Origin of Earth's N atmosphere, whilst Mars & Venus CO2

[wd40]

The atmospheres of Mars and Venus are both 95% CO2.

Earth's is 80% N.

How did this come about?

[Romanus]

Note that even though nitrogen is only 3.5% of Venus's atmosphere, because the planet's atmosphere is much more massive than ours the total mass of nitrogen is far greater than ours as well...

[ravens_cry]

Also, a lot of oxygen on Earth is bonded with the rocks and minerals, as is a lot of carbon.

[Ara Pacis]

Carbon cycle

[Tzarkoth]

From memory, according to Stephen L. Gillett in his book World Building, the Earth's present atmosphere couldn't be primordial ... It would have been completely stripped during this or that impact event while the solar system was still forming, and in fact most of the gas/liquids we have today would have been shipped in via comets and such during the late heavy bombardment phase.

[NEOWatcher]

I found this interesting page on the evolution of the Atmosphere.
While it doesn't explain the nitrogen content, it is a good indication about how complex the factors are.

From other little snippets during my search, it seems like the nitrogen has a lot to do with the way it got chemically bound in relation to the Earth being in the sweet zone.

[swampyankee]

Nitrogen is common, and its molecular weight is great enough so not too much of it escapes. In molecular form it's pretty non-reactive, mostly because the triple bond in the N₂ molecule is, if I recall, the strongest chemical bond.

[Swift]

Nitrogen is common, and its molecular weight is great enough so not too much of it escapes. In molecular form it's pretty non-reactive, mostly because the triple bond in the N₂ molecule is, if I recall, the strongest chemical bond.

Yes, yes, and yes (actually I'm not sure the nitrogen triple is the strongest, but it is strong).

But don't forget, nitrogen can be "activated" (nitrogen fixation) and there is a nitrogen cycle, so that there is a reservoir of inorganic nitrogen (nitrates) and organic nitrogen compounds.

[wd40]

Carbon cycle

The Earth's mere 0.03% CO2 compared to the 95% on Mars is because of a billion years of plant photosynthesis?

In theory, could a plant, tree or algae be transported to Mars, and assuming it had water and could survive the radiation, start reducing the CO2 and oxygenate the planet?

[Jens]

In theory, could a plant, tree or algae be transported to Mars, and assuming it had water and could survive the radiation, start reducing the CO2 and oxygenate the planet?

In theory, yes, or sort of. In addition to the problems you mentioned, there's the problem that the atmosphere of Mars is very thin. So you're not going to get all that much oxygen in total.

[Tobin Dax]

The Earth's mere 0.03% CO2 compared to the 95% on Mars is because of a billion years of plant photosynthesis?

In part. Earth also has liquid water, unlike Mars or Venus, which can dissolve CO2 and help transform some CO2 into limestone.

[chornedsnorkack]

In part. Earth also has liquid water, unlike Mars, which can dissolve CO2 and help transform some CO2 into limestone.

Is it a pure coincidence how close the pressure of Martian atmosphere is to triple point of water?

[moozoo]

The atmospheres of Mars and Venus are both 95% CO2.
Earth's is 80% N.
How did this come about?

All of this and more is covered in the book "Evolution of the Atmosphere" by James Callan Gray Walker
It's slightly dated and not in print any more but I don't know of any book more recent that fully covers these topics.
University Libraries might have it. Amazon has used copies for sale.

[Ara Pacis]

The Earth's mere 0.03% CO2 compared to the 95% on Mars is because of a billion years of plant photosynthesis?

In theory, could a plant, tree or algae be transported to Mars, and assuming it had water and could survive the radiation, start reducing the CO2 and oxygenate the planet?

Did you not read farther down the page?

[Tobin Dax]

Is it a pure coincidence how close the pressure of Martian atmosphere is to triple point of water?

If you're asking if it's a coincidence that Mars is where it is in the solar system, the size it is, etc., I'd say yes. If you're asking about liquid vs. vapor, I'm not sure.

[John Xenir]

But where did Mars' nitrogen go?

[swampyankee]

But where did Mars' nitrogen go?

I believe the reasons are a mix of some percentage of the nitrogen molecules in the exosphere having velocities (due to temperature) exceeding Mars' escape velocity and stripping from the solar wind. See, for http://sprg.ssl.berkeley.edu/~brain/papers/atmesc.pdf

People were surprised when Mars was found to have so little nitrogen in its atmosphere.