The Deep Sea Runs on Chemicals, Not Sunlight
Almost all life on Earth is powered by the sun. In the deep ocean, an entire food web runs instead on chemical energy from the rocks — and it was discovered by accident.
6 min readPublished November 1, 2026
The 1977 discovery
Geologists diving at the Galápagos Rift expected hot rock and bare basalt. They found dense clusters of clams, mussels and tube worms around cracks venting warm, mineral-rich water. Sunlight does not reach that depth, so photosynthesis was impossible. The community was running on chemosynthesis: bacteria oxidising hydrogen sulphide to make organic matter, with animals feeding on them or hosting them internally.
How the symbiosis works
Giant tube worms have no mouth or gut. Their body is largely a sac of tissue packed with symbiotic bacteria that convert sulphide into food, and the worm's blood carries both sulphide and oxygen to them. Similar arrangements appear in vent mussels and clams — independent lineages converging on the same strategy.
Why it matters beyond the vents
Chemosynthetic ecosystems change the calculation for life elsewhere: a world with liquid water and chemical gradients but no sunlight could still support a biosphere. They also make deep-sea mining a live ethical question, since the same mineral deposits that make vents attractive commercially are the substrate for these communities.
Sources
References point to third-party sources. Esurranty summarises them in its own words; check the original for the full argument.