# Would a settlement on Mars need to import Nitrogen?

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.

• 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. Jun 20 '14 at 20:01
• The partial pressure of oxygen should not be too high, but mixtures with more than 20 % oxygen are possible if the partial pressure of oxygen is not more than about 0.3 bar.
– Uwe
Oct 17 '17 at 10:10
• Probably not good enough to answer this question, but note that Curiosity has found nitrates on Mars. The nitrates were detected as evolved nitrogen oxides upon heating soil samples. Dec 30 '20 at 11:02

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.

• I question the list of nitrogenous minerals used in this answer. Most of them appear to have organic origins, particularly urea & guanine. Many of the others have ammonium (NH4) as a key component & are associated with various forms of guano - bird & bat droppings, again, organic chemicals. Just because these minerals occur on Earth does not mean they will occur on Mars.
– Fred
Dec 30 '20 at 7:25
• Given Fred's concerns, this answer could be imprived by a reference to Curiosity finding nitrates in Martian soil. The nitrates are called "biologically useful", but they are also synthetically useful because they can be turned to nitric acid, which is a common reagent for introducing nitrogen into organic compounds. Jan 5 '21 at 2:42

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.

• "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 :) May 1 '14 at 3:25

Martian atmosphere can be collected by good compressors. Such a compressor is centuries old technology and is very cheap.

After that, nitrogen can be extracted by fractional distillation, roughly as we do it on the Earth (cooling will make $$CO_2$$ quickly solidify, rest effort will be spent to separate it from the $$O_2$$ part).

This all does not require any high technology, and not even too much energy.

It is even easier than the next steps (converting the nitrogen to ammonia or fertilizers).

All of these is far more easy than importing nitrogen from other bodies (like from Earth).

Probably there are also various nitrogenous minerals in the Martian soil, because it is also one of the most common element in the Solar System, but our current samples/probes are not qualify yet as a mining research.

The Wikipedia article 'Atmosphere of Mars' lists the nitrogen fraction of the atmosphere of Mars as 2.6%. It is possible then that nitrogen could be obtained from the atmosphere using a compressor, with other components like the CO2 removed.

The Wikipedia article on Cabin pressurization; Spacecraft indicates that the U.S. Mercury, Gemini, and Apollo programs did not use Nitrogen and that modern space suits use low pressure pure oxygen without Nitrogen mixed in to keep flexible.

However the modern ISS and the Russian programs all use Nitrogen, an inert gas.

The Wikipedia article Martian polar ice caps says:

During a pole's winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25–30% of the atmosphere into slabs of CO2 ice (dry ice).

It describes the deposition as 'frost' and not snow, but I am not sure if it has an exact description of it. I have not been able to find much on whether solid or liquid ammonia exists admixed with either the water ice or the carbon dioxide dry ice.

I notice you did not mention terraforming in the question, so I assume you are asking about breathing gas for a Mars colony. Possibly nitrogen fixation for greenhouse agriculture as well?

According to https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html, Mars atmosphere is

95.1% Carbon Dioxide (CO2),

2.6% Nitrogen (N2) and

2% Argon (Ar). Don't forget the Argon.

For short term, pure O2 can be used as a breathing gas at physiologic partial pressure (about 5 psi). For prolonged use (weeks+) it is necessary to mix it with an inert gas to prevent atelectasis (collapse of air sacs in the lungs). N2 and Ar are interchangeable as inert diluent gases for breathing O2. As well, they are both recyclable in rebreather circuits. Since they are not consumed, a very small supply is required.

For extracting gasses from the atmosphere, cryogenics is a mature industrial-scale technology. If Methane is to be manufactured in situ from CO2 on Mars, there will be a glorious overabundance of available N2, Ar and O2.

For purification to breathable air, trace CO2 is readily separated from Nitrogen and Argon using Pressure Swing Adsorption, another mature chemical engineering process.

No worries, mate, for pressurized colonies. If you are planning to terraform, you are out of luck.

Mars's atmosphere is roughly 2.6% Nitrogen. This means that, just in the atmosphere, there is some 6.5e14kg of nitrogen.

Any colony or even longterm explorer on Mars will already be extracting gases from the atmosphere. CO2 for fuel and Oxygen, at a minimum.
Nitrogen is similarly abundant in Mars air as Argon is in Earth air. Easily available, easy to get to, but requires a good bit of machinery and a lot of energy to get to. And almost a free byproduct if you are already compressing and liquefying the air.
P.S. Mars also has Argon, in very similar amounts. Get it while you get the N2, its handy stuff.

6.5e14kg total.

