Terraforming is the process of transforming a celestial body to become habitable by Earth-like life.

Even when I try to imagine an advanced civilization, the cost, time and complexity to terraform a planet seems like a real challenge. Terraforming Mars seems like an easy job compared to other planets and yet it would be a daunting task:

  • Mars's mass is much smaller than Earth's and it has no magnetic field. This means that there is nothing to stop the ultraviolet radiation and only a thin atmosphere. Less gravity makes it harder to have a thicker atmosphere.

  • Mars is cold, we would need to make it warmer possibly using the greenhouse effect but for this we need to add tons of gases on the planet. We would to take the gases form Earth or directly from Mars. Considering the quantity we produce on Earth and that it's only starting to warm up the climate, it would take a lot more to get Mars to have the same temperature as Earth. And it would take a lot of time. At least a century, because we have to warm it and make sure it stabilizes at the end.

And I will stop there because it is not really the point of the question.

I make the assumption that terraforming is really complicated. But I admit that maybe, in a distant future, (or in a distant science fiction future) advanced civilizations might have enough wealth and technology to consider terraforming a planet. The problem is that, with advanced space travel, they might be better to search for another planet, it would be much simpler in my point of view.

Terraforming could be a solution for us since we have problems on Earth but it's not feasible right now. By the time it will becomes possible to do such wonders, space travel will be a better option. Finding a planet with less challenges might be easier.

So, I'm trying to understand why in a lot of science fiction stories and games, civilizations would favor terraforming a planet instead of looking elsewhere.

  • 2
    $\begingroup$ Also keep in mind that terraforming can be 'good enough'. On Mars, for instance, despite the low gravity it could still hold on to any atmosphere we give it for many millenia, and we could just 'top it off' as needed. Also, there are a lot of gasses in solid form on the planet now so we don't even need to go anywhere to get them. With careful planning, the costs may not be as high as you think, especially compared to transporting millions of people lightyears across the galaxy. $\endgroup$
    – Nicholas
    Commented Oct 9, 2014 at 13:03
  • $\begingroup$ Not an answer, but have you read Robert Morgan's Broken Angels, second of a trilogy? He expands some really interesting ideas about terraforming through the main character, who recounts - in the futuristic SF universe - how initial terraforming attempts on Mars went disastrously wrong, because trying to graft a piece of Earth onto an alien planet with a different atmosphere and organisms was never going to turn out well. So when they colonised new planets, they started by killing every single organism on the planet. $\endgroup$
    – Lou
    Commented Oct 9, 2014 at 16:41
  • 3
    $\begingroup$ I can't imagine how terraforming a planet could be a better solution than healing our own. $\endgroup$
    – mouviciel
    Commented Nov 3, 2014 at 18:10
  • $\begingroup$ Earth can't be in two places at once. $\endgroup$
    – Oldcat
    Commented Dec 5, 2014 at 19:56
  • $\begingroup$ @Oldcat of course not but what is your point ? $\endgroup$
    – Vincent
    Commented Dec 5, 2014 at 20:22

7 Answers 7


The first reason off the top of my head is the time it would take to find a new world that is already habitable or easier to terraform, versus the time it would take to terraform a world that's close by.

Habitable planets are not that easy to find

Faster-than-light travel is a not a trivial problem and it may take much longer to solve than terraforming. Even if you do manage to achieve FTL travel, the speeds might not be ideal - at light speed, it can take a decade to reach a close-by star system only 10 light years away (a short distance by astronomical standards) and that's assuming that you have one that close that has habitable planets. If you're unlucky, even achieving many times the speed of light could still not be enough.

In fiction, FTL travel tends to be extremely fast - moving between star systems is a matter of hours or days. At those speeds, it is indeed a preferable choice to terraforming because you can search hundreds of star systems in a time shorter than it would take to build a basic colony.

An additional problem could be how much you can carry with your faster-than-light ship - if the cost is too high, perhaps terraforming is still cheaper despite the enormous cost. To colonize a planet you need thousands of people (44 thousand by 2013 estimates[1]) and a lot of materials and resources. Perhaps you're not sure if it's actually habitable and you have to check first - that's extra time and resources.

FTL drives are, at this moment, purely theoretical - we don't even know if they're possible and indeed in some fiction, there is no FTL. Terraforming on the other hand, while a huge engineering task that requires a lot more knowledge than we have, is almost certainly possible.


Even if it's easy to travel to distant star systems in search of habitable planets, it's going to be much cheaper to move within one if you have that capability (unless you're using mass drivers and only make very few of them).

By terraforming a planet that's close by, like Mars, you get a whole new planet where people can live and very close to the homeworld. That means it's going to be faster to develop it, trade is cheaper, people can move faster between planets etc. . Another advantage is that we've studied our own solar system enough and its planets as well. A new star system might have configurations we're not experienced with - you could have celestial phenomena that surprise you or geological phenomena that do the same.

To put it in Earth terms: it might be hard to grow food in the desert that's next to your city, but you might still prefer working with it in order to expand this city instead of moving far away to found a new city.

All of this of course depends on the relative energy and time costs of traveling astronomical distances, versus the engineering costs of transforming an entire planet.

Prior establishment

You might prefer to terraform a planet, not because it's cheaper, but because you already have colonies on it, but they have to live in habitats. If you, for example, colonize Mars before you have cheap FTL travel and by the time it's cheap enough to search for habitable planets there's already hundreds of millions of people living on Mars colonies, you can't just relocate all of them. You might find new worlds but eventually decide to terraform Mars as well, so that it's friendlier to human life.

