EXTREME AND LIMITING ENVIRONMENTAL PARAMETERS OF LIFEThe question of the existence of extraterrestrial life is one of the most important and interesting biological questions facing mankind and has been the subject of much controversial discussion and conjecture. Many of the quantitative, and even qualitative, environmental constituents of the planets also are still subjects of controversy and speculation. Best guesses about a relatively unknown planetary environment, combined with lack of information about the capabilities of Earth life to grow in extreme environments, do not provide the basis for making informed scientific estimates.Life on Earth is usually considered to be relatively limited in its ability to grow, reproduce, or survive in extreme environmental conditions. While many common plants and animals (including man) are quite sensitive to, or incapable of, surviving severe chemical and physical changes or extremes of environment, a large number of micro-organisms are highly adapted and flourish in environments usually considered lethal. Certain chemoautotrophic bacteria require high concentrations of ammonia, methane, or other chemicals to grow. Anaerobic bacteria grow only in the absence of oxygen.Besides adapting to the extremes of environments on Earth, life is also capable of growing and reproducing under extreme environmental conditions not normally encountered: e.g., from a few rad of radiation in normal habitats to 106or more rad from artificial sources, from 0.5 gauss of Earth magnetism to 167 000 gauss in manmade magnetic fields, and from 1-g force of gravity to 110 000 g. The extreme ranges of physical and chemical environmental factors for growth, reproduction, and survival for Earth micro-organisms are phenomenally large.Life is ubiquitous on Earth and is found in almost every possible environment, including the most severe habitats, from the bottom of theocean to the highest mountain tops and from cold Arctic habitats to hot springs, as well as in volcanic craters, deep wells, salt flats, and mountain snowfields. Earth life has become adapted to, and has invaded, nearly every habitat, no matter how severe. The physiological and morphological adaptations of life are exceedingly diverse and complex.Surprisingly, the extreme parameters or ranges of the physical and chemical environmental factors permitting growth, reproduction, and other physiological processes of Earth organisms have not been critically compiled. A partial compilation of certain selected environmental factors has been made by Vallentyne ([ref.76]). A compilation of available published data on certain environmental extremes, particularly from recent NASA-supported research (compiled by Dale W. Jenkins, in press), is presented in tablesIIItoVI. These data can serve as a starting point for a more intensive literature review by specialists, critical evaluation, standardization of end points, and especially to point out areas where critical experimentation is urgently needed.This critical compilation involves a review of a very broad and complex range of subjects involved in many different disciplines with widely scattered literature. Since the effects of many of the specific environmental factors are harmful, it is difficult to select a point on a scale from no effect to death and use some criteria to say that normal or even minimal growth and reproduction are occurring. The effects of environmental factors are dependent on (1) the specific factor, times, (2) the concentration or energy, times, (3) the time of exposure or application of the factor. Many reports, especially older ones, do not give all of the necessary data to permit proper evaluation. A complicating factor is that the effect of each factor depends on the other factors before, during, and after its application. The condition of the organism itself is a great variable. Proper evaluation requires the critical review by a variety of biological specialists, physicists, and chemists.To determine the potential of Earth organisms to survive or grow under other planetary environmental conditions, a number of experiments have been carried out attempting to simulate planetary environments, especially of Mars, as reviewed previously. While the results are of real interest, they do not provide much basic information. Further, as the Martian environment is more accurately defined, the experimental conditions are changed. In addition, some experimenters have altered certain factors, such as water content, to allow for potential microhabitats or for areas which might contain more water at certain times.Table III.—Extreme Physical Environmental FactorsPhysical factorsMinimumOrganismTemperature-30° CAlgae (photosynthesis), pink yeast (growth)Magnetism0-50 gamma (=×10-5gauss)HumanGravity0 gHuman, plants, animalsPressure10-9mm Hg (5 days)MycobacteriumsmegmatisMicrowave0 W/cm2Visible0 ft-cAnimals, fungi, bacteriaUltraviolet0 erg/cm2X-ray0 radGamma ray0 radAcoustic0 dyne/cm2Table III.