Typescript (photocopy). / Digitized by Kansas Correctional Industries

Existing martian relative age chronologies rely entirely or predominantly on Mariner 9 images, extrapolated numbers of craters, and craters 500(DEGREES)K) for the planet are consistent with the derived chronology.

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Despite its ubiquity in planetary science, analogue-based reasoning largely has remained unbounded by guidelines of use. Establishing analogical guidelines and putting them to the test is the main aim of the thesis. Towards this end, I discuss the philosophical foundations of analogical reasoning in planetary geomorphology and posit rules of use that facilitate the evaluation of analogical hypotheses. Subsequently, I present four hypotheses concerning aeolian, fluvial and periglacial processes on Mars. Each of these hypotheses is evaluated in terms of the analogical rules presented. The fourth hypothesis is original to this thesis and suggests that a periglacial landscape comprising pingos and small-scale polygonal ground exists in an impact crater located in northwest Utopia Planitia.

The subsurface igneous biome contains a vast portion of Earth's total biomass, yet we still know so little about it. Igneous environments such as iron-rich ocean crust and lava tubes may also host analogs to chemolithotrophically-driven life on other planets, so studying life in this biome is essential to understanding how life may survive on other planets. In this study, three igneous surface and subsurface environments were investigated for microbial preference for olivine, microbial physiologies and phylotypes present on olivine, and microbial growth on olivine in the laboratory via iron oxidation. These environments include a subseafloor borehole drilled into the ocean crust basalt basement, a lava tube with perennial ice, and a trio of Columbia River basalt-hosted freshwater terrestrial habitats. The subseafloor borehole (IODP Hole 1301A) is situated on the eastern flank of Juan de Fuca Ridge (JFR) and was used in the first long-term deployment of microbial enrichment flow cells using osmotically-driven pumps. The flow cells contained igneous minerals and glasses, for which cell density and microbial abundances were evaluated. Total cell density and viable oligotrophs were highest for Fe(II)-rich olivines. Organotrophic bacterial isolates were capapble of iron oxidation and nitrate reduction, and grew on olivine in the laboratory. Putative neutrophilic iron oxidizers were also isolated from igneous riparian and cave environments in northwest and central Oregon. Isolated bacteria from all three environments were capable of chemolithotrophic growth with olivine and oxygen or nitrate in the laboratory. Bacteria isolated from river basalt were putatively capable of producing alteration textures on olivine surfaces in culture. Microbial life in the igneous subsurface preferentially attach to Fe²⁺-rich minerals, which suggests that life in the subsurface is heterogeneously distributed. The isolation of oligotrophic iron oxidizers that grow on olivine suggests that olivine supports a chemolithotrophic subsurface community based on primary productivity via iron oxidation. This generation of biomass on olivine surfaces creates organic carbon-rich coated mineral surfaces that may support a more complex community. The identification of Mars analogs living in Oregon lava tubes and the discovery that iron oxidizers may produce biosignatures on olivine surfaces are key findings that may provide the foundation for a new chapter in the search for life on Mars.

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