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 106 or 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 the ocean 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 tables [III] to [VI]. 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 (=×10-5 gauss) | Human |
| Gravity | 0 g | Human, plants, animals |
| Pressure | 10-9 mm Hg (5 days) | Mycobacterium smegmatis |
| 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 |
Physicalfactors | Maximum | Organism | Activity |
|---|---|---|---|
Temperature | 104° C(1000 atm) | Desulfovibriodesulfuricans | Grows and reducessulfate |
Magnetism | 167 000gauss | Neurospora Arbacia Drosophila | 1 hr—no effect,Arbaciadevelopment delayed |
Gravity | 400 000 g | Ascaris eggs | 1 hr—eggs hatch,40 days' growth |
110 000 g | Escherichia coli | ||
Pressure | 1400 atm | Marine organisms | Growth |
Microwave | 2450 Mc/sec0.3 to1 W/cm2 | Drosophila | 68 hr, growth notaffected |
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 | 2×106 rad | Bacteria | Growth |
Gamma ray | 2.45×106rad | Microcoleus Phormidium Synechococcus | Continued growth |
Acoustic | 140 db or 6500dyne/cm2at 0.02 to4.8 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 (P32 metabolism) |
| 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 erici from 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 |