—Extreme Physical Environmental FactorsPhysical factorsMaximumOrganismActivityTemperature104° C (1000 atm)Desulfovibrio desulfuricansGrows and reduces sulfateMagnetism167 000 gaussNeurosporaArbaciaDrosophila1 hr—no effect,Arbaciadevelopment delayedGravity400 000 gAscariseggs1 hr—eggs hatch, 40 days' growth110 000 gEscherichia coliPressure1400 atmMarine organismsGrowthMicrowave2450 Mc/sec 0.3 to 1 W/cm2Drosophila68 hr, growth not affectedVisible50 000 ft-cChlorella,higher plantsSeconds, recurrentlycontinuous17 000 ft-cUltraviolet108erg/cm2,2537 ÅBean embryosSuppressed growthX-ray2×106radBacteriaGrowthGamma ray2.45×106radMicrocoleusPhormidiumSynechococcusContinued growthAcoustic140 db or 6500 dyne/cm2at 0.02 to 4.8 kcs/secManThreshold of painTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMinimum temperature, °COrganismActivity or condition-11BacteriaGrowth (on fish)-12BacteriaGrowth-12MoldsGrowth-15PyramidomonasSwimming-15Dunaliella salinaSwimming-18MoldGrowth-18YeastGrowth-18Aspergillus glaucusGrowth (in glycerol)-18 to -20MoldGrowth (in fruit juice)-18 to -20PseudomonadsGrowth (in fruit juice)-20BacteriaGrowth-20BacteriaGrowth-20BacteriaLuminescence development accelerated-20 to -24Insect eggs (diapause)-30AlgaePhotosynthesis-30Pink yeastGrowth (on oysters)-30LichensPhotosynthesis-20 to -40Lichens and conifersPhotosynthesis-44Mold sporesSporulation and germinationTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMaximum temperature, °COrganismActivity or condition73Thermophilic organismsGrowth (P32metabolism)73Phormidium(alga)Acclimatized70 to 73Bacillus calidusGrowth and spore germination70 to 74Bacillus cylindricusGrowth and spore germination70 to 75Bacillus tostatusGrowth and spore germination80Bacillus stearothermophilusCultured in laboratory83Sulfate-reducing bacteriaFound in a well89Sulfate-reducing a bacteriaFound in oil waters65 to 85Sulfate-reducing a bacteriaCultured in laboratory89Micro-organismsFound in hot springs95Bacillus coagulansIn 80 min. sporulation activation110Bacillus coagulansIn 6 min, sporulation activation104Desulfovibrio desulfuricansGrow and reduce sulfate at 1000 atmTable V.—Extreme Temperature Limits of SurvivalMinimum temperature °COrganism-190Yeast bacteria, 10 species-197Trebouxia ericifrom lichens-197Protozoa,Anguillula-252Yeasts, molds, bacteria, 10 species-253Black currant, birch-273Bacteria, many species-273Bacteria, many species-272Desiccated rotifers-269Human spermatozoaTable V.—Extreme Temperature Limits of SurvivalMaximum temperature °COrganismTime of exposure140Bacterial spores5-hr immersion170-200Desiccated rotifers5 min151Desiccated rotifers35 min150Clostridium tetani180 min170Aerobic bacteria, molds. actinomycetes5 days at 6×10-9mm Hg127 (dry)Bacteria (in activated charcoal)60 min110 (wet)Bacillus subtilisvar.niger400 min120Bacillus subtilisvar.niger400 min141Bacillus subtilisvar.niger70 min160Bacillus subtilisvar.niger15 min180Bacillus subtilisvar.niger2 min188Bacillus subtilisvar.niger1 min120 (wet)Bacillus stearothermophilus25 min120 (dry)Bacillus stearothermophilus100 min141Bacillus stearothermophilus12 min160Bacillus stearothermophilus2 min166Bacillus stearothermophilus1 minTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMinimumOrganismO20%HeLa cells,Cephalobus, anaerobic bacteriaO3(ozone)0%H20%H2OAw 0.48Pleurococcus vulgarisAw 0.5Xenopsylla cheopis(prepupae)H2O20%He0%CO0%CO20%CH40%CH2O0%CH3OH0%N20%NO0%NO20%N2O0%Ar0%NaCl, Na2SO4, NaHCO3H2S0%H2SO40%Cu++Zn++pH0Acontium velatumThiobacillus thioodixansEh-450 mV at pH 9.5Sulfate-reducing bacteriaTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMaximumPressure, atmTime, daysOrganismActivityO2100%1Plants, animalsGrowthO3(ozone)100 ppm5Armillaria melleaGrowth500 ppm5Light emissionH2100%Various plantsGerminationH2OAw 1.01Various aquatic organismsGrowthH2O20.34%RyeGermination enhancedHe100%Wheat, rye, riceGerminationCO100%RyeGermination80%1.14HydrogenomonasGrowthCO2100%1.14RyeGrowth and germinationCH4100%1.14RyeGerminationCH2O50%RyeGerminationCH3OH50%RyeGerminationN2100%.110Various plantsGermination and root growthNO18%.01810Sorghum, riceGermination and root growthNO218%.01810Rye, riceGermination and root growthN2O100%1.24RyeGermination96.5%1.7RyeGerminationTenebrio molitorSurvivalAr100%1.22RyeGerminationNaCl, Na2SO4, NaHCO367%Photosynthetic bacteriaGrowthH2S0.96 g/literDesulfovibrio desulfuricansGrowthH2SO47%Acontium velatumGrowthThiobacilliGrowth, reproductionCu++12 g/literThiobacillus ferrooxidansGrowthZn++17 g/literThiobacillus ferrooxidansGrowthpH13Plectonema nostocorumGrowthNitrobacterGrowthNitrosomonasGrowthEh850 mV at pH 3Iron bacteriaGrowth
