An accidental scientific discovery at the bottom of the Pacific Ocean could change our understanding of life on Earth. Researchers at the Scottish Association for Marine Science (SAMS) have found oxygen-producing electric rocks 13,000 feet below the ocean’s surface, challenging the long-held belief that photosynthetic organisms are the planet’s only oxygen “manufacturers.”
Oxygen is present nearly everywhere we look, but until now, we’ve pinned all of the life-giving element’s production on just two types of organisms: plants and algae. As these organisms convert light into sustenance via photosynthesis, they release oxygen, perpetuating the carbon dioxide-for-oxygen exchange that the rest of Earth’s organisms rely on. The idea that only plants and algae can provide oxygen offers scientists a tidy constraint upon which they can build other theories, including those that attempt to explain the origins of aerobic life.
Some of those theories could be complicated by SAMS’s deep ocean finding. A group of polymetallic nodules, which are rocks containing multiple metals and producing oxygen at the Pacific Ocean bottom, were described by researchers in a paper released on Monday through Nature Geoscience. It is believed by the team that these nodules achieve their production via seawater electrolysis: a small electric current split seawater into hydrogen and oxygen.
The individual who didn’t have any intention of changing the narrative on the origins of oxygen was Andrew Sweetman, who is the head of SAMS Seafloor Ecology and Biogeochemistry division as well as the corresponding author of the paper. His focus had been on leading a prolonged investigation into how deep-sea mining affects the Clarion-Clipperton Zone— a mineral-laden area in the Pacific. In what turned out to be a decade-long research, Sweetman’s team noticed a peculiar trend: they kept registering increased levels of oxygen concentration via their deep-sea sensors, which they initially perceived as erroneous readings.
“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 in a SAMS release. “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 to the optode sensors we were using, and when both methods came back with the same result, we knew we were onto something ground-breaking and unthought-of.”
With the help of chemist Franz Geiger at Northwestern University, Sweetman’s team confirmed that the nodules at the bottom of the ocean contained cobalt, nickel, copper, lithium, and manganese—conductive minerals often used in batteries. When these minerals interact with seawater, they might generate electricity, leading to seawater electrolysis. Further investigation revealed that the surfaces of some individual nodules featured 0.95 volts of electricity. While 1.5 volts are required to facilitate seawater electrolysis, Sweetman and his team believe clusters of nodules might offer enough electricity for hydrogen and oxygen to split.
“The discovery of oxygen production by a non-photosynthetic process requires us to rethink how the evolution of complex life on the planet might have originated,” Sweetman 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.”