Editing Terraforming (section)

==History of scholarly study==
The astronomer [[Carl Sagan]] proposed the [[planetary engineering]] of Venus in an article published in the journal ''[[Science (journal)|Science]]'' in 1961.<ref name="The Planet Venus">{{cite journal| journal=Science| year=1961|doi=10.1126/science.133.3456.849  |title=The Planet Venus| first=Carl| last=Sagan|bibcode = 1961Sci...133..849S| volume=133| issue=3456| pages=849–58| pmid=17789744 }}</ref> Sagan imagined seeding the atmosphere of [[Venus]] with [[algae]], which would convert water, nitrogen and carbon dioxide into [[organic compound]]s. As this process removed [[carbon dioxide]] from the atmosphere, the [[greenhouse effect]] would be reduced until surface temperatures dropped to "comfortable" levels. The resulting plant matter, Sagan proposed, would be [[Pyrolysis|pyrolyzed]] by the high surface temperatures of Venus, and thus be [[Carbon sequestering|sequestered]] in the form of "graphite or some involatile form of carbon" on the planet's surface.<ref name="Sagan276">Sagan 1997, pp. 276–7.</ref> However, later discoveries about the conditions on [[Venus]] made this particular approach impossible. One problem is that the clouds of Venus are composed of a highly concentrated [[sulfuric acid]] solution. Even if atmospheric algae could thrive in the hostile environment of Venus's upper atmosphere, an even more insurmountable problem is that its atmosphere is simply far too thick: the high atmospheric pressure would result in a "atmosphere of nearly pure molecular oxygen"<ref name="Sagan276"/> at high pressure. This volatile combination could not be sustained through time. Any carbon that had been reduced by photosynthesis would be quickly oxidized in this atmosphere through combustion, "short-circuiting" the terraforming process.<ref name="Sagan276"/>

Sagan also visualized making [[Mars]] habitable for human life in an article published in the journal ''[[Icarus (journal)|Icarus]]'', "Planetary Engineering on Mars" (1973).<ref name=":3">{{cite journal |last1=Sagan |first1=Carl |title=Planetary engineering on Mars |journal=Icarus |date=December 1973 |volume=20 |issue=4 |pages=513–514 |doi=10.1016/0019-1035(73)90026-2 |bibcode=1973Icar...20..513S }}</ref> Three years later, NASA addressed the issue of planetary engineering officially in a study, but used the term "planetary ecosynthesis" instead.{{sfn|Averner|MacElroy|1976|pp=front cover, study results}} The study concluded that it was possible for Mars to support life and be made into a [[Planetary habitability|habitable planet]]. The first conference session on terraforming, then referred to as "Planetary Modeling", was organized that same year.

In March 1979, NASA engineer and author [[James Oberg]] organized the First Terraforming Colloquium, a special session at the [[Lunar and Planetary Science Conference]] in Houston. Oberg popularized the terraforming concepts discussed at the colloquium to the general public in his book ''New Earths'' (1981).<ref>{{cite book|last=Oberg| first=James Edward| year=1981| title=New Earths: Restructuring Earth and Other Planets| publisher=Stackpole Books, Harrisburg, Pennsylvania}}</ref> Not until 1982 was the word ''terraforming'' 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]]''.<ref>{{cite journal |last1=McKay |first1=Christopher P. |title=On Terraforming Mars |journal=Extrapolation |date=January 1982 |volume=23 |issue=4 |pages=309–314 |doi=10.3828/extr.1982.23.4.309 }}</ref> The paper discussed the prospects of a self-regulating Martian biosphere, and the word "terraforming" has since become the preferred term.{{citation needed|date=July 2021}}

In 1984, [[James Lovelock]] and Michael Allaby published ''The Greening of Mars''.<ref>{{cite book|year=1984| title=The Greening of Mars|url=https://archive.org/details/greeningofmars00mich|url-access=registration|author1=Lovelock, James  |author2=Allaby, Michael | publisher=Warner Books| isbn=9780446329675|name-list-style=amp }}</ref> Lovelock's book was one of the first to describe a novel method of warming Mars, where [[chlorofluorocarbon]]s (CFCs) are added to the atmosphere to produce a strong greenhouse effect.

Motivated by Lovelock's book, biophysicist [[Robert Haynes (geneticist)|Robert Haynes]] worked behind the scenes{{citation needed|date=December 2016}} to promote terraforming, and contributed the [[neologism]] '''''Ecopoiesis''''',<ref>Haynes, RH (1990), "Ecce Ecopoiesis: Playing God on Mars", in MacNiven, D. (1990-07-13), ''Moral Expertise: studies in practical and professional ethics,'' Routledge. pp. 161–163. {{ISBN|0-415-03576-7}}.</ref> forming the word from the Greek {{lang|grc|οἶκος}}, ''oikos'', "house",<ref>{{LSJ|oi{{=}}kos1|οἶκος|ref}}.</ref> and {{lang|grc|ποίησις}}, ''poiesis'', "production".<ref>{{LSJ|poi/hsis|ποίησις|shortref}}.</ref> Ecopoiesis refers to the ''origin of an ecosystem''. In the context of space exploration, Haynes describes ecopoiesis as the "fabrication of a sustainable ecosystem on a currently lifeless, sterile planet". Fogg defines ecopoiesis as a type of [[planetary engineering]] and is one of the first stages of terraformation. This primary stage of ecosystem creation is usually restricted to the initial seeding of microbial life.<ref name="EPE">{{cite book| last=Fogg| first=Martyn J.| year=1995| title=Terraforming: Engineering Planetary Environments| publisher=SAE International, Warrendale, PA.}}</ref> A 2019 opinion piece by Lopez, Peixoto and Rosado has reintroduced microbiology as a necessary component of any possible colonization strategy based on the principles of microbial symbiosis and their beneficial [[ecosystem service]]s.<ref>{{cite journal |last1=Lopez |first1=Jose V |last2=Peixoto |first2=Raquel S |last3=Rosado |first3=Alexandre S |title=Inevitable future: space colonization beyond Earth with microbes first |journal=FEMS Microbiology Ecology |date=22 August 2019 |volume=95 |issue=10 |doi=10.1093/femsec/fiz127 |pmid=31437273 |pmc=6748721 }}</ref> As conditions approach that of Earth, plant life could be brought in, and this will accelerate the production of oxygen, theoretically making the planet eventually able to support animal life.

===Aspects and definitions===
In 1985, [[Martyn Fogg]] started 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 1992. In his book ''Terraforming: Engineering Planetary Environments'' (1995), Fogg proposed the following definitions for different aspects related to terraforming:<ref name="EPE" />

* [[Planetary engineering]]: the application of technology for the purpose of influencing the global properties of a planet.
* [[Climate engineering|Geoengineering]]: planetary engineering applied specifically to Earth. It includes only those macro engineering 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 extraterrestrial planetary environment to support life as we know it. The ultimate achievement in terraforming would be to create an open planetary [[ecosystem]] emulating all the functions of the [[biosphere]] of Earth, one that would be fully habitable for human beings.

Fogg also devised definitions for candidate planets of varying degrees of human compatibility:<ref>Fogg, 1996</ref>

* Habitable planet (HP): A world with an environment sufficiently similar to Earth's 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 suggests that [[Mars]] was a biologically compatible planet in its youth, but is not now in any of these three categories, because it can only be terraformed with greater difficulty.<ref>{{Cite book|title=Terraforming : engineering planetary environments|last=Fogg|first=Martyn J.|date=1995|publisher=Society of Automotive Engineers|isbn=1560916095|oclc=32348444}}</ref>