Space colonization is a form of permanent human habitation and exploitation of natural resources outside of planet Earth. Space colonization as a concept is not solely constructed on the availability of additional resources that could enable expansion of human society from Earth into the solar system as we go forward in time, it is also built to escape the dreadful state that our planet and the biosphere is in, especially in the event of a planetary-scale disaster. Is it space colonisation even possible?
Professor Stephen Hawking and other scientists believe that to secure the future of the human species we must colonize another planet. He says the risks that may face humanity and cause its extinction could be an asteroid hitting the Earth, a new virus, climate change, nuclear war, and artificial intelligence. We can and must use our curiosity and intelligence to look at the stars, we must do it now before humanity is so overtaken by some disaster that we can neither anticipate nor control”.
For humans to survive we need to find a planet that is rocky and about the same size and density as Earth so that its gravity is similar to our own, then the crucial thing we need to sustain life with is liquid water at the surface. This means we need to find a planet that orbits in the habitable zone of its star, the distance where the temperature is just perfect for liquid water. For our sun, a yellow dwarf star, the habitable zone stretches from around the orbit of Venus to the orbit of Mars, Earth sits neatly right in the middle.
Vast resources of space
Resources in space, in terms of both materials and energy, are enormous. The solar system alone has, according to different estimates, enough material and energy to support anywhere from several thousand to over a billion times that of the current Earth-based human population, mostly from the Sun itself. Outside the Solar System, several hundred billion other planets in the Milky Way alone provide opportunities for both colonization and resource collection. Yet, travel to any of them is impossible on any practical time-scale without interstellar travel by use of generation ships or revolutionary new methods of travel, such as faster-than-light (FTL).
Asteroid mining will play a key role in space colonization. Water and materials to make structures and shielding can be easily found in asteroids. Instead of resupplying on Earth, mining and fuel stations need to be established on asteroids to facilitate better space travel.] Optical mining is the term NASA uses to describe extracting materials from asteroids. NASA believes that by using propellant material derived from asteroids for exploration missions to the Moon, Mars and beyond, up to a $100 can be saved. If funding and technology come sooner than is estimated, asteroid mining might be possible within a decade.
All these planets and other bodies offer a virtually endless supply of resources providing a limitless growth potential. Harnessing these resources can lead to great economic development.
Life Support
In space settlements, a life support system must recycle or import all the nutrients without “crashing”. The closest terrestrial analogue to space life support is possibly that of a nuclear submarine. Nuclear submarines use mechanical life support systems to support humans for months without surfacing, and this same basic technology could presumably be employed for space use. However, nuclear submarines run an “open-loop” by extracting oxygen from seawater, recycling existing oxygen, and typically dumping carbon dioxide overboard. Recycling of carbon dioxide has been approached in the literature using the Sabatier process (the Sabatier process produces methane and water from the reaction of hydrogen with carbon dioxide at elevated temperatures) or the Bosch reaction (the Bosch reaction is a chemical reaction between carbon dioxide and the hydrogen that produces elemental carbon– graphite, water, and a 10% return of invested heat)
Location
Finding a location for colonization is incredibly difficult, many propose that Jupiter and Saturn’s moons may provide a good habitat for future generations. Looking beyond the Solar System, there are up to several hundred billion potential stars that are possible colonization targets. The main difficulty is the vast distances to other stars; roughly a hundred thousand times farther away than the planets in the Solar System. This means that a combination of very high speed (some more-than-fractional percentage of the speed of light) or travel times lasting centuries or millennia, would be required. Based on Kepler’s space mission data, there could be as many as 40 billion earth-sized planets orbiting in the habitable zone of Sun-like stars and dwarfs in the Milky Way alone.
Jupiter’s Moon
The Artemis Project designed a plan to colonize Europa, one of Jupiter’s moons. Scientists were to inhabit igloos and drill down into the Europa’s ice crust, exploring any subsurface oceans. This plan opposes the possible use of “Air Pockets” for human habitation. Europa is considered one of the more habitable bodies in the Solar System and so merits investigation as a possible abode for life.
NASA performed a study called HOPE (Revolutionary Concepts for Human Outer Planet Exploration) which focuses on the future exploration of the Solar System. The target chosen was Callisto due to its distance from Jupiter, and thus the planet’s harmful radiation. It could be possible to build a surface base on Callisto that would produce fuel for further exploration of the Solar System.
Three of the Galilean moons (Europa, Ganymede, Callisto) have an abundance of volatiles that may support human colonization.