EXTREME AND LIMITING ENVIRONMENTAL PARAMETERS OF LIFEThe question of the existence of extraterrestrial life is one of the most important and interesting biological questions facing mankind and has been the subject of much controversial discussion and conjecture. Many of the quantitative, and even qualitative, environmental constituents of the planets also are still subjects of controversy and speculation. Best guesses about a relatively unknown planetary environment, combined with lack of information about the capabilities of Earth life to grow in extreme environments, do not provide the basis for making informed scientific estimates.Life on Earth is usually considered to be relatively limited in its ability to grow, reproduce, or survive in extreme environmental conditions. While many common plants and animals (including man) are quite sensitive to, or incapable of, surviving severe chemical and physical changes or extremes of environment, a large number of micro-organisms are highly adapted and flourish in environments usually considered lethal. Certain chemoautotrophic bacteria require high concentrations of ammonia, methane, or other chemicals to grow. Anaerobic bacteria grow only in the absence of oxygen.Besides adapting to the extremes of environments on Earth, life is also capable of growing and reproducing under extreme environmental conditions not normally encountered: e.g., from a few rad of radiation in normal habitats to 106or more rad from artificial sources, from 0.5 gauss of Earth magnetism to 167 000 gauss in manmade magnetic fields, and from 1-g force of gravity to 110 000 g. The extreme ranges of physical and chemical environmental factors for growth, reproduction, and survival for Earth micro-organisms are phenomenally large.Life is ubiquitous on Earth and is found in almost every possible environment, including the most severe habitats, from the bottom of theocean to the highest mountain tops and from cold Arctic habitats to hot springs, as well as in volcanic craters, deep wells, salt flats, and mountain snowfields. Earth life has become adapted to, and has invaded, nearly every habitat, no matter how severe. The physiological and morphological adaptations of life are exceedingly diverse and complex.Surprisingly, the extreme parameters or ranges of the physical and chemical environmental factors permitting growth, reproduction, and other physiological processes of Earth organisms have not been critically compiled. A partial compilation of certain selected environmental factors has been made by Vallentyne ([ref.76]). A compilation of available published data on certain environmental extremes, particularly from recent NASA-supported research (compiled by Dale W. Jenkins, in press), is presented in tablesIIItoVI. These data can serve as a starting point for a more intensive literature review by specialists, critical evaluation, standardization of end points, and especially to point out areas where critical experimentation is urgently needed.This critical compilation involves a review of a very broad and complex range of subjects involved in many different disciplines with widely scattered literature. Since the effects of many of the specific environmental factors are harmful, it is difficult to select a point on a scale from no effect to death and use some criteria to say that normal or even minimal growth and reproduction are occurring. The effects of environmental factors are dependent on (1) the specific factor, times, (2) the concentration or energy, times, (3) the time of exposure or application of the factor. Many reports, especially older ones, do not give all of the necessary data to permit proper evaluation. A complicating factor is that the effect of each factor depends on the other factors before, during, and after its application. The condition of the organism itself is a great variable. Proper evaluation requires the critical review by a variety of biological specialists, physicists, and chemists.To determine the potential of Earth organisms to survive or grow under other planetary environmental conditions, a number of experiments have been carried out attempting to simulate planetary environments, especially of Mars, as reviewed previously. While the results are of real interest, they do not provide much basic information. Further, as the Martian environment is more accurately defined, the experimental conditions are changed. In addition, some experimenters have altered certain factors, such as water content, to allow for potential microhabitats or for areas which might contain more water at certain times.Table III.—Extreme Physical Environmental FactorsPhysical factorsMinimumOrganismTemperature-30° CAlgae (photosynthesis), pink yeast (growth)Magnetism0-50 gamma (=×10-5gauss)HumanGravity0 gHuman, plants, animalsPressure10-9mm Hg (5 days)MycobacteriumsmegmatisMicrowave0 W/cm2Visible0 ft-cAnimals, fungi, bacteriaUltraviolet0 erg/cm2X-ray0 radGamma ray0 radAcoustic0 dyne/cm2Table III.