The deep sea is home to “dark oxygen”
Nodules on the seabed, rather than photosynthesis, are the source of the gas
THE VAST majority of Earth’s oxygen is made as a by-product of photosynthesis, the use of light to convert water and carbon dioxide into sugars. Any oxygen found in regions where photosynthesis is impossible—such as the abyssal seafloor, a pitch-black realm up to 6,000 metres deep—was thought to be surface gas on the move.
This article appeared in the Science & technology section of the print edition under the headline “Deep breaths”
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