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Art by Stefan Morrell. Sources: Christopher McKay, NASA Ames Research Center; James Graham, University of Wisconsin–Madison;
Robert Zubrin, Mars Society; Margarita Marinova, California Institute of Technology. Earth and Mars images: NASA

Most of the work in terraforming, says NASA planetary scientist Chris McKay, would be done by life itself. “You don’t build Mars,” McKay says. “You just warm it up and throw some seeds.” Perfluorocarbons, potent greenhouse gases, could be synthesized from elements in Martian dirt and air and blown into the atmosphere; by warming the planet, they would release the frozen CO2, which would amplify the warming and boost atmospheric pressure to the point where liquid water could flow. Meanwhile, says botanist James Graham of the University of Wisconsin, human colonists could seed the red rock with a succession of ecosystems—first bacteria and lichens, which survive in Antarctica, later mosses, and after a millennium or so, redwoods. Coaxing breathable oxygen levels out of those forests, though, could take many millennia.

Enthusiasts such as Robert Zubrin, president of the Mars Society, still dream of Martian cities; Zubrin, an engineer, believes civilization cannot thrive without limitless expansion. Only research outposts seem plausible to McKay. “We’re going to live on Mars the way we live in Antarctica,” he says. “There are no elementary schools in Antarctica.” But he thinks the lessons learned in terraforming Mars—a horrifying prospect to some—would help us manage our limited Earth better.

There is time to debate the point; Mars is in no immediate danger. A White House–appointed panel recently recommended going to the moon or an asteroid fi rst—and pointed out the space agency lacks the budget to go anywhere. It didn’t estimate the cost of gardening a dead planet. —Robert Kunzig

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