With new space-race contestants, both countries and private corporations, human colonization in the inner Solar System is a common conversation. According to some prominent scientists, like Stephen Hawking, space colonization will represent the only way of saving mankind within the next thousand years, unless colonies are established in space.
“There is no way back into the past; the choice, as Wells once said, is the universe—or nothing. Though men and civilizations may yearn for rest, for the dream of the lotus-eaters, that is a desire that merges imperceptibly into death. The challenge of the great spaces between the worlds is a stupendous one; but if we fail to meet it, the story of our race will be drawing to its close.” – Arthur C. Clarke
There are companies, like Mars One, that plan to establish a permanent human settlement on Mars starting in 2024. Crews of four will depart every two years. The companies has scheduled the first unmanned mission for 2018.
What about possible targets? A few have been proposed as possible destinations for future human settlements in space.
“It is essential that we colonize space. I believe that we will eventually establish self-sustaining colonies on Mars, and other bodies in the solar system, although probably not within the next 100 years. I am optimistic that progress within science and technology will eventually allow humans to spread beyond the solar system and out into the far-reaches of the universe.” – Stephen Hawking
The moon has been one of the first to be considered for colonization, for obvious reasons of proximity, but Mars has been attracting greater attention.
Yet more targets, even farther away, have been imagined for medium-term human colonization. Europa, one of the main moons of Jupiter, is one of the favorites for its geophysical features—a possible ocean under its glaciers—hinting at some likelihood that human life can be sustained. But others, more exotic, have been proposed, like Ceres. The dwarf planet located between Mars and Jupiter has some interesting characteristics, including a supposed abundance of water on its surface.
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Challenges to space colonization are formidable, in terms of resources needed and overall feasibility. Distance is the first—even for Mars, the nearest destination once you discard the Moon—but not the only one, with factors like synodic periods, length (in months) of the travels and environmental conditions on the target settlement ranking high.