Three cyanobacteria (Anabaena sp., Plectonema boryanum and Chroococcidiopsis CCMEE171) and an alga (Chlorella ellipsoidea) were grown under simulated martian ecopoesis conditions. A xenon arc lamp with a solar filter provided simulated martian sunlight, and temperature cycled diurnally from −80°C to 26°C. A Mars-like atmosphere of 100% CO2 was provided at 50, 100, 300, 500 and 1000 mbar. The cyanobacteria and alga were inoculated into JSC Mars-1 soil simulant and exposed to each atmospheric pressure for five weeks. Survival and growth were determined via extractable chlorophyll a and total esterase (fluorescein diacetate hydrolysis) activity. Maximum survival occurred at 100 and 300 mbar. At 50, 500 and 1000 mbar, esterase activity was near zero, and extractable chlorophyll a was less than 10% of control samples. Overall, the cyanobacteria survived better than the alga. Low survival at 50 mbar was probably due to desiccation. Low survival at 500 and 1000 mbar may have been due to CO2 toxicity.
