Elements -- Free Issues

Nitrogen is the most abundant element in Earth’s atmosphere and a key component of the biosphere. It is also a critical part of the surface/near-surface cycling of nutrients, thus directly impacting our lives. Changes in the biogeochemical cycling of nitrogen through Earth’s history could reflect fundamental changes in its pathways from inorganic to biological reservoirs in response to change in the environment (e.g. oxygen fugacity in the atmosphere and oceans). Recognition of the importance of nitrogen to life on Earth, and likely elsewhere in the Solar System, has led to the mantra “Follow the Nitrogen” as one vehicle for focusing efforts in the search for extraterrestrial life. Nitrogen serves as a useful tracer of the transfer of “organic” signatures into the deep Earth (in records preserved in metamorphic and igneous rocks and in volcanic gases and rocks). It has been speculated that biological fixation of nitrogen and storage in rapidly forming continental crust has led to drawdown of nitrogen from the early-Earth atmosphere, strongly influencing the chemical evolution of the atmosphere and related surface conditions.