It's not often you hear a prominent CEO talk about nuking Mars, so when SpaceX founder Elon Musk broached the idea on the "Late Show With Stephen Colbert" on Wednesday night, people took notice.
No, Musk has not declared interplanetary war on Mars. The idea is to "terraform" it so that future generations of humans could one day live there.
"It's a fixer-upper of a planet," Musk told Colbert. "Eventually you could transform Mars into an Earth-like planet."
(NBC News reached out to SpaceX for comment but the company did not respond).
Making Mars habitable is a goal of some very smart people, mostly because one day — either due to environmental disaster, an expanding sun, or any other number of disaster scenarios — the Earth will become uninhabitable.
But is nuking Mars really the best way to create a new Earth?
Why it might work
Right now, Mars seems like a dry, dead planet. But its polar ice caps contain about equal parts water and carbon dioxide.
Nuclear weapons could be used to vaporize them, releasing those materials into the atmosphere. Once the atmosphere got thick enough, the greenhouse effect would kick in: energy from the sun, absorbed by the planet and released as infrared radiation, would be trapped.
That would continue heating up the planet, releasing more carbon dioxide, setting off a chain reaction until, ideally, the surface pressure of Mars would increase enough for liquid water to exist — making it much more habitable for oxygen-producing plants.
"You could start turning Mars from a red planet into a green planet," Michael Shara, curator of the American Museum of Natural History's astrophysics department, told NBC News.
Nuclear weapons aren't the only way that humans could melt the planet's polar caps. Shara offered some alternatives, like finding a way to guide asteroids to Mars' poles, or covering the poles in a fine, black dust to absorb sunlight and heat them up.
But many ideas involve transporting heavy equipment to Mars, which would be very expensive. Nukes are fairly compact and immensely powerful, offering a lot of bang for the buck.
Using nukes might not be the best public relations move. But modern thermonuclear weapons can be designed to leave very little fallout, Shara said, and wouldn't pose much danger centuries after they hit.
It could take firing thousands of them over the course of decades to start the greenhouse effect, Shara said. After that, it might only be centuries before people could start buying vacation homes on Mars.
Why nuking Mars might fail
"It's a clever idea in principle," Shara said. "Whether it would really work, I don't think anyone has worked up the physics in enough detail to say it would."
Even the most advanced computer simulations would have trouble predicting the aftermath of starting a runaway greenhouse effect. Gary King, a microbiologist at Louisiana State University, thinks bombing the Red Planet would not be the best approach.
"Cloud formation could have a dampening effect, for instance, cooling Mars rather than warming it," King told NBC News.
Plus, there are ethical questions to be considered, especially since we haven't thoroughly explored the planet yet.
It would be good to know that there are no microorganisms left over from an earlier period still lingering in the ice, he said. "The odds aren’t high, but no one can say that they are zero either."
King prefers a different approach — sending hardy, genetically modified microorganisms to Mars to transform the atmosphere, setting the stage for more advanced forms of life.