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Facts & Faith, Second Quarter 1997 IssuePublished statements that life requires a temperature range between freezing and boiling has been challenged in recent media reports. Researchers have found life surviving at 113°C (235°F)1 and at crustal depths of about two miles.2,3 These findings have been interpreted by enthusiasts of exobiology (extraterrestrial life) as proof that life can tolerate much broader parameters and, therefore, that it might exist in abundance on thousands if not millions of planets and moons.4
The key point overlooked in the euphoria is the effect of pressure on the freezing and boiling points of water. The archaebacteria surviving temperatures between 90°C and 113°C were found at an ocean depth of 3,650 meters (12,000 feet). The extreme pressure exerted at such a depth, namely, 2.6 tons per square inch, changes the boiling point of water. Taking the pressure factor into account, we find that the "heat-loving" archaebacteria live at temperatures roughly the same distance between water’s freezing and boiling points as do bacteria living at sea level. This is also true of the microorganisms found in rocks two miles below the surface.
The greater problem for microorganisms’ survival two miles below Earth’s surface would seem to be the lack of light for photosynthesis. And yet even at surface level, we find a variety of bacteria amazingly adept at taking advantage of virtually any energy source available. We find bacteria subsisting on hydrogen, sulfurous compounds, and petroleum seepages near the earth’s surface; so we can imagine that such creatures exploit unusual energy sources at great depths.
Subsisting seems the appropriate word. Unlike flourishing life near the earth’s surface, deep underground microbial life has insufficient energy available for much growing or reproduction. This form of life exists in a state that resembles suspended animation.
The only life found at great depths are bacteria and archaebactefia. These life forms have populations greater than several hundred quadrillion at the surface level, and their generations span just a few minutes. Since the capacity for change through natural selection depends directly on the population size and inversely on the generation time, these creatures can adapt to changing environmental conditions much more efficiently than other species can. Thus, as surface layers are slowly driven deep underground by plate tectonics, at least some microorganisms embedded in these layers have time to adapt to the changing conditions. And, some of the microorganisms need not change much. They simply must survive until competing microorganisms are wiped out.
The conclusion that life requires a long list of narrowly-timed parameters has not been overturned. Neither has the conclusion that even the simplest possible life form is so incredibly complex and loaded with information that only a Being as wise and powerful as the biblical God suffices to explain it.
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Return to the table of contents for the
Facts & Faith, Second Quarter 1997 Issue