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.^[1][2] Major features of the Solar System (not to scale, from left to right): Pluto, Neptune, Uranus, Saturn, a comet, Jupiter, Ceres which lies in the asteroid belt, the Sun, Mercury, Venus, Earth & Moon, and Mars. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Uncrewed aerostats can carry instruments and sensors for long durations that are impractical for humans and other aircraft. ... Helium-3 is a non-radioactive and light isotope of helium. ...

The Jovian system

The Jovian 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.^[3] Adjectives: Jovian Atmosphere Surface pressure: 70 kPa Composition: ~86% Hydrogen ~14% Helium 0. ... A gravity well is the scientific/science fictional term for the distortion in space-time caused by a massive body such as a planet. ... Radiation Hazard symbol. ... Atmospheric characteristics Atmospheric pressure trace Sulfur dioxide 90% Io (eye-oe, IPA: , Greek Ῑώ) is the innermost of the four Galilean moons of Jupiter. ...

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.^[3]

Jupiter has an atmospheric depth with the same pressure as Earth at 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 nominal acceleration due to gravity at sea level on the Earths surface, also known as standard gravity, is defined as exactly 9. ...

Europa

Main article: Colonization of Europa

The Artemis Project designed a plan to colonize Europa.^[4][5] 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. The Artemis Project designed a plan to colonize Europa. ... The Artemis Project is a private venture to establish a permanent, self-supporting community on the Moon. ... Atmospheric characteristics Atmospheric pressure 1 µPa Oxygen 100% Europa (ew-roe-pÉ™, IPA:  ; Greek Ευρώπη) is a moon of the planet Jupiter. ... It has been suggested that this article or section be merged into Updraft and Downdraft. ...

Ganymede

Ganymede is the largest moon in the Solar System, making it a possible target for colonization. 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 Ganymede relatively energy-intensive and therefore expensive.^[3] Atmospheric characteristics Atmospheric pressure trace Oxygen 100% Ganymede (gan-ə-meed, IPA: ; Greek Γανυμήδης) is Jupiters largest moon, and indeed the largest moon in the entire solar system; it is larger in diameter than Mercury but only about half its mass. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ...

Callisto

NASA performed a study called HOPE (Revolutionary Concepts for Human Outer Planet Exploration) regarding the future exploration of the solar system.^[6] 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 Jovian 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.^[3] For other uses, see NASA (disambiguation). ... This article or section does not cite its references or sources. ...

Trojan asteroids

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 proposed 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 Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ... Image of the Trojan asteroids in front of and behind Jupiter along its orbital path. ... 617 Patroclus is the second Jovian Trojan asteroid to be discovered. ... Artists concept of the Interplanetary Transport Network. ... An artists rendering of a lunar base. ... Mercury Mercury has been suggested as one possible target for space colonization of the inner solar system, along with Mars, Venus, the Moon and the asteroid belt. ... Asteroid 243 Ida with its moon, Dactyl. ...

The Saturnian system

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.^[7] Robert Zubrin is an aerospace engineer and author best known for his advocacy of manned Mars exploration. ... Adjective Saturnian Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Adjective Uranian Atmospheric characteristics Atmospheric pressure 120 kPa (at the cloud level) Hydrogen 83% Helium 15% Methane 1. ... Note: This article contains special characters. ... It has been suggested that Persian Gulf States be merged into this article or section. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...

Titan

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."^[8] The surface of Titan is mostly uncratered and thus inferred to be very young and active, and probably composed of mostly water ice, and lakes of liquid hydrocarbons (methane/ethane) in its polar regions. While the temperature is cryogenic (95 K) 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, such as potential flash floods, are also factors to consider. No solid plans or studies have been made regarding manned missions to Titan, or colonization of that world, at least not outside of science fiction. ... Titan (tye-tən, IPA: , Greek Τιτάν) or Saturn VI is the largest moon of Saturn and the second largest moon in the solar system,[3] after Jupiters moon Ganymede. ...

