| Abstract: | The precise amount of O2 and O3 in the Earth's prebiological paleoatmosphere has been a topic of considerable discussion in the past. Since the photolysis of H2O and CO2, the prebiological mechanisms to produce O2, depends on the ultraviolet (UV) flux from the Sun, a reliable quantification of the problem requires detailed knowledge of such flux. Using the most recent astronomical observation of young stars from the International Ultraviolet Explorer, as well as a detailed photochemical model of the paleoatmosphere, we find that the amount of O2 in the prebiological paleoatmosphere may have been as much as 106 times greater than previously estimated.Some of the implications of this new value are discussed. |
