Subsurface Halophiles: An Analogue for Potential Life on Mars

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 Environments. K. Horikoshi and W. D. Grant, [5] Norton, C.F., T.J. McGenity, and W.D. Grant, Journal of General Microbiology, 1993. 139(5): p. 1077-1081. [6] Cockell, C.S., et al., 2013. 54(2): p. 2.25-2.27