NASA Astrobiology Institute (NAI)

Spacecraft sent to Mars stow terrestrial bacteria onboard which may survive the interplanetary transit. Such organisms might compromise the search for life beyond Earth, if capable of proliferating on the Red Planet. This study explored the survival capacity of a psychrophilic microorganism, Psychrobacter cryohalolentis strain K5, on the surface of Mars using simulated environmental variables including ultraviolet irradiation, desiccation, temperature, atmospheric pressure and dust composition. Because Martian surface conditions can overlap with the terrestrial niche of P.
cryohalolentis, it has been suggested that the bacterium might possibly survive on Mars. In order to explore survivability, experiments measured the desiccation tolerance of P. cryohalolentis, in a transit and planetary surface context. Subsequent experiments were conducted in a Mars Simulation Chamber at NASA’s Kennedy Space Center, exploring UV irradiation resistance of the bacterium. All P. cryohalolentis cells were killed within 8 hours of exposure due to a Martian UV flux. In experiments where a simulated atmospheric dust level was dense (shielding UV light), the survivability of the bacterium increased moderately, although overall population levels continued to decline from desiccation. These results have important implications for future Mars exploration protocols and astrobiology-related missions. This senior research thesis is being prepared for publication in the journal Astrobiology.