A discovery that “encourages us to rethink how life appeared on Earth,” nothing less. Professor Nicholas Owens, director of the Scottish Association for Marine Science (SAMS), is enthusiastic. During a scientific cruise on the functioning of the ocean floor, he observed a fascinating phenomenon described in an article published in the journal Nature Geoscience this Monday, July 22. Oxygen created at the bottom of the ocean by… pebbles.
Let’s start again. A SAMS vessel was commissioned by The Metals Company and UK Seabed Resources to take samples at a depth of more than four kilometres, in the abyssal plain of the Clarion-Clipperton geological fracture zone, in the central Pacific. This area is of particular interest to the mining industry. The exploitation of the abyss is the subject of fierce international negotiations. It contains polymetallic nodules, mineral concretions rich in metals (manganese, nickel, cobalt, etc.) needed in particular for the manufacture of batteries for electric vehicles, wind turbines, photovoltaic panels and mobile phones.
The aim of the research was to assess the impact of such prospecting on an ecosystem where the absence of light prevents photosynthesis and therefore the presence of plants, but which is full of unique animal species. “We were trying to measure oxygen consumption” from the ocean floor by placing the sediments it contains under bell jars called benthic chambers, explains Andrew Sweetman, first author of the study. Logically, the seawater thus trapped should have seen its oxygen concentration decrease, as the latter was consumed by the organisms living at these depths. However, the opposite is what was observed: “the oxygen level increased in the water above the sediments, in complete darkness and therefore without photosynthesis,” “This is a very important step in the process of developing a global network of researchers,” says Professor Sweetman, head of the SAMS Seafloor Ecology and Biogeochemistry research group.
Perspectives on the existence of extraterrestrial life
The surprise was such that the researchers initially thought that their underwater sensors had made a mistake. They conducted experiments aboard their ship to see if the same thing happened on the surface, by incubating, in the dark, these same sediments and the nodules they contained. And found once again that the oxygen level increasedt. “On the surface of the nodules we detected an electrical voltage almost as high as in an AA battery,” describes Andrew Sweetman, comparing these nodules to “Batteries in the rock”. These astonishing properties could be at the origin of a process of electrolysis of water, that is to say the separation of the components of the water molecule (H2O), into molecules of hydrogen and oxygen with the help of an electric current. This chemical reaction occurs from 1.5 volts – the voltage of a battery – that the nodules could reach when they are grouped, according to a press release from the SAMS association attached to the study. They called this gas produced so deep that the rays of the sun do not penetrate that far, “dark oxygen”.
And here is the whole modern story about the appearance of life called into question. The vision “conventional” being that oxygen “was first made about 3 billion years ago by cyanobacteria which led to the development of more complex organisms”explains Nicholas Owens. “Life could have started somewhere other than on land and near the surface of the ocean”enthuses Andrew Sweetman. For him, this discovery also opens up perspectives on the existence of extraterrestrial life. “Since this process exists on our planet, it could generate oxygenated habitats in other oceanic worlds like Enceladus or Europa (moons of Saturn and Jupiter)” and create the conditions for the emergence of extraterrestrial life. The dream is allowed. More prosaically, this result pleads, once again, for strict supervision of the seabed, a fragile area, largely unknown, but which arouses the covetousness of industrialists.