Colonization of the outer solar system
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Some of the moons of the outer planets of the solar system are large enough to be suitable places for colonization. Many of the larger moons contain water ice, liquid water, and organic compounds that might be useful for rocket fuel production among other things. Colonies in the outer solar system could also serve as centres for long term investigation of the planet and the other moons. In particular, robotic devices could be controlled by humans without the very long time delays needed to communicate with Earth. There have also been proposals to place robotic aerostats in the upper atmospheres of the gas giant planets for exploration and possibly mining of helium-3, which could have a very high value per unit mass as a thermonuclear fuel. Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: Settling the Outer Solar System: The Sources of Power, pp. 158-160, Tarcher/Putnam, 1999, ISBN 1585420360Jeffrey Van Cleve (Cornell University) et al., ["Helium-3 Mining Aerostats in the Atmosphere of Uranus"], Abstract for Space Resources Roundtable, accessed May 10, 2006
The idea of using asteroids as a source of minerals (asteroid mining) for space colonization is common in science fiction, since they are plentiful, rocky, and have low escape velocities. Some have proposed hollowing out asteroids to serve as large space stations.
The
The Jupiter system in general poses particular disadvantages for colonizing because of its severe radiation environment and its particularly deep gravity well. Its radiation would deliver about 3,600 rems per day to unshielded colonists at Io and about 540 rems per day to unshielded colonists at Europa, while somewhere around 75 rems within only a few days is generally enough to cause radiation poisoning, and somewhere around 500 rems within only a few days is fatal. Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: Colonizing the Jovian System, pp. 166-170, Tarcher/Putnam, 1999, ISBN 1585420360
The radiation and gravity well issues are likely to make Jupiter persistently infeasible relative to the more distant gas giants as a source for mining helium-3. However, its gravity is a considerable advantage in providing a spacecraft with a gravitational boost to shorten its trip time to those outer gas giants. The advantage of its gravitational boost could make it economical to operate a way station, with Callisto the likeliest spot, and allow spacecraft that have had maintenance or re-supply on a Callisto station to take off for one of the outer gas giants, with the gravity boost more than making up for the delta-V lost in stopping in the Jovian system. Provided that short-term radiation shielding is provided for electronics and any crew on board a spacecraft, expending six km/s of delta-V - feasible with today's chemical rockets - while skimming 7,150 km above the cloud surface, can be leveraged into a departure speed of 24 km/s, i.e. 5 AU/year.
Jupiter has an atmospheric depth with the same pressure as Earth sea level, where there is also a blue sky, though it is colder than on Earth; further down, Jupiter has an atmospheric depth that is the same average temperature as the surface of the Earth, where the pressure is about five bars. However, even here, airborne colonies such as floating cities would be unlikely, because Jupiter has a gravitational acceleration of around 2.4 g near the surface of its atmosphere. Also, because the atmosphere is dominated by hydrogen, any leak of an oxygen atmosphere or a liquid oxygen bipropellant would present a significant risk of catastrophic explosion.
The Artemis Project designed a plan to colonize Europa. [Artemis Society International] official websitePeter Kokh et al., "Europa II Workshop Report", Moon Miner's Manifesto #110, Nov. 1997 Scientists are to inhabit igloos and drill down into the Europan ice crust, exploring any sub-surface ocean. It also discusses use of air pockets for human inhabitation. This Europa surface base would also make use of inflatable structures. Exploration of Europa and its subglacial ocean would be carried out with submarines. [Humans on Europa: A Plan for Colonies on the Icy Moon], Space.com, June 6, 2001, accessed May 10, 2006
There are some difficulties related to colonization of Europa; one significant problem is a high level of radiation from Jupiter's radiation belt, which is approximately 10 times as strong as Earth's Van Allen radiation belts. A human being would not survive at or near the surface of Europa for long without very large scale radiation shielding. Colonists on Europa would want to descend to and ascend from the surface relatively quickly, though not while Europa is passing through Jupiter's magnetotail, and stay in habitats buried under the surface while they're there.
Colonization of Europa in fiction
In his short story "A Spy in Europa", set in his Revelation Space universe, Alastair Reynolds depicts an advanced human society called the Demarchists who are based in colonies on Europa, that mainly cling to the underside of the ice crust at the top of the subsurface ocean. They go on in later novels to become one of three social groups that dominate interstellar colonization.
In the remote future, the Jovian moon Ganymede is a probable place for the installation of a base—the Base Ganymede, as it is the largest moon in the Solar System; Ganymede is also the only moon with a magnetosphere. Ganymede is far enough away from Jupiter that it only receives around 8 rems per day of radiation from Jupiter's radiation belts, well within the range to be managed with shielding; while Ganymede is also close enough to Jupiter that models indicate it likely experiences significant tidal stresses from Jupiter, which should make geothermal energy and liquid water available underground. Ganymede also possesses water ice, carbonaceous material, metals, and silicates. Ganymede is still fairly deep within Jupiter's gravity well, however, making travel to and from this Ganymede relatively energy-intensive and therefore expensive.
