Despite the rich diversity of our eight planetary neighbors (Pluto is a planet and I will die on this hill, dammit!), as far as we know Earth is the only celestial body in the solar system that comes ready to support a wide array of life, no assembly required. Nevertheless, generations of science fiction authors and planetary scientists have proposed ways of engineering habitable conditions on other worlds, a process known as terraforming.
In the 1960s, for instance, Carl Sagan came up with the first scientific terraforming plan, which involved nuking Venus with genetically engineered bacteria that would devour the planet’s atmospheric carbon and produce organic molecules. More recently, Elon Musk suggested dropping thermonuclear bombs on the Martian ice caps to “warm it up.”
Yet according to a NASA-sponsored study published on Tuesday, terraforming Mars would be impossible with current day technology—and that includes nuclear bombs.
Generally speaking, terraforming Mars means at least one of three things need to happen. One possibility is to change the composition of the atmosphere so that it is mostly oxygen and nitrogen like Earth’s atmosphere. Another is to increase the atmospheric pressure so that humans can exist on the planet without pressure suits. And finally, there’s the possibility of releasing enough greenhouse gasses into the Martian atmosphere to warm the planet to the point where liquid water can exist on its surface. The release of these greenhouse gasses would also contribute to an increase in atmospheric pressure.
The problem is that the Martian atmospheric pressure is only 0.6 percent of the pressure found at sea level on Earth. In other words, it would require a lot of greenhouse gasses to raise the pressure to a point that is suitable for humans. Mars comes stocked with greenhouse gasses in the form of water vapor trapped in the ice at its poles and carbon dioxide trapped in its soil. It seemed like all that was needed was a little human ingenuity to extract these greenhouse gasses and release them into the Martian atmosphere.
According to the NASA study, there probably isn’t enough carbon dioxide left on Mars to increase the planet’s atmospheric pressure much higher than about 7 percent of Earth’s atmospheric pressure. In fact, releasing all of Mars’ greenhouse gasses would only increase the temperature on the surface to about one-sixth what is needed to support liquid water.
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That’s the best case scenario. Most of the greenhouse gasses on Mars would be remarkably energy intensive to extract. The easiest greenhouse gas to get at is the water vapor trapped in the polar ice caps, yet even if we vaporized the Martian poles like Musk suggested, the NASA researchers calculated that this would only double the atmospheric pressure to about 1.2 percent of the atmospheric pressure on Earth.
Although researchers concede that there may be more carbon dioxide trapped in minerals beneath the Martian surface, perhaps even enough to raise the atmospheric pressure to a suitable level. Still, the researchers argue that “it would not be feasible to mobilize it” since “doing so would require processing a major fraction of the surface (analogous to regional- or planet-scale strip mining) to release it into the atmosphere.”
So it looks like any Martians in the future are going to be stuck with spacesuits and imported water, unless they feel like strip mining the entire planet.