In researching Mars development, there are a few recurring themes I see that are important to find the best solution:

• Prefer the simplest solution, which may change.
• No idea is too crazy to be examined as possible.
• Try to solve the problem with materials on Mars.
• The best solution is harder to find than a really good solution.

Terraforming the whole atmosphere is likely not the place to start. Humans will live in enclosures that provide a livable atmosphere. We know that as about 30% oxygen and 70% nitrogen, and the chemistry can vary depending upon the air pressure. It is for at least the atmosphere of the enclosures that nitrogen will be needed.

The lesson of imported versus sourced locally has multiple facets, but the two I’m most concerned with are importation cost, which is associated with rocket fuel, and importation machinery cost, which is a rocket ship. Roughly, to import something to Mars you’ll always need at least four times more rocket fuel by weight than the commodity you are importing, and that number could be as high as twenty-five times. If you can source a kilogram of nitrogen locally that saves making — let’s call it five — five kilograms of methane.

And, there should be enough nitrogen on Mars in the atmosphere, and if we can substitute argon as part of the nitrogen needed, then we’re even more flexible. Argon is a non-radioactive noble gas that for atmospheric chemistry is very similar to nitrogen in the atmosphere (i.e. inert).

Compressing the Mars atmosphere and removing the carbon dioxide eventually arrives at the goal atmospheric pressure of 11psi, but the quantity of oxygen is about one-third the quantity needed. Supplementing with pure oxygen to 14psi produces the correct ratio.

The compression needed to achieve this level is about 6,600-times the Mars air pressure. Straight through compression would require about 85 stages.

Removal of carbon dioxide would be done in a repeated cycle of about 15 compressor stages as carbon dioxide becomes dry ice and thus removable if the pressure drops significantly. One individual turbine can have 5 to 15 stages of compression. With twenty air compressor designs to pack the air and remove the CO2, importing nitrogen should not be necessary.

Nitrogen in the enclosure atmosphere is not directly consumed, so though nitrogen is the primary component in the inner atmosphere, it may not be the primary gas needed to be produced.