Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Geology
Collaborative Specialization
Planetary Science and Exploration
Supervisor
Osinski, Gordon R.
2nd Supervisor
Tornabene, Livio L.
Co-Supervisor
Abstract
Present-day Mars is shaped by multiple dynamic processes involving the action of wind and ice/frost. To understand their formation and evolution, better (i) detection, (ii) characterization, and (iii) interpretation of observed surface changes are crucial. This dissertation contributes to each of these aspects through three interconnected studies. Temporal changes since 2006 have been tracked using visual comparative techniques, leveraging instruments like the High-Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO). Nonetheless, challenges arise when using data from instruments on non-sun-synchronous orbits (like Colour and Stereo Surface Imaging System; CaSSIS), where difficulties in feature interpretation are amplified due to varying illumination geometries between image-pairs. To address this, I present a novel semi-quantitative spectral approach that can enhance change-identification and monitoring from high-resolution multispectral instruments. These methods effectively characterize ice/frost-related changes and slope processes, while also offering unique spectral insights into potential triggers.
I additionally investigate the spectral sensitivity of HiRISE and present a novel quantitative method to distinguish high-purity ice-rich materials from ice-poor ones at unprecedented resolutions of ~50 cm/pixel. It is observed that when atmospheric scattering contributions are minimized, HiRISE’s three broadbands may potentially resolve the effects of weak VNIR water-ice absorptions through spectral shape and parametric methods. With the recent deactivation of MRO’s spectrometer, this approach holds significant promise to continue to understand the distribution and role of ice in present-day Martian climate.
Unraveling mechanisms responsible for Martian surface changes is challenging from remote sensing alone. Hence, exploring functional terrestrial analogue sites with similar geodynamic processes can be insightful. I further investigate the gullies at the Haughton impact structure, Devon Island, Canadian High Arctic to help inform on gully formation mechanisms on both Earth and Mars. The role of impact cratering in shaping gullies is evident, with gullies in impact-fractured bedrock exhibiting distinct slope differences to those incising into bedrock outside the crater. Alongside snowmelt, varieties of periglacial features are also identified near gully alcoves, indicative of near-surface/subsurface water-ice, implying ground-ice contribution to gullies. This could provide key insights into Martian gully formation, for which CO2 frost-based mechanisms have been suggested.
In summary, this dissertation enriches the detection and interpretation of present-day Martian active processes, which are pivotal to comprehend its contemporary climate variables and its intricate Amazonian history.
Summary for Lay Audience
The Martian surface is shaped by various dynamic processes, involving wind and ice/frost. This dissertation, through three connected works, aims to contribute ways to better detect, characterize, and interpret observed surface changes to gain a holistic understanding of formation and evolution of these active processes. Currently, visual comparison methods using remote sensing images (like High Resolution Imaging Science Experiment; HiRISE) have been utilized to track temporal changes. However, challenges in using this approach arise when dealing with data from instruments that are not sun-synchronous (like the Colour and Stereo Surface Imaging System; CaSSIS), leading to difficulties in interpreting features due to varying lighting conditions between image-pairs. To address this, I present a novel semi-quantitative spectral approach enabling enhanced change-identification and monitoring from high-resolution multispectral instruments. This approach effectively characterizes ice/frost-related changes and slope processes, offering unique spectral insights into potential triggers. A second study focuses on investigating HiRISE's spectral sensitivity to detect high-purity water-ice exposures, where I present a novel quantitative method that can confidently distinguish between ice-rich and ice-poor materials at unprecedented resolutions of ~50 cm/pixel. It is observed that, when effects of atmospheric scattering are minimized, HiRISE's three broad spectral bands can potentially detect the effects of weak water-ice absorptions in the VNIR. With the recent shutdown of the highest spectral resolution instrument on Mars, these methods become vital to continue to understand the distribution and role of ice in Mars’ present climate.
Investigating functional terrestrial analogous sites with similar geodynamic processes can be helpful to better understand the processes responsible for Martian surface changes. Hence, I also investigate gullies at the Haughton impact structure to better understand how Martian gullies form. We observe that fracture in bedrock caused by impact affects gully characteristics, particularly its slope. Varieties of periglacial features are also identified and mapped near gully heads, suggesting that ground-ice may also be contributing to gullies alongside snowmelt. This may point to a comparable formation process for Mars, where currently, CO2 frost-based mechanisms have been suggested. Understanding Mars' current state is crucial for understanding current and past climate variables and the collective results from this dissertation can play key a role in better comprehending the variety of processes that continue to shape its surface.
Recommended Citation
Rangarajan, Vidhya Ganesh, "Studies of Martian Active Processes using Remote Sensing" (2023). Electronic Thesis and Dissertation Repository. 9766.
https://ir.lib.uwo.ca/etd/9766
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