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Recent discoveries have reopened the idea that, in the past, Mars had a period of wetness where conditions were similar to those on Earth [1]. If this was the case then it is feasible that these environments may have harboured life. The martian surface today is dry, cold and heavily bombarded by UV radiation, making it an environment unsuitable for any known terrestrial life [2]; the martian subsurface might be considerably more hospitable. Subsurface microbial communities would not have access to sunlight for photosynthesis to drive their food chains, so primary production would have to be driven by chemolithoautotrophic organisms. Every successful Mars landing site has been found to have abundant surface salt [3], and halite has been detected in Martian meteorites [4]. While subsurface halite deposits have not yet been detected on Mars, areas on the surface consisting of unidentified chlorine deposits have been detected with evaporation as one of the main theories to explain their creation [5]. On Earth, chloride evaporites are home to halophiles, and they have been suggested as an analogue for potential Martian life. Halophiles are micro-organisms which display a high salt tolerance. Despite being found in evaporite deposits, they are normally studied in surface brines. Brines form when the rate of evaporation of water is greater than the rate that water enters an area [6], so eventually most brines evaporate and form salt crystals. Halophiles in a brine are able to alter the size and formation rate of fluid inclusions within these salt crystals so as to entomb themselves inside until the crystals can re-dissolve [7]. It is uncertain how long halophiles can spend entombed within crystals, but there are some who speculate that it could be up to millions of years, if not longer [8]. If life had arisen on Mars during an earlier, more hospitable, wet period, as it did on Earth, then when the planet cooled, organisms analogous to terrestrial halophiles might have had

The present day martian surface is cold, dry, exposed to UV radiation and bombarded with heavy ions [1]. Any remaining water in the near subsurface is likely to have a high salt concentration because of the likely evaporative processes occurring in those environments. Halophiles are UV resistant [3] and have an ability to entomb themselves within salt crystals during periods of desiccation [4], halophiles have therefore been proposed as analogues for potential martian life. Boulby Salt and Potash Mine in Yorkshire has excavations up to 1.4 km underground and is the second deepest mine in Europe. Despite this depth and the darkness, Norton et al., [5] isolated halophiles from the halite deposits. In this project, we will attempt to isolate and characterize halophiles from halite and other salt-rich sediments from Boulby Mine such as potash, sylvinite, anhydrite and polyhalite, in order to gain an understanding of potential life in the subsurface of Mars. Although the Boulby Mine is used as a martian analogue environment [6], it does possess certain key differences from modern Mars, in particular its aerobic environment and warm temperature. Our long-term goals, once we have characterized the micro-organisms present, are to expose them to Mars conditions (past and present) to determine their ability to grow in such environments. Elements of the martian environment being considered include variations in temperature, lack of oxygen and variations in brine composition. , We will then focus on defining molecular biomarkers and geochemical bio-signatures that may be used as evidence of past or present life on Mars. [1] [1] Mahaffy, P., et al., Science, 2014. [2] Sawyer, D.J., et al., Meteoritics & Planetary Science, 2000. 35(4): p. 743-747 [2] Fischer, E., et al. (2014). Geophysical Research Letters 41(13) [3] Landis, G.A., Astrobiology, 2001. 1(2): p. 161-4 [4] Grant, W. D., R. T. Gemmell and T. J. McGenity (1998). Halophiles. Extremophiles: Microbial Life in Extreme Envi

Recent discoveries have reopened the idea that, in the past, Mars had a period of wetness where conditions were similar to those on Earth [1]. If this was the case then it is feasible that these environments may have harboured life. The martian surface today is dry, cold and heavily bombarded by UV radiation, making it an environment unsuitable for any known terrestrial life [2]; the martian subsurface might be considerably more hospitable. Subsurface microbial communities would not have access to sunlight for photosynthesis to drive their food chains, so primary production would have to be driven by chemolithoautotrophic organisms. Every successful Mars landing site has been found to have abundant surface salt [3], and halite has been detected in Martian meteorites [4]. While subsurface halite deposits have not yet been detected on Mars, areas on the surface consisting of unidentified chlorine deposits have been detected with evaporation as one of the main theories to explain their creation [5]. On Earth, chloride evaporites are home to halophiles, and they have been suggested as an analogue for potential Martian life. Halophiles are micro-organisms which display a high salt tolerance. Despite being found in evaporite deposits, they are normally studied in surface brines. Brines form when the rate of evaporation of water is greater than the rate that water enters an area [6], so eventually most brines evaporate and form salt crystals. Halophiles in a brine are able to alter the size and formation rate of fluid inclusions within these salt crystals so as to entomb themselves inside until the crystals can re-dissolve [7]. It is uncertain how long halophiles can spend entombed within crystals, but there are some who speculate that it could be up to millions of years, if not longer [8]. If life had arisen on Mars during an earlier, more hospitable, wet period, as it did on Earth, then when the planet cooled, organisms analogous to terrestrial halophiles might have had

The present day martian surface is cold, dry, exposed to UV radiation and bombarded with heavy ions [1]. Any remaining water in the near subsurface is likely to have a high salt concentration because of the likely evaporative processes occurring in those environments. Halophiles are UV resistant [3] and have an ability to entomb themselves within salt crystals during periods of desiccation [4], halophiles have therefore been proposed as analogues for potential martian life. Boulby Salt and Potash Mine in Yorkshire has excavations up to 1.4 km underground and is the second deepest mine in Europe. Despite this depth and the darkness, Norton et al., [5] isolated halophiles from the halite deposits. In this project, we will attempt to isolate and characterize halophiles from halite and other salt-rich sediments from Boulby Mine such as potash, sylvinite, anhydrite and polyhalite, in order to gain an understanding of potential life in the subsurface of Mars. Although the Boulby Mine is used as a martian analogue environment [6], it does possess certain key differences from modern Mars, in particular its aerobic environment and warm temperature. Our long-term goals, once we have characterized the micro-organisms present, are to expose them to Mars conditions (past and present) to determine their ability to grow in such environments. Elements of the martian environment being considered include variations in temperature, lack of oxygen and variations in brine composition. , We will then focus on defining molecular biomarkers and geochemical bio-signatures that may be used as evidence of past or present life on Mars. [1] [1] Mahaffy, P., et al., Science, 2014. [2] Sawyer, D.J., et al., Meteoritics & Planetary Science, 2000. 35(4): p. 743-747 [2] Fischer, E., et al. (2014). Geophysical Research Letters 41(13) [3] Landis, G.A., Astrobiology, 2001. 1(2): p. 161-4 [4] Grant, W. D., R. T. Gemmell and T. J. McGenity (1998). Halophiles. Extremophiles: Microbial Life in Extreme Envi