Could We Terraform Mars?

Terraforming Mars hinges on one bottleneck: building a thick, breathable atmosphere that can survive long enough to support liquid water and protect humans from radiation. Mars’ current air pressure is only about 0.6% of Earth’s, which would cause rapid circulatory failure for unprotected people and leaves almost no greenhouse effect. With the Sun’s light largely escaping back to space and water freezing at roughly -60°C, even warming Mars wouldn’t help much—liquid water would still sublimate in the thin air. The planet also lacks the shielding that Earth’s atmosphere and magnetic environment provide against harmful cosmic rays and ultraviolet radiation, so the first priority is atmospheric mass, not just temperature.

The core obstacle is that Mars likely lost much of its original atmosphere to space. Mars is only about 11% of Earth’s mass, so its gravity holds onto gases less effectively. Its smaller size also let its core cool and solidify earlier, shutting down a global magnetic field. Without that magnetic protection, the solar wind could gradually strip away the remaining atmosphere over billions of years—an outcome directly observed by NASA’s MAVEN spacecraft and supported by measurements of the Martian surface.

A tempting sci-fi shortcut—melting the polar caps by “nuking” them to kickstart greenhouse warming—runs into hard limits. Carbon dioxide is the only greenhouse gas present in meaningful abundance, and studies using data from Mars Reconnaissance Orbiter and Mars Odyssey suggest that releasing accessible CO2 reserves cannot raise Mars anywhere near Earth’s atmospheric pressure with near-future technology. The south polar icecap contains CO2 mixed with water ice, but even releasing it would at best double the current atmospheric CO2—still about 100 times too little. CO2 trapped in near-surface regolith can shift over long timescales, yet even heating the entire top layer would only reach roughly 4% of Earth’s pressure.

The remaining hope is buried carbonates in the crust, which would require mining and processing—either heating them to around 300°C or using acid to extract CO2. A back-of-the-envelope calculation shows how extreme the scale is: matching Earth’s atmospheric pressure would require on the order of 10,000 kg of CO2 per square meter. With limestone-like material yielding about 44% CO2 by mass, that implies digging more than 10 meters deep across the entire planet just to access enough carbon—before accounting for the real need to reach deeper deposits. Processing such quantities would demand energy on the order of several septillion joules, thousands of times Earth’s annual consumption.

If that energy problem is solved, a plausible “finish in one generation” scenario still looks industrially absurd: cover much of Mars with solar power or build vast fusion capacity, then run robotic mining and processing networks while pumping water from the icecaps. The end state would likely be a CO2–oxygen atmosphere, not Earth-like air. CO2 is toxic to humans and animals and not ideal for plant life, so oxygen would need to be managed through photosynthesis—potentially using cyanobacteria-like organisms to prevent oxygen from being rapidly consumed by oxidation. Even then, the atmosphere would still require long-term protection. Mars can’t easily regain a global magnetic field, but an external magnetic “umbrella” in space could reduce solar wind erosion.

Given the improbability of full terraforming, the transcript pivots to an alternative: paraterraforming via “worldhouses”—airtight, city-scale bubble domes that create Earth-like microenvironments without building a planet-wide atmosphere. These structures would still face radiation and micrometeor impacts, but they could be filled with air and water from comets and polar ice, offering a more material-efficient path to habitable landscapes. Either way, Mars becomes a proving ground—less about turning a planet green overnight, and more about demonstrating whether humanity can manufacture an environment where life can persist.