For decades, scientists have speculated about dark matter, which is believed to hold galaxies together through its gravitational pull. The mystery of dark matter endures, and now researchers have discovered what they call “dark oxygen” on the ocean floor.
A recent study published in Nature Geoscience, a journal dedicated to Earth sciences research, reveals oxygen emitted from mineral deposits 4,000 meters (about 13,000 feet) below the ocean’s surface in the Pacific Ocean’s Clarion-Clipperton Zone (CCZ). This depth is nearly half the height of Mount Everest.
The study, led by Andrew Sweetman, a professor at the Scottish Association for Marine Science (SAMS) and head of the institution’s seafloor ecology and biogeochemistry research group, provides evidence of an additional oxygen source on Earth apart from the oxygen produced by photosynthesis.
Previously, scientists understood that the planet’s only oxygen source was photosynthetic organisms like plants and algae, which produce oxygen for humans and other animals to breathe, according to Al-Jazeera.com
So, what is the significance of this newly discovered dark oxygen, and what questions does it raise about the origins of life on Earth?
What is dark oxygen?
The Clarion-Clipperton Zone (CCZ), which spans 4.5 million square kilometers (1.7 million square miles) in the Pacific Ocean, has coal-like mineral rocks called polymetallic nodules. These nodules typically contain manganese and iron. Scientists have found that these nodules produce oxygen without the process of photosynthesis.
This discovery could potentially change scientists’ views on how life began on Earth.
“The other implication of this research is it potentially sheds light on where life began on the planet. This discovery has shown that, well, maybe there was another source of oxygen a long time ago and aerobic life or life that breathes oxygen could have persisted before the rise of photosynthesis — and if it’s happening on our planet could it be happening on other planets too,” Sweetman stated in a SAMS video.
How did they find the dark oxygen?
The discovery comes more than 10 years after the source of dark oxygen itself was found. A 2013 research mission aimed to understand how much oxygen was consumed by organisms on the CCZ seafloor.
Landers, mechanical platforms that can free-fall to the seafloor, were sent down 4,000 meters (13,000 feet) to track how oxygen levels in the water decreased with depth.
However, researchers discovered that oxygen levels increased at the ocean bed.
This finding surprised Sweetman and his team. Until now, scientists believed that oxygen available in the deep ocean came from the upper ocean and land, produced by plants, plankton, and algae using the process of photosynthesis. As a result, oxygen levels usually decrease with depth. Not in this case.
Thinking his measuring equipment was faulty, Sweetman had the equipment recalibrated and repeated the experiment several times over many years—with the same results.
Through more experiments, they discovered that manganese nodules were the source of oxygen production. They brought these nodules back to the ship for testing and noticed they had an electric charge equivalent to an AA battery.
A process known as seawater electrolysis allows a charge to split seawater into hydrogen and oxygen. This was observed in their lab experiments.
