Could lumpy metallic rocks in the deepest, darkest reaches of the ocean be making oxygen in the absence of sunlight?

Some scientists think so, but others have challenged the claim that so-called “dark oxygen” is being produced in the lightless abyss of the seabed.

The discovery—detailed last July in the journal Nature Geoscience —called into question long-held assumptions about the origins of life on Earth, and sparked intense scientific debate.