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The search for extraterrestrial life begins with understanding how life developed and evolved on our own planet. Earth's polar regions provide a unique setting conducive to developing the methodologies and techniques that will be needed to find new life forms either as living organisms or as some biological signal in a sedimentary record. / The highest latitude perennial spring system in a region of thick, continuous permafrost resides in the Arctic archipelago of northern Canada. At Expedition Fiord on Axel Heiberg Island there are two sets of springs that provide useful analogs to liquid water habitats that may have existed on Mars. The springs occur in a region with a mean annual air temperature of -15.5° C. Spring flow rates and discharge temperatures are constant throughout the year. Filamentous bacteria, biofilms and mineral precipitates occur in association with the emergent, anoxic brine flowing from the springs. / Preliminary data on the microbial composition of the spring water has been obtained by applying the culture-independent approach. The majority (76%) of the fifty-five environtaxa showed high sequence similarity to Thiomicrospira species (sulfur-oxidizing organism). Other sequences show high similarity to sulfate-reducing members of the delta (Desulfocapsa sp.) and epsilon (Sulfurospirillum sp.) proteobacterium groups. A single sequence was found to have 99% sequence similarity to species of the genus Haloanaerobium a group of low G+C Gram positive, anaerobic, halophiles (Rainey et al. 1995). / A combined flow and thermal model of the Axel Heiberg springs has demonstrated how such springs are able to persist throughout the year despite temperatures that fall to below -50°C during the winter darkness. Dissolved gases emanating from the springs provide evidence of the origin of the water for the springs as well as placing constraints upon the residence time. The gas is composed primarily of N2 with relative concentrations of Ar, Kr, and Xe almost identical to air. No O2 is detectable and Ne is 60% of air values. We believe that ~50% of this gas originates from the direct release of air by nearby alpine glaciers and local ice sheets into groundwater that infiltrates sub-ice sedimentary deposits.

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