View source for Terraforming of Mars

{{Short description|Hypothetical modification of Mars into an Earth-like habitable planet}}
{{About|the technological process|the board game|Terraforming Mars (board game)}}
{{Use mdy dates|date=May 2018}}
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[[File:Terraforming of Mars.gif|thumb|upright=1.4|alt=A series of four illustrations of a planet, each successive one featuring more liquid water, vegetation, clouds, and atmospheric haze|Artist's conception of the process of terraforming [[Mars]].]]

The '''terraforming of Mars''' or the '''terraformation of Mars''' is a hypothetical procedure that would consist of a [[planetary engineering]] project or concurrent projects aspiring to transform [[Mars]] from a planet hostile to life to one that could sustainably [[colonization of Mars|host humans]] and other lifeforms free of protection or mediation. The process would involve the modification of the planet's extant [[climate of Mars|climate]], [[atmosphere of Mars|atmosphere]], and surface through a variety of resource-intensive initiatives, as well as the installation of a novel [[Ecosystem|ecological system]] or systems.<ref>{{cite book |last1=Beech |first1=Martin |last2=Seckbach |first2=Joseph |last3=Gordon |first3=Richard |title=Terraforming Mars |date=2022 |publisher=Scrivener publishing |location=Hoboken Beverly |doi=10.1002/9781119761990 |isbn=9781119761969 |url=https://onlinelibrary.wiley.com/doi/book/10.1002/9781119761990}}</ref>

Justifications for choosing Mars over other potential terraforming targets include the presence of water and a geological history that suggests it once harbored a dense atmosphere similar to Earth's. Hazards and difficulties include low gravity, toxic soil, low light levels relative to Earth's, and the lack of a [[magnetic field]].

The terraforming of Mars is considered to be infeasible using present-day technology.<ref>{{Cite web|url=https://www.nasa.gov/news-release/mars-terraforming-not-possible-using-present-day-technology/|title=Mars Terraforming Not Possible Using Present-Day Technology - NASA}}</ref><ref>{{Cite web|url=https://www.planetary.org/articles/can-we-make-mars-earth-like-through-terraforming|title=Can we make Mars Earth-like through terraforming?|website=The Planetary Society}}</ref> Disagreement exists about whether [[hypothetical technology|future technology]] should render the planet habitable. Reasons for supporting terraforming the planet include allaying concerns about [[resource consumption]] and [[resource depletion|depletion]] on Earth and arguments that the altering and subsequent or concurrent settlement of other planets decreases the odds of [[human extinction|humanity's extinction]]. Reasons for objecting to terraforming the planet include [[ethics of terraforming|ethical concerns about terraforming]], and the considerable energy and resource costs that such an undertaking would involve.

== Motivation and side effects ==
{{Further|Ethics of terraforming}}

[[File:Mars Food Production - Bisected.jpg|thumb|Illustration of plants growing in a hypothetical Mars base.<ref name="keeter-20180206">{{Cite web |last=Keeter |first=Bill |date=February 6, 2018 |title=ISS Daily Summary Report – 2/06/2018 |url=https://blogs.nasa.gov/stationreport/2018/02/06/iss-daily-summary-report-2062018/ |url-status=live |archive-url=https://web.archive.org/web/20220119173434/https://blogs.nasa.gov/stationreport/2018/02/06/iss-daily-summary-report-2062018/ |archive-date=January 19, 2022 |access-date=May 26, 2019 |publisher=[[NASA]]}}</ref>]]

Future population growth, demand for resources, and an alternate solution to the [[doomsday argument]] may require human colonization of [[astronomical object|bodies]] other than [[Earth]], such as [[Mars]], the [[Moon]], and other objects. [[Space colonization]] would facilitate harvesting the [[Solar System]]'s energy and material resources.<ref name="MTS-1994">{{cite book|last=Savage|first=Marshall Thomas|title=The Millennial Project: Colonizing the Galaxy in Eight Easy Steps|url=https://books.google.com/books?id=EgyzQgAACAAJ|year=1992|publisher=[[Little, Brown and Company]]|isbn=978-0-316-77163-4|access-date=April 19, 2018|archive-date=July 2, 2019|archive-url=https://web.archive.org/web/20190702083956/https://books.google.com/books?id=EgyzQgAACAAJ|url-status=live}}</ref>

