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How did Earth develop its current atmosphere? A study published in the journal Nature Geoscience links the composition of Earth’s nitrogen-rich atmosphere to the same tectonic forces that drive mountain-building and volcanism on our planet. It goes some way to explaining why, when compared to our nearest neighbors Venus and Mars, Earth’s air is richer in nitrogen.
The chemistry of the air we breathe is partially the result of billions of years of photosynthesis. Plant life has transformed our world from one cloaked in a carbon dioxide-rich atmosphere, as seen on Mars or Venus, to one with significant oxygen. About a fifth of the air is made up of oxygen, but almost all the rest is nitrogen—completely unlike Mars and Venus. The origins of the relatively high nitrogen content of Earth’s air have been something of a mystery.
Geoscientists Sami Mikhail and Dimitri Sverjensky of the Carnegie Institution of Washington have calculated what nitrogen is expected to do when the churning cycle of plate tectonics cycles it through the rocks of the deep Earth. Active volcanoes not only shower volcanic rock and superheated ash as they erupt molten rock into the air; they also vent huge amounts of gas from Earth’s depths. The latest eruptions in Iceland, for example, have been noted for the amount of sulfurous fumes they have emitted.
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