Among the things that make the Earth hospitable to life is that atmosphere, which is rich
in nitrogen.
But why?
Hey everyone, Amy here for DNews, breathing in this lovely, life supporting air we have
on Earth.
The chemical composition of the air that sustains all life on Earth is due in large part to
photosynthesis.
For millions of years, plants have been removing carbon dioxide from the air and replacing
it with oxygen.
But only about a fifth of our atmosphere is oxygen; the rest is largely nitrogen, the
source of which has been a mystery.
But geoscientists from the Carnegie Institution of Washington have a possible explanation,
and it all comes down to plate tectonics.
The theory of plate tectonics says that the Earth’s uppermost layer, called the lithosphere,
is divided into seven plates - all of which move relative to one another.
When they collide, they change the global landscape, forming mountain ridges, rearranging
continents, and sometimes even pushing eachother deeper into the planet, a process called subduction.
When the ocean’s crust is subducted in this way, it often releases volatile elements containing
nitrogen into the rock above it.
Buried in the Earth’s crust, that nitrogen tends to form ammonium ions that are readily
incorporated into solid silicate minerals and among the most abundant on the planet.
And under the right conditions and in the presence of compounds containing oxygen, these
ammonium molecules can break down into water and nitrogen.
So here’s where the other part of the puzzle comes in.
Active volcanoes don’t just vent hot ash and molten rock when they erupt, they also
vent a significant amount of gases that would otherwise stay locked in the earth’s depths.
And it turns out that volcanoes near active plate tectonics vent more nitrogen than any
other gas.
This goes a long way in explaining why the Earth alone has a nitrogen rich atmosphere,
at least in our solar system: neither Mars nor Venus have active plate tectonics like
our own planet has, and the have just trace amounts of nitrogen to show for this inactivity.
So how do you guys think this link between plates tectonic and our atmosphere will change
the way we look for life on other planets?
Let us know in the comments below and don’t forget to subscribe for more DNews every day
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