The Dark Photosynthesis Hypothesis: Proposing a Novel Electrotrophic-Oxygenic Metabolic Pathway Independent of Solar Radiation

The recent discovery of “dark oxygen” production at the abyssal seafloor through electrochemical processes involving polymetallic nodules has challenged fundamental assumptions about oxygen generation on Earth. Building upon this breakthrough, this paper proposes the “Dark Photosynthesis Hypothesis”—a theoretical framework suggesting that microorganisms may have evolved, or could evolve, the capacity to perform oxygenic carbon fixation using electrical energy rather than light. This hypothetical metabolic pathway would combine electrotrophic electron uptake mechanisms with oxygen-evolving reactions and carbon dioxide fixation, effectively creating a photosynthesis-like process that operates in complete darkness. We explore the biochemical feasibility of this pathway by examining existing electrotrophic organisms (such as Geobacter, Shewanella, and Thiomicrorhabdus), the electrochemical properties of polymetallic nodules as natural “geobatteries,” and the catalytic potential of transition metal surfaces for water oxidation. The hypothesis suggests that dark photosynthesis could have preceded conventional photosynthesis in Earth’s evolutionary history, may currently sustain deep-sea ecosystems, and could enable aerobic life on ocean worlds such as Europa and Enceladus. Finally, we propose specific experimental approaches to test this hypothesis and discuss its profound implications for evolutionary biology, astrobiology, and our understanding of life’s metabolic diversity.