Vent Illumination

Another mystery is the source of the vent chimneys' glow and sometimes flickering light. The light cannot be seen by the unaided human eye. Its source is neither sunlight nor entirely light from the heat of the water. It may be from crystallizing chemicals, or crystalloluminescence; the sound of bursting bubbles, or sonoluminescence; cracking rock crystals,or triboluminescence; or the radioactive decay of elements in the vent water, known as Cerenkov radiation and scintillation. Marine biologist Cindy Van Dover of the College of William and Mary hopes to discover its source, and whether it could support a type of "sunless photosynthesis" by vent organisms.

Van Dover and Alan Nesbit of the University of London have speculated that photosynthesis may have begun in the faint light in ancient vents. They suggest that photosynthesis could have begun with some chemosynthetic bacteria's serendipitous phototaxis, or ability to move toward or away from light. Being able to sense their position in relation to the light at the top of chimneys would help them stay in the best location-- not too far away to freeze or starve, or too close to cook. In time, these survivors moved up to hot springs closer to the ocean's surface and the light of the sun. There they managed to harnass the sun's energy to make food through photosynthesis.

To support this theory, Nisbet cites two facts:

1. the main light frequencies absorbed by today's most primitive forms of bacterial are those most common in vents, and


2. vents today have elemental iron, manganese and sulfur that is used in photosynthesis.