on Mars, at 32.9°S. After observing the ice disappear, and new gully channels form, I
proposed a model for gully formation. In this model, dusty ice gets exposed by slumping,
leading to melting in the subsurface and channels eroding within the ice and the wall rock
beneath. Access to liquid water within this ice could provide potential abodes for any
extant life.
Next, I developed novel methodology to search for CO2 frosts within the entire
Thermal Emission Imaging System (THEMIS) infrared dataset and found that about half
of all gullies overlap with CO2 frost detections. I also used the Thermal Emission
Spectrometer (TES) water vapor retrievals to assess the formation and distribution of
H2O frosts on Mars.
Additionally, I used radar data from the Mars Advanced Radar for Subsurface and
Ionospheric Sounding (MARSIS) instrument to investigate Mars’ ice-rich South Polar Layered Deposits (SPLD). I discovered radar signals similar to those proposed to be
caused by a subglacial lake throughout the martian SPLD.
Finally, I mapped martian polygonal ridge networks thought to represent
fossilized remnants of ancient groundwater near the Perseverance rover landing site with
the help of citizen scientists across a fifth of Mars’ total surface area and analyzed their
thermophysical properties.
All these studies highlight the key role that ices and liquid water have played in
shaping Mars’ landscape through time, and provide an intriguing path forward in martian
exploration and the search for alien life.
ContributorsKhuller, Aditya Rai (Author) / Christensen, Philip R (Thesis advisor) / Ruff, Steven W (Committee member) / Whipple, Kelin X (Committee member) / Sharp, Thomas G (Committee member) / Shim, Sang-Heon (Committee member) / Arizona State University (Publisher)
Created2023