Constraint IV · Carbon Disposal
The carbon has togo somewhere.
§07Constraint IV · Carbon Disposal
If you built a 1 bar CO₂ atmosphere, how much carbon must you later remove?
1 bar CO₂ = 3.88×10¹⁸ kg → C = 1.06×10¹⁸ kg = 7,340 kg C / m²
The shortfall, in Earth reservoirs
| Reservoir | Carbon (kg) | Shortfall vs. Mars |
|---|---|---|
| Earth living biomass (~550 Gt C) | 5.5×10¹⁴ | 1,900× short |
| Earth biomass + soil carbon (~2,500 Gt C) | 2.5×10¹⁵ | 420× short |
| Earth ocean dissolved inorganic carbon (~38,000 Gt C) | 3.8×10¹⁶ | 28× short |
| Mars requirement (1 bar CO₂) | 1.06×10¹⁸ | reference |
Rate, at Earth's burial rate
Rate is the killer. CA-001 applied Earth's bulk silicate weathering rate and obtained 3.5 million years. Using the Mars-specific sequestration rate measured by Kite et al. (2025), 1×10⁻⁴ mbar/yr or 0.106 Gt C/yr, the correct figure is ~10 million years. Two independent methods converge: weathering-front advance at terrestrial rates gives 0.9 to 8.9 million years. The earlier number was optimistic by roughly a factor of three.
Ocean absorption
Even at 100× Earth's dissolved-carbon concentration, a Mars ocean falls ~90× short of the required 1.06×10¹⁸ kg.
Skip the thick-CO₂ stage entirely. Warm with aerosols. Make oxygen from water. Import buffer gas. Never build an atmosphere you must later dismantle.