NASA performed a study called HOPE (Revolutionary Concepts for Human Outer Planet Exploration) regarding the future exploration of the solar system. Patrick A. Troutman (NASA Langley Research Center) et al., [Revolutionary Concepts for Human Outer Planet Exploration (HOPE)], accessed May 10, 2006 (.doc format) The target chosen was Callisto. It could be possible to build a surface base that would produce fuel for further exploration of the solar system. Since it is outside of Jupiter's radiation belt and also geologically very stable, it could prove to be a suitable place for a base. This base would also be a centre for exploration of the Jupiter system, for example remote exploration of Europa. It would also be the ideal location for a Jovian system way station that could service spacecraft headed farther into the outer Solar System, using a gravity assist from a close fly-by of Jupiter after departing Callisto.
The 2006 [announcement] by the Keck Observatory that the binary Trojan asteroid 617 Patroclus, and possibly large numbers of other Trojan objects in Jupiter's orbit, are likely composed of water ice, with a layer of dust, suggests that mining water and other volatiles in this region and transporting them elsewhere in the Solar system, perhaps via the Interplanetary Transport Network, may be feasible in the not-so-distant future. This could make colonization of the Moon, Mercury and main-belt asteroids more practical.
The
Robert Zubrin identified Saturn, Uranus and Neptune as "the Persian Gulf of the solar system", as the largest sources of deuterium and helium-3 to drive the pending fusion economy, with Saturn the most important and most valuable of the three, because of its relative proximity, low radiation, and excellent system of moons. Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: The Persian Gulf of the solar system, pp. 161-163, Tarcher/Putnam, 1999, ISBN 1585420360
- Main article: Colonization of Titan
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, and saying "In certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization." Robert Zubrin, Entering Space: Creating a Spacefaring Civilization, section: Titan, pp. 163-166, Tarcher/Putnam, 1999, ISBN 1585420360
The surface of Titan is very young and active, and contains large amounts of water ice and perhaps oceans and canals of liquid organic compounds. It should be able to support a base, but more information regarding Titan's surface and the activities on it is necessary. The thick atmosphere and the weather are also factors to consider.
Incidentally, a widely published expert on terraforming, Christopher McKay, is also a co-investigator on the Huygens probe that landed on Titan in January 2005.
On March 9th, 2006, NASA's Cassini space probe found possible evidence of liquid water on Enceladus. http://www.nasa.gov/mission_pages/cassini/media/cassini-20060309.html According to that article, "pockets of liquid water may be no more than tens of meters below the surface." If these findings are confirmed, it would mean liquid water could be collected much more easily on Enceladus than on, for instance, Europa (see above). Discovery of water, especially liquid water, generally improves a celestial body's consideration for colonization dramatically.
Because Uranus has the lowest escape velocity of the four gas giants, it has been proposed as a mining site for helium-3. If human supervision of the robotic activity proved necessary, one of Uranus' natural satellites might serve as a base. An alternative is to place floating cities in its atmosphere. By using balloons filled with hydrogen, large masses can be suspended underneath at roughly Earth gravity. Saturn and Neptune could be suitable as well, but Jupiter would likely not be, due to its high gravity, escape velocity, and radiation.
Neptune and its satellites could also be used for colonization, but are farther away, and Neptune has a higher surface gravity than Uranus. Its satellites, especially Triton, could also be colonized.
The noted physicist Freeman Dyson identified comets, rather than planets, as the major potential habitat of life in space. Freeman Dyson, "The World, the Flesh, and the Devil", Third J.D. Bernal Lecture, May 1972, reprinted in Communication with Extraterrestrial Intelligence, Carl Sagan, ed., MIT Press, 1973, ISBN 0262690373 It is thought that several trillion comets or iceteroids exist outside the orbit of Uranus. These may harbour all the ingredients for life (water ice and organic compounds) including significant amounts of deuterium, tritium, and helium-3. Estimates indicate the ratio of deuterium to standard hydrogen in the comets to be about 1 part per 10,000 to 100,000, which would provide around 50,000 to 100,000 metric tonnes of deuterium in an average comet, which may be used as fusion fuel to provide sufficient power to a comet colony for thousands of years. Richard P. Terra, "Islands in the Sky: Human Exploration and Settlement of the Oort Cloud", in [[Islands in the Sky: Bold New Ideas for Colonizing Space]], Stanley Schmidt and Robert Zubrin, eds. Wiley, 1996, ISBN 0471135615 Two astrophysicists have also proposed that an average comet may include enough aluminum to create a solar power collector with a radius in the thousands of kilometers, which could collect starlight from the brightest star even when the comet is deep into the Oort Cloud or interstellar space, to provide enough indefinitely sustainable power for a colonized comet with around 500 colonists. Ben R. Finney and Eric M. Jones, eds., Interstellar Migration and the Human Experience, University of California Press, 1986, ISBN 0520058984 Colonies sent to these far flung worldlets could build rotating habitats or live in dug-out spaces and light them with fusion reactors for thousands or millions of years before moving on. It is envisaged that over the eons humanity could migrate to neighbouring star systems, which may have similar clouds, without the need for large interstellar starships, by using comets as slow interstellar vessels with substantial natural resources; and that such interstellar comet colonies could also serve as way-stations for faster, smaller interstellar ships. David G. Stephenson, "Comets and Interstellar Travel", in Journal of the British Interplanetary Society, 36, 1983, pp. 210-214.
