Because organisms subjected to sterilizing conditions for a sufficient time period pose no threat to terrestrial ecosystems, it is important to assemble a database on the survival capacity of a wide range of terrestrial organisms under extreme conditions. Despite the existence of a rich literature on the survival of microorganisms exposed to radiation and high temperatures, the studied taxa represent only a small sampling of the microbial diversity known to exist in the biosphere and, in general, have not been taken from extreme environments. Little is known about the radiation and temperature resistance of microorganisms from environments on Earth that have the chemical and physical characteristics likely to be encountered in or on small solar system bodies.

Recommendation: NASA should sponsor research that will lead to a better understanding of the radiation and temperature resistance of microorganisms from environments on Earth that have the chemical and physical characteristics likely to be encountered in or on small solar system bodies. Information on the survival of organisms subjected to long- or short-term ionizing radiation needs to be collected for both metabolically active and dormant stages of diverse groups of microorganisms, including hyperthermophiles, oligotrophic chemoorganotrophs, and chemolithoautotrophs. Likewise, it is important to establish short- and long-term temperature survival curves for similarly broad groups of metabolically active and dormant organisms. In particular, data are required on survival of diverse microorganisms under flash heating (1- to 10-second exposures) to temperatures between 160 °C and 400 °C.

REFERENCES

National Research Council (NRC). 1992. Biological Contamination of Mars: Issues and Recommendations. Washington D.C.: National Academy Press.

National Research Council (NRC). 1997. Mars Sample Return: Issues and Recommendations. Washington D.C.: National Academy Press.



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