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. Artists conception of a terraformed Mars in four stages of development. ... Dr. Christopher McKay of NASA Ames Research Center. ... The Huygens probe, supplied by the European Space Agency (ESA) and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry probe carried to Saturns moon Titan as part of the Cassini-Huygens mission. ...

Enceladus

On March 9th, 2006, NASA's Cassini space probe found possible evidence of liquid water on Enceladus.^[9] 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. An alternative model of Enceladus' activity is the decomposition of methane/water clathrates - a process requiring lower temperatures than liquid water eruptions. The relatively higher density of Enceladus indicates a larger than Saturnian average silicate core that should provide materials for base operations. For other uses, see NASA (disambiguation). ... Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... [5] Atmospheric characteristics Pressure trace, significant spatial variability [6], [7] Water vapour 91% [8] Carbon dioxide 3. ...

Uranus

Because Uranus has the lowest escape velocity of the four gas giants, it has been proposed as a mining site for helium-3.^[2] 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^{[citation needed]} 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. Adjective Uranian Atmospheric characteristics Atmospheric pressure 120 kPa (at the cloud level) Hydrogen 83% Helium 15% Methane 1. ... Space Shuttle Atlantis launches on mission STS-71 In physics, for a given gravitational field and a given position, the escape velocity is the minimum speed an object without propulsion, at that position, needs to have to move away indefinitely from the source of the field, as opposed to falling... Uranus has 27 known moons. ... In science fiction, floating cities are settlements that use buoyancy to remain in the atmosphere of a planet. ... This article is about the chemistry of hydrogen. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ...

Neptune

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. Triton's surface shows signs of extensive geological activity implying a sub-surface ocean, perhaps of ammonia/water^[10]. Such geothermal energy would make colonising a cryogenic world like Triton feasible. Note: This article contains special characters. ... Triton (trye-tÉ™n, IPA: , Greek Τρίτων), or Neptune I, is the planet Neptunes largest moon. ...

Kuiper Belt and Oort Cloud

See also Colonization of Pluto

The noted physicist Freeman Dyson identified comets, rather than planets, as the major potential habitat of life in space.^[11] It is thought that several trillion comets or iceteroids exist outside the orbit of Neptune. 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 to 100 kilotonnes 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.^[12] 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.^[13] 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.^[14] Plutos Mantle, Crust, and Outer core // Pluto is an ideal planet to colonilize because its land is consistant with the rock of earth and the ice made of H2O in the crust and mantle of the planet. ... ... Freeman John Dyson (born December 15, 1923) is an English-born physicist and mathematician, famous for his work in quantum mechanics, nuclear weapons design and policy, and for his serious theorizing in futurism and science fiction concepts, including the search for extraterrestrial intelligence. ... Comet Hale-Bopp Comet McNaught as seen from Swifts Creek, Victoria, Australia on 23 January 2007 A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of... For the astrological concept, see Planets in astrology. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... The outer solar system (as opposed to the outer planets) is that part of the Solar System which begins at roughly the orbit of Neptune and terminates at maximum orbit distance, approximately one light year from the sun in terms of orbital measurements. ... Water Ice, sometimes referred to as Italian Water Ice, is a snack item served during the summer. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and elementary carbon are not organic (see below for more on the definition controversy... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of planet Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ... Helium-3 is a non-radioactive and light isotope of helium. ... This article is about the chemistry of hydrogen. ... Kilo (symbol: k) is a prefix in the SI system denoting 103 or 1000. ... A tonne or metric ton (symbol t), sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Wikipedia does not yet have an article with this exact name. ... This article is about the vehicle for interstellar travel. ...

See also

• Floating cities
• Solar System in fiction

The Artemis Project designed a plan to colonize Europa. ... No solid plans or studies have been made regarding manned missions to Titan, or colonization of that world, at least not outside of science fiction. ... Plutos Mantle, Crust, and Outer core // Pluto is an ideal planet to colonilize because its land is consistant with the rock of earth and the ice made of H2O in the crust and mantle of the planet. ...

References