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The air on Earth is about 20% oxygen and about 78% nitrogen. Best case, there seems to be sufficient oxygen (in water) to support colonization in the polar ice caps. What about the other 4/5 of the atmosphere? Too much oxygen can be harmful. On Earth, we achieve balance by the ratio of oxygen to nitrogen.

According to NASA the Martian Atmosphere is 2.7% nitrogen (N2) and 0.13% oxygen (O2) is it reasonable to assume that we would be able to harvest sufficient nitrogen from the atmosphere or would it need to be imported, or obtained someplace else?

Note that nitrogen plays other important roles in the ecosystem and should be considered as well.

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up vote 11 down vote accepted

I think it's fairly safe to assume that Mars has plenty of nitrogen locked in its mineral deposits, since it's one of the most abundant elements of the Solar system and the planet formed out of the same protoplanetary disk as Earth has. Some nitrogen rich minerals are a safe bet, especially the ones of magmatic origins that might be easily accessible in top layers of the Martian soil in regions that were volcanically more active. Since we know of many such regions, this shouldn't be a problem. For example, silicate minerals are known to lock substantial amounts of environmental nitrogen when superheated (lava / magma), and chondrites can lock up to 27.96 % of nitrogen per weight (e.g. sinoite Si2N2O).

Such nitrogen rich mineral deposits could be used either directly as a fertilizer and let the plants and bacteria slowly enrich the atmosphere with it through their nitrogen cycle, or extract it chemically, with superheating, or other processes, possibly as a byproduct of extracting other sought after minerals and ores, perhaps titanium mineral osbornite (TiN) that consists of 22.63 % of nitrogen per weight.

So this extraction of nitrogen depends on how much of it you'd need. As an atmospheric gas, it's not really essential and could be substituted with other non-toxic inert gases (perhaps argon that's already roughly 2% of the Martian atmosphere?) to, e.g. increase the atmospheric pressure. Plants naturally don't take nitrogen from air (although we now have the technology to enable that for them), so it isn't essential for that, and the industry needs could be satisfied through already mentioned nitrogen gas byproduct of other processes, such as ore mining.

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Nitrogen is usually considered the key missing element to terraforming Mars. There might be some in existence somewhere, but yes, Mars would need a lot more nitrogen than it currently has in it's atmosphere. According to this article, it is very difficult to detect Nitrates via spectroscopy, and they typically would only exist at least 1 meter below the surface. Until we start digging on Mars, we won't know if it has enough nitrogen to be self-sufficient. But yes, Nitrogen will be the key to life as we know it on Mars, everything else life needs we know we can find there.

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"Until we start digging on Mars": isn't there the Curiosity rover? It's not there for only taking pictures :p, isn't it? – user1397 Jan 16 '14 at 11:16
@Liviu Yup, MSL SAM is packed with mass spectrometer, gas chromatograph, and tunable laser spectrometer. It can detect nitrogen, and MSL just drilled a new hole in Mars yesterday. But it also took some pictures of it, and a new selfie two days before. So it's doing both :) – TildalWave May 1 '14 at 3:25

Actually oxygen-only atmosphere is not harmful if its pressure is equal to the partial pressure of oxygen on the Earth. Cosmonauts who travelled to the Moon had spent weeks in the oxygen-only atmosphere without any serious harm. At earth atmospherical pressure oxygen-only atmosphere is both harmful and flammable.

As to the need for nitrogen for long-term life function, it is another question.

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Which cosmonauts travelled to the Moon? :O – TildalWave Jan 13 '14 at 8:47
Anixx, welcome to Space Exploration! We have a standard here that we use "astronaut" to refer generically to all that have been to space regardless of nationality. Other terms such as "cosmonaut" we only use when they refer specifically to an astronaut of a nationality that would use such a term. For example, we only use cosmonaut to refer to Soviet/Russian astronauts. – called2voyage Jan 13 '14 at 19:02
Regardless of our nomenclature, which is due to the fact that the website is in English, there were quite specifically only astronauts that landed on and/or orbited the Moon. The point about the oxygen-only atmosphere not being harmful is also moot. First, pure oxygen atmosphere was abandoned and a switch to two-gas environment was made since Apollo 1 disaster. Second, Apollo astronauts didn't use open fire or use equipment that might spark. You would want that ability on Mars, and be safe on landing and occasional meteorids, otherwise there's no point in going there to burn in flames. – TildalWave Jan 17 '14 at 3:57
@Anixx Nitrogen would be needed for a long term colony, simply for nutrition. It makes up a significant part of protein. – Aron Jan 30 '15 at 6:59

For breathing, the cheapest and most plentiful source of N2 is going to be the martian tenuous as it is, it is rather simple and lost cost procedure to compress it, and the ratio of N2/O2 in the result will actually be HIGHER than our atmosphere on earth 20:1 as opposed to 3.7:1. In order to breath this, we would need some way of getting rid of the excess N2 actually, and the major gas CO2. This could be done with cyanobacteria which love both N2 and CO2. Terraforming would require release of N2 chemically from mineral sources however. But for settlements this shouldn't be an issue.

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Given the small number of people likely to be going to live on Mars (100's or 1000's as opposed to billions living on Earth) the tiny amount in Mars' atmosphere - 2.7% of an atmosphere whose total surface pressure is less than 1% of Earth's - should still be enough for an indefinite time.

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The Apollo 1 fire happened because they used an atmosphere without nitrogen or other essentially inert gas at sufficiently high percentage. Thus nitrogen is probably a good idea to have. Of course you now have concerns with the 'bends' during spacewalks, unless the suits maintain a similar pressure and gas mix. The pressure is the hard part, since it balloons the suits, and makes it hard to bend the joints, so they end up running lower pressure than the rest of the mission.

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It should be noted that the Apollo missions used a pure oxygen system throughout their service. However, after Apollo 1, the procedure on the launch pad changed, and the gas mix at launch as 40% oxygen, 60% nitrogen at 6 PSI. After launch, the command module's pure oxygen system kicked in, and the gas mix gradually changed to 100% oxygen as the mission progressed. The pure oxygen environment was only considered a danger on the launch pad.

Regarding the original question, given that Nitrogen is the fifth most common element in the universe, it is very likely that it is abundantly available on Mars, but we'll need more extensive mineral studies before we know for certain. The fact that we don't know this for certain shows that we've a lot to learn before we can establish a permanent presence on Mars.

I don't think this is the biggest problem Mars settlers will face. Protection from Radiation will be a more serious concern (probably solved by covering the base in a few metres of Mars soil). We also don't know how living in 1/3 Earth's gravity will affect us long term. Maybe it will turn out to be sufficient, but muscle and bone loss could be a very serious problem.

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