Scientists who recently discovered that metallic lumps on the dark sea floor are generating oxygen have announced plans to study the deepest parts of Earth’s oceans to understand the strange phenomenon.
Their mission could “change the way we look at the possibility of life on other planets as well,” the researchers say.
The initial discovery puzzled marine scientists. It was previously accepted that plants could only produce oxygen in sunlight – in a process called photosynthesis.
If oxygen – a vital component of life – is created in the dark from clumps of metal, researchers believe the process could be happening on other planets, creating oxygen-rich environments where life could thrive.
Research leader, prof. Andrew Sweetman, explained: “We are already talking to experts at NASA who believe that dark oxygen could reshape our understanding of how life could be sustained on other planets without direct sunlight.
“We want to go there and figure out exactly what’s going on.”
The original discovery sparked a global scientific row – it was criticism of findings from some scientists and from deep-sea mining companies that plan to harvest precious metals from nodules on the seabed.
If oxygen is produced at these extreme depths, in complete darkness, it raises the question of what kind of life could survive and thrive on the sea floor, and what impact mining activities could have on that marine life.
This means that seabed mining companies and environmental organizations – some of whom have argued that the findings provide evidence that seabed mining plans should be halted – will be watching this new investigation closely.
The plan is to work in places where the seabed is deeper than 10 km (6.2 miles), using remotely controlled underwater equipment.
“We have instruments that can go to the deepest parts of the ocean,” explained prof. Sweetman. “We’re pretty confident that we’re going to find that it’s happening 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 could allow microscopic life to thrive beneath the oceans found on other planets and moons.
“If there is oxygen,” said prof. Sweetman, “there could be microbial life that could take advantage of it.”
The first, biologically puzzling findings were published last year in the journal Nature Geoscience. They came from several expeditions into the deep sea area between Hawaii and Mexico, where Professor Sweetman and his colleagues sent sensors to the seabed – to a depth of about 5km (3.1 miles).
The area is part of a vast swath of seabed that is covered in natural metal nodules, which form when dissolved metals in seawater collect on fragments of shells – or other debris. It is a process that takes millions of years.
Sensors that the team constantly placed showed a rise in oxygen levels.
“I just ignored it,” Professor Sweetman told BBC News at the time, “because I was taught that you only get oxygen through photosynthesis.”
Eventually, he and his colleagues stopped ignoring their readings and instead set out to understand 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 generating oxygen from the seawater. The lumps, they discovered, generated an electrical current that could split (or electrolyze) seawater molecules into hydrogen and oxygen.
Then came the backlash, in the form of rebuttals – published online – by 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 was aimed at “a lack of scientific rigor in the experimental design and data collection”. Basically, he and other critics argued that there was no oxygen production – just bubbles produced by the equipment during sample collection.
“We’ve ruled that out,” replied Professor Sweetman. “But these [new] experiments will provide the proof.”
This may seem like a niche, technical argument, but several multi-billion pound mining companies are already exploring the possibility of extracting tonnes of these metals from the seabed.
The natural deposits they target contain metals critical to making batteries, and demand for those metals is growing rapidly as many economies shift from fossil fuels to, for example, electric vehicles.
The race to exploit these resources has raised concerns among environmental groups and researchers. More than 900 marine scientists from 44 countries have signed the petition highlighting the risks to the environment and calling for a pause in mining activities.
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 we can – understand [deep sea] ecosystem.
“I think the right decision is to wait before we decide whether this is the right thing to do as a global society.”
