Argon is the third most abundant element in the martian atmosphere, 1.6%. It is an oderless, colorless nobel gas. Like the other nobel gasses, it is chemically inert. As such, it has many uses in industry. Argon is easily produced from the atmosphere by cooling to feeze 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.