—Extreme Physical Environmental FactorsPhysical factorsMaximumOrganismActivityTemperature104° C (1000 atm)Desulfovibrio desulfuricansGrows and reduces sulfateMagnetism167 000 gaussNeurosporaArbaciaDrosophila1 hr—no effect,Arbaciadevelopment delayedGravity400 000 gAscariseggs1 hr—eggs hatch, 40 days' growth110 000 gEscherichia coliPressure1400 atmMarine organismsGrowthMicrowave2450 Mc/sec 0.3 to 1 W/cm2Drosophila68 hr, growth not affectedVisible50 000 ft-cChlorella,higher plantsSeconds, recurrentlycontinuous17 000 ft-cUltraviolet108erg/cm2,2537 ÅBean embryosSuppressed growthX-ray2×106radBacteriaGrowthGamma ray2.45×106radMicrocoleusPhormidiumSynechococcusContinued growthAcoustic140 db or 6500 dyne/cm2at 0.02 to 4.8 kcs/secManThreshold of painTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMinimum temperature, °COrganismActivity or condition-11BacteriaGrowth (on fish)-12BacteriaGrowth-12MoldsGrowth-15PyramidomonasSwimming-15Dunaliella salinaSwimming-18MoldGrowth-18YeastGrowth-18Aspergillus glaucusGrowth (in glycerol)-18 to -20MoldGrowth (in fruit juice)-18 to -20PseudomonadsGrowth (in fruit juice)-20BacteriaGrowth-20BacteriaGrowth-20BacteriaLuminescence development accelerated-20 to -24Insect eggs (diapause)-30AlgaePhotosynthesis-30Pink yeastGrowth (on oysters)-30LichensPhotosynthesis-20 to -40Lichens and conifersPhotosynthesis-44Mold sporesSporulation and germinationTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMaximum temperature, °COrganismActivity or condition73Thermophilic organismsGrowth (P32metabolism)73Phormidium(alga)Acclimatized70 to 73Bacillus calidusGrowth and spore germination70 to 74Bacillus cylindricusGrowth and spore germination70 to 75Bacillus tostatusGrowth and spore germination80Bacillus stearothermophilusCultured in laboratory83Sulfate-reducing bacteriaFound in a well89Sulfate-reducing a bacteriaFound in oil waters65 to 85Sulfate-reducing a bacteriaCultured in laboratory89Micro-organismsFound in hot springs95Bacillus coagulansIn 80 min. sporulation activation110Bacillus coagulansIn 6 min, sporulation activation104Desulfovibrio desulfuricansGrow and reduce sulfate at 1000 atmTable V.—Extreme Temperature Limits of SurvivalMinimum temperature °COrganism-190Yeast bacteria, 10 species-197Trebouxia ericifrom lichens-197Protozoa,Anguillula-252Yeasts, molds, bacteria, 10 species-253Black currant, birch-273Bacteria, many species-273Bacteria, many species-272Desiccated rotifers-269Human spermatozoaTable V.—Extreme Temperature Limits of SurvivalMaximum temperature °COrganismTime of exposure140Bacterial spores5-hr immersion170-200Desiccated rotifers5 min151Desiccated rotifers35 min150Clostridium tetani180 min170Aerobic bacteria, molds. actinomycetes5 days at 6×10-9mm Hg127 (dry)Bacteria (in activated charcoal)60 min110 (wet)Bacillus subtilisvar.niger400 min120Bacillus subtilisvar.niger400 min141Bacillus subtilisvar.niger70 min160Bacillus subtilisvar.niger15 min180Bacillus subtilisvar.niger2 min188Bacillus subtilisvar.niger1 min120 (wet)Bacillus stearothermophilus25 min120 (dry)Bacillus stearothermophilus100 min141Bacillus stearothermophilus12 min160Bacillus stearothermophilus2 min166Bacillus stearothermophilus1 minTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMinimumOrganismO20%HeLa cells,Cephalobus, anaerobic bacteriaO3(ozone)0%H20%H2OAw 0.48Pleurococcus vulgarisAw 0.5Xenopsylla cheopis(prepupae)H2O20%He0%CO0%CO20%CH40%CH2O0%CH3OH0%N20%NO0%NO20%N2O0%Ar0%NaCl, Na2SO4, NaHCO3H2S0%H2SO40%Cu++Zn++pH0Acontium velatumThiobacillus thioodixansEh-450 mV at pH 9.5Sulfate-reducing bacteriaTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMaximumPressure, atmTime, daysOrganismActivityO2100%1Plants, animalsGrowthO3(ozone)100 ppm5Armillaria melleaGrowth500 ppm5Light emissionH2100%Various plantsGerminationH2OAw 1.01Various aquatic organismsGrowthH2O20.34%RyeGermination enhancedHe100%Wheat, rye, riceGerminationCO100%RyeGermination80%1.14HydrogenomonasGrowthCO2100%1.14RyeGrowth and germinationCH4100%1.14RyeGerminationCH2O50%RyeGerminationCH3OH50%RyeGerminationN2100%.110Various plantsGermination and root growthNO18%.01810Sorghum, riceGermination and root growthNO218%.01810Rye, riceGermination and root growthN2O100%1.24RyeGermination96.5%1.7RyeGerminationTenebrio molitorSurvivalAr100%1.22RyeGerminationNaCl, Na2SO4, NaHCO367%Photosynthetic bacteriaGrowthH2S0.96 g/literDesulfovibrio desulfuricansGrowthH2SO47%Acontium velatumGrowthThiobacilliGrowth, reproductionCu++12 g/literThiobacillus ferrooxidansGrowthZn++17 g/literThiobacillus ferrooxidansGrowthpH13Plectonema nostocorumGrowthNitrobacterGrowthNitrosomonasGrowthEh850 mV at pH 3Iron bacteriaGrowth