Saturn’s Moons
Titan is suggested as a target for colonization because it is the only moon in the Solar System which has a dense atmosphere and is rich in carbon-bearing compounds. Titan contains water ice and large methane oceans. Robert Zubrin identified Titan as possessing an abundance of all the elements necessary to support life, making Titan perhaps the most advantageous locale in the outer Solar System for colonization. Zubrin adds that “in certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization”.
Enceladus is a small, icy moon orbiting close to Saturn, notable for its extremely bright surface and the geyser-like plumes of ice and water vapour that erupt from its southern polar region. If Enceladus has liquid water, it joins Mars and Jupiter’s moon Europa as one of the prime places in the Solar System to look for extraterrestrial life and possible future settlements.
Titan is the largest moon of Saturn and the only moon in the solar system with a substantial atmosphere. It contains a thick orange haze of complex organic molecules and a methane weather system in place of water – complete with seasonal rains, dry periods and surface sand dunes created by wind.
Other large satellites: Rhea, Lapiteus, Dione, Tethys, and Mimas, all have large quantities of resources, which can be used to support settlements.
Welcome to Proxima-b
Proxima Centauri-b is an exoplanet orbiting in the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and is a part of a triple star system. It is approximately 4.2 light-years away from Earth and is in the constellation Centaurus making it and Proxima-c the closest known exoplanets to our solar system. It’s a little bit larger than Earth and is almost certainly a rocky planet. Moreover, there might be liquid water at the surface. Proxima-b could be the best destination for mankind’s new home. The picture above is a simulation of the planet because we do not have the technology to take such photos yet. Although Proxima-b is the nearest habitable planet, it is still a very long journey away. Getting there even with the fastest rockets we have today would take thousands of years. Professor Hawking believes this will be one of our biggest hurdles, yet he adds, “I have no doubt that we will eventually find ways of crossing the immense distances of space in just a few years.”
Habitability
The habitability of Proxima Centauri b has not been established but the planet is subject to stellar wind pressures of more than 2,000 times those experienced by Earth from the solar wind. Radiation and the stellar winds would likely blow any atmosphere away, leaving the subsurface as the only potentially habitable location on that planet
The exoplanet is orbiting within the habitable zone of Proxima Centauri, the region where, with the correct planetary conditions and atmospheric properties, liquid water also may exist on the surface of this planet. The host star, with about an eighth of the mass of the sun, has a habitable zone between ∼0.0423–0.0816 AU (an astronomical unit is about 9.5 trillion kilometers). In October 2016, researchers at France’s CNRS research institute stated that there is a considerable chance of the planet harbouring surface oceans and having a thin atmosphere. However, unless the planet transits in front of its star from the perspective of Earth, it is would be difficult to test these hypotheses.
Radiation Protection
Cosmic rays and Solar flares create a lethal radiation environment in space. In Earth’s orbit, the Van Allen belts make living above the Earth’s atmosphere difficult. To protect life, settlements must be surrounded by sufficient mass to absorb most incoming radiation, unless magnetic or plasma radiation shields were developed.
Passive mass shielding of four metric tons per square meter of surface area will reduce radiation well below the rate of some populated high natural background areas on Earth. This can be leftover material from processing lunar soil and asteroids into oxygen, metals, and other useful materials, eventually in order to move onto another planet we have to solve all of these obstacles first.
Without an ozone layer, the surface of Proxima Centauri b would be stripped of its protection from UV radiation. During the Proxima super-flare, the radiation dose without the protective ozone would be 65 times larger than that needed to kill 90% of one of the most UV-resilient organisms on Earth.
Robert Howard, the Habitability Domain Lead in the Habitability and Human Factors at NASA, believes that “life would have to undergo extreme adaptation to UV or exist underground or underwater.” Howard adds that “only the most resistant organisms could survive on the surface in this environment.”
Magnetic Field
The simulation assumes that Proxima Centauri-b does not have a magnetic field. Such a shield could channel the particles from the coronal mass ejection to the poles, forming the aurora as on Earth and reducing the damage to the atmosphere.
However, orbiting so close to the star, Proxima Centauri-b is likely to be in the tidal lock as the moon is to the Earth. This is expected to weaken the magnetic field, as the slower rotation makes it harder to create a magnetic dynamo within the planet.
Conclusion
To conclude all that has been said, I believe that the best choice for human civilization in the future is moving to Titan as it possesses an abundance of all the elements necessary to support life. In different ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization. The atmosphere contains plentiful nitrogen and methane. Evidence indicates the presence of liquid water and ammonia under the surface, which can be delivered to the surface by volcanic activity. While this water can be used to generate breathable oxygen, we should not depend on moving to a different planet because there is no planet as special as ours. So, why search for a different one when we can still save our own?