Colonization of comets in science fiction
In his Revelation Space series, particularly in the novel Redemption Ark, Alastair Reynolds depicts a future human civilization's most advanced society, the Conjoiners, living in the interior of a comet in the very distant Oort Cloud of another star.
See also
References
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- Main article: Colonization of Titan
Incidentally, a widely published expert on terraforming, Christopher McKay, is also a co-investigator on the Huygens probe that landed on Titan in January 2005.
On March 9th, 2006, NASA's Cassini space probe found possible evidence of liquid water on Enceladus. http://www.nasa.gov/mission_pages/cassini/media/cassini-20060309.html According to that article, "pockets of liquid water may be no more than tens of meters below the surface." If these findings are confirmed, it would mean liquid water could be collected much more easily on Enceladus than on, for instance, Europa (see above). Discovery of water, especially liquid water, generally improves a celestial body's consideration for colonization dramatically.
Because Uranus has the lowest escape velocity of the four gas giants, it has been proposed as a mining site for helium-3. If human supervision of the robotic activity proved necessary, one of Uranus' natural satellites might serve as a base. An alternative is to place floating cities in its atmosphere. By using balloons filled with hydrogen, large masses can be suspended underneath at roughly Earth gravity. Saturn and Neptune could be suitable as well, but Jupiter would likely not be, due to its high gravity, escape velocity, and radiation.
Neptune and its satellites could also be used for colonization, but are farther away, and Neptune has a higher surface gravity than Uranus. Its satellites, especially Triton, could also be colonized.
The noted physicist Freeman Dyson identified comets, rather than planets, as the major potential habitat of life in space. Freeman Dyson, "The World, the Flesh, and the Devil", Third J.D. Bernal Lecture, May 1972, reprinted in Communication with Extraterrestrial Intelligence, Carl Sagan, ed., MIT Press, 1973, ISBN 0262690373 It is thought that several trillion comets or iceteroids exist outside the orbit of Uranus. These may harbour all the ingredients for life (water ice and organic compounds) including significant amounts of deuterium, tritium, and helium-3. Estimates indicate the ratio of deuterium to standard hydrogen in the comets to be about 1 part per 10,000 to 100,000, which would provide around 50,000 to 100,000 metric tonnes of deuterium in an average comet, which may be used as fusion fuel to provide sufficient power to a comet colony for thousands of years. Richard P. Terra, "Islands in the Sky: Human Exploration and Settlement of the Oort Cloud", in [[Islands in the Sky: Bold New Ideas for Colonizing Space]], Stanley Schmidt and Robert Zubrin, eds. Wiley, 1996, ISBN 0471135615 Two astrophysicists have also proposed that an average comet may include enough aluminum to create a solar power collector with a radius in the thousands of kilometers, which could collect starlight from the brightest star even when the comet is deep into the Oort Cloud or interstellar space, to provide enough indefinitely sustainable power for a colonized comet with around 500 colonists. Ben R. Finney and Eric M. Jones, eds., Interstellar Migration and the Human Experience, University of California Press, 1986, ISBN 0520058984 Colonies sent to these far flung worldlets could build rotating habitats or live in dug-out spaces and light them with fusion reactors for thousands or millions of years before moving on. It is envisaged that over the eons humanity could migrate to neighbouring star systems, which may have similar clouds, without the need for large interstellar starships, by using comets as slow interstellar vessels with substantial natural resources; and that such interstellar comet colonies could also serve as way-stations for faster, smaller interstellar ships. David G. Stephenson, "Comets and Interstellar Travel", in Journal of the British Interplanetary Society, 36, 1983, pp. 210-214.
Colonization of comets in science fiction
In his Revelation Space series, particularly in the novel Redemption Ark, Alastair Reynolds depicts a future human civilization's most advanced society, the Conjoiners, living in the interior of a comet in the very distant Oort Cloud of another star.All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.