EXTREME AND LIMITING ENVIRONMENTAL PARAMETERS OF LIFEThe question of the existence of extraterrestrial life is one of the most important and interesting biological questions facing mankind and has been the subject of much controversial discussion and conjecture. Many of the quantitative, and even qualitative, environmental constituents of the planets also are still subjects of controversy and speculation. Best guesses about a relatively unknown planetary environment, combined with lack of information about the capabilities of Earth life to grow in extreme environments, do not provide the basis for making informed scientific estimates.Life on Earth is usually considered to be relatively limited in its ability to grow, reproduce, or survive in extreme environmental conditions. While many common plants and animals (including man) are quite sensitive to, or incapable of, surviving severe chemical and physical changes or extremes of environment, a large number of micro-organisms are highly adapted and flourish in environments usually considered lethal. Certain chemoautotrophic bacteria require high concentrations of ammonia, methane, or other chemicals to grow. Anaerobic bacteria grow only in the absence of oxygen.Besides adapting to the extremes of environments on Earth, life is also capable of growing and reproducing under extreme environmental conditions not normally encountered: e.g., from a few rad of radiation in normal habitats to 106or more rad from artificial sources, from 0.5 gauss of Earth magnetism to 167 000 gauss in manmade magnetic fields, and from 1-g force of gravity to 110 000 g. The extreme ranges of physical and chemical environmental factors for growth, reproduction, and survival for Earth micro-organisms are phenomenally large.Life is ubiquitous on Earth and is found in almost every possible environment, including the most severe habitats, from the bottom of theocean to the highest mountain tops and from cold Arctic habitats to hot springs, as well as in volcanic craters, deep wells, salt flats, and mountain snowfields. Earth life has become adapted to, and has invaded, nearly every habitat, no matter how severe. The physiological and morphological adaptations of life are exceedingly diverse and complex.Surprisingly, the extreme parameters or ranges of the physical and chemical environmental factors permitting growth, reproduction, and other physiological processes of Earth organisms have not been critically compiled. A partial compilation of certain selected environmental factors has been made by Vallentyne ([ref.76]). A compilation of available published data on certain environmental extremes, particularly from recent NASA-supported research (compiled by Dale W. Jenkins, in press), is presented in tablesIIItoVI. These data can serve as a starting point for a more intensive literature review by specialists, critical evaluation, standardization of end points, and especially to point out areas where critical experimentation is urgently needed.This critical compilation involves a review of a very broad and complex range of subjects involved in many different disciplines with widely scattered literature. Since the effects of many of the specific environmental factors are harmful, it is difficult to select a point on a scale from no effect to death and use some criteria to say that normal or even minimal growth and reproduction are occurring. The effects of environmental factors are dependent on (1) the specific factor, times, (2) the concentration or energy, times, (3) the time of exposure or application of the factor. Many reports, especially older ones, do not give all of the necessary data to permit proper evaluation. A complicating factor is that the effect of each factor depends on the other factors before, during, and after its application. The condition of the organism itself is a great variable. Proper evaluation requires the critical review by a variety of biological specialists, physicists, and chemists.To determine the potential of Earth organisms to survive or grow under other planetary environmental conditions, a number of experiments have been carried out attempting to simulate planetary environments, especially of Mars, as reviewed previously. While the results are of real interest, they do not provide much basic information. Further, as the Martian environment is more accurately defined, the experimental conditions are changed. In addition, some experimenters have altered certain factors, such as water content, to allow for potential microhabitats or for areas which might contain more water at certain times.Table III.—Extreme Physical Environmental FactorsPhysical factorsMinimumOrganismTemperature-30° CAlgae (photosynthesis), pink yeast (growth)Magnetism0-50 gamma (=×10-5gauss)HumanGravity0 gHuman, plants, animalsPressure10-9mm Hg (5 days)MycobacteriumsmegmatisMicrowave0 W/cm2Visible0 ft-cAnimals, fungi, bacteriaUltraviolet0 erg/cm2X-ray0 radGamma ray0 radAcoustic0 dyne/cm2Table III.