Web edition: August 12, 2011
Print edition: August 27, 2011; Vol.180 #5 (p. 4)
EARTH ONCE GLOWED — The earth’s surface in its early years of life may have glowed like a beautiful rainbow, shimmering with the colorful array of light emitted by primitive organisms. Light emission may have occurred soon after life appeared on earth, when the atmosphere lacked oxygen…. As small amounts of oxygen appeared in the atmosphere, not all of the organisms could tolerate the presence of oxygen. However, those that could quickly and rapidly remove the oxygen by reduction with hydrogen or electrons from primitive foodstuffs survived. In removing the oxygen by the use of organic reducing substances, an excited state was produced resulting in the emission of light. The surviving organisms were therefore all potentially luminescent.