A deep-sea shark and several eels are attracted by bait placed on top of Cook’s seamount, as seen from the submarine Pisces V during a dive to the previously unexplored seamount off the Big Island of Hawaii on September 6, 2016.
Caleb Jones/AP
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Caleb Jones/AP
Researchers studying the lightless land at the bottom of the Pacific Ocean say they have observed “dark oxygen” being produced there, potentially challenging popular beliefs about how oxygen is produced on Earth.
Until now, it was thought that oxygen was created only through photosynthesis, a process that requires sunlight. But this discovery casts doubt on that theory and raises new questions about the origin of life.
“I think we therefore need to revisit questions like: where might aerobic life have originated?” Andrew Sweetman saida professor at the Scottish Association for Marine Science in Oban, Scotland, in a news release.
Research team led by Sweetman published his findings Monday in a magazine article Natural Earth Science.
Scientists aren’t sure how oxygen is created at such dark depths, but they believe it’s created by electrically charged minerals called polymetallic nodules. Size range from a tiny seed to the size of a potato.
These nodules — “essentially batteries in the rock,” Sweetman says — can use their electrical charge to split seawater into hydrogen and oxygen in a process called seawater electrolysis.
“The conventional view is that oxygen was first produced around three billion years ago by ancient microbes called cyanobacteria and that complex life then gradually evolved,” said Nicholas Owens, director of the Scottish Association for Marine Science, in a news release. “The possibility of an alternative source requires a radical rethink.”
The researchers conducted tests on the seafloor and collected samples for testing on land, and they came up with similar results: increased oxygen concentrations near the polymetallic nodules.
Seawater can be split into hydrogen and oxygen with 1.5 volts of electricity, about the same as in an AA battery. The researchers found that some nodules had as much as 0.95 volts, and multiple nodules together produced even higher voltages.
This discovery could impact deep-sea mining.
Polymetallic nodules contain metals such as manganese, nickel and cobalt, which can be used to make lithium-ion batteries used in consumer electronics, appliances and electric vehicles.
Franz Geiger, a chemistry professor at Northwestern University who was involved in the study, said in a separate news release that there may be enough polymetallic nodules in an area of the Pacific Ocean called the Clarion-Clipperton Zone to meet global energy needs for decades to come.
But he also said mining must be done in a way that does not remove oxygen that is the lifeblood of life in that ocean area.
“We need to be really careful if deep-sea mining becomes an opportunity that is pursued… that it is done at a level and frequency that does not harm life there,” Geiger told NPR.
He said companies conducted deep-sea mining exploration missions in the 1970s and 1980s, and recent research suggests those missions may have had consequences for marine life in the area for decades.
“A few years ago, a group of marine biologists went back to areas that had been mined 40 years ago and found basically no life,” Geiger said. “And then a few hundred meters to the left and right, where the nodules were intact, there was a lot of life.”
