Researchers have unveiled two world-first deep-ocean landers designed to probe the origins of dark oxygen, which is produced in complete darkness thousands of feet below the ocean’s surface.

The two landers can reportedly withstand 1,200 times the pressure of the planet’s surface. They are designed to help uncover the origins of dark oxygen, one of the ocean’s best-kept secrets. They resemble space-exploration equipment.

Dark oxygen, produced about 13,000 feet below the seafloor was first spotted by Andrew Sweetman, PhD, a professor and member of the Scottish Association for Marine Science (SAMS), in the Clarion-Clipperton Zone (CCZ) of the Pacific Ocean in 2013.

It then returned to the spotlight after Sweetman’s findings were confirmed and reported in July 2024. The research, published in Nature Geoscience, showed that polymetallic nodules can act like natural batteries, splitting seawater into oxygen and hydrogen.

Solving oxygen mysteries

Led by The Nippon Foundation, the new project once again brings in Sweetman. He will join forces with Jeffrey Marlow, PhD, a geologist at Boston University and Mars-rover veteran, and Franz M. Geiger, PhD, a leading chemist at Northwestern University.

The three-year-long initiative will investigate how oxygen forms in environments completely devoid of sunlight. According to the team, polymetallic nodules, also known as manganese nodules, contain highly sought-after metals such as nickel, cobalt and manganese.

These could help clarify how animal life distributed thousands of feet beneath the waves. “There’s so much we still don’t know about how our planet works – these are the kinds of big questions often reserved for exploring other worlds, not our own,” Marlow said.

Metallic nodules found in the deep ocean produce oxygen.
Credit: Darren Cool / The Nippon Foundation

To uncover the answer, The Nippon Foundation’s Dark Oxygen Research Initiative (DORI), designed two highly specialized landers. They resemble equipment often associated space exploration.

Named after Sweetman’s daughters, Alisa and Kaia, the landers will determine if the nodules spontaneously interact with salt and water to create electricity. They will also investigate whether a biochemical process drives the phenomenon or whether another unknown factor stands behind it.

The team will submerge Alisa and Kaia in the Clarion Clipperton Zone in the central Pacific Ocean later this year. They will be deployed alongside an Aquatic Eddy Covariance (AEC) lander. It will measure oxygen ‘flux’ in the area to identify patterns in oxygen production.

Dark oxygen landers

The two landers will collect water samples, measure electrical activity around the nodules and introduce chemical tracers. They will additionally look for signs of electrochemical or biological processes that could explain oxygen generation in darkness.

According to Sweetman the landers are the only instruments in the UK that can go to the deepest parts of the ocean. “This truly is a global research initiative, and one which has global implications,” he emphasized.

The Intergovernmental Oceanographic Commission (IOC) of UNESCO has backed the project as a United Nations (UN) Ocean Decade activity. “Given the amazing abilities that microbes have developed over evolutionary time, we’re excited to see what exactly they’re doing inside polymetallic nodules,” Marlow stated.

Metallic or manganese nodules are mineral concretions on the seabed.
Credit: Darren Cool / The Nippon Foundation

Geiger noted that the team has already measured significant electrical voltages in controlled lab experiments using recovered nodules. “But we still don’t know exactly how the electrical potential is established and how oxygen is being produced at the very high pressures found at the abyssal seafloor,” he added.

“We know there are several areas of the ocean where dark oxygen may have been identified,” Sweetman concluded. “It is very exciting because whatever the research shows could help us answer some of the biggest mysteries about life on Earth.”

The team revealed details of their world-first landers at a conference in London. They also showcased the technology designed to probe the phenomenon.