Atmospheric mining
Atmospheric mining is the process of extracting substances out of the Martian atmosphere and use them as raw material for further processing. Unlike surface and sub-surface mining, the atmospheric mining does not require the movement of large amounts of regolith or rock with heavy machinery, nor is expensive transport per rover or railroad necessary. The atmosphere can simply be sucked in through a pipe at every location, and the processing is done inside of buildings. Also, the maintenance of all the mining machinery is in-house, which is a major safety advantage.
Wanted Substances
Dust
The Martian atmosphere contains variable amounts of dust, which consists of similar minerals like regolith. Electro-static filters may be used to collect the dust.
Water
The 0.03 % water vapor (H2O) is equivalent to about 10 % air humidity after adiabatic compression and cooling to around 1°C. A device similar to an air dehumidifier can be used to extract this water.
Carbon Dioxide
Carbon dioxide is the main part of the Martian atmosphere with 96 %. It can be used for the hydrocarbon synthesis.