Preface on Making Oxygen

Abstract

Imagine a planet whose atmosphere is irreversibly changed
\nby the dominant lifeform inhabiting it. The lifeform releases a gas--a waste gas--trillions and trillions of tons of it. The atmosphere becomes so altered that evolution on the planet is forever changed. Science fiction? Not at all! The planet is Earth, but the waste gas is not carbon dioxide and the time is not now. Instead, the unwanted gas is oxygen, the subject of this issue’s Forum, and the time is long, long ago. On primordial Earth, the atmosphere was reducing, most likely made up mainly of nitrogen, methane, ammonia, and water vapor. While oxygen is the most abundant element in the Earth’s crust, it did not exist in the atmosphere in primordial times to even a small fraction of the extent that it does today.