The “Dark Oxygen” mission hits other worlds

Scientists who recently discovered that metallic grains in the dark seabed produce oxygen have announced plans to study the deepest parts of Earth’s oceans to understand the rare phenomenon.

Their mission “may also change the way we look at the possibility of life on other planets,” the researchers say.

The initial findings puzzled marine scientists. It was previously believed that oxygen could only be produced by plants in sunlight – in a process called photosynthesis.

If oxygen – an essential ingredient for life – is created in the dark by metal grains, the researchers believe that this process could occur on other planets, creating oxygen-rich environments where life can grow.

Lead researcher Andrew Sweetman explained: “We are already talking to NASA experts who believe that dark oxygen could reshape our understanding of how life can be sustained on other planets without sunlight.

“We want to go there and find out what’s going on.”

The initial discovery caused a worldwide scientific row criticism of the findings from scientists and from deep-sea mining companies that plan to collect precious metals in nodules on the seabed.

If oxygen is produced at these extreme depths, in total darkness, this raises the question of what could survive and grow on the seabed, and what impact mining activities might have on that marine life.

That means seabed mining companies and environmental groups – some of whom said the findings provided evidence that seabed mining plans should be halted – will be watching this new research closely.

The plan is to work in areas deeper than 10 km (6.2 miles) on the seabed, using remotely operated underwater equipment.

“We have instruments that can go to the deepest parts of the ocean,” explains Professor Sweetman. “We’re pretty sure it’s going to happen somewhere else, so we’re going to start looking at what’s causing it.”

Some of these experiments, in collaboration with NASA scientists, will aim to understand whether the same process would allow microscopic life to grow beneath the oceans of other planets and moons.

“If there’s oxygen,” said Professor Sweetman, “there could be microbial life taking advantage of it.”

The biologically puzzling initial findings were published last year In the journal Nature Geoscience. They came from several expeditions to an area of ​​the deep sea between Hawaii and Mexico, where Professor Sweetman and his colleagues sent sensors to the sea floor, about 5 kilometers deep.

The area is part of a vast sea floor covered in naturally occurring metal nodules, which form when metals dissolved in seawater collect on pieces of shell or other debris. It is a process that takes millions of years.

Sensors deployed by the team repeatedly showed rising oxygen levels.

“I ignored it,” Professor Sweetman told BBC News at the time, “because it taught me that you only get oxygen through photosynthesis.”

Eventually, he and his colleagues stopped doing their readings and set out to understand what was going on. The experiments carried out in their laboratory – with the nodules collected by the team immersed in vessels in the sea – led the scientists to the conclusion that the metal particles were extracting oxygen from the seawater. The nodules, they discovered, produced electric currents that could split (or electrolyze) seawater molecules into hydrogen and oxygen.

Then came the backlash, in the form of a rebuttal from scientists and seabed mining companies – published online.

One of the critics, Michael Clarke of the Metals Company, a Canadian deep-sea mining company, told BBC News that the criticism focused on “a lack of scientific rigor in the experimental design and data collection”. Essentially, he and other critics said there was no oxygen production, just bubbles created by the equipment as it collected samples.

“We’ve ruled out that option,” replied Professor Sweetman. “But these (new) experiments will provide proof.”

This may sound like a niche, technical argument, but some multibillion dollar mining companies are already exploring the possibility of harvesting tons of these metals from the seabed.

The natural deposits being targeted contain the metals essential to making batteries, and the demand for these metals is increasing rapidly as many economies transition from fossil fuels to electric vehicles.

The race to extract these resources has caused concern among environmental groups and researchers. It has more than 900 marine scientists from 44 countries signed a petition highlighting the environmental risks and calling for the suspension of mining activity.

Speaking at a press conference on Friday about his team’s latest research mission, Professor Sweetman said: “Before we do anything, we need to understand the (deep-sea) ecosystem as well as possible.

“I think the right decision is to hold back before deciding whether it’s the right thing to do as a global society.”