—Extreme Physical Environmental FactorsPhysical factorsMaximumOrganismActivityTemperature104° C (1000 atm)Desulfovibrio desulfuricansGrows and reduces sulfateMagnetism167 000 gaussNeurosporaArbaciaDrosophila1 hr—no effect,Arbaciadevelopment delayedGravity400 000 gAscariseggs1 hr—eggs hatch, 40 days' growth110 000 gEscherichia coliPressure1400 atmMarine organismsGrowthMicrowave2450 Mc/sec 0.3 to 1 W/cm2Drosophila68 hr, growth not affectedVisible50 000 ft-cChlorella,higher plantsSeconds, recurrentlycontinuous17 000 ft-cUltraviolet108erg/cm2,2537 ÅBean embryosSuppressed growthX-ray2×106radBacteriaGrowthGamma ray2.45×106radMicrocoleusPhormidiumSynechococcusContinued growthAcoustic140 db or 6500 dyne/cm2at 0.02 to 4.8 kcs/secManThreshold of painTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMinimum temperature, °COrganismActivity or condition-11BacteriaGrowth (on fish)-12BacteriaGrowth-12MoldsGrowth-15PyramidomonasSwimming-15Dunaliella salinaSwimming-18MoldGrowth-18YeastGrowth-18Aspergillus glaucusGrowth (in glycerol)-18 to -20MoldGrowth (in fruit juice)-18 to -20PseudomonadsGrowth (in fruit juice)-20BacteriaGrowth-20BacteriaGrowth-20BacteriaLuminescence development accelerated-20 to -24Insect eggs (diapause)-30AlgaePhotosynthesis-30Pink yeastGrowth (on oysters)-30LichensPhotosynthesis-20 to -40Lichens and conifersPhotosynthesis-44Mold sporesSporulation and germinationTable IV.—Extreme Low and High Temperature Effects Permitting Life ProcessesMaximum temperature, °COrganismActivity or condition73Thermophilic organismsGrowth (P32metabolism)73Phormidium(alga)Acclimatized70 to 73Bacillus calidusGrowth and spore germination70 to 74Bacillus cylindricusGrowth and spore germination70 to 75Bacillus tostatusGrowth and spore germination80Bacillus stearothermophilusCultured in laboratory83Sulfate-reducing bacteriaFound in a well89Sulfate-reducing a bacteriaFound in oil waters65 to 85Sulfate-reducing a bacteriaCultured in laboratory89Micro-organismsFound in hot springs95Bacillus coagulansIn 80 min. sporulation activation110Bacillus coagulansIn 6 min, sporulation activation104Desulfovibrio desulfuricansGrow and reduce sulfate at 1000 atmTable V.—Extreme Temperature Limits of SurvivalMinimum temperature °COrganism-190Yeast bacteria, 10 species-197Trebouxia ericifrom lichens-197Protozoa,Anguillula-252Yeasts, molds, bacteria, 10 species-253Black currant, birch-273Bacteria, many species-273Bacteria, many species-272Desiccated rotifers-269Human spermatozoaTable V.—Extreme Temperature Limits of SurvivalMaximum temperature °COrganismTime of exposure140Bacterial spores5-hr immersion170-200Desiccated rotifers5 min151Desiccated rotifers35 min150Clostridium tetani180 min170Aerobic bacteria, molds. actinomycetes5 days at 6×10-9mm Hg127 (dry)Bacteria (in activated charcoal)60 min110 (wet)Bacillus subtilisvar.niger400 min120Bacillus subtilisvar.niger400 min141Bacillus subtilisvar.niger70 min160Bacillus subtilisvar.niger15 min180Bacillus subtilisvar.niger2 min188Bacillus subtilisvar.niger1 min120 (wet)Bacillus stearothermophilus25 min120 (dry)Bacillus stearothermophilus100 min141Bacillus stearothermophilus12 min160Bacillus stearothermophilus2 min166Bacillus stearothermophilus1 minTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMinimumOrganismO20%HeLa cells,Cephalobus, anaerobic bacteriaO3(ozone)0%H20%H2OAw 0.48Pleurococcus vulgarisAw 0.5Xenopsylla cheopis(prepupae)H2O20%He0%CO0%CO20%CH40%CH2O0%CH3OH0%N20%NO0%NO20%N2O0%Ar0%NaCl, Na2SO4, NaHCO3H2S0%H2SO40%Cu++Zn++pH0Acontium velatumThiobacillus thioodixansEh-450 mV at pH 9.5Sulfate-reducing bacteriaTable VI.—Extremes of Chemical Environmental Factors Permitting Growth or ActivityChemical factorMaximumPressure, atmTime, daysOrganismActivityO2100%1Plants, animalsGrowthO3(ozone)100 ppm5Armillaria melleaGrowth500 ppm5Light emissionH2100%Various plantsGerminationH2OAw 1.01Various aquatic organismsGrowthH2O20.34%RyeGermination enhancedHe100%Wheat, rye, riceGerminationCO100%RyeGermination80%1.14HydrogenomonasGrowthCO2100%1.14RyeGrowth and germinationCH4100%1.14RyeGerminationCH2O50%RyeGerminationCH3OH50%RyeGerminationN2100%.110Various plantsGermination and root growthNO18%.01810Sorghum, riceGermination and root growthNO218%.01810Rye, riceGermination and root growthN2O100%1.24RyeGermination96.5%1.7RyeGerminationTenebrio molitorSurvivalAr100%1.22RyeGerminationNaCl, Na2SO4, NaHCO367%Photosynthetic bacteriaGrowthH2S0.96 g/literDesulfovibrio desulfuricansGrowthH2SO47%Acontium velatumGrowthThiobacilliGrowth, reproductionCu++12 g/literThiobacillus ferrooxidansGrowthZn++17 g/literThiobacillus ferrooxidansGrowthpH13Plectonema nostocorumGrowthNitrobacterGrowthNitrosomonasGrowthEh850 mV at pH 3Iron bacteriaGrowth
The question of the existence of extraterrestrial life is one of the most important and interesting biological questions facing mankind and has been the subject of much controversial discussion and conjecture. Many of the quantitative, and even qualitative, environmental constituents of the planets also are still subjects of controversy and speculation. Best guesses about a relatively unknown planetary environment, combined with lack of information about the capabilities of Earth life to grow in extreme environments, do not provide the basis for making informed scientific estimates.
