why you can’t nuke your way to a second earth

Someone should tell Elon Musk that a nuclear bombardment of Mars into habitability won't be much of a shortcut.

Illustration by Marcel Labbé-Laurent

Mars has been calling humans for centuries and with every year we seem more eager to come and set up the groundwork for a lasting presence, so much so, there’s someone very seriously thinking about making the planet its own nation state. But living on Mars is far easier said than done because it’s atmosphere is a ghostly shell, it’s cold, dry, and barren, its magnetic field will offer so little protection from cosmic radiation that its surface can even kill bacteria that happily live inside nuclear reactors, and there are serious question about whether its soil will grow food and plants necessary for long term survival. And that’s not to mention the challenges of getting there safely, and the astronauts’ mental health tens of millions of miles from home. Now, when we do solve the problem of actually getting there comfortably, intact, and quickly, we could deal with the problems of living in a frigid alien desert by building vast, complex, expensive habitats, and hope for the best. Or we could get really ambitious and turn Mars into a livable world.

Plans for terraforming Mars have been around in both science and science fiction for decades, calculated to take several hundred years, cost trillions, and start out by pumping a noxious mix of greenhouse gases into the atmosphere to build it up and melt the polar icecaps. The process should essentially allow for a similar runaway greenhouse effect as Venus’, but keeping Mars at very warm and comfortable temperatures for us. Solar panels the size of Texas hovering over a few strategic points near the poles to redirect sunlight and melt the ice faster, have also been a periodic part of the plan. After the planet starts to warm up, hearty algae can be planted to feed on the toxic gasses and start replacing them with oxygen, much like on primeval Earth on a fast forward setting. If everything goes well, some 125 years after we begin, trees could grow in the Martian soil to speed the process up even more and stabilize the oxygen levels for humans.

Of course, those very interested in terraforming Mars do not want to wait over a century before genetically engineered super trees create the first forests on their chosen planet. They’d like to speed things up a bit using nuclear weapons. That’s right, under one terraforming scenario that Elon Musk explained to Colbert a few night ago, the process of making Earth 2.0 starts with the apocalyptic nuclear bombardment of the Martian poles. Once you’ve basically converted much of the dry ice to vapor after 500 to 800 mushroom clouds finally dissipate, the hot steam could, in theory, start the runaway feedback loop that would puff up the atmosphere and trap enough sunlight to raise the planet’s average temperature to a toasty 15° C or 60° F, although there will be so much fallout that the plants needed to convert much of that to oxygen and nitrogen would have to wait at least a few centuries. And that’s the downside of this plan, really. It is a cheaper, easier way to start terraforming, but over the long term it would really slow things down.

In general, since Mars is already a radioactive desert, there isn’t much that nuclear fallout could do to it that the sun isn’t already doing on a daily basis on the surface. But the surface is not an issue here, it’s the soil underneath. Radioactive elements like cesium will leach into it, poisoning the plant life we’ll ultimately need to sustain. You can see a similar problem in the Bikini Atoll as nuclear tests have rendered growing food there dangerous when cesium-137 mimicked the role of potassium and was absorbed into the local flora. It would take massive remediation efforts to prepare Mars for its greening, something which would run up the budget significantly, or we can just wait for the century or two it would take for the soil to be safe enough for the algae. And for my money, no one is going to choose the far more expensive and resource-consuming process when just waiting would do the job. But that means that we paid for cheapening out on starting the greenhouse effect we needed with an additional century, in the best case scenario.

However, thinking about this game me an idea. We do know of a way to get the oomph of huge nukes and create the same kind of damage without any of the complicated weapons we’d have to somehow convince nuclear powers to give up after modifying complex treaties that are taken so seriously that violating them could open the way to turning Mad Max into a preview of much of our world’s future. Large kinetic missiles dropped from satellites could easily kick start a huge polar melt and our terraforming factories could immediately get to work on making sure that the feedback loop does begin by surgically adding extra greenhouse gasses when needed. And as the kinetic impactors would be just solid spikes of hardened alloys, manufacturing thousands of them should actually be orders of magnitude cheaper than getting nuclear warheads ready and secure enough to be launched into space. This way, we could get the benefit of a nuclear-scale bombardment for a tiny fraction of the price, none of the radiation, and none of the delays. The only things that would be left in the aftermath are craters that we’d help erode away.

So the process sounds good so far, once again. There’s just the small question of whether the hard work of terraforming the red planet will actually stick, which is still a matter of debate. You see, the problem is that Mars may be too small to hold on to a large, thick atmosphere like ours and its lack of volcanic activity and weak magnetic field would only make it worse. Technically, a planet capable of holding on at an adequate atmosphere for 10 billion years can be as small as just 5,690 km across while Mars is almost 6,800 km in diameter, so you’d think there’s a rather comfortable 12% margin above the minimum. But this is a spherical chicken in a vacuum figure which isn’t capturing the complexity of chemical reaction between the sun, surface, and air, and don’t take the solar wind into account. We could invest 250 years into creating a thick, luxurious atmosphere only to see it scoured away to barely breathable in less than twice that time as the planet’s weak magnetic field can’t protect it. We’d have to add 70,000 tons of gas to the Martian atmosphere every year to offset the loss. Hey, no one said terraforming a world will be easy.

Ultimately there will be many challenges to creating Earth 2.0 and the end product might never resemble our home world. Costs will mount, political and legal questions will have to be tackled, and the project could only be accomplished if every advanced economy works together to keep it moving along for longer than something close to two thirds of the nations we recognize today existed. It would be the biggest mega-engineering project ever undertaken, which is why it’s not going to happen in the foreseeable future to be blunt. But it seems that we understand much of the underlying science and have a good idea how to actually make it happen, so if money could one day cease to be a hindrance to this idea, or it suddenly became a top priority after a major catastrophe loomed on Earth and millions needed an escape route within a few hundred years, we may just turn Mars into our second home world with kinetic missiles and a greenhouse gas spewing network of factories. Should you ever be legally able to buy land on Mars, maybe you should shell out for a hundred acres. Your great-great-grandchildren might thank you…