Argon is the third most abundant element in the martian atmosphere, 1.6%. It is an oderless, colorless noble gas. Like the other noble gasses, it is chemically inert. As such, it has many uses in industry. Argon is easily produced in-situ from the martian atmosphere by cooling to condense out carbon dioxide and distillation to separate out the nitrogen. For use as a buffer gas in a colony atmosphere, the nitrogen need not be separated. Mixed nitrogen and argon can be added to oxygen to dilute it to 20% mole fraction oxygen, the concentration of the standard Earth atmosphere. The substitution of nitrogen by argon for a breathable atmosphere seems straightforward.
- As an atmospheric filler produced alongside nitrogen
- As an inert gas in certain industrial processes
- As propellant for electrical space propulsion