Life on Earth is usually considered to be relatively limited in its ability to grow, reproduce, or survive in extreme environmental conditions. While many common plants and animals (including man) are quite sensitive to, or incapable of, surviving severe chemical and physical changes or extremes of environment, a large number of micro-organisms are highly adapted and flourish in environments usually considered lethal. Certain chemoautotrophic bacteria require high concentrations of ammonia, methane, or other chemicals to grow. Anaerobic bacteria grow only in the absence of oxygen.
Besides adapting to the extremes of environments on Earth, life is also capable of growing and reproducing under extreme environmental conditions not normally encountered: e.g., from a few rad of radiation in normal habitats to 106or more rad from artificial sources, from 0.5 gauss of Earth magnetism to 167 000 gauss in manmade magnetic fields, and from 1-g force of gravity to 110 000 g. The extreme ranges of physical and chemical environmental factors for growth, reproduction, and survival for Earth micro-organisms are phenomenally large.
Life is ubiquitous on Earth and is found in almost every possible environment, including the most severe habitats, from the bottom of theocean to the highest mountain tops and from cold Arctic habitats to hot springs, as well as in volcanic craters, deep wells, salt flats, and mountain snowfields. Earth life has become adapted to, and has invaded, nearly every habitat, no matter how severe. The physiological and morphological adaptations of life are exceedingly diverse and complex.
Surprisingly, the extreme parameters or ranges of the physical and chemical environmental factors permitting growth, reproduction, and other physiological processes of Earth organisms have not been critically compiled. A partial compilation of certain selected environmental factors has been made by Vallentyne ([ref.76]). A compilation of available published data on certain environmental extremes, particularly from recent NASA-supported research (compiled by Dale W. Jenkins, in press), is presented in tablesIIItoVI. These data can serve as a starting point for a more intensive literature review by specialists, critical evaluation, standardization of end points, and especially to point out areas where critical experimentation is urgently needed.
This critical compilation involves a review of a very broad and complex range of subjects involved in many different disciplines with widely scattered literature. Since the effects of many of the specific environmental factors are harmful, it is difficult to select a point on a scale from no effect to death and use some criteria to say that normal or even minimal growth and reproduction are occurring. The effects of environmental factors are dependent on (1) the specific factor, times, (2) the concentration or energy, times, (3) the time of exposure or application of the factor. Many reports, especially older ones, do not give all of the necessary data to permit proper evaluation. A complicating factor is that the effect of each factor depends on the other factors before, during, and after its application. The condition of the organism itself is a great variable. Proper evaluation requires the critical review by a variety of biological specialists, physicists, and chemists.
To determine the potential of Earth organisms to survive or grow under other planetary environmental conditions, a number of experiments have been carried out attempting to simulate planetary environments, especially of Mars, as reviewed previously. While the results are of real interest, they do not provide much basic information. Further, as the Martian environment is more accurately defined, the experimental conditions are changed. In addition, some experimenters have altered certain factors, such as water content, to allow for potential microhabitats or for areas which might contain more water at certain times.
Physical factors
Minimum
Organism
Temperature
-30° C
Algae (photosynthesis), pink yeast (growth)
Magnetism
0-50 gamma (=×10-5gauss)
Human
Gravity
0 g
Human, plants, animals
Pressure
10-9mm Hg (5 days)
Mycobacteriumsmegmatis
Microwave
0 W/cm2
Visible
0 ft-c
Animals, fungi, bacteria
Ultraviolet
0 erg/cm2
X-ray
0 rad
Gamma ray
0 rad
Acoustic
0 dyne/cm2
Physical factors
Maximum
Organism
Activity
Temperature
104° C (1000 atm)
Desulfovibrio desulfuricans
Grows and reduces sulfate
Magnetism
167 000 gauss
NeurosporaArbaciaDrosophila
Neurospora
Arbacia
Drosophila
1 hr—no effect,Arbaciadevelopment delayed
