https://www.space.com/amp/we-dont-understand-exoplanet-habitable-zones In the link above is an article about how atmospheric nitrogen could affect habitability of a planet. Examples given are a wet world where the nitrogen's added pressure would app up the greenhouse effect and a dry world where more nitrogen would disperse the light and cool things down. What I'm asking for is some way to figure out the other details of either world. Why would they have so much nitrogen for a start, assuming they're rocky worlds like Earth?

  • $\begingroup$ Why does Earth have so much nitrogen? Where did it come from? Why wouldn't other planets get it in the same way? $\endgroup$
    – AlexP
    Feb 12, 2021 at 7:37
  • $\begingroup$ First nitrogen came primarily from rocks after crust cools down then switch to mostly sedimentary rock which is mostly organic since life started to flourish everywhere... then you asked where did the element Nitrogen came from? Supernova! isn't that cool ;D $\endgroup$
    – user6760
    Feb 12, 2021 at 9:38
  • $\begingroup$ @user6760 You don't need supernovae to get elements lighter than iron/nickel. (They do come from stars, but the stars don't have to be big enough to supernova.) $\endgroup$
    – Ian
    Feb 12, 2021 at 15:31

1 Answer 1


Why would they have so much nitrogen for a start, assuming they're rocky worlds like Earth?

In the conditions of pressure and temperature found on Earth, nitrogen is not that reactive, surpassed in chemical inertness only by noble gases. It takes high temperatures and pressures to move it out of its chemical couch.

Therefore, even assuming that you start with an homogenous mix where all the gases from the first 3 periods of the periodic table are present in equal amount, over time some of them will react and be trapped in compounds (oxygen, halogens, hydrogen), some other will escape the gravity well (hydrogen, helium and neon), while nitrogen, being both heavy enough to be trapped by the gravity and not so reactive to be trapped in compound, will remain as gas.


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