Terraforming Mars in under ~30 years is possible in an idealistic case.
Trees, greenery, warm, wet, walkable, with no suit, and no mask.
The one requirement. Everything hinges on a single unlock: a self-replicating, self-powering industrial seed. A machine that makes the machines that make itself, from raw rock sunlight water.
Crack that once and Mars stops being an engineering problem and becomes a scheduling problem.
Yrs 0–10 — the patient decade.
—————
4 seeds (Moon, Mars, Titan, asteroids). Power doubles yearly. Looks like nothing’s happening — you’re below human civilization’s output the whole time.
This is the part that tests faith. The exponential is loading the spring.
Yrs 10–15 — takeoff.
—————
Crosses all of human power around yr 13. Then keeps doubling.
Titan ships nitrogen organics. Moon ships metals solar. Asteroids fall in for the trace elements. Mars already has its own water phosphorus. The trade network ignites.
Yrs 15–20 — the sky thickens.
—————
Megastructures of frozen nitrogen fling themselves to Mars. Atmosphere pressurizes. CO₂ outgasses, ice sublimates, liquid water goes stable.
Around here the bottleneck flips: you’re no longer limited by your industry. You’re limited by how fast a planet can physically respond.
Yrs 20–30 — habitable.
—
~20 yrs: walk outside in just an O₂ mask. Warm, wet, shirtsleeves Mars.
~25–30 yrs: breathe free.
The numbers:
🟢 Optimistic: ~20 yrs to mask-and-shirtsleeves, ~25–30 to breathable.
🟢 Base case: ~30 idealized, ~50–80 with real friction.
Either way — inside a human lifetime.