Scientists who recently discovered that metallic lumps on the dark sea floor produce oxygen have announced plans to explore 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 said.
The initial discovery confused marine scientists. It was previously thought that oxygen could only be produced in sunlight by plants – in a process called photosynthesis.
If oxygen – a vital component of life – is produced in the dark from clumps of metal, researchers believe this process could be happening on other planets, creating an oxygen-rich environment where life can thrive.
The leading researcher Prof. Andrew Sweetman explained: “We are already talking to experts at NASA who believe that dark oxygen could change our understanding of how life can be supported on other planets without direct sunlight.
“We want to go there and find out exactly what's going on.”
The initial discovery caused a worldwide scientific controversy – there was critique of the findings by some scientists and by deep-sea mining companies that plan to collect the precious metals in the nodules on the sea floor.
If oxygen is produced at these extreme depths, in total darkness, it raises the question of what life could 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 groups – some of which have argued 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 more than 10 km (6.2 mi) deep, using remotely operated submersible equipment.
“We have instruments that can reach the deepest parts of the ocean,” explained Prof. Sweetman. “We're pretty confident that we're going to find that it's happening elsewhere, so we're going to start looking into what's causing it.”
Some of these experiments, in collaboration with NASA scientists, will aim to find out if the same process could allow microscopic life to thrive beneath the oceans of other planets and moons.
“If there is oxygen,” said Prof. Sweetman, “there may be microbial life that takes advantage of that.”
The initial, biologically puzzling findings were published last year in the journal Nature Geoscience. They come from several expeditions in the deep sea region between Hawaii and Mexico, where Prof. Sweetman and his colleagues sent sensors to the sea floor — about 5 km (3.1 miles) deep.
This area is part of a vast swath of seafloor that is covered in naturally occurring metal nodules that form when dissolved metals in seawater collect on fragments of shells or other debris. It's a process that takes millions of years.
Sensors the team used repeatedly showed rising oxygen levels.
“I just ignored it,” said Prof. Sweetman told BBC News “because I was taught that you only get oxygen through photosynthesis.”
Eventually, he and his colleagues stopped ignoring their testimony and instead set out to find out what was going on. Experiments in their lab—with nodules the team collected submerged in beakers of seawater—led the scientists to the conclusion that the metal lumps produce oxygen from seawater. They discovered that the knots generate electrical currents that can 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 deepwater mining company, told BBC News that the criticism was directed 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—only bubbles that the equipment produced during sampling.
“We have ruled out that possibility,” answered Prof. 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 harvesting tonnes of these metals from the seabed.
The natural deposits they are targeting contain metals vital to battery production, and demand for these metals is growing rapidly as many economies shift 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 halt to 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 understand the (deep-sea) ecosystem as best we can.
“I think the right decision is to wait before we decide whether this is the right thing to do as a global society.”