Editing Planetary engineering (section)

==Terraforming==
{{Main|Terraforming}}
[[File:SRMtemperature-projections.jpg|thumb|Projected temperature and precipitation changes relative to preindustrial; end-of-century response without (a) and with (b) geoengineering to avoid temperature rise above 1.5C.<ref>{{cite journal |last1=MacMartin |first1=Douglas G. |last2=Ricke |first2=Katharine L. |last3=Keith |first3=David W. |title=Solar geoengineering as part of an overall strategy for meeting the 1.5°C Paris target |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |date=13 May 2018 |volume=376 |issue=2119 |page=20160454 |doi=10.1098/rsta.2016.0454 |pmid=29610384 |pmc=5897825 |bibcode=2018RSPTA.37660454M }}</ref>]]
[[File:Terraforming_of_Mars.jpg|thumb|A theoretical design for a power station on Mars. Terraforming designs are not yet planned.]]
Terraforming is the process of modifying the [[atmosphere]], [[temperature]], surface topography or [[ecology]] of a planet, moon, or other body in order to replicate the environment of Earth.

=== Technologies ===
A common object of discussion on potential terraforming is the planet Mars. To terraform Mars, humans would need to create a new atmosphere, due to the planet's high carbon dioxide concentration and low atmospheric pressure. This would be possible by introducing more greenhouse gases to below "freezing point from indigenous materials".<ref name="Pollack & Sagan 1993">{{cite book |last1=Pollack |first1=James B. |last2=Sagan |first2=Carl |chapter=Planetary engineering |pages=921–950 |chapter-url=http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources33.pdf |archive-url=https://web.archive.org/web/20100624205541/http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources33.pdf |archive-date=24 June 2010 |editor1-last=Lewis |editor1-first=John S. |editor2-last=Matthews |editor2-first=Mildred Shapley |editor3-last=Guerrieri |editor3-first=Mary L. |title=Resources of Near-Earth Space |date=1993 |publisher=University of Arizona Press |isbn=978-0-8165-1404-5 }}</ref> To terraform Venus, carbon dioxide would need to be converted to graphite since Venus receives twice as much sunlight as Earth. This process is only possible if the greenhouse effect is removed with the use of "high-altitude absorbing fine particles" or a sun shield, creating a more habitable Venus.<ref name="Pollack & Sagan 1993"/>

NASA has defined categories of habitability systems and technologies for terraforming to be feasible.<ref name=":1">{{Cite web |title=Habitats, Habitability, and Human Factors |url=https://sbir.nasa.gov/content/habitats-habitability-and-human-factors |access-date=5 November 2021 |website=NASA SBIR & STTR Program |archive-date=27 October 2021 |archive-url=https://web.archive.org/web/20211027102422/https://sbir.nasa.gov/content/habitats-habitability-and-human-factors |url-status=live }}</ref> These topics include creating power-efficient systems for preserving and packaging  food for crews, preparing and cooking foods, dispensing water, and developing facilities for rest, trash and recycling, and areas for crew hygiene and rest.<ref name=":1" />

=== Feasibility ===
A variety of planetary engineering challenges stand in the way of terraforming efforts. The atmospheric terraforming of Mars, for example, would require "significant quantities of gas" to be added to the Martian atmosphere.<ref name=":2">{{cite journal |last1=Jakosky |first1=Bruce M. |last2=Edwards |first2=Christopher S. |title=Inventory of {{CO2}} available for terraforming Mars |journal=Nature Astronomy |date=August 2018 |volume=2 |issue=8 |pages=634–639 |doi=10.1038/s41550-018-0529-6 |bibcode=2018NatAs...2..634J |s2cid=133894463 }}</ref> This gas has been thought to be stored in solid and liquid form within Mars' polar ice caps and underground reservoirs. It is unlikely, however, that enough {{CO2}} for sufficient atmospheric change is present within Mars' polar deposits, and liquid {{CO2}} could only be present at warmer temperatures "deep within the crust".<ref name=":2" /> Furthermore, sublimating the entire volume of Mars' polar caps would increase its current atmospheric pressure to 15 millibar, where an increase to around 1000 millibar would be required for habitability.<ref name=":2" /> For reference, Earth's average sea-level pressure is [[Atmospheric pressure|1013.25 mbar]].

First formally proposed by astrophysicist Carl Sagan, the terraforming of Venus has since been discussed through methods such as organic molecule-induced carbon conversion, sun reflection, increasing planetary spin, and various chemical means.<ref name=terra1>{{cite journal | last1 = Fogg | first1 = M. J. | year = 1987 | title = The Terraforming of Venus | journal = Journal of the British Interplanetary Society | volume = 40 | pages = 551–564 | bibcode=1987JBIS...40..551F}}</ref> Due to the high presence of sulfuric acid and solar wind on Venus, which are harmful to organic environments, organic methods of carbon conversion have been found unfeasible.<ref name=terra1/> Other methods, such as solar shading, hydrogen bombardment, and magnesium-calcium bombardment are theoretically sound but would require large-scale resources and space technologies not yet available to humans.<ref name=terra1/>

=== Ethical considerations ===
While successful terraforming would allow life to prosper on other planets, philosophers have debated whether this practice is morally sound. Certain ethics experts suggest that planets like Mars hold an intrinsic value independent of their utility to humanity and should therefore be free from human interference.<ref name=":6">{{Cite web |title=The Ethics of Terraforming {{!}} Issue 38 |url=https://philosophynow.org/issues/38/The_Ethics_of_Terraforming |access-date=5 November 2021 |website=Philosophy Now |archive-date=5 November 2021 |archive-url=https://web.archive.org/web/20211105014517/https://philosophynow.org/issues/38/The_Ethics_of_Terraforming |url-status=live }}</ref> Also, some argue that through the steps that are necessary to make Mars habitable - such as fusion reactors, space-based solar-powered lasers, or spreading a thin layer of soot on Mars' polar ice caps - would deteriorate the current aesthetic value that Mars possesses.<ref>{{cite journal |last1=Sparrow |first1=Robert |title=The Ethics of Terraforming |journal=Environmental Ethics |date=Fall 1999 |volume=21 |issue=3 |pages=227–245 |doi= 10.1007/978-90-481-9920-4_124 |url=https://robsparrow.com/wp-content/uploads/The-ethics-of-terraforming.pdf |access-date=April 21, 2023}}</ref> This calls into question humanity's intrinsic ethical and moral values, as it raises the question of whether humanity is willing to eradicate the current ecosystem of another planet for their benefit.<ref>{{cite journal |last1=Sparrow |first1=Robert |title=The Ethics of Terraforming |journal=Environmental Ethics |date=Fall 1999 |volume=21 |issue=3 |pages=227–245 |doi=10.1007/978-90-481-9920-4_124 |url=https://robsparrow.com/wp-content/uploads/The-ethics-of-terraforming.pdf |access-date=April 21, 2023}}</ref> Through this ethical framework, terraforming attempts on these planets could be seen to threaten their intrinsically valuable environments, rendering these efforts unethical.<ref name=":6" />