Earth’s nitrogen-rich atmosphere attributed to plate tectonics

The Earth may have its nitrogen-rich atmosphere, as compared with Venus and Mars, because only Earth has plate tectonics, reports a study published online in Nature Geoscience. This potentially helps to explain why Venus and Mars, planets that formed with similar amounts of nitrogen to Earth, do not have similar atmospheres.

Sami Mikhail and Dimitri Sverjensky calculated the chemical behaviour of nitrogen in the fluids of a planet’s mantle. Under conditions expected in most parts of the Earth’s upper mantle, and throughout the mantles of Venus and Mars, they find that nitrogen remains locked within mantle minerals as ammonium. However, if a sufficient amount of oxygen is present, nitrogen can be released into fluids as molecular nitrogen, which does not incorporate with mantle minerals, and can then be degassed easily through volcanism. The oxygen-rich mantle material beneath subduction zones on Earth - where one tectonic plate slides beneath another, bringing more oxygen-rich surface material with it - uniquely meets these requirements.

doi: 10.1038/ngeo2271

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