Evaporites: Analogs for Martian Life
Abstract
Recent data from Mars missions suggest that Mars almost certainly had abundant liquid water on its surface at some time in the past. As a result, Mars has emerged as a key Solar System target which could have harbored some form of life in its past and which could perhaps still possess some remnant in brine containing permafrost. As mars lost its atmosphere it became cold and dry. If any water remained to form permafrost high salt brine pockets would have formed within the ice. These brine pockets may either be an "oasis" for an extant Martian biota, or the last refuge of an extinct Martian biota. Eventually these brine pockets would have dried to form evaporites. Evaporites are deposits that result from the evaporation water containing salts, on earth consisting primarily of halite (NaCl) gypsum (CaSO4 . 2H2O) or anhydrite (CaSO4). Evaporites containing bacterial and algal assemblages exist on earth today and are well-known in the fossil record. The most likely organism type to survive in a salty brine or evaporite is a halophile. Washed mid-log phase and stationary phase cultures of Halobacterium salinarium either suspended in brine (25% NaCl), dried, or in the form of a paste prepared from a centrifuge pellet were exposed to -20 oC or -80 oC. As a control, E. coli was treated similarly except was suspended in 0.8% NaCl or deionized water. Periodically samples of the cells were removed and tested for survival. Preliminary data from these experiments suggest that under these conditions Halophiles can survive exposure to such low temperatures better than E. coli. This would suggest that halophiles may survive in permafrost containing evporites.
- Publication:
-
34th COSPAR Scientific Assembly
- Pub Date:
- 2002
- Bibcode:
- 2002cosp...34E1920M