oxygen oasis
Quick Summary
The term "oxygen oasis" refers to a localized environment where the concentration of molecular oxygen (O2) rose significantly above background levels, likely due to the emergence of oxygenic photosynthesis. This process, where organisms use sunlight to convert carbon dioxide and water into energy, releases oxygen as a byproduct.12
Initially, Earth's early atmosphere lacked oxygen, and abundant oxidizable materials readily absorbed any O2 produced. Over time, as these materials were consumed and the rock cycle exposed new ones, the capacity to absorb oxygen was gradually exhausted.1
The development of oxygenic photosynthesis, possibly as early as 3.5 billion years ago, marked the beginning of these oxygen oases. Evidence from sedimentary rocks around 2.8 billion years ago, including geochemical and microfossil data, suggests that oxygenic photosynthesis had become established. These oases allowed for aerobic metabolism to occur in restricted areas, even before the atmosphere as a whole became oxidizing.1
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