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Item Hydrogen production from mechanically-activated basalt under experimental conditions simulating subglacial environments(Montana State University - Bozeman, College of Letters & Science, 2019) Mitchell, Kari Rebecca; Chairperson, Graduate Committee: Mark L. SkidmoreShearing of rocks containing silicate followed by reaction with water has previously been shown to produce hydrogen under experimental conditions relevant to subglacial environments. The abiotic production of hydrogen, carbon dioxide, methane, and other hydrocarbon gases has also been demonstrated in laboratory comminution experiments on rocks from glaciated catchments. Thus, the generation of these biologically useful gases (e.g. hydrogen and methane) beneath glaciers could serve as a source of reductant capable of sustaining microbial ecosystems beneath the ice. Despite the ubiquitous nature of basalt on both Earth and other planetary bodies, production of hydrogen and other gases from basalt through mechanical shearing and reaction with water has not been demonstrated. Basalts were collected from glaciated catchments in Iceland to test whether hydrogen and other gases were produced under laboratory conditions simulating glacial comminution. Rock samples were milled under an inert atmosphere, after which water was added and hydrogen and methane production measured over time. An average of 6.6 nmol hydrogen and 2.6 nmol methane per gram rock were produced after 168 hours from basalt samples tested; additionally, hydrogen peroxide and radicals were produced during grinding. The abiogenic production of hydrogen and methane under these simulated subglacial basaltic environments demonstrated in this study also has implications for supporting subglacial microbial communities during periods of extended glaciation, such as glacial-interglacial cycles in the Pleistocene and during the pervasive low-latitude glaciation of the Cryogenian. This mechanism of hydrogen production also has implications for the potential for life on icy worlds like Mars.Item Methane flux from recently exposed subglacial sediments, Robertson Glacier, Canada(Montana State University - Bozeman, College of Letters & Science, 2014) Spotts, Terra Marie; Chairperson, Graduate Committee: Mark L. SkidmoreMethane is over 20 times more effective than CO 2 as a greenhouse gas. Thus, its atmospheric concentration and the processes controlling it are important components of the global climate system. Recent research has shown methanogenesis in subglacial sediments. However, the net contribution from subglacial systems to the global methane budget is poorly understood due to a dearth of empirical data. Using measurements via the static chamber method, the flux of methane from recently exposed subglacial sediments at Robertson Glacier, Canadian Rockies was quantified. Methane concentrations were measured from surface gas flux chambers in transects both parallel and perpendicular to the glacier terminus. Over 300 measurements were made during the 2012 melt season (July to September) and used to determine both spatial and temporal variability in the gas fluxes. The chamber farthest from the glacier terminus, approximately 50 m down valley, had an average flux close to zero whereas the chambers nearest the terminus had the highest average fluxes. The average methane efflux from the sediment surface to atmosphere was 0.22 micromoles m -2 d -1. The highest methane efflux during the season, 11.0 micromoles m -2 d -1, was measured in close proximity to the glacier terminus. Shallow sediment cores were collected adjacent to the static chambers and vertical gas concentration profiles were measured from the cores. Within the profiles, methane concentrations were greater than atmospheric concentrations at all depths. Additionally, CO 2, CO and H 2 gas concentrations were analyzed in the cores to evaluate potential microbial metabolic pathways of methane production. Previous studies on methane fluxes from glacial sediments in Greenland and the Swiss Alps used single time point flux measurements during a melt season from multiple locations. This study concludes that such point measurements are unlikely representative for determining a net seasonal flux as they do not consider temporal variability. There was a two order of magnitude difference between the annual source contribution of methane based on the average melt season flux and the highest measured surface flux. This indicates that single sampling periods may significantly over or underestimate the net seasonal flux of methane from recently exposed glacial sediments to the atmosphere.