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The terraforming (literally, "Earth-shaping") of a Planet , Moon , or other body is the Hypothetical process of deliberately modifying its Atmosphere , Temperature , or Ecology to be similar to those of Earth in order to make it Habitable by humans. The term is sometimes used broadly as a synonym for Planetary Engineering in general. The concepts of terraforming are rooted both in Science Fiction and actual Science . The term was probably coined by Jack Williamson in a science-fiction story published in 1942 in '' Astounding Science Fiction '',1 but the actual concept pre-dates this work. Olaf Stapledon 's '' Last And First Men '' (1930)2 provides an example in fiction in which the planet Venus is modified after a long and destructive war with the original inhabitants of the planet. Humans currently do not possess the technological or economic means to terraform another planet or moon. Since space exploration is in its infancy, terraforming techniques remain speculative. Based on experiences with Earth, the Environment of a planet can be altered in a deliberate way; however the feasibility of creating an unconstrained planetary biosphere that mimics Earth on another planet has yet to be verified. Mars is considered by many to be the most likely candidate for terraformation. Much study has gone into the possibility of heating the planet and altering its atmosphere, and NASA has even hosted debates on the subject. However, a multitude of obstacles stand between the present and an active terraforming effort on Mars or any other world. The long timescales and practicality of terraforming are the subject of debate. Other unanswered questions relate to the Ethics , Logistics , Economics , Politics and methodology of altering the environment of an extraterrestrial world. HISTORY OF SCHOLARLY STUDY Carl Sagan , an astronomer and popularizer of science, proposed the planetary engineering of Venus in a 1961 article published in the journal '' Science '' entitled, "The Planet Venus."3 Sagan imagined seeding the atmosphere of Venus with Algae , which would remove Carbon Dioxide and reduce the Greenhouse Effect until surface temperatures dropped to "comfortable" levels. 3 billion years ago, the Earth had a carbon dioxide atmosphere. Blue-green Algae and water evaporation changed the earth's atmosphere into oxygen and hydrogen gas. Later discoveries about the conditions on Venus made this particular approach impossible since Venus has too much atmosphere to process and sequester. Even if atmospheric algae could thrive in the hostile and arid environment of Venus's upper atmosphere, any carbon that was fixed in organic form would be liberated as carbon dioxide again as soon as it fell into the hot lower regions. Sagan also visualized making Mars habitable for human life in "Planetary Engineering on Mars," a 1973 article published in the journal '' Icarus ''.4 Three years later, NASA officially addressed the issue of planetary engineering in a study, but used the term Planetary Ecosynthesis instead.5 The study concluded that it was possible for Mars to support life and be made into a Habitable Planet . That same year, in 1976, one of the researchers, Joel Levine, organized the first conference session on terraforming, which at the time was called "Planetary Modeling." In March 1979, NASA engineer and author James Oberg organized the "First Terraforming Colloquium," a special session on terraforming held at the Lunar and Planetary Science Conference in Houston. Oberg popularized the terraforming concepts discussed at the colloquium to the general public in his 1981 book, ''New Earths''.6 It wasn't until 1982 that the word ''terraforming'' was used in the title of a published journal article. Planetologist Christopher McKay wrote "Terraforming Mars," a paper for the '' Journal Of The British Interplanetary Society ''.7 The paper discussed the prospects of a self-regulating Martian biosphere, and McKay's use of the word has since become the preferred term. In 1984, James Lovelock and Michael Allaby published ''The Greening of Mars''.8 Lovelock's book was one of the first books to describe a novel method of warming Mars, where chlorofluorocarbons are added to the atmosphere. Motivated by Lovelock's book, biophysicist Robert Haynes worked behind the scenes to promote terraforming, and contributed the word Ecopoiesis to its lexicon. Beginning in 1985 , Martyn J. Fogg began publishing several articles on terraforming. He also served as editor for a full issue on terraforming for the ''Journal of the British Interplanetary Society'' in 1991 , and in 1995 published the book ''Terraforming: Engineering Planetary Environments''.9 Fogg also maintains an active website called The Terraforming Information Pages.10 Fogg used the following definitions for different aspects related to terraforming:
Fogg also devised definitions for candidate planets of varying degrees of human compatibility:
Fogg designates Mars as having been a biocompatible planet in its youth, but not being in any of these three categories in its present state, since it could only be terraformed with relatively greater difficulty. Mars Society founder Robert Zubrin produced a plan for a Mars return mission called Mars Direct that would set up a permanent human presence on Mars and steer efforts towards eventual terraformation.11 The principal reason given to pursue terraforming is the creation of an Ecology to support worlds suitable for habitation by humans. However, some researchers believe that Space Habitat s will provide a more economical means for supporting Space Colonization . If research in Nanotechnology and other advanced chemical processes continues apace, it may become feasible to terraform planets in centuries rather than millennia. On the other hand, it may become reasonable to modify humans so that they don't require an Oxygen / Nitrogen atmosphere in a 1 ''g'' Gravity field to live comfortably. That would then reduce the need to terraform worlds, or at least the degree to which other worlds' environments would need to be altered. REQUIREMENTS FOR SUSTAINING TERRESTRIAL LIFE See Also: Planetary habitability The only absolute requirement for life is an energy source but the notion of planetary habitability implies that many other geophysical, geochemical, and astrophysical criteria must be met before the surface of an astronomical body is able to support life. Of particular interest is the set of factors that has sustained complex, multicellular animals and not merely unicellular organisms on this planet. Research and theory in this regard is a component of planetary science and the emerging discipline of astrobiology. Not only are there planetary requirements, there are theories as to the type and age of the star. FURTHER STAGES OF TERRAFORMING See Also: Ecopoiesis Once conditions become more suitable to life from Earth, the importation of microbial life could begin. As conditions approach that of Earth, plant life could also be brought in. This would accelerate the production of oxygen, which theoretically would make the planet eventually able to support animal and human life. PROSPECTIVE PLANETS Mars See Also: Terraforming of Mars See Also: Colonization of Mars There is some scientific debate over whether it would even be possible to terraform Mars, or how stable its climate would be once terraformed. It is possible that over geological timescales - tens or hundreds of millions of years—Mars could lose its water and atmosphere again, possibly to the same processes that reduced it to its current state. Indeed, it is thought that Mars once did have a relatively Earthlike environment early in its history, with a thicker atmosphere and abundant water that was lost over the course of hundreds of millions of years. The exact mechanism of this loss is still unclear, though several mechanisms have been proposed. The lack of a and/or some other greenhouse gases would trap incoming Solar Radiation and the raised temperature would put the greenhouse gases into the atmosphere, the two processes would augment one another. 12 Venus .]] See Also: Terraforming of Venus See Also: Colonization of Venus Terraforming Venus requires two major changes; removing most of the planet's dense 9 MPa carbon dioxide atmosphere and reducing the planet's 500 °C (770 K ) surface temperature. These goals are closely interrelated, since Venus's extreme temperature is due to the greenhouse effect caused by its dense atmosphere. Sequestering the atmospheric carbon would likely solve the temperature problem as well. Venus, unlike Mars, is Tectonic ally active, and could therefore function as a biospherically viable copy of our Earth. Europa (moon) Europa , a moon of Jupiter , is a potential prospect for terraforming. One of the advantages to Europa is the presence of liquid water which could be extremely helpful for the introduction of complex life.13 The difficulties are numerous; Europa is in the middle of a huge radiation belt around Jupiter, and a human would die from the radiation within 10 minutes on the surface. This would require the building of massive radiation deflectors, which is currently impractical. Additionally, this satellite is covered in ice and would have to be heated, and there would need to be a supply of oxygen.14 Other planets and solar system entities See Also: Colonization of the Moon Colonization of Mercury Colonization of the outer solar system Colonization of Ceres Other possible candidates for terraformation include Titan , Mercury , Ganymede , Io , Callisto , Earth's Moon , and even the dwarf planet Ceres . Most, however, have too little mass to hold an atmosphere indefinitely (although it is possible, but not certain, that an atmosphere could remain for tens of thousands of years or be replenished as needed). In addition, aside from the Moon , most of these worlds are so far from the Sun that adding sufficient heat would be much more difficult than even Mars would be. PARATERRAFORMING Also known as the "worldhouse" concept, or domes in smaller versions, paraterraforming involves the construction of a habitable enclosure on a planet which eventually grows to encompass most of the planet's usable area. The enclosure would consist of a transparent roof held one or more kilometres above the surface, pressurized with a breathable atmosphere, and anchored with tension towers and cables at regular intervals. Proponents claim worldhouses can be constructed with technology known since the 1960s. Paraterraforming has several advantages over the traditional approach to terraforming. For example, it provides an immediate payback to investors; the worldhouse starts out small in area (a Domed City for example), but those areas provide habitable space from the start. The paraterraforming