  • $\begingroup$ There's a reason why you're quickly climbing the rep scale. You're answers are everywhere! $\endgroup$
    – DonyorM
    Commented Oct 9, 2014 at 5:41
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    $\begingroup$ Don't forget about strategic positioning. Assuming the galaxy isn't entirely peaceful, you might want colonies in certain places where there isn't an already-habitable planet. This would probably remain true even if FTL travel is very fast/cheap. $\endgroup$
    – Geobits
    Commented Jan 16, 2015 at 20:32
  • $\begingroup$ I know this is late, but I thought that the numbers were closer to 100 than 44,000. The amount of people needed for sufficent genetic diversity is not as much as you would expect. $\endgroup$ Commented Dec 9, 2023 at 21:05

Some terraforming could actually be fairly simple (as such things go).

Mars is a weak candidate as it has low gravity and no magnetic field but you could still work with. Imagine creating a bunch of machines that go out to the asteroid belt and start looking for ice asteroids and redirecting them into Mars, rain ice asteroids down onto the surface and over time you increase the supply of water and atmospheric thickness and slightly increase the planet's mass.

A better candidate would have a magnetic field and already have an atmosphere of some kind.

In that case "all" you would need to do is seed it with appropriate genetically modified bacteria/fungus/plants/etc. Those lifeforms would the convert the atmosphere towards the one we wanted. A small team would monitor the process and seed it with updated terraforming species as needed for each stage of the process. As the environment starts to become more like we wanted early animal life could then be seeded as well and we build up an entire ecosystem from there.

The process would take a long time (centuries probably) but not actually be very expensive when you consider the value of an entire new habitable world.


Terraforming Technology Outpacing Space Travel Technology

Space travel is not an easy task. We've been at it for a little less than 70 years and still haven't broken out of our Ort Cloud, and as far as getting people off the surface of our planet, we haven't even made it to another one yet.

And yet, we as a society are already considering the possibility of utilizing water sources (and other resources) on local celestial bodies to mine resources and even as habitable land. This is why scientists get really excited about finding sources of water on celestial bodies in our own solar system.

And it's not as if we have no experience with terraforming - we regularly alter the water flow and construct habitable spaces out of the resources on our own planet. It's simply a matter of finding a planet or celestial body that would make a good candidate. (Mars is actually not all that promising in this regard, unless we can get its magnetic field up and running. The Dwarf Planet Ceres, and our own moon, are better candidates).

  • $\begingroup$ But our moon is not too well equipped with a magnetic field either. $\endgroup$
    – Ghanima
    Commented Dec 1, 2014 at 22:46
  • $\begingroup$ @Ghanima No, and that would be a hurdle to surmount. But it is abundant with ice and, most importantly, it is very close to Earth - which alone makes resupplying during any major operation more viable, or even just getting a 'terraforming payload' that far. $\endgroup$
    – Zibbobz
    Commented Dec 2, 2014 at 14:11

Terraforming in fiction is big in fiction for a couple of reasons it has only been recently that we have come to see how prolific planets are out there. What in general is considered even more rare is a planet with life already on it.

The assumption is that most planets we will find are going to be barren whatever their makeup. On top of that if there is already life on a planet, who is on it? Even if the life was just crawling out of the oceans, doesn't mean that it would be good for humans and their crops and livestock. The indigenous life could be very dangerous on it's own, the predators, the plants, the microbes. Starting with a barren planet you don't have to worry about unknown effects of indigenous species, either they on you or you on them.


It would be nice to have biomass on a planet before you got there. As well as any target byproducts you might engineer them to make. I'd add that Deinococcus radiodurans can survive anywhere you can't engineer other bacteria to. So you're pretty much guaranteed to be able to just launch a can across the universe at any planet, even if you can't quite fly to it yet. If your lucky the locals may have evolved before you got there and be able to contribute to science with their "un-poisoned" paradigms. (Panspermia anyone?)


Planets are more resistant to the kinds of dangers that exist in space.

It's played down in fiction but persistent radiation is a big problem in space, both just the ambient background radiation and peak events like solar storms.

Hunkering down under a blanket of atmosphere gives lots of protection. If the planet has a magnetic field, all the better.

Also, a planet scale biosphere could buffer a lot of manmade catastrophes like nukes, hacking, biological attacks, nano attacks, even run away robots. Anything in space will have a lot of people, in a small area, dependent utterly on a meshwork of tech to keep them alive. Hit the small area, contaminate it or wreck the life support and everybody dies.

Conversely, on a planet, you could loose most or all of your tech and still survive in the biosphere.


You should (as an civilization) advanced enough to the point of "not to bothering the answer of the question".

Such questions only relevant to civilizations like us / ours, (behind the point). Other civilizations "beyond to point" simply they do because they can.

If you "on the point" (to see whether they can terraform a planet) terraform a planet...

  • $\begingroup$ Hmm. I like to think that more advanced civilizations will have enough wisdom to do things for good reasons, not just "because they can." Seems to me that too many "civilized" humans have not advanced beyond "because we can" or "because we see some reason to", and that this crude mode of decision-making is leading us to do extremely unwise things, which may actually have us killing ourselves off if we don't become more intelligent. $\endgroup$
    – Dronz
    Commented Dec 21, 2014 at 16:40
  • $\begingroup$ A very civilized reason would be "because it's fun". Or, even better "because we want to see what happens if we push this button... oops! $\endgroup$
    – Burki
    Commented Feb 3, 2016 at 15:55

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