Autonomous Landers to Investigate Non-Photosynthetic Oxygen Production Near Pacific Nodules

A scientific mission is scheduled for the spring of 2026 to deploy two novel deep-sea landers, named Alisa and Kaia, within the Pacific Ocean's Clarion-Clipperton Zone (CCZ). This endeavor is specifically designed to rigorously examine the phenomenon termed 'Dark Oxygen Production' (DOP), which challenges established paradigms of oceanic oxygen generation.

The CCZ, a vast geological submarine fracture zone extending approximately 4,500 miles between Hawaii and Mexico, is estimated by the International Seabed Authority (ISA) to hold over 21 billion tons of polymetallic nodules rich in nickel, copper, and cobalt—minerals attracting growing deep-sea mining interest. The concept of DOP was first introduced in 2024 by a research contingent led by Professor Andrew Sweetman of the Scottish Association for Marine Science (SAMS). Their initial research, published in Nature Geoscience, indicated that deep-sea metallic nodules generate oxygen in the absence of sunlight, a process previously thought to require photosynthesis.

The current three-year investigation, known as the Nippon Foundation - Dark Oxygen Research Initiative (DORI), unites scientific expertise from SAMS, Boston University (BU), and Northwestern University. DORI aims to definitively ascertain whether electrolysis, driven by electrical potentials on the nodule surfaces, or an unknown biochemical pathway is responsible for DOP near manganese oxides. The specialized autonomous landers, Alisa and Kaia, are engineered to withstand hydrostatic pressures reaching 1,200 times surface levels, permitting direct, in-situ measurement of oxygen flux and chemical tracer deployment at depths potentially reaching 11,000 meters.

Preparations are underway, with the lander 'Alisa' having arrived at SAMS, marking a key milestone ahead of the 2026 expeditions, which will include planning sessions between SAMS and BU researchers in November 2025. This project has received endorsement from the Intergovernmental Oceanographic Commission (IOC) UNESCO, aligning it with the United Nations Ocean Decade activities. Polymetallic nodules, typically measuring two to eight centimeters, are abundant in the CCZ at depths generally between 4,000 and 6,000 meters. Initial 2024 findings, observed in the Nauru Ocean Resources Inc. (NORI-D) license area, showed oxygen concentrations increasing in over 93% of enclosed chamber experiments.

The central hypothesis suggests nodules function as 'geo-batteries,' with surface voltage potentials up to 0.95 V potentially splitting seawater into hydrogen and oxygen through electrolysis. The research, supported by a £2 million package from The Nippon Foundation, seeks to clarify this mechanism and its ecological significance, as this oxygen source may sustain deep-sea benthic organisms. Furthermore, NASA has expressed interest in how this non-photosynthetic oxygen creation could inform the search for extraterrestrial life. This comprehensive investigation is positioned critically, as the ISA has granted 16 exploration contracts within the CCZ, prompting scientific concern over potential irreversible ecological damage from seafloor scraping for mineral harvest. Professor Sweetman’s research seeks fundamental answers in deep-ocean biogeochemistry while providing data relevant to ongoing international negotiations regarding deep-sea mining regulations.