Artist's conception of a terraformed Mars in four stages of development.
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:
★ Planetary Engineering: the application of technology for the purpose of influencing the global properties of a planet.
★ Geoengineering: planetary engineering applied specifically to the Earth. It includes only those macroengineering concepts that deal with the alteration of some global parameter, such as the greenhouse effect, atmospheric composition, insolation or impact flux.
★ Terraforming: a process of planetary engineering, specifically directed at enhancing the capacity of an extra-terrestrial planetary environment to support life. The ultimate in terraforming would be to create an uncontained planetary biosphere emulating all the functions of the biosphere of the Earth, one that would be fully habitable for human beings.
★ Astrophysical Engineering: taken to represent proposed activities, relating to future habitation, that are envisaged to occur on a scale greater than that of "conventional" planetary engineering.
Fogg also devised definitions for candidate planets of varying degrees of human compatibility:
★ 'Habitable Planet' (HP): A world with an environment sufficiently similar to the Earth as to allow comfortable and free human habitation.
★ 'Biocompatible Planet' (BP): A planet possessing the necessary physical parameters for life to flourish on its surface. If initially lifeless, then such a world could host a biosphere of considerable complexity without the need for terraforming.
★ 'Easily Terraformable Planet' (ETP): A planet that might be rendered biocompatible, or possibly habitable, and maintained so by modest planetary engineering techniques and with the limited resources of a starship or robot precursor mission.
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 habitats 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
Main articles: 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.
Photorealistic conception of a terraformed Mars. In the middle showing the Mariner Bay which was once the Mariner Valley and way up in the north part of the arctic Acidalia Planitia Sea.
Further stages of terraforming
Main articles: 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
Artist's conception of a terraformed Mars in three stages of development.
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
magnetosphere surrounding Mars may have allowed the
solar wind to erode the atmosphere, the relatively low gravity of Mars helping to accelerate the loss of lighter gases to space. The lack of
plate tectonics on Mars is another possibility, preventing the recycling of gases locked up in sediments back into the atmosphere. The core of Mars, which is made of mostly Iron, originally held up the magnetic field of Mars. However, once the core cooled down, the magnetic force weakened. The lack of magnetic field and geologic activity may both be a result of Mars's smaller size allowing its interior to cool more quickly than Earth's, though the details of such processes are still unrealized. Re-heating the core of Mars is considered an impractical solution; one only theoretically practical (but still impossible) method would be to hold some sort of giant 'magnifying glass' over the planet to melt it, and possibly re-liquify the core. However, none of these processes are likely to be significant over the typical lifespan of most animal species, or even on the timescale of human civilization, and the slow loss of atmosphere could possibly be counteracted with ongoing low-level artificial terraforming activities. Terraforming Mars would entail two major interlaced changes: building the atmosphere and heating it. Since a thicker atmosphere of
carbon dioxide 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
Artist's conception of a terraformed
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
tectonically 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
Artist's conception of what the Moon might look like terraformed. As seen from Earth.
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
asteroids) 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
Main articles: 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
Robert Zubrin,
Martyn J. Fogg, and
Richard L. S. Taylor who believe that it is humanity's moral obligation to make other worlds suitable for life, as a continuation of the history of life transforming the environments around it on Earth.
[15][16] They also point out that Earth would eventually be destroyed if nature takes its course, so that humanity faces a very long-term choice between terraforming other worlds or allowing all terrestrial life to become extinct. In any case, terraforming totally barren planets, it is asserted, is not morally wrong as it does not affect any other life. Some more cautious thinkers believe terraforming would be an unethical interference in nature, and that given humanity's past treatment of the Earth, other planets may be better off without human interference. Still others strike a middle ground, such as
Christopher McKay, who argues that terraforming is ethically sound only once we have completely assured that an alien planet does not harbor life of its own; but that if it does, while we should not try to reshape the planet to our own use, we should engineer the planet's environment to artificially nurture the alien life and help it thrive and coevolve.
[17]
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.
[18] 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 satellites,
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.
[19]
Popular culture
Main articles: 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
★
Planetary habitability
★
Globus Cassus
★
Extrasolar planets
★
Project Genesis
★
Weather control
★
Space colonization
★
Futurology
References
1. Science Fiction Citations: terraforming
2. Last and First Men, , Olaf, Stapledon, , 1930,
3. The Planet Venus, , Carl, Sagan, Science, 1961
4. Planetary Engineering on Mars, , Carl, Sagan, Icarus, 1973
5. On the Habitability of Mars: An Approach to Planetary Ecosynthesis, , M, Averner, NASA SP-414, 1976
6. New Earths: Restructuring Earth and Other Planets, , James Edward, Oberg, Stackpole Books, Harrisburg, PA, 1981,
7. Terraforming Mars, , Christopher, McKay, Journal of the British Interplanetary Society, 1982
8. The Greening of Mars, , , , , 1984,
9. Terraforming: Engineering Planetary Environments, , Martyn J., Fogg, SAE International, Warrendale, PA, 1995,
10. The Terraforming Information Pages
11. Building a Solid Case
12. Technological Requirements for Terraforming Mars
13. Terraforming: Human Destiny or Hubris?
14. Humans on Europa: A Plan for Colonies on the Icy Moon
15. Robert Zubrin, ''The Case for Mars: The Plan to Settle the Red Planet and Why We Must'', pp. 248-249, Simon & Schuster/Touchstone, 1996, ISBN 0-684-83550-9
16. The Ethical Dimensions of Space Settlement
17. Christopher McKay and Robert Zubrin, "Do Indigenous Martian Bacteria have Precedence over Human Exploration?", pp. 177-182, in '', Apogee Books Space Series, 2002, ISBN 1-896522-90-4
18. The Political Economy of Very Large Space Projects
19. China's Moon Quest Has U.S. Lawmakers Seeking New Space Race
External links
★
Red Colony
★
Terraformers Society of Canada
★
Visualizing the steps of solar system terraforming
★
Research Paper: Technological Requirements for Terraforming Mars
★
An approach to terraforming Venus
★
The Terraforming Information Pages
★
The Terraforming of Worlds
★
Terraformation de Mars
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