Mars (Planet)

The composition of the atmosphere is one of the most significant long-term changes that human settlement brings to a planet. A thicker atmosphere rich in oxygen leads to a stabler day-night-temperature, but also provides oxygen for plants and animals to thrive outside of shielded habitats, on the bare surface. On top of that, in increases the total pressure of the atmosphere, making liquid water on the surface possible.

If CO~2~ from the martian atmosphere is reduced and turned into O~2~ (the carbon could be stuck in plants or plastics, deposited in landfills), then new CO~2~ would evaporate from the poles to refill what was lost, because the solid CO~2~ from the poles is in balance with the gaseous CO~2~ of the atmosphere. But the atmosphere would still be enriched in O~2~, so the total atmospheric pressure would increase.

The industrial revolution has added 200 μbar (20 Pascal) of CO~2~ to Earth's atmosphere, at a rate of 3.5 μbar per year since 2000.

Assuming that martian settlers will emit O~2~ instead of CO~2~ at a similar rate, it would take roughly 286 000 years to reach an atmospheric pressure of 1 bar (what we have on Earth today) on Mars.