In many aspects, Mars is the most Earth-like of all the other planets in the Solar System.{{Citation needed|date=July 2024}} It is thought<ref name="Space-20130408">{{Cite news |last=Wall |first=Mike |date=April 8, 2013 |title=Most of Mars' Atmosphere Is Lost in Space |url=https://www.space.com/20560-mars-atmosphere-lost-curiosity-rover.html |url-status=live |archive-url=https://web.archive.org/web/20160130143450/http://www.space.com/20560-mars-atmosphere-lost-curiosity-rover.html |archive-date=January 30, 2016 |access-date=April 9, 2013 |work=[[Space.com]] }}</ref> that Mars had a more Earth-like environment early in its [[geological history of Mars|geological history]], with a thicker [[atmosphere]] and abundant water that was lost over the course of hundreds of millions of years through [[atmospheric escape]]. Given the foundations of similarity and proximity, Mars would make one of the most plausible terraforming targets in the Solar System.

Side effects of terraforming include the potential displacement or destruction of any [[Life on Mars|indigenous life]] if such life exists.<ref>{{cite web|url=http://www.escapistmagazine.com/articles/view/video-games/columns/criticalintel/12238-Bungie-s-Destiny-and-the-Science-of-Terraforming.3|title=Bungie's Destiny and the Science of Terraforming – Critical Intel – The Escapist|date=September 11, 2014|work=The Escapist|access-date=June 2, 2015|archive-date=September 24, 2015|archive-url=https://web.archive.org/web/20150924034011/http://www.escapistmagazine.com/articles/view/video-games/columns/criticalintel/12238-Bungie-s-Destiny-and-the-Science-of-Terraforming.3|url-status=live}}</ref><ref name="fogg-1999">{{Cite conference |last=Fogg |first=Martyn J. |date=October 1999 |title=The Ethical Dimensions of Space Settlement |url=http://www.users.globalnet.co.uk/~mfogg/EthicsDTP.pdf |conference=50th International Astronautical Congress |location=Amsterdam, The Netherlands |publisher=[[International Astronautical Federation]] |id=IAA-99-IAA.7.1.07 |archive-url=https://web.archive.org/web/20170923000050/http://www.users.globalnet.co.uk/%7Emfogg/EthicsDTP.pdf |archive-date=September 23, 2017 |url-status=live }}</ref><ref name="igem-ethics">{{Cite web |year=2010 |title=The ethics of terraforming Mars: a review |url=http://igem.org/wiki/images/6/60/Valencia_Ethics_Review.pdf |archive-url=https://web.archive.org/web/20191205034604/http://igem.org/wiki/images/6/60/Valencia_Ethics_Review.pdf |archive-date=December 5, 2019 |access-date=May 26, 2019 |publisher=iGEM Valencia Team }}</ref><ref name="ontomars">{{Cite book |editor-last=Zubrin |editor-first=Robert |last=McKay |first=Christopher |title=On to Mars: Colonizing a New World |publisher=Apogee Books Space Series |year=2002 |isbn=1-896522-90-4 |pages=177–182 |chapter=Do Indigenous Martian Bacteria have Precedence over Human Exploration? }}</ref><!-- are many more refs, some of them you can find in the Ethics of Terraforming article -->

