'Dark oxygen' discovered deep in Pacific Ocean questions origins of life on Earth
A discovery from the "complete darkness" of the Pacific Ocean seafloor is testing the scientific consensus on how oxygen is made and has even called into question the origins of life on Earth, a new study says.
Until now, scientists thought oxygen was only made using energy from sunlight. The discovery of "dark oxygen" being made at more than 13,000 feet below the ocean’s surface challenges that theory, according to a news release from the Scottish Association for Marine Sciences (SAMS)
"For aerobic life to begin on the planet, there had to be oxygen and our understanding has been that Earth’s oxygen supply began with photosynthetic organisms. But we now know that there is oxygen produced in the deep sea, where there is no light. I think we therefore need to revisit questions like: where could aerobic life have begun?" Sweetman said.
A team led by Andrew Sweetman of SAMS first observed the "dark oxygen" in 2013 while doing fieldwork on a ship in the Pacific Ocean. They published their findings this week in the journal Nature Geoscience.
Scientists were studying the seafloor in the Clarion-Clipperton Zone of the Pacific to assess the possible impacts of deep-sea mining – or extracting metals like manganese, nickel and cobalt used to produce lithium-ion batteries.
While studying the nodules that contain metals, Sweetman and colleagues found them to carry a very high electric charge, "which could lead to the splitting of seawater into hydrogen and oxygen in a process called seawater electrolysis," SAMS explains.
"When we first got this data, we thought the sensors were faulty, because every study ever done in the deep sea has only seen oxygen being consumed rather than produced," Sweetman said. "We would come home and recalibrate the sensors but over the course of 10 years, these strange oxygen readings kept showing up.
"We decided to take a back-up method that worked differently … and when both methods came back with the same result we knew we were onto something ground-breaking and unthought-of."
Researchers are calling it "one of the most exciting findings in ocean science in recent times."
"The process requires us to rethink how the evolution of complex life on the planet might have originated," SAMS Director Nicholas Owens said. "The conventional view is that oxygen was first produced around three billion years ago by ancient microbes called cyanobacteria and there was a gradual development of complex life thereafter.
"The potential that there was an alternative source requires us to have a radical rethink."
The discovery could also change how the deep-sea nodules are mined for metals.
"Through this discovery, we have generated many unanswered questions and I think we have a lot to think about in terms of how we mine these nodules, which are effectively batteries in a rock," Sweetman said.
