Terrestrial analogues for astrobiological investigations of Mars should include Earth's polar regions and as such, the Canadian high Arctic offers several unique cryoenvironments (sub zero saline springs, permafrost) that resemble the conditions that are known or are suspected to exist on Mars. This presentation will describe our recent research focused on detecting and examining microbial life in the unique cold saline/brine springs on Axel Heiberg Island with the overall goals of determining the low temperature limits of microbial life on Earth and if microbial communities inhabiting such cryoenvironments are active at ambient subzero temperatures. The presentation will focus on the microbiology and geochemistry of the Gypsum Hill (GH) and Lost Hammer Spring (LH) sites (Perreault et al, 2008; Niederberger et al. 2010). These unique subzero (0 to -5ºC) hypersaline springs (7.5 to 23% salinity) are characterized by thick extensive permafrost in an area with an average annual air temperature of -15°C and with air temperatures below -40°C common during the winter months. The presence of geomorphological features linked to water movement, such as fluvial valleys and flood channels on the surface of Mars signifies that water once flowed through the Martian landscape and thus, they could have been a potential abode for past or extant microbial life. These springs support viable microbial communities capable of activity at temperatures as low as -10ºC. The LH site also provides a model of how a methane seep can form in cryoenvironments and presents a mechanism that could possibly be contributing to reported methane plumes on Mars. The GH springs sulfide (25-100 ppm) and sulfate (2300-3700 mg/L) abundant system serving as an analogue for the abundant sulfate deposits and potential sulfate-rich brines on Mars that may have originated in the presence of sulfur-rich groundwater. Gas composition (C1-C4 hydrocarbons, He, H2, O2, N2, Ar, and CO2) and stable isotope (d13C and d2H values using compound specific isotope analysis) analyses of the saline spring gas samples has revealed the small amounts of hydrocarbons in gases exsolving from the Gypsum Hill springs (0.38 to 0.51% CH4) were compositionally and isotopically consistent with microbial methanogenesis and possible methanotrophy (Perreault et al. 2008) while the major gas emitted from LH spring is methane (~50 %) with carbon and hydrogen isotope signatures consistent with a thermogenic origin (Niederberger et al. 2010). However, the presence of anaerobic methane oxidizing archaea (ANME) in the LH source provide a model of methane-based metabolism in this extreme hypersaline, subzero environment.