== Challenges and limitations ==
{{See also|Colonization of Mars}}
[[File:Solar_system_escape_velocity_vs_surface_temperature.svg|lang=mt|thumb|upright=1.3|This diagram shows the change in the [[Atmospheric escape|atmosphere escaping]] from Mars if it was close to the average temperature on Earth. Mars is thought to have been warm in the past (due to evidence of liquid water on the surface) and terraforming would make it warm again. At these temperatures oxygen and nitrogen would escape into space much faster than they do today.]]
The Martian environment presents several terraforming challenges to overcome and the extent of terraforming may be limited by certain key environmental factors. The process of terraforming aims to mitigate the following distinctions between Mars and Earth, among others:
* Reduced light levels (about 60% of Earth)<ref name="tomatoes">{{cite web |title=Sunlight on Mars – Is There Enough Light on Mars to Grow Tomatoes? |url=https://www.firsttheseedfoundation.org/resource/tomatosphere/background/sunlight-mars-enough-light-mars-grow-tomatoes/ |website=first the seed foundation |access-date=26 November 2018 |archive-date=November 26, 2018 |archive-url=https://web.archive.org/web/20181126221359/https://www.firsttheseedfoundation.org/resource/tomatosphere/background/sunlight-mars-enough-light-mars-grow-tomatoes/ |url-status=live }}</ref>
* Low surface gravity (38% of Earth's)
* Unbreathable atmosphere<ref name="Mars atmosphere composition">{{Cite journal |last1=Franz|first1=Heather B. |last2=Trainer|first2=Melissa G. |last3=Malespin|first3=Charles A. |last4=Mahaffy|first4=Paul R. |last5=Atreya|first5=Sushil K. |last6=Becker|first6=Richard H. |last7=Benna|first7=Mehdi |last8=Conrad|first8=Pamela G. |last9=Eigenbrode|first9=Jennifer L. |date=2017-04-01 |title=Initial SAM calibration gas experiments on Mars: Quadrupole mass spectrometer results and implications |journal=Planetary and Space Science |volume=138 |pages=44–54 |doi=10.1016/j.pss.2017.01.014 |issn=0032-0633 |bibcode=2017P&SS..138...44F}}</ref>
* Low atmospheric pressure (about 1% of Earth's; well below the [[Armstrong limit]])
* Ionizing solar and [[cosmic radiation]] at the surface<ref name="radiationrules">{{Cite news |last1=Gifford |first1=Sheyna E. |date=February 18, 2014 |title=Calculated Risks: How Radiation Rules Manned Mars Exploration |url=https://www.space.com/24731-mars-radiation-curiosity-rover.html |url-status=live |archive-url=https://web.archive.org/web/20191210010540/https://www.space.com/24731-mars-radiation-curiosity-rover.html |archive-date=December 10, 2019 |access-date=November 26, 2018 |work=[[Space.com]] }}</ref>
* Average temperature {{convert|−63|C|K F}} compared to Earth average of {{convert|14|C|K F}}<ref>{{Cite web |title=Focus Sections :: The Planet Mars |url=http://marsnews.com/the-planet-mars |url-status=usurped |archive-url=https://web.archive.org/web/20150407230246/http://marsnews.com/the-planet-mars |archive-date=April 7, 2015 |access-date=September 8, 2007 |publisher=MarsNews.com }}</ref>
* Molecular instability — bonds between atoms break down in critical molecules such as [[organic compound]]s
* Global dust storms
* No natural food source<ref name="NYT-20231127">{{Cite news |last=Scoles |first=Sarah |date=November 27, 2023 |title=Mars Needs Insects — If humans are ever going to live on the red planet, they're going to have to bring bugs with them. |url=https://www.nytimes.com/2023/11/27/science/mars-needs-insects.html |url-status=live |archive-url=https://archive.today/20231128053332/https://www.nytimes.com/2023/11/27/science/mars-needs-insects.html |archive-date=November 28, 2023 |access-date=November 28, 2023 |work=[[The New York Times]] }}</ref>
* [[Martian soil#Toxicity|Toxic soil]]<ref name="toxicsoil1">{{Cite news |last=Sample |first=Ian |date=July 6, 2017 |title=Mars covered in toxic chemicals that can wipe out living organisms, tests reveal |url=https://www.theguardian.com/science/2017/jul/06/mars-covered-in-toxic-chemicals-that-can-wipe-out-living-organisms-tests-reveal |url-status=live |archive-url=https://web.archive.org/web/20210218180154/https://www.theguardian.com/science/2017/jul/06/mars-covered-in-toxic-chemicals-that-can-wipe-out-living-organisms-tests-reveal |archive-date=February 18, 2021 |access-date=November 26, 2018 |work=[[The Guardian]] }}</ref><ref name="toxicmars">{{Cite news |last=David |first=Leonard |date=June 13, 2013 |title=Toxic Mars: Astronauts Must Deal with Perchlorate on the Red Planet |url=https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html |url-status=live |archive-url=https://web.archive.org/web/20201120151522/https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html |archive-date=November 20, 2020 |access-date=November 26, 2018 |work=[[Space.com]] }}</ref>
* No global magnetic field to shield against the [[solar wind]]

