Chemosynthesis is the biological conversion of 1-carbon molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic molecules (e.g. hydrogen gas, hydrogen sulfide) or methane as a source of energy, rather than sunlight, as in photosynthesis. Large populations of animals can be supported by chemosynthetic primary production at hydrothermal vents, methane clathrate cold seeps, and whale falls.

Many bacteria in the sea-bottoms use chemosynthesis as a way to produce energy without sunlight, in contrast to photosynthesis. They convert the matters to cultivate energy. Many of these bacteria are the source of food for other organisms on the ocean floor.

Chemosynthesis might also support life on Mars the Jovian moon Europa, and other planets.

da:kemosyntese