As long as we’ve known the general layout of the solar system, our nearest neighbors have fascinated us, maybe Mars most of all. Early scientific and fictional imagination about Mars was often driven by the idea that our neighboring planet was strange, but not ultimately that different from Earth. H.G. Wells’s Martians had some trouble adapting to Earth, but Edgar Rice Burroughs sent his hero John Carter to Mars without any undue fuss about temperature or oxygen (though an atmosphere plant maintains habitable conditions for humans and Barsoomians alike). Decades later, Ray Bradbury likewise imagined a near-future Mars where human colonists could live in relative comfort, though maybe not totally as expected.
Now, of course, we know none of that is possible. A crewed mission to Mars is a distinct possibility for the future, but with such a thin atmosphere and no magnetic field, the brave colonists will have to deal with many of the same issues astronauts do now. More importantly for any long-term arrangement, sciencing our way through the risks inherent in a sealed environment won’t get us past the cumulative physical and psychological effects of a long stay in a limited safe area surrounded by a hostile planet.
Clearly, many scientists, visionaries, and assorted futurists agree, we’re going to have to find a way to make things a little more homey. The study of how exactly to achieve this (ideally with breathable air and survivable temperatures) has spawned a lot of interesting ideas for terraforming, or remaking Mars in our image.
One idea that’s been around for decades is to warm Mars up to match our picky insistence on it not getting down to -100°, whether it’s Fahrenheit or Celsius. (Some people are just never satisfied.) To do this, we could use some of our hard-earned expertise and apply some of the same techniques that are serving us so well right here on Earth. That’s right, I’m talking about melting the polar ice caps and releasing some of the nice CO2 that’s trapped there!
This idea was proposed by Carl Sagan in 1973 (undoubtedly by others, but he got published in Icarus) in “Planetary Engineering on Mars.” His paper suggested warming the ice caps by covering them in dark material like plants or dust from Mars’s moons Phobos and Deimos. Another possibility for warming things up a little is to use giant mirrors to reflect and concentrate sunlight on the poles.
However it’s done, melting the ice caps would give us liquid water as well as carbon dioxide that could help with a greenhouse effect and a thicker atmosphere. Many terraforming plans include plants at this stage as well, to help convert some of that CO2 to oxygen for us Earthlings.
One of the most exciting ideas for terraforming is to lasso a bunch of meteors (probably figuratively) and crash them right into Mars, probably at the poles. During the resulting upheaval, the ice caps will melt and we’ll get a warming effect and free up some CO2 as discussed above.
A variation on this idea is to mine chunks of methane- and ammonia-containing ice from moons like Titan and Ganymede. These chunks could then be hurled at Mars (are you sensing a very thematically appropriate violence in these Martian ideas?) and the ammonia would provide nitrogen and hydrogen, which would produce more water in combination with oxygen from the existing CO2. The methane would help the greenhouse effect, and the impact itself would kick up some nice dust to help thicken the atmosphere, so it seems like a win all around.
Also, hurling meteors and ice chunks into a planet sounds really fun, which probably hasn’t escaped anyone’s notice even if it doesn’t make it into scientific discussions.
If we end up with a nice stew of greenhouse gases and water sloshing around on Mars, we’ll need some way to keep it all there while we try to make these changes permanent. Without a strong magnetic field like Earth’s, any atmosphere is going to be more difficult to protect from the scouring solar wind (which likely helped Mars lose its atmosphere in the first place).
Engineers and scientists like Ken Roy think that a planet-encompassing shell of dirt, steel, and Kevlar might be a workable solution to the atmosphere problem. It’s hard to say whether this would be a temporary or permanent feature for Mars, since that solar wind isn’t going anywhere. Either way, a shell would reduce the volume of atmosphere needed to make Mars habitable and potentially make the whole process much easier.
The biggest downside other than the cost and effort of assembling such an enormous structure in the first place is that Kevlar, steel, and dirt aren’t particularly transparent, so colonists wouldn’t get to enjoy a real sky. Unless we use different materials, nobody’s going to go to Mars for the view from indoors, but we could at least cut the resources significantly by only putting a dome over just part of the planet.
Will We? (Should We?)
Of course, none of these ideas are going to be quick or easy to implement. It’d take a very good reason and an even better source of funding to get terraforming efforts off the ground, so to speak. Many have darkly speculated that we’re probably going to render the Earth uninhabitable at some point and be forced to look elsewhere, which would certainly be good motivation, assuming we have the time and money to put together a colony at that stage. Others prefer to think that our scientific curiosity and sense of adventure will carry us, which might happen, but probably not incredibly soon.
A different aspect to all of this is the ethics of settling another possibly inhabited world. We don’t know where there is or ever was life on Mars, and if it’s around, it’s probably buried deep and extremely simple. Nevertheless, Earth has a slight history of people colonizing without being too bothered about what or whom they’re displacing, and if we’re going to make drastic changes to Mars, it’s worth considering whether any future discovery of life should change our plans.
Even if we do find life, the Martians probably aren’t going to have much to say about terraforming or anything else, so the decision will likely be up to us. Whatever happens with future interest (or lack of it) in colonizing Mars, it’s been a source of curiosity and inspiration and a huge part of our drive to explore beyond our own sphere.