ABSTRACT
I. INTRODUCTION The earth is very dynamic and has undergone dramatic changes in its history. All of the elements, including those common in living things, were synthesized from primordial hydrogen in the interior of stars [1]. Supernovas and other stellar instabilities dispersed many elements into space. Because hydrogen and the noble gases are greatly depleted on earth as compared with their cosmic abundances [2], it is likely that the chunks of matter giving rise to the protoplanet did not carry with them gaseous shells of their own. As a result of contraction and redistribution of materials in the developing planet, a hydrosphere and atmosphere developed that were highly reduced [3]. The surface of the earth today is much more oxidized, even to 21% O2 in the atmosphere [4]. Was this oxidation linear or have there been fluctuations several times during the history of the earth resulting in major species extinctions [5]?
