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Unformatted text preview: 1 Extraterrestrial Life: Spring 2008 Limits of life on Earth Some archaea and bacteria ( extremophiles ) can live in environments that we would consider inhospitable to life (heat, cold, acidity, high pressure etc) Distinguish between growth and survival: many organisms can survive intervals of harsh conditions but could not live permanently in such conditions (e.g. seeds, spores) Interest: analogs for extraterrestrial environments `extreme conditions may have been more common on the early Earth - origin of life? some unusual environments (e.g. subterranean) are very widespread Extraterrestrial Life: Spring 2008 Thermophiles Temperatures up to ~55C are common, but T > 55C is associated usually with geothermal features (hot springs, volcanic activity etc) Thermophiles are organisms that can successfully live at high temperatures Best studied extremophiles: may be relevant to the origin of life. Very hot environments tolerable for life do not seem to exist elsewhere in the Solar System Extraterrestrial Life: Spring 2008 Grand Prismatic Spring, Yellowstone National Park Colors on the edge of the spring are caused by different colonies of thermophilic cyanobacteria and algae ~50 species of such thermophiles - mostly archae with some cyanobacteria and anaerobic photosynthetic bacteria Sulfolobus : optimum T ~ 80C, minimum 60C, maximum 90C, also prefer a moderately acidic pH. Live by oxidizing sulfuralso prefer a moderately acidic pH....
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- Spring '08