Life learns to fix nitrogen
Microbes crack the triple bond in atmospheric nitrogen, and stop depending on lightning for fertiliser.
- When
- Known to
- ± 100 million years
- Era
- Paleoarchean, Archean
Nitrogen isotopes in 3.2-billion-year-old sediments match the signature of the molybdenum-dependent nitrogenase enzyme still used today, the oldest evidence for biological nitrogen fixation. Before this, fixed nitrogen came only from lightning and hydrothermal chemistry, a hard ceiling on how much life the planet could support. Breaking that limit made the biosphere's later expansion possible.