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No. 108: Nov-Dec 1996

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The Glow Below

Is there such a thing as sunless photosynthesis? Did photosynthesis evolve at the earth's surface or deep in the oceans near hydrothermal vents? Such questions are engendered by the strength of the mysterious glow that emanates from these deep-sea vents. It is at these cracks in the ocean floor that very hot, mineralladen water gushes forth, and where colonies of bizarre tube worms, blind shrimp, and hyperthermophilic (high temperature-loving) bacteria thrive. (For details, see SF#60 or p. 238 in Science Frontiers, the book)

The first anomaly is the strength of the glow itself. It is not all thermal radiation emitted by the 350�C water spewing forth from the vents; in fact, it is 19 times more intense than expected from theory. Something else is contributing energy, but no one knows what it is so far.

The unexpected intensity of the vent glows also asks some provocative questions of the biologists:

  1. Is the glow strong enough to sup port photosynthesis? Quite likely, seems to be the answer.
  2. Are life forms in the vicinity of the vents employing photosynthesis? We don't know yet, but some bacteria do photosynthesize.
  3. Might not life and perhaps photo synthesis, too, have originated at the vents rather than on the planet's surface? This is an attractive possi bility, because very early in the earth's history the surface was con tinually blasted by meteorites, comets, etc. -- a very inhospitable place.

The above questions are so fascinating that we might easily neglect another vent anomaly; one involving those blind shrimp. Like many cave creatures, these shrimp dispensed with eyes long ago. This being so, how do they find the vents, those rich oases of energy and food on the otherwise bleak sea floor? Rather than re-evolve their eyes, they "somehow" grew light-sensitive patches on their backs. Apparently, these patches guide the shrimp to the vents.

(Monastersky, Richard; "The Light at the Bottom of the Ocean," Science News, 150:156, 1966)

Comments. Anomalists instinctively recognize that the "somehow" in the above paragraph glosses over formidable problems. We suppose that a few eyeless shrimp originally blundered into a deepsea vent, and those that were lucky enough to be favored by the long sequence of random mutations that led to the light-sensitive patches on their backs outcompeted their unlucky companions. Assuming this happened at a single vent somewhere in the Stygian darkness of the sea floor, how did the mutated shrimp find the other glowing sea-floor vents hundreds of kilometers away? Their back patches cannot be that sensitive!

From Science Frontiers #108, NOV-DEC 1996. � 1996-2000 William R. Corliss