approach also allows for a modular approach that can be tailored to the needs of the planet's population, growing only as fast and only in those areas where it is required. Finally, paraterraforming greatly reduces the amount of atmosphere that one would need to add to planets like Mars in order to provide Earthlike atmospheric pressures. By using a solid envelope in this manner, even bodies which would otherwise be unable to retain an atmosphere at all (such as Asteroid s) could be given a habitable environment. The environment under an artificial worldhouse roof would also likely be more amenable to artificial manipulation. It has the disadvantage of requiring a great deal of construction and maintenance activity, the cost of which could be ameliorated to some degree through the use of automated manufacturing and repair mechanisms. A worldhouse could also be more susceptible to catastrophic failure in the event of a major breach, though this risk can likely be reduced by compartmentalization and other active safety precautions. Meteor strikes are a particular concern in the absence of any external atmosphere in which they would burn up before reaching the surface. ETHICAL ISSUES See Also: Ethics of terraforming There is a philosophical debate within biology and ecology as to whether terraforming other worlds is an ethical endeavor. On the pro-terraforming side of the argument, there are those like '', Apogee Books Space Series, 2002, ISBN 1-896522-90-4 ECONOMIC ISSUES The initial cost of such projects as planetary terraforming would be gigantic, and the infrastructure of such an enterprise would have to be built from scratch. Such technology is not yet developed, let alone financially feasible at the moment. John Hickman has pointed out that almost none of the current schemes for terraforming incorporate economic strategies, and most of their models and expectations seem highly optimistic.16 Access to the vast resources of space may make such projects more economically feasible, though the initial investment required to enable easy access to space will likely be tremendous (see Asteroid Mining , Solar Power Satellite s, In-Situ Resource Utilization , Bootstrapping , Space Elevator ). Some advocates of Space Colonization have argued that the same financial investment required to terraform Mars or Venus could produce a larger area of "land" if used to build Space Habitats instead. They argue that a civilization that knows how to live in space can survive anywhere in the solar system, whereas terraforming Mars will only help us to live in one place. Some view terraforming as Planetary Chauvinism . POLITICAL ISSUES There are many potential political issues arising from terraforming a planet, such as who gets to own the extra terrestrial land on the new planet, with contenders being national governments, trans-national organizations like the United Nations , Corporations or individual settlers themselves. Such settlements may become part of national disputes as countries try to make parts of other planets part of their own national territory. Rivalries between nations continue to be a primary motivation for shaping Space projects.17 POPULAR CULTURE See Also: Terraforming in popular culture Terraforming is a common concept in science fiction, ranging from television, movies, and video games. The concept of changing a planet for habitation precedes the use of the word 'terraforming', with H. G. Wells describing a reverse-terraforming, where aliens in his story '' The War Of The Worlds '' change Earth for their own benefit. Also, Olaf Stapledon 's '' Last And First Men '' (1930) provides the first example in fiction in which Venus is modified, after a long and destructive war with the original inhabitants, who naturally object to the process. Terraforming has also been explored on television and in feature films, most prominently and famously in the '' Star Trek '' universe. In the '' Star Trek '' movie '' The Wrath Of Khan '', the film's antagonist Khan steals the " Genesis Device ", a device developed to quickly terraform barren planets, and wields it as a weapon (the Genesis Torpedo), threatening to use it against already populated planets in order to conquer the Galaxy . In Joss Whedon's short-lived hit television series '' Firefly '', and its feature film sequel '' Serenity '', giant "terraformers" (ships or factories designed to generate atmosphere and perform other functions of terraforming) were used to transform the ecosystems of hundreds of planets and moons across a huge solar system into human-livable environments. It is shown in the movies '' Alien '' and '' Aliens ''. In the first film, the atmosphere of LV-426 is unbreathable and John Hurt 's character must wear an environment suit; sixty years later an atmospheric factory has been utilized to withdraw sulphur and replace it with oxygen; producing a stormy but breathable atmosphere. In the anime '' Cowboy Bebop '' humanity has terraformed dozens of moons and planets after a hyperspace gate accident fractured the Moon, raining debris on Earth. Asteroids have also been colonized to sustain human life. Also, the manga and anime series Aria takes place on a terraformed Mars. In '' Stargate SG1 '' episode " Scorched Earth " an alien ship terraforms a planet recently inhabited by Enkarans with the help of humans. SEE ALSO
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