The potato-sized lumps contain metals such as manganese, nickel, and cobalt key ingredients in lithium-ion batteries.
They were acting like natural rock batteries.
Just 1.5 volts the same voltage as a typical AA battery is enough to split seawater.
Sweetman and his team recorded voltages of up to 0.95 volts on the surface of single nodules.
Sweetman and his team first detected the presence of dark oxygen in theClarion-Clipperton Zoneover 10 years ago.
But over the course of 10 years, these strange oxygen readings kept showing up.
But for decades, scientists have feared that these activities could causeirreparable damageto deep sea life.
Nodule-rich areas of the ocean floor cansupport more biodiversitythan tropical rainforests.
In unmined regions, however, marine life flourished.
Why such dead zones persist for decades is still unknown.
However, this puts a major asterisk onto strategies for sea-floor mining.
Story bySion Geschwindt
Sion is a freelance science and technology reporter, specialising in climate and energy.
