[dogscoff]

It is mostly CO2 with some water vapor. N2 is not important for us to breath, Appolo astronauts used pure oxygen. Proved to be very dangerous though - Appolo 1.

Yeah, pure O2 would be a bad idea for several reasons. Nitrogen would be crucial if you planned to have any plant life (which you would need for food, oxygen, medication, fabrics and more) because it is required in the soil. I seem to remember from school something about a "nitrogen cycle", which involved nitrogen going from the air to the soil or something. I guess I ought to look it up.

I'm not so sure there's quite that much {Co2 on Mars}. And the thinness of the atmosphere is going to slow down the conVersion.

Well, I'm not talking about doming the entire planet, just a few limited domes. Also, the atmosphere doesn't have to be thin inside the dome- you can keep pumping CO2 in until you reach an Earth-like pressure, dump a load of plants and soil in there, then wait. Once the plants have done their job, you bottle the oxygen for use in inhabitted domes, lather, rinse and repeat.

A good source for terraforming Mars is one particular sci-fi series: Red Mars, Green Mars, Blue Mars.

Well, I've read "White Mars" by someone or other (it was terrible) and also an excellent book by Clarke about the possibilities for terraforming. Personally I think terraforming on Mars is a bad idea, unless you can do something to prevent the atmosphere being stripped away again by the solar winds. Mars is something of an obsession of mine.

On Earth it's about 70% N2, 22%O2, 4% Argon, and the remaining 4% everything else (very small amount of CO2). But it's not the percentage of Oxygen that's important, it's the amount of O2 molecules per Liter of 'air'. So at lower pressures it's important to have a greater percentage of O2 and at higher pressures it's not only important to have a lower percentage of O2, but also to have less N2 or no N2. A high enough pressures N2 will act as an intoxicant, so an inert gas, such as He (elemental Helium), is used.

Well for a permanent colony, I should think it would be important to have air pressure and content as close to Earth's as possible for morale and health reasons. However it seems as though O2 and N2 are the only important ones for humans, and CO2 will be required for any plant life. Maybe the pressure could be maintained at one earth atmosphere, with a mix of (say) 70% N2, ~26% O2, ~4% CO2. A balanced excess of CO2 could counter any ill-effects caused by the excess of oxygen. Maintaining that balance would be hard, what with all those life-forms on there respiring away, but there would be ways and means.

So my main question remains: Would nitrogen be available on Mars? If it's not iin the air, is it likely to be found in rocks, soil etc?