2024-07-23 22:17:59
This discovery in the depths of the ocean floor, already unusual, does not come from living beings, which surprised scientists, leading them to “rethink the way life appeared on Earth.”
In the depths of the Pacific Ocean and total darkness, scientists have discovered, to their astonishment, oxygen deriving not from living organisms but from types of pebbles containing metals, which raises questions about the theory of the origins of life on Earth. This strange “black oxygen” was detected more than 4 kilometers deep, in the abyssal plain of the Clarion-Clipperton geological fracture zone, in the central Pacific, according to a study published on Monday.
A prime target for deep-sea mining due to the presence of polymetallic nodules, mineral concretions rich in metals (manganese, nickel, cobalt…) necessary for the production of batteries for electric vehicles, wind turbines, photovoltaic panels, and mobile phones. It is in this area that a ship from the Scottish Association for Marine Science (SAMS) took samples, funded by The Metals Company and UK Seabed Resources, which are eager for these precious nodules.
“The oxygen levels were rising in the water”
The aim of the research: to assess the impact of such prospecting on an ecosystem where the absence of light prevents photosynthesis and thus the presence of plants, yet teems with unique animal species. “We were trying to measure the oxygen consumption” of the ocean floor, by placing its sediments under bells called benthic chambers, explains Andrew Sweetman, the lead author of the study published in Nature Geoscience.
Logically, the seawater thus trapped should have seen its oxygen concentration decrease, as it was consumed by living organisms at those depths. However, the opposite was observed: “the oxygen levels were rising in the water above the sediments, in complete darkness and thus without photosynthesis,” elaborates Professor Sweetman, head of the research group on marine ecology and biogeochemistry at SAMS.
“Batteries in the rock”
The surprise was such that the researchers initially thought their underwater sensors had made a mistake. They conducted experiments aboard their ship to see if the same thing occurred at the surface, incubating in the dark the same sediments and the nodules they contained. And once again found that the oxygen levels increased.
“At the surface of the nodules, we detected an electrical tension almost as high as that of an AA battery,” describes Professor Sweetman, comparing these nodules to “batteries in the rock.”
These astonishing properties could be at the origin of an electrolysis process of water, which separates its molecules into hydrogen and oxygen using an electric current. This chemical reaction occurs from 1.5 volts – the voltage of a battery – that the nodules could reach when grouped together, according to a statement from SAMS accompanying the study.
“Life first under the ocean?”
“The discovery of oxygen production by a process other than photosynthesis prompts us to rethink the way life appeared on Earth,” related to the emergence of oxygen, comments Professor Nicholas Owens, director of SAMS. The “conventional” view is that oxygen “was produced for the first time about 3 billion years ago by cyanobacteria that led to the development of more complex organisms,” explains the scientist.
“Life could have started elsewhere than on land and near the ocean surface,” suggests Professor Sweetman. “Since this process exists on our planet, it could generate oxygenated habitats in other ‘ocean worlds’ like Enceladus or Europa (moons of Saturn and Jupiter)” and create the conditions for the emergence of extraterrestrial life.
He hopes that his findings will allow for “better regulation” of deep-sea mining, based on more accurate environmental information.