“Black” oxygen has been discovered in the ocean and questions the origin of life on Earth.
Oxygen is well known for being an invisible and odorless gas, essential for life. It is produced by photosynthetic organisms, which depend on light. This being said, another type of oxygen, called “black” oxygen, has been discovered and would have a completely different origin, as reported in a study published in the journal Nature Geoscience.
This black oxygen was detected during a mission of the SAMSthe Scottish Association for Marine Sciences, which was to take samples at a depth of more than four kilometers in the central Pacific, and more precisely in the abyssal plain of the Clarion-Clipperton area. The scientists then noted that at this depth “the oxygen level increased in the water above the sediments, in complete darkness and therefore without photosynthesis”, explained Professor Sweetman, head of the research group on the ecology and biogeochemistry of the seabed of the association SAMS.
In this area, numerous polymetallic nodules are present: these are kinds of pebbles filled with precious minerals such as nickel or cobalt, for example. These nodules, according to the samples taken, are in fact electrically charged with quite high power. Due to their condensed presence in this area, they could have caused an electrolysis process, separating hydrogen and oxygen from the water (H2O) using their electric current. The gas thus produced, without light intervention, was then named “black oxygen”.
This discovery calls into question the origin of life on Earth, which has always been linked to the appearance of oxygen three billion years ago, thanks to cyanobacteria. Oxygen available at the ocean floor was previously thought to come from photosynthesis in the upper ocean and mid-term. But today it is believed that the deep sea could ultimately produce its own oxygen.
“The discovery of oxygen production by a process other than photosynthesis encourages us to rethink how life appeared on Earth,” said Professor Nicholas Owens, director of SAMS. Life could therefore have started elsewhere than on the surface. This process could also be found in other “ocean worlds like Enceladus or Europa”, which are moons of Saturn and Jupiter, and create the conditions necessary for life. Further studies are still needed to establish the scope of this phenomenon.