Scientists who recently discovered that metallic lumps on the dark seabed produce oxygen have announced plans to study the deepest parts of Earth’s oceans in order to understand the strange phenomenon.
Their mission could “change the way we look at the possibility of life on other planets,” the researchers say.
The initial discovery baffled marine scientists. It was previously accepted that oxygen could only be produced in sunlight by plants – in a process called photosynthesis.
If oxygen – a vital component of life – is made in the dark by the metal lump, researchers believe the process could occur on other planets, creating oxygen-rich environments where life can flourish.
Lead researcher Prof Andrew Sweetman explained: “We are already in conversation with experts at NASA who believe that dark oxygen could reshape our understanding of how life can be sustained on other planets without direct sunlight.
“We want to get out there and figure out what exactly is going on.”
The initial discovery caused a global scientific row – it wasn’t criticism of the findings by some scientists and by deep-sea mining companies that plan to collect the precious metals in the joints of the seabed.
If oxygen is produced at these extreme depths, in total darkness, it raises the question of what life can survive and thrive on the sea floor and what impact mining activities might have on that marine life.
That means seabed mining companies and environmental organizations – some of which claimed the findings provided evidence that seabed mining plans should be stopped – will be watching the new investigation closely.
The plan is to work in places where the seabed is more than 10 km (6.2 miles) deep, using remotely operated submersibles.
“We have instruments that can go into the deepest parts of the ocean,” Prof Sweetman explained. “We’re pretty sure we’ll find it happening elsewhere, so we’ll start investigating what causes it.”
Some of these experiments, in collaboration with scientists at NASA, will aim to understand whether the same process could allow microscopic life to thrive beneath the oceans that are on other planets and moons.
“If there’s oxygen,” Prof Sweetman said, “there could be microbial life taking advantage of that.”
The initial, biologically puzzling 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 Prof Sweetman and his colleagues sent sensors to the seabed – about 5km (3.1 miles) deep.
This area is part of a large area of sea that is covered with naturally occurring metal nodules, which form when metals dissolved in seawater collect on fragments of shell – or other debris. It is a process that takes millions of years.
Sensors the team deployed repeatedly indicated that oxygen levels were rising.
“I just ignored it,” Professor Sweetman told BBC News at the time, “because I had been taught that you only get oxygen through photosynthesis.”
Eventually, he and his colleagues stopped ignoring their readings and set out to figure out what was going on. Experiments in their lab—with the nodules the team collected submerged in beakers of seawater—led the scientists to the conclusion that the metal lumps were creating oxygen from the seawater. The knots, they discovered, generated electric currents that could split (or electrolyze) seawater molecules into hydrogen and oxygen.
Then came the backlash, in the form of objections – posted online – from scientists and seabed mining companies.
One of the critics, Michael Clarke of the Metals Company, a Canadian deep-sea mining company, told BBC News that the criticism centered on a “lack of scientific rigor in the experimental design and data collection”. Essentially, he and other critics claimed there was no oxygen production—only the bubbles the device produced while collecting the sample.
“We have ruled out that possibility,” replied Prof Sweetman. “But these [new] experiments will provide proof.”
This may seem like a specious technical argument, but several multi-billion pound mining companies are already exploring the possibility of scooping up tons of these metals from the bottom of the sea.
The natural deposits they target contain metals vital to battery production, and demand for these metals is growing rapidly as many economies move from fossil fuels to, for example, electric vehicles.
The race to extract these resources has caused concern among environmental groups and researchers. More than 900 marine scientists from 44 countries have signed a petition highlighting the environmental risks and calling for a pause in mining activity.
Speaking about his team’s latest research mission at a press conference on Friday, Prof Sweetman said: “Before we do anything, we need to – as best as possible – understand [deep sea] ecosystem.
“I think the right decision is to pause before deciding whether this is the right thing to do as a global society.”
