|MadSci Network: Earth Sciences|
Differences between oxidizing and reducing atmospheres depend on the composition of the surface and atmospheric gases. In an oxidizing atmosphere, such as ours, the dynamic equilibrium favors conversion of surface minerals, compounds, and released gases to higher oxidation states. An example is the conversion of iron to iron oxide (rust) or sulfur (from combustion impurities) to sulfur dioxide.
Two reasons why our atmosphere favors oxidation is the abundance of molecular oxygen and the presence of sunlight. Sunlight photolyzes ozone to produce hydroxyl radicals which are the crucial molecules necessary to initiate the oxidation of hydrocarbons. It is conceivable that there exists reducing atmospheres. In fact, our own atmosphere may have been reducing prior to the presence of oxygen. An atmosphere full of a reducing compound such as ammonia may by reducing.
Hope this helps. Browse some chemistry textbooks on redox chemistry for an understanding of reduction and oxidation processes.
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