===Countering the effects of space weather===
{{See also|Health threat from cosmic rays}}
Mars has no intrinsic global magnetic field, but the [[solar wind]] directly interacts with the atmosphere of Mars, leading to the formation of a magnetosphere from [[Flux tube|magnetic field tubes]].<ref name="Vaisberg2018">{{Cite journal |last1=Vaisberg |first1=O. L. |last2=Ermakov |first2=V. N. |last3=Shuvalov |first3=S. D. |last4=Zelenyi |first4=L. M. |last5=Halekas |first5=J. |last6=DiBraccio |first6=G. A. |last7=McFadden |first7=J. |last8=Dubinin |first8=E. M. |date=March 23, 2018 |title=The Structure of Martian Magnetosphere at the Dayside Terminator Region as Observed on MAVEN Spacecraft |journal=Journal of Geophysical Research: Space Physics |publisher=[[American Geophysical Union]] |publication-date=April 2018 |volume=123 |issue=4 |pages=2679–2695 |doi=10.1002/2018JA025202 |issn=2169-9380 |eissn=2169-9402 |doi-access=free |arxiv=1801.08878 |bibcode=2018JGRA..123.2679V }}</ref> This poses challenges for mitigating [[solar radiation]] and retaining an atmosphere.

The lack of a magnetic field, its relatively small mass, and its atmospheric photochemistry, all would have contributed to the evaporation and loss of its surface liquid water over time.<ref name="green2017"/> [[Solar wind]]–induced ejection of Martian atmospheric atoms has been detected by Mars-orbiting probes, indicating that the solar wind has stripped the Martian atmosphere over time. For comparison, while Venus has a dense atmosphere, it has only traces of water vapor (20&nbsp;ppm) as it lacks a large, dipole-induced, magnetic field.<ref name="Vaisberg2018"/><ref name="Svedhem2007">{{Cite journal |last1=Svedhem |first1=Hakan |last2=Titov |first2=Dmitry V. |last3=Taylor |first3=Fredric W. |last4=Witasse |first4=Oliver |date=November 29, 2007 |title=Venus as a more Earth-like planet |journal=[[Nature (journal)|Nature]] |volume=450 |issue=7170 |pages=629–632 |bibcode=2007Natur.450..629S |doi=10.1038/nature06432 |pmid=18046393 |s2cid=1242297 }}</ref><ref name="green2017">{{cite conference |url = https://www.lpi.usra.edu/meetings/V2050/pdf/8250.pdf |title = A Future Mars Environment for Science and Exploration |last1 = Green |first1 = J.L. |last2 = Hollingsworth |first2 = J. |conference = Planetary Science Vision 2050 Workshop 2017 |access-date = August 4, 2020 |archive-date = October 1, 2021 |archive-url = https://web.archive.org/web/20211001060242/https://www.hou.usra.edu/meetings/V2050/pdf/8250.pdf |url-status = live }}</ref>
Earth's [[ozone layer]] provides additional protection. Ultraviolet light is blocked before it can dissociate water into hydrogen and oxygen.<ref>{{Cite web |url= http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars |title=How to Protect Astronauts from Space Radiation on Mars |last=Garner|first=Rob |website=NASA |date=September 30, 2015 |access-date=2016-03-03 |archive-date=March 6, 2016 |archive-url= https://web.archive.org/web/20160306095331/http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars/ |url-status=live}}</ref>

=== Low gravity and pressure ===
The [[surface gravity]] on Mars is 38% of that on Earth. It is not known if this is enough to prevent the health problems associated with [[Weightlessness#Human health effects|weightlessness]].<ref>[https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ Gravity Hurts (so Good)] {{Webarchive|url=https://web.archive.org/web/20170528223301/https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ |date=May 28, 2017 }} – NASA 2001</ref>

Mars's