Mars has no global magnetic field, so the solar wind continuously strips molecules from the top of its atmosphere — slowly, but without ever stopping. That stripping scales with how much atmosphere is there to strip, so it barely matters at today's thin 6 mbar, but it grows into a real drag the moment terraforming starts thickening the air.
- Addition rate > stripping rate — pressure climbs and, as release infrastructure scales up, the climb accelerates.
- Addition rate < stripping rate, or halted — the gain stalls and pressure decays back toward the thin natural baseline, because the loss process never pauses.
- L1 magnetic shield — a dipole shield deflects the solar wind before it reaches Mars, cutting the stripping rate itself. The same addition effort then reaches a far higher, more permanent equilibrium pressure.