Many believe that this century – perhaps as soon as the next several decades – will see a marked change in space exploration, notably in colonization of other planets or near-earth objects.

Multiple private companies already offer space travel, including Space Adventures, whose co-founder Eric Anderson has stated that the establishment of space colonies is the next step once the economics are worked out:

“In the next generation or two—say the next 30 to 60 years—,” Anderson told the Atlantic, “there will be an irreversible human migration to a permanent space colony.”

Anderson is placing his bets on Mars, but the question of if and when are up for the debate of other space optimists. Here are the current possible location for space colonies– and the likelihood of their future existence.

1. The Moon



To many, our beloved natural satellite, the moon, seems the obvious choice for colonization as our closest neighbor.

Russia, anxious to beat out competitors, has proposed to begin lunar colonization by 2030. The three-step plan, outlined in a paper by the Russian Academy of Science, Moscow University, and Russian space research institutes, would begin preparing as soon as 2016.

Though Russia’s deputy Prime Minister has stated of the goal that “we are going to the moon forever,” professionals doubt the feasibility of this plan in terms of time and cost.

2. Mars

As we’ve written about previously, private company Mars One plans to begin establishing — and televising — the first colony on neighboring planet Mars starting in 2024. Over 700 applicants are currently in the running for this one-way trip.

Elon Musk’s SpaceX company is also anticipating human travel to Mars in similar timeframe as Mars One, perhaps as soon as 2026, while NASA’s more cautious goal is 2035.

NASA, which has the most expertise, has also said that it would review the technology and safety of private companies’ missions, offering advice, but not assets to assure their attempts won’t cause any human endangerment.

3. Venus

Though our sun-side neighbor Venus has no habitable land, a recent proposal by science fiction writer Charles Stross has been fleshed out by fellow writer and scientist Geoffrey Landis in what has been called a “surprisingly strong case” for colonization.

Due to the planet’s hostile atmosphere, cities could in theory (pfd) be built 50 kilometers from the surface, where the atmosphere is more earth-like than anywhere in the solar system, besides, well, Earth.

Also unlike the moon and Mars, Venusian gravity would be less likely to deteriorate human bones and muscles with extreme pressure.

4. Asteroids

Asteroids have long been suggested as possible colonization grounds, especially a more stable asteroid belt like the one between Mars and Jupiter. With much lower gravity than the moon or Mars, landing would be easier and more cost-efficient.

Asteroids are also ideal for mining purposes, a process that could begin as early as 2015. It has been suggested that the hollowing of asteroids would be ideal for space colonies, as they contain all the resources needed and could be inhabited by many.

5. Exoplanets

Lastly, exoplanets remain the literally most far-out locations for potential colonization. NASA and other space organizations have been on the hunt for potentially habitable exoplanets for decades, having already discovered nearly 2000.

The closest, Gliese 832c, was only recently identified. At only 16 light years from Earth, it orbits a star less bright than our sun, and receives about the same amount of energy from it.

Obviously, interstellar travel comes with serious challenges, if it will ever be possible at all. Still, as wild as it seems, the transport of cryonically preserved human embryos to exoplanets has been theorized as a potential solution. The planet would be colonized by robots before the unfreezing and subsequent human takeover began.