Application of glacial flow models to Mars with Asmin Pathare (Planetary Science Institute), Ed Waddington (UW), and Claire Todd (Pacific Lutheran University), funded by NASA
Understanding the formation and evolution of Martian ice masses is critical to our understanding of Martian climate. In particular, the Lobate Debris Aprons (LDAs) are the largest non-polar reservoir of bulk surface water ice on Mars. Radar observations suggest that they are at least 90% water ice and their global distribution is reasonably well known; however, when and how LDAs formed remains poorly understood. To infer the histories of LDA evolution, we must interpret the present-day shapes of LDAs, which are complicated by a surface debris cover that protects the underlying LDA ice from rapid sublimation-driven loss. Indeed, due to the large uncertainties associated with modeling ablation through a partially protective debris cover, recent LDA flow models either do not emplace the debris cover until after most of the significant flow has already occurred, or models do not consider surface mass exchange (i.e., accumulation and ablation) as LDAs flowed. However, from terrestrial experience we know that surface mass exchange shapes glaciers on Earth; we need to consider how Martian surface processes affect LDA dynamics and how we use LDA shapes to interpret Martian paleoclimate. We aim to advance upon previous work by studying the effects of debris cover on terrestrial glaciers in order to best apply terrestrial flow models to debris-covered Martian LDAs. We will incorporate the effects of debris cover into existing ice-flow models that we have already developed. Our modeling will simulate internal deformation of ice due to gravitational driving stress subject to a physically based surface mass-exchange pattern that accounts for the effects of debris cover, and we will consider rock avalanche events, spatial variations in debris, and evolution of debris cover. Additionally, our terrestrial model will be constrained by our proposed terrestrial analogue field studies of debris-covered glaciers on Mt. Rainier.
Investigating the causes of radar-detected layering in ice, with Lynn Carter (NASA Goddard), Lora Koenig (NSIDC), Zoe Courville (CREEL), and Rebecca Ghent (Planetary Science Institute), funded by NASA
The polar caps and glaciers of both Earth and Mars display internal layering that preserves a record of past climate. These layers are apparent both in optical datasets (high resolution images, core samples) and in ground penetrating radar data. On Mars, the SHARAD radar on the Mars Reconnaissance Orbiter shows fine layering that changes spatially and with depth across the pole. This layering within ice sheets has been attributed to changes in fractional dust contamination due to obliquity-induced climate variations, but there are other processes that can lead to internal layers visible in radar data. In particular, terrestrial sounding of glaciers compared with core samples have revealed that ice density and composition differences account for the majority of the radar reflectors. The goal of this research is to use experiments and analysis of terrestrial analogues to quantitatively measure how changes in dust contamination and density influence the appearance of ground penetrating radar (GPR) profiles, and use this information to assess what the SHARAD data reveals about the evolution of the Mars polar caps. Our results will provide important constraints on the degree to which global climate cycles—or other processes, such as large volcanic eruptions—may or may not be recorded in polar ice. We will use a multi-disciplinary approach consisting of laboratory experiments, field studies, modeling, and comparison to SHARAD data products. We will investigate layered density changes in ice and layered dust contaminates in ice in both natural and laboratory settings to determine the layering structures and compositions that cause the largest radar return.
History of polar ice on Mars with Ed Waddington (UW), Dale Winebrenner (UW), and Asmin Pathare (Planetary Science Institute)
Terrestrial glaciologists play an important role in Mars polar science because recent imagery, topography, radar, thermal inertia, and ground-based observations show there are extensive ice deposits on Mars. My research has addressed implications for ice flow on Mars, and how to interpret martian internal layers. The history of ice flow on Mars is a topic of active research, and there are many open questions that can be tackled with the network of researchers at UW. Assuming that martian ice did flow in the past, how would martian internal layers be shaped by possible transitions between flow and stagnation? How can analysis of the flow of terrestrial ice masses be adapted to understand martian ice masses? For the large Martian polar ice caps, do we expect stratigraphic records and dynamic processes in the north to be similar to the south, and is an interhemispheric comparison possible? Our recent research has focused on a specific region of the large north polar ice deposit, and we need to better understand why the history of this region appears different from the rest of the north polar ice.