Do We Really Want To Terraform Mars?
According to scientists and science fiction writers, if we wanted to make Mars a blue planet, like it may have been billions of years ago, the process would take up to a thousand years and start with a massive release of greenhouse gases. The goal would be twofold; to make the Martian atmosphere thicker, increasing surface pressure, and to trap more heat from the sun to warm up the planet enough for liquid water to flow on the surface. Successfully doing both is vital to everything that comes next. If the atmospheric pressure is too low, the water will boil at much lower temperatures than it should, and without water, we couldn’t start seeding the surface with algae to convert that carbon dioxide into breathable oxygen.
Once there’s enough hearty algae and moss growing in what were once icy deserts, a little over a century after terraforming would have began, we can start planting resilient trees to speed up oxygen production. A few centuries later, we can plant a wider variety of flora and start walking on the surface without space suits. Domed and underground habitats could turn into open cities as the air grows more breathable. Roughly a thousand years after the first factories on Mars started belching greenhouse gases upwards, the Red Planet will be a second blue marble that welcomes human visitors. Or at least that’s the general idea.
Unfortunately, studies show that we’ll have some serious hurdles with the first step. For one, there doesn’t appear to be nearly enough carbon dioxide on Mars to sufficiently increase atmospheric pressure, which is currently just 6 millibars. Releasing the gas from every carbon sink we know of would raise the pressure to 33 millibars. While that sounds like a very impressive increase, consider that at lea level, we enjoy 1,000 millibars of pressure. At anything less than 61.8 millibars all the fluids in your body would start to boil. (This is known as the Armstrong Limit, named after military doctor Harry George Armstrong, and corresponds to pressures at an altitude of about 63,000 feet.)
We’d need a minimum of 122 millibars for an Olympic class athlete to function, provided he or she had a pure oxygen tank. The lowest pressure at which typical humans could live and work is around 475 millibars, and even then, long term habitability would demand special adaptations like a boost in certain blood cells, or more efficient oxygen processing, traits that natives of Tibet and Patagonia have evolved over the millenia. So as you can see, there’s a huge shortfall here, and to bridge it would require efforts beyond anything we’ve ever done, at tremendous expense and requiring extra decades of work. Which could be undone by Mars’ lack of a strong magnetic field. As the charged particles in solar winds collide with the atmosphere up to 3,200 tons of air to be stripped away every year, versus the 90 tons we lose in the same timeframe.
Even worse, that weak magnetic field means lethal UV rays scour the surface, effectively sterilizing it, and a thicker atmosphere won’t do much to stop them as evidenced by the fact that even on Earth these rays can burn flesh and trigger cancers. We can use very low frequency waves to push back against the solar wind, as we’ve accidentally done here on Earth, but we can’t do much about the incoming radiation. It’s hard to imagine even the heartiest of algae taking root in an environment which kills the sort of bacteria happily to live in pools cooling nuclear reactors within minutes.
In other words, Mars is an alien place that won’t just be very difficult to make livable, there will be powerful forces of nature actively fighting our efforts. We could keep replenishing the air and devising new ways to create a magnetosphere with everything from orbiting magnets or enormous magnetic field generators scattered across the planet, but it would make terraforming an active, ongoing process rather than a single self-sustaining megaproject, with all the attendant costs and effort.
And that prompts the question of whether we even want to bother with it. We already have a planet for which we’ve evolved, even if aliens on a world we think would be the typical habitable oasis in space might find its air and water poisonous. We should absolutely explore what lies beyond it, but when we start enumerating all the challenges of living in alien environments, it seems more worthwhile to channel our resources not into changing other planets but into changing ourselves. What if we didn’t terraform Mars because we had the appropriate robotic and genetic augmentations to set foot on another world with minimal protection?
If Mars was ever home to life, trying to turn it into a smaller Earth could easily wipe out all record of it and any survivors that may have evaded us. Likewise, the process would cost fortunes and offer no guarantee it would work or be sustainable long term. But if we focused on making ourselves a lot more resilient, learning how we really function as organisms as we do, we could open the final frontier in a way no cluster of terraforming factories or colony ship ever could. After all, it’s a lot easier to edit DNA and implant biocompatible, nerve-reading machinery than to turn an icy alien desert spanning the same area as all the land on Earth and immolated by radioactive rays, into a low gravity paradise.