New Worlds: Colonizing Planets, Moons and Beyond

More than 7.9 billion people currently inhabit Earth, and the population is growing. Halting this growth, although possible, would lead to Global economic and social collapse. Furthermore, the modern economy has a constantly growing demand for resources. Finally, demographic growth is inextricably linked to overall progress. Continuous growth versus a limited living space on Earth leads to an unavoidable crisis.

Currently, the human settlement of planet Earth is suboptimal, roughly covering some 15% of its surface. Remediating this problem involves several approaches. Inhospitable land areas can be "greened” by using modern technology, while the efficiency of current settlements can be improved. But humans could also take advantage of such new technologies to colonize the surface of still water bodies, underground and underwater environments. This enterprise would help us learn revolutionary new ways of providing food, light, heat and electricity to human populations, techniques that would also be applicable to other celestial bodies. 

The first obstacle to overcome in large-scale space colonization is represented by the elevated costs of launching payloads into Earth’s orbit. The main reasonable solution is using non-rocket space launch methods, which are rather numerous. In the long term, an even more efficient approach is investing in megastructures, such as stratospheric towers, space elevators or orbital rings, that would dramatically ease our access to space, while also allowing us to harness the energy in Earth’s atmosphere. Another strategy to support the space race is to make it profitable through space mining. Asteroids and planets host huge deposits of valuable ores, water and fuels, while technical solutions for extraction are already at our ease.

Among the planets in our Solar System, Mars is the closest to Earth in terms of distance and similarity. However, current environmental conditions on its surface are hostile to any life form. While it provides enough space for sheltered, enclosed settlements, the final goal should be terraforming the Red Planet, which is perfectly achievable at our current technological level. Terraformation consists of two stages. Ecosynthesis (creating conditions for microbial life) can be accomplished within a century, by a synergistic approach using nuclear blasts, greenhouse gasses, orbital mirrors, thermal aquifer drilling, directed asteroidal impacts, etc., Caeliformation (creating a breathable atmosphere for humans) would take several centuries, involving the controlled introduction of terrestrial life forms and atmospheric conversion through photosynthesis. Even after that, a continuous effort would be required to ensure habitability in the long term.

Another valuable target is at our ease. The two gas giants of the Solar System, Jupiter and Saturn, host their mini-systems of various-sized moons. Among these, the four Galilean moons (Io, Europa, Ganymede and Callisto) and Titan are the largest. While all these moons can be settled, they do not have enough light and heat to allow terraformation. The way to change this is by helioforming the two gas giants. Turning Jupiter and Saturn into mini-stars would efficiently thaw the major moons, creating atmospheres, hydrospheres and landmasses needed for life seeding. Once triggered, the process might be even faster than on Mars. At the same time, some engineering effort is needed to correct the rotation rate of these tidally-locked worlds and ensure full human habitability.

The Inner Solar System hosts several valuable planet-sized objects, that should be targeted by human colonization. The Moon has the major advantage of being close to Earth, plus also having several useful features, such as low gravity (perfect for space launch) and useful mineral resources. It hosts vast areas suitable for enclosed settlements of limited terraformation. However, there are clues that, in time, it could be fully terraformed. Mercury is a small, hot and dry planet, a tough target for future colonists. Planetary engineering could also work in these conditions, eventually allowing terraforming, or at least large-scale paraterraformation, under a planetary "shell”. Finally, in the Main Asteroid belt, Ceres could be the easiest terraformable object in the whole System. There are also technical solutions that could turn other planetoids and small moons into new homeworlds for humankind.

Although our planet’s “twin” in any other aspect and object of several terraformation scenarios, Venus is a very difficult target for human settlement. Due to its extreme atmospheric pressure and temperature, it is the most inhospitable celestial body in our Solar System. This does not mean that terraforming it cannot be done, but in order to do it in a reasonable time, some technologies that are currently out of our reach need to be applied. Wormholes are the best option, coupled with some large-scale megastructure buildings, plus “regular” planetary engineering means. Fortunately, even if it seems like SF, scientists are currently making serious advances towards achieving such technologies. At the end of the process, Venus could be transformed into the most habitable world in our System, a true paradise.

The Outer Solar System is an enormous region, offering plenty of potential living space and valuable resources for humankind. It comprises Uranus and Neptune with their moon systems, myriads of trans-Neptunian dwarf planets and planetoids including Pluto, Charon, Eris etc. and putative planetary or substellar-sized objects.
The most feasible approach for ice giant planets seems to be helioformation, followed by terraforming and colonizing their moons, using methods similar to those that should be employed on Jupiter and Saturn.
Since many other celestial bodies are too far from any light source, turning them into habitable worlds requires altering their orbit. While such a process requires a carefullyplanned and sustained effort, it would be made easier by the low mass of these planetoids.

Our Solar System represents just a tiny fraction of the Galaxy and the whole Universe. Now we know for sure that many stars host planetary systems, starting with our close “neighbor”, Alpha Centauri. However, the first problem on the way to our Universe-wide expansion is getting there in reasonable amounts of time. This can only be done by faster-than-light travel, which, in turn, needs “bypassing” normal space-time. There are some ideas on how we could accomplish these, even if research is still at its beginnings. Until then, thousands of exoplanets were already discovered. Some of them seem to be rather easy to terraform and settle, while others could also be colonized, by using synergistic means of planetary engineering.

Space settlement, while drawing much support from public opinion, also has its critics. They bring various counterarguments, from the need to "fix” Earth’s problems first to the use of nuclear explosives and military devices, which might go against international treaties. However, the main argument is the desire to preserve eventual life forms, including microscopic ones, that might be encountered in the C. Here, we argue that the highest likelihood is that of life scarcity in our Universe. Life forms are, most probably, rare, usually microbial and living in environmental niches which would not be affected by terraforming. Intelligent life should be even much scarcer. Furthermore, we argue that space expansion is not just a desire but an imperative for preserving and growing our species and our entire Biosphere.