As human population continues to grow and need for raw resources grow, various nations and private organizations begin colonization efforts of our Solar System beyond the blue and green sphere we call home.

For this question we are assuming that there have been no drastic changes to:

  • World cultures
  • World governments
  • World economies
  • Current human technologies

So, while all of these can advance or shift, they are fundamentally comparable to what we have today, in late 2016. To this end, planet-wide terraforming, for example, is out of the question, and we're probably not crafting Dyson structures. Colonization efforts are limited to what is remotely realistic through the filter of where we stand today, and will stand over the next handful of decades.

The question has two sides to it:

  • What planetary bodies would these colonization efforts realistically extend over (the first half dozen or so)
  • What order of colonization/approximate timespan is reasonable for these efforts?
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    $\begingroup$ Earth population will only keep growing if we keep a large fraction of it poor and uneducated. In which case there will never be space colonisation, but a global civil war instead. $\endgroup$
    – Karl
    Sep 23 '16 at 6:09
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    $\begingroup$ Related: worldbuilding.stackexchange.com/q/2507/28 $\endgroup$ Sep 25 '16 at 19:53

The driving force for colonization will be to access some sort of valuable resources for the colonists to use. Most of the needs of the colonists can be broken into broad categories:

  1. Energy, to allow them to do all their other activities
  2. Water, to support life
  3. Elements like Carbon, Hydrogen, Oxygen and Nitrogen in order to support life
  4. Metals and rock for construction and shielding

Luckily, modern space research has allowed us to discover that most of what we need is relatively close at hand. The Moon is the first place we'll go because it is quite close and has everything in categories 1,2 and 4. It is convenient to develop and refine techniques before taking the next big jump.

The next easily available source of valuable resources is the NEO's (Near Earth Objects). These are much smaller and easier in terms of deltaV to reach than even the Moon, and collectively have all the major categories in abundance. Being very small, mining and accessing the resources requires that you learn how to operate in microgravity environments, but this experience will lay the foundations for moving to the asteroid belt, the Jovian Trojans and even (in the distant future) the Oort cloud.

Unlike many space enthusiasts, I would actually give Mars a pass. As a planet it is too small to maintain a thick atmosphere, but large enough for gravity to become an issue with launching and so on. Energy is also an issue, since Mars is far enough from the Sum to make solar panels less efficient, so you would have to haul nuclear reactors there.

The next major nexus of colonization will be Jupiter. The Jovian system has all the categories in abundance, with a powerful magnetosphere which can be mined for energy and 67 moons orbiting the planet itself. Europa alone has 3X the water as all the Earth's oceans combined. Because of the tremendous concentration of resources, it is entirely plausible that Jupiter becomes a civilization or nation on its own, a polity independent of Earth and quite capable of standing on its own.

I can see a fork happening at this point in the timeline. Some projects like building giant lightsails for space development and interstellar flight, creating antimatter as a compact energy storage medium and so on will require settling Mercury. Mercury is very abundant in category 1 and 4, and will have to import its water and life supporting elements. In return, gigantic lasers can be used to beam power to deep space targets far beyond the limits where solar energy would be useful.

Deep space colonies in Saturn would mostly be focused on the moon Titan, which has a thick nitrogen atmosphere, and the planet Uranus, which has the gravity field and radiation environment which allows for atmospheric mining, especially of 3He, which would be a valuable fuel for deep space colonies and spacecraft. Settling beyond might actually be a race between rising populations needing room and the building of a Dyson swarm around the Sun to harvest energy and create living space for trillions of sentient beings.

You can see in a setting like this here will be a multitude of opportunities for trade (not every place haas all th elements needed for successful colonization), as well as some fairly well defined "zones" for separate cultures and civilizations to develop. From Mercury to the Asteroid belt will probably be the "Solar" zone, where cheap solar energy is the economic driver. Jupiter will be its own zone for the reasons described above. Deep space will be its own zone because of distance and the need to either import energy from Mercury or mine 3He from the atmosphere of Uranus.

  • $\begingroup$ I was thought no way I will upvote Thucydides today again, to much for today, but you did it, nice thing u mention zones of colonization, nice touch to answer. Do not skip mars for real, it is important to research it, for me it was very convincing youtube.com/watch?v=j2Mu8qfVb5I . Moon, mars, venus, jupiter for my taste. $\endgroup$
    – MolbOrg
    Sep 23 '16 at 3:43
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    $\begingroup$ If you want to stay on Mars, more power to you. Come visit Jupiter, though. The view is spectacular. $\endgroup$
    – Thucydides
    Sep 23 '16 at 4:28
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    $\begingroup$ prefer Venus for my self, strategic reserves of carbon, u know, for your Jupter. $\endgroup$
    – MolbOrg
    Sep 23 '16 at 4:40
  • $\begingroup$ Moon, some rock, and pass on Mars: sounds like we have the same general idea. $\endgroup$
    – JDługosz
    Sep 23 '16 at 6:22
  • $\begingroup$ Even if Mars is a no-go, some of its moons might be viable. $\endgroup$ Sep 25 '16 at 19:55

Moon first.

It’s close and it offers a staging area for subsequent space industrial development.

Belt second

Follow the money: people will prospect and mine the asteroids. An intermediate structure between moon industry and pure open-space structures would be to build out from Ceres and Vesta. Huge heavy industry of mining and refining!


It's been pointed out that the Gobi Desert is more habitable than Mars and people could go there cheaply now. Why don't they?

The technology of closed ecosystems and self-sustained cities that would allow people to live on Mars would also allow them to live in extreme environments on Earth, first. Areas without water or other resources are open just as much as Mars is, and the tech that’s not perfected yet will be applicable here because you can still go get more water etc. when you have to supplement the imperfect system.

from there, everywhere

Once space technology is mature and life support systems are mature enough, they can go anywhere. So the local economy and politics at the time will dictate what comes next.

  • $\begingroup$ It's been pointed out that the Gobi Desert is more habitable than Mars and people could go there cheaply now. Why don't they? - spare those places, we might need them for energy production for our future space program, specially people evacuating, specially with absence of space elevator (it can't be build from earth, as my thoughts today), even with spacex 100times re-usability it needs tooons of energy. We do not lack places to live, food production and energy is problem. $\endgroup$
    – MolbOrg
    Sep 22 '16 at 20:07
  • $\begingroup$ The NatGeo program Mars made a more accurate comparison to Antarctica, the most uninhabitable place on the planet. Almost no life lives there, at certain times of year close to zero life is living there (except for the permanent research outposts). Very little resources available there, it's mostly ice and snow, and sometimes not even rocks. The bases are 100% dependent on care packages and supply ships, which are only able to travel there during certain times of the year. If they find microbial life there, we're more likely to find life on Mars too. Their results have shown nothing so far. $\endgroup$
    – IT Bear
    Jan 12 '17 at 22:10
  • $\begingroup$ "If they find microbial life there, we're more likely to find life on Mars too. Their results have shown nothing so far." - My understanding is that this isn't true - there's plenty of microbial life on Antarctica, but it's all under pack ice $\endgroup$
    – Chris K
    Jan 30 '17 at 21:04

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