Scientists recently discovered that chunks of metal on the dark sea floor can produce oxygen, and they have announced plans to study the deepest parts of Earth's oceans to understand this strange phenomenon.

The researchers say their mission could "change the way we look at the possibility of life on other planets."

The initial findings baffled marine scientists. It was previously widely believed that plants could only produce oxygen in the presence of sunlight, a process called photosynthesis.

If oxygen - a vital component of life - is produced in the dark from lumps of metal, researchers believe this process could occur on other planets, creating oxygen-rich environments where life could thrive.

Lead researcher Professor Andrew Sweetman explained: "We are already in conversations with experts at NASA who believe dark oxygen could reshape our understanding of how to sustain life on other planets without direct sunlight .

"We wanted to get out and see what was going on."

Initial discovery sparks global scientific debate - with some Criticism of the findings From some scientists and deep-sea mining companies planning to harvest precious metals from seafloor nodules.

If oxygen is produced at extreme depths in complete darkness, it raises questions about what life can survive and thrive on the seafloor, and what impact mining activities might have on marine life.

That means seabed mining companies and environmental groups, some of which claim the findings provide evidence that seabed mining plans should be halted, will be watching the new investigation closely.

The plan is to use remotely operated diving equipment to work at locations where the seabed is deeper than 10 kilometers (6.2 miles).

"We have instruments that can reach the deepest parts of the ocean," explains Professor Sweetman. "We are very confident that we will find this happening elsewhere, so we will start investigating what is causing this."

Some of the experiments were conducted in collaboration with NASA scientists to understand whether the same process could allow microscopic life to thrive beneath the oceans of other planets and moons.

"If oxygen is available," Professor Sweetman said, "microbial life may be able to use it."

The original, biologically puzzling findings were published last year In Nature Geoscience. Coming from multiple expeditions to the deep-sea region between Hawaii and Mexico, Professor Sweetman and his colleagues sent sensors to the seafloor to a depth of about 5 kilometers (3.1 miles).

The area is part of a large swath of seafloor covered in naturally occurring metal nodules, which form when dissolved metals in seawater collect on fragments of shells or other debris. This is a process that takes millions of years.

Sensors deployed by the team repeatedly showed rising oxygen levels.

"I just ignored it," Professor Sweetman told BBC News at the time, "because I was told that oxygen can only be obtained through photosynthesis".

Eventually, he and his colleagues stopped ignoring their readings and began to understand what was going on. Experiments conducted in their laboratory - in which the team collected nodules submerged in beakers of seawater - led the scientists to conclude that the metal chunks were creating oxygen from seawater. They found that the electric current generated by these nodules can split (or electrolyze) seawater molecules into hydrogen and oxygen.

Backlash followed in the form of online rebuttals from scientists and seafloor mining companies.

One of the critics, Michael Clarke of Canadian deep-sea mining company Metals, told BBC News that the criticism focused on a "lack of scientific rigor in the experimental design and data collection." Basically, he and other critics claim no oxygen is produced — just bubbles created by the device during the sample collection process.

"We have ruled out that possibility," Professor Sweetman replied. "But these (new) experiments will provide evidence."

It 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 seafloor.

The natural deposits they are targeting contain metals critical for making batteries, demand for which is growing rapidly as many economies shift away from fossil fuels and toward things like electric vehicles.

The race to extract these resources has raised concerns among environmental groups and researchers. More than 900 marine scientists from 44 countries signed the petition Highlighting environmental risks and calling for a moratorium on mining activities.

Professor Sweetman said of his team's latest research mission at a press conference on Friday: "Before we can do anything, we need to understand the (deep-sea) ecosystem as much as possible.

"I think the right decision is to hold off until we decide whether this is the right thing for the global community to do."