Dark oxygen: How the discovery of new oxygen deep underwater has reignited the search for alien life

In an extraordinary breakthrough, scientists have recently uncovered a phenomenon that might reshape our understanding of life on Earth — and beyond. Dubbed "dark oxygen," this newly discovered form of oxygen is produced deep underwater, far below the sunlit zones where photosynthesis has long been thought to be the sole producer of oxygen on our planet. This finding, announced in late July 2024, has not only challenged long-standing beliefs about the origins of aerobic life but has also sparked renewed interest in the search for extraterrestrial life.

The discovery and how it works

The discovery took place in the depths of the Pacific Ocean, within the mysterious Clarion-Clipperton Zone, a vast underwater region renowned for its polymetallic nodules — metal-rich deposits scattered across the seafloor. For over a decade, researchers led by Andrew Sweetman of the Scottish Association for Marine Science (SAMS) encountered perplexing data indicating the presence of oxygen in this lightless environment. Initially dismissing these findings as sensor errors, the team eventually confirmed that the oxygen was indeed real and originating from the nodules themselves.
The key to this process lies in the electrochemical properties of the polymetallic nodules. These nodules, composed of metals like cobalt, nickel, and manganese, act like "geobatteries" capable of generating small electrical currents through a process called seawater electrolysis. This reaction splits water molecules, producing both hydrogen and oxygen. The voltage required is minimal — comparable to that of a standard AA battery — but when nodules are clustered together, their collective energy is sufficient to produce significant amounts of oxygen.

Implications for alien life

This discovery has profound implications for the search for extraterrestrial life. Previously, the existence of oxygen was considered a strong indicator of photosynthetic life forms. However, if oxygen can be produced in such an unconventional and lightless environment on Earth, it opens the door to the possibility that similar processes might occur on other celestial bodies with comparable conditions. This raises the tantalising prospect that life — or at least oxygen production — could exist on planets or moons without the need for sunlight.
While the discovery is thrilling, it also presents challenges, particularly in the context of deep-sea mining. As industries look to exploit the mineral wealth of the ocean floor, there's now a pressing need to consider the environmental impact of such activities. The destruction of these oxygen-producing nodules could have severe consequences for deep-sea ecosystems, potentially creating more "dead zones" where life struggles to recover.