Studies of Martian Active Processes using Remote Sensing
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.