Nitrogen in atmosphere

[repoman]

Everyone knows that the oxygen in our atmosphere is replenished by plant life. But if there were no life on Earth would there be the same amount of nitrogen in the atmosphere would there be ammonia or nitric acid? I guess I don't understand how the nitrogen cycle works exactly.

[premjan]

smell of decomposing fish, and urine, is partially due to Nitrogen compounds (i.e. mainly Ammonia)? Then there are bacterial root nodules that fix nitrogen from the atmosphere.

[ZikZak]

Without life, there is no nitrogen cycle, but there is also nowhere for the atmospheric nitrogen to go. In the absense of life, nitrogen remains in the atmosphere. As an example, there is almost exactly the same amount of nitrogen in the atmosphere of lifeless Venus as in the Earth's. Mars's atmosphere also contains some nitrogen, although most of it has escaped to space due to the planet's lesser gravity.

[llanitedave]

Without life, there is no nitrogen cycle, but there is also nowhere for the atmospheric nitrogen to go. In the absense of life, nitrogen remains in the atmosphere. As an example, there is almost exactly the same amount of nitrogen in the atmosphere of lifeless Venus as in the Earth's. Mars's atmosphere also contains some nitrogen, although most of it has escaped to space due to the planet's lesser gravity.

That's true. The Nitrogen molecule is pretty strongly bound, and tends to persist unchanged over time. The availability of Nitrogen in the solar system overall is probably related to the pre-solar history of the region in which the sun was formed. Some systems might have less Nitrogen, some more. Nitrogen is injected into space by supernovae, and some novae.

One of these days we may be able to do stellar archeology, and determine the conditions under which many different stars, including the sun, formed.

[Berthold]

In the presence of oxygen, elementary nitrogen is unstable and forms nitrate. Under reducing conditions, the stable form is ammonia. In the absence of a biological nitrogen cycle, special conditions must prevail for molecular nitrogen to persist.

[Shadowy Man]

I know that molecular nitrogen is very uncommon in the interstellar medium.