Gravity
400 000 g
Ascariseggs
1 hr—eggs hatch, 40 days' growth
110 000 g
Escherichia coli
Pressure
1400 atm
Marine organisms
Growth
Microwave
2450 Mc/sec 0.3 to 1 W/cm2
Drosophila
68 hr, growth not affected
Visible
50 000 ft-c
Chlorella,
higher plants
Seconds, recurrently
continuous
17 000 ft-c
Ultraviolet
108erg/cm2,2537 Å
Bean embryos
Suppressed growth
X-ray
2×106rad
Bacteria
Growth
Gamma ray
2.45×106rad
MicrocoleusPhormidiumSynechococcus
Microcoleus
Phormidium
Synechococcus
Continued growth
Acoustic
140 db or 6500 dyne/cm2at 0.02 to 4.8 kcs/sec
Man
Threshold of pain
Minimum temperature, °C
Organism
Activity or condition
-11
Bacteria
Growth (on fish)
-12
Bacteria
Growth
-12
Molds
Growth
-15
Pyramidomonas
Swimming
-15
Dunaliella salina
Swimming
-18
Mold
Growth
-18
Yeast
Growth
-18
Aspergillus glaucus
Growth (in glycerol)
-18 to -20
Mold
Growth (in fruit juice)
-18 to -20
Pseudomonads
Growth (in fruit juice)
-20
Bacteria
Growth
-20
Bacteria
Growth
-20
Bacteria
Luminescence development accelerated
-20 to -24
Insect eggs (diapause)
-30
Algae
Photosynthesis
-30
Pink yeast
Growth (on oysters)
-30
Lichens
Photosynthesis
-20 to -40
Lichens and conifers
Photosynthesis
-44
Mold spores
Sporulation and germination
Maximum temperature, °C
Organism
Activity or condition
73
Thermophilic organisms
Growth (P32metabolism)
73
Phormidium(alga)
Acclimatized
70 to 73
Bacillus calidus
Growth and spore germination
70 to 74
Bacillus cylindricus
Growth and spore germination
70 to 75
Bacillus tostatus
Growth and spore germination
80
Bacillus stearothermophilus
Cultured in laboratory
83
Sulfate-reducing bacteria
Found in a well
89
Sulfate-reducing a bacteria
Found in oil waters
65 to 85
Sulfate-reducing a bacteria
Cultured in laboratory
89
Micro-organisms
Found in hot springs
95
Bacillus coagulans
In 80 min. sporulation activation
110
Bacillus coagulans
In 6 min, sporulation activation
104
Desulfovibrio desulfuricans
Grow and reduce sulfate at 1000 atm
Minimum temperature °C
Organism
-190
Yeast bacteria, 10 species
-197
Trebouxia ericifrom lichens
-197
Protozoa,Anguillula
-252
Yeasts, molds, bacteria, 10 species
-253
Black currant, birch
-273
Bacteria, many species
-273
Bacteria, many species
-272
Desiccated rotifers
-269
Human spermatozoa
Maximum temperature °C
Organism
Time of exposure
140
Bacterial spores
5-hr immersion
170-200
Desiccated rotifers
5 min
151
Desiccated rotifers
35 min
150
Clostridium tetani
180 min
170
Aerobic bacteria, molds. actinomycetes
5 days at 6×10-9mm Hg
127 (dry)
Bacteria (in activated charcoal)
60 min
110 (wet)
Bacillus subtilisvar.niger
400 min
120
Bacillus subtilisvar.niger
400 min
141
Bacillus subtilisvar.niger
70 min
160
Bacillus subtilisvar.niger
15 min
180
Bacillus subtilisvar.niger
2 min
188
Bacillus subtilisvar.niger
1 min
120 (wet)
Bacillus stearothermophilus
25 min
120 (dry)
Bacillus stearothermophilus
100 min
141
Bacillus stearothermophilus
12 min
160
Bacillus stearothermophilus
2 min
166
Bacillus stearothermophilus
1 min
Chemical factor
Minimum
Organism
O2
0%
HeLa cells,Cephalobus, anaerobic bacteria
O3(ozone)
0%
H2
0%
H2O
Aw 0.48
Pleurococcus vulgaris
Aw 0.5
Xenopsylla cheopis(prepupae)
H2O2
0%
He
0%
CO
0%
CO2
0%
CH4
0%
CH2O
0%
CH3OH
0%
N2
0%
NO
0%
NO2
0%
N2O
0%
Ar
0%
NaCl, Na2SO4, NaHCO3
H2S
0%
H2SO4
0%
Cu++
Zn++
pH
0
Acontium velatumThiobacillus thioodixans
Acontium velatum
Thiobacillus thioodixans
Eh
-450 mV at pH 9.5
Sulfate-reducing bacteria
Chemical factor
Maximum
Pressure, atm
Time, days
Organism
Activity
O2
100%
1
Plants, animals
Growth
O3(ozone)
100 ppm
5
Armillaria mellea
Growth
500 ppm
5
Light emission
H2
100%
Various plants
Germination
H2O
Aw 1.0
1
Various aquatic organisms
Growth
H2O2
0.34%
Rye
Germination enhanced
He
100%
Wheat, rye, rice
Germination
CO
100%
Rye
Germination
80%
1.1
4
Hydrogenomonas
Growth
CO2
100%
1.1
4
Rye
Growth and germination
CH4
100%
1.1
4
Rye
Germination
CH2O
50%
Rye
Germination
CH3OH
50%
Rye
Germination
N2
100%
.1
10
Various plants
Germination and root growth
NO
18%
.018
10
Sorghum, rice
Germination and root growth
NO2
18%
.018
10
Rye, rice
Germination and root growth
N2O
100%
1.2
4
Rye
Germination
96.5%
1.7
Rye
Germination
Tenebrio molitor
Survival
Ar
100%
1.2
2
Rye
Germination
NaCl, Na2SO4, NaHCO3
67%
Photosynthetic bacteria
Growth
H2S
0.96 g/liter
Desulfovibrio desulfuricans
Growth
H2SO4
7%
Acontium velatum
Growth
Thiobacilli
Growth, reproduction
Cu++
12 g/liter
Thiobacillus ferrooxidans
Growth
Zn++
17 g/liter
Thiobacillus ferrooxidans
Growth
pH
13
Plectonema nostocorum
Growth
Nitrobacter
Growth
Nitrosomonas
Growth
Eh
850 mV at pH 3
Iron bacteria
Growth