[naravara]

The closest thing I’ve heard of is genetically engineering some extremophile bacteria to seed some bacterial colonies with, and then building some domed habitats and dropping plants and fungi into it. And then you could allow some of that life to grow outside the dome and spread over time, slowly bulking up the oxygen levels. There are also proposals that you could have orbital focusing mirrors to beam additional heat at the planet and start to melt some of the water and frozen greenhouse gases.

Any effort is only temporary though, because Mars doesn’t have a magnetic field, so the sun is constantly stripping atmosphere off it. It’s not a renewable resource there like it is here.