Could the study of manganese oxides produced by bacteria aid the search for life on other planets? During the first billion years of Earth's history, when the conditions resembled a seething caldron of hot gases and steam, the planet's only inhabitants were bacteria. With constant bombardment by debris left over from the formation of the solar system, along with massive volcanic outgassing, the early atmosphere consisted primarily of sulfuric acid, methane, carbon monoxide, and carbon dioxide; there was little, if any, oxygen. Without abundant oxygen molecules to form atmospheric ozone (1), microbial colonies living at the surface would have had no protection from unattenuated solar UV radiation. Eventually, photosynthetic microorganisms evolved in the protective depths of the seas. There, they began the long process of releasing oxygen molecules--a byproduct of their metabolism--into the atmosphere.
展开▼
