A New Science-Nonfiction Discovery: Dark Oxygen

Scientists thought sunlight was required to create oxygen but newly discovered "battery rocks" proves otherwise

Hiya!

As far as I’m concerned, Earth’s global ocean, which takes up most of our planet, is as much of its own world as Space is. Both environments are mysterious, beautiful, and utterly hostile to our fragile human bodies. The lack of breathable oxygen in both places is a big reason.

Of course, the ocean is bursting with oxygen-producing plants and algae, but only in areas where sunlight can pierce the depths. The rest of the ocean, anywhere deeper than a few thousand feet, is seemingly as devoid of oxygen as Space is — or so we thought.

Previous Thoughts

For a long time, scientists viewed oxygen as a byproduct of life itself, specifically photosynthesis, the process plants and algae use to convert sunlight, water, and carbon dioxide into oxygen and sugar for energy. Scientists thought complex life evolved only after photosynthesizing life expelled enough oxygen to accommodate it — although this theory has recently been challenged.

Still, Nicholas Owens, the director of the Scottish Association for Marine Science (SAMS), explained in a news release about a study I’ll tell you about soon:

“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.”

This view was so ingrained in scientists that when Andrew Sweetman, an ecologist at SAMS, discovered contradictory evidence of the idea in 2013, he dismissed it outright. Sweetman told Victoria Gill of BBC News:

“I just ignored it because I’d been taught you only get oxygen through photosynthesis.”

At the time, Sweetman was part of a team of researchers measuring the amount of oxygen organisms on the bottom of the Pacific Ocean’s Clarion-Clipperton Zone (CCZ) were consuming.

The CCZ spans over 3,000 miles (5,000 km) across the central Pacific Ocean in international waters, where the floor is between 12,000 and 18,000 feet (4,000 - 5,500 meters) deep. The bottom of the CCZ is utterly and completely devoid of light, which dissipates underwater between about 650 and 3,200 feet (200 to 1,000 meters).

So, when Sweetman and his team sent landers to the CCV floor that would track oxygen levels, they expected to see them decrease over time because photosynthesis can’t occur without sunlight, which can’t reach the CCV seabed.

Yet, the equipment reported that oxygen levels did not fall but, in fact, increased substantially. At the time, Sweetman told Shi En Kim of Smithsonian Magazine that he assumed the results were due to faulty equipment and sent the sensors back to the manufacturer to be recalibrated — not once or twice, but four to five times over five years. He told Kim,

“I literally told my students, ‘Throw the sensors in the bin. They just do not work.’”

But as fate would have it, Sweetman returned to the same CCZ location in 2021. This time, he was part of a survey team for a deep-sea mining firm called Metals Company, which sent them to survey the seabed.

New Research

This time, Sweetman and his team used a different technique to measure oxygen levels on the seabed, but they got the same unexpected results showing that oxygen levels rose dramatically over time despite the lack of sunlight. Sweetman told Allison Parshall of Scientific American:

“Suddenly I realized that … I’d been ignoring this hugely significant process, and I just kicked myself. My mindset completely changed [to] focus on what is causing this.”