So, as buffer gas for any number of domes, and as part of fertilizer for any contained greenhouse ecosysyems, it is more than ample.

We will not need to import Nitrogen for colonies, but we will need to invest in the concentration and extraction infrastructure for it.

But we would not be able to use it frivolously. Using N2 as a disposable flushing gas, or as cold-gas thrusters for common surface operations, would likely be inadvisable. But there is plenty of Co2 to use in those roles.

First here is the big answer of what we have to start with on Mars. This is from the Atmosphere of Mars Wikipedia article.

This pressure is well below the Armstrong limit for the unprotected human body. Mars's atmospheric mass of 25 teratonnes compares to Earth's 5148 teratonnes; Mars has a scale height of 11.1 kilometres (6.9 mi) [2] versus Earth's 8.5 kilometres (5.3 mi). [3]

The Martian atmosphere consists of approximately 96% carbon dioxide, 1.9% argon, 1.9% nitrogen, and traces of free oxygen, carbon monoxide, water and methane, among other gases, [1] for a mean molar mass of 43.34 g/mol. [4] [5] There has been renewed interest in its composition since the detection of traces of methane in 2003 [6] [7] that may indicate life but may also be produced by a geochemical process, volcanic or hydrothermal activity. [8]

There are several ways that might work.

1. Concentration on the atmosphere on Mars the 1.9 % oxygen and 1.9 % argon components of a breathable atmosphere.
2. Photosynthesis
3. Using energy sources such as solar and geothermal to turn CO2 into O2 and CO this is and a serious amount of energy

Here is a NASA experiment in to doing just that

http://sciencenordic.com/scientists-are-trying-brew-oxygen-mars

How to brew oxygen on Mars

There is practically no oxygen in Mars's atmosphere, but the MOXIE device will “brew” oxygen from carbon dioxide (CO2), which there is plenty of in the planet’s atmosphere.

A carbon dioxide molecule consists of a carbon atom (C) and two oxygen atoms (O2), and it will be the job of the MOXIE apparatus to split the carbon dioxide molecules apart.

The splitting process requires energy, but the end result will be oxygen molecules and a by-product in the form of carbon monoxide (CO).

"MOXIE works like a sort of fuel cell in reverse. A fuel cell produces energy by melting together hydrogen and oxygen to produce water. Instead, we'll be using energy to remove an oxygen atom from CO2," says Madsen.

He explains that MOXIE will get its energy from a Radio Thermal Generator (RTG) which generates electricity from heat developed in radioactive plutonium.

Will provide oxygen people on Mars

Around 96 per cent of the Martian atmosphere consists of carbon dioxide so there is plenty of raw material for oxygen production.

NASA spokespersons have stated that MOXIE is only the beginning of oxygen production on Mars.

"Having the ability to produce oxygen on the surface of Mars is a great step forward when it comes to mankind's future exploration of Mars," said Michael Meyer, a leading scientist at NASA's Mars Exploration Program, to Space.com.

The plan is to build an entire oxygen factory on the red planet which will be about 100 times the size of the first MOXIE prototype which is to be launched from Earth with the Mars 2020 mission.

The prototype oxygen factory will have to be ready when NASA sends the first humans to Mars at some time in the 2030s.

• Welcome to Space.SE. I am not sure this is an answer to the question. The first paragraph seems to focus on the atmosphere of mars, while the question assumes a sealed colony (but does not specifically say that), the rest of your answer focus on oxygen and the question is clearly about nitrogen. Oct 17 '18 at 12:10

Mars has lost it's atmosphere over time as it dissipated into space. To support human life, the atmosphere would need to be restored, not generated. There is not enough resources on Mars to regenerate enough atmosphere to support human life. Atmospheric restoration would have to be done AFTER creating an artificial magnetosphere to shield Mars from the Sun's solar wind and cosmic radiation.

To restore the atmosphere of Mars would require dropping vast amounts of water ice into the atmosphere. Where would we get this water? Comets maybe. Catch them and drop them onto Mars... Mine water ice from Titan maybe... Monumental undertaking that would be... Even then, we would have to find a way to drop vast amounts of nitrogen onto Mars. Where would we be able to get that much nitrogen in our solar system? Even if we could manage to collect enough nitrogen from somewhere, we'd have to keep dropping it into the Mars atmosphere until the atmospheric pressure increased to a comfy 14.7 PSI with the correct proportion of nitrogen to oxygen - 78% nitrogen to 21% oxygen.

Only if we could do all of that, would we be able to terra-form Mars.

• Good points, but the question does not mention terraforming. I think (but I've been wrong before) the question was about gas supply for a colony. Dec 12 '21 at 2:34