Notes
Colonizing and Terraforming Mars
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Two different dreams hide under the word "Mars," and confusing them is how most arguments about the Red Planet go wrong. One is colonizing: putting people there soon, sealed inside pressurized domes and buried lava tubes, breathing canned air on a planet that is still trying to kill them. The other is terraforming: re-engineering the entire world over centuries or millennia until a human can walk outside in shirtsleeves. The first is an enormous engineering project that might begin within our lifetimes. The second is closer to planetary myth — a thing we can sketch on a whiteboard but cannot, with anything we currently possess, actually do.
The colonists: a base before a biosphere
The near-term vision is overwhelmingly Elon Musk's. SpaceX has organized itself around a single sentence — "making humanity multiplanetary" — and Musk has delivered the pitch twice as a keynote: the 2016 International Astronautical Congress in Guadalajara ("Making Humans a Multiplanetary Species," September 27), where he unveiled the giant reusable rocket then called the Interplanetary Transport System, and again in 2017 at the IAC in Adelaide ("Making Life Multiplanetary," September 29), where the vehicle had become the Starship/Super Heavy stack that SpaceX is still flight-testing today. The stated goal is audacious to the point of absurdity: a self-sustaining city of about one million people on Mars, which Musk has repeatedly pinned to roughly 2050, requiring on the order of 1,000 Starships and decades of launches timed to the ~26-month windows when Earth and Mars align. The bumper-sticker version — "Occupy Mars" — sells the romance. The serious version is a single grim test: the city has to survive if the resupply ships from Earth ever stop coming.
The intellectual godfather of practical Mars settlement, though, is Robert Zubrin. In The Case for Mars (1996) he laid out Mars Direct, an architecture whose central trick is to stop hauling everything from Earth. A robotic factory lands first and runs the Sabatier reaction — combining hydrogen with carbon dioxide drawn straight from the thin Martian air to manufacture methane and oxygen — so the crew's return propellant is waiting, made on Mars, before they ever launch. Zubrin founded the Mars Society in 1998 and has spent the decades since as the movement's loudest evangelist and sharpest internal critic, insisting Mars is reachable now with engineering we already understand, not a far-future fantasy.
The planet fights back
Colonists would not arrive in a hostile environment so much as a lethal one. Surface radiation is brutal — Mars has no global magnetic field and almost no atmosphere to absorb cosmic rays and solar particles, so habitats likely need meters of regolith or water overhead. The soil itself is laced with perchlorates at roughly 0.5–1%, salts that are toxic to the human thyroid and that will inevitably get tracked indoors as dust. Gravity is only 0.38 g, and we genuinely do not know whether a human — or a developing fetus — can stay healthy in it long-term, because the experiment has never been run. None of these are reasons it can't be done. They are reasons the honest near-term picture is a small, shielded, fragile base, not a frontier town.
The terraformers: a planet on geological deadline
Terraforming is the older and grander idea. Carl Sagan opened the scientific conversation in 1973 with "Planetary Engineering on Mars," imagining darkening the poles to melt them. Christopher McKay of NASA Ames pushed it into rigor, coining the language of planetary ecosynthesis and, with Zubrin, proposing orbital mirrors and super-greenhouse gases to thicken the air. The most complete imagining is fiction: Kim Stanley Robinson's Red Mars / Green Mars / Blue Mars trilogy (beginning 1992), which remains the definitive treatment precisely because it takes the politics, ethics, and centuries-long timescale as seriously as the chemistry.
Then the science delivered a cold verdict. In 2018, Bruce Jakosky and Christopher Edwards published "Inventory of CO₂ available for terraforming Mars" in Nature Astronomy, tallying every accessible reservoir of carbon dioxide — the polar caps, the dust, the near-surface minerals — using two decades of orbiter data. The conclusion was blunt: releasing all of it would roughly triple Mars's atmosphere to only a few percent of the pressure a human needs, nowhere near the ~1 bar required. The remaining carbon is locked in deep rock we cannot reach. Their summary line has become the field's reality check: "terraforming Mars is not possible using present-day technology." And the planet keeps leaking — NASA's MAVEN mission (which operated for eleven years before losing signal in December 2025) measured the solar wind stripping gas to space at roughly 100 grams per second, the slow erosion that turned a once-warmer, wetter world into today's frozen desert after it lost its magnetic field billions of years ago. Thicken the air and the same physics begins draining it again.
The dissenters, the ethics, and the honest timeline
Not everyone thinks planets are even the right target. Jeff Bezos calls surface-settlement thinking "planetary chauvinism" and would instead build O'Neill colonies — spun-up orbital habitats holding a million people each, scaling to a trillion humans across the solar system — arguing the planetary surfaces are simply too small (see the sibling page). Buzz Aldrin has pushed the Mars Cycler, spacecraft on a permanent gravity-assisted loop between the two worlds so crews ride a shuttle that never stops. And Kim Stanley Robinson, of all people, has cooled on the whole project: "Mars is just a distraction for a few escapists," he now argues, until we have built a sustainable civilization on the planet we already have. Underneath it all sits a real ethical knot — planetary protection. If even microbial life exists on Mars, do we have the right to bulldoze its world into a second Earth, or to contaminate the one clean sample of a second genesis we may ever find?
Strip away the salesmanship and a defensible timeline emerges. A crewed landing and a small, shielded base are genuinely plausible this century — hard, expensive, dangerous, but not science fiction. Mining the air for fuel is real chemistry. Living underground is engineering. Terraforming an open-air Mars is not on that list. It is the part of the dream that, for now, lives in the future tense — a thing to imagine carefully, and to be honest about not yet being able to do.
Related concepts
Watch and read
Making Life Multiplanetary — Elon Musk, IAC 2017 (Adelaide) — SpaceX's official upload of the full keynote that defined the Starship-to-Mars plan.
Making Humans a Multiplanetary Species — Elon Musk, IAC 2016 (Guadalajara) — the original SpaceX talk that launched the "million people on Mars" vision.
Dr. Robert Zubrin — Opening Plenary, 15th International Mars Society Convention — the Mars Direct case, straight from its author, on the Mars Society's own channel.
NASA Mission Reveals Speed of Solar Wind Stripping Martian Atmosphere — the MAVEN findings on why Mars lost its air.
Mars terraforming not possible using present-day technology — the Jakosky & Edwards (2018, Nature Astronomy) CO₂ inventory, the major scientific counterweight.
The Mars Society — the advocacy organization Zubrin founded in 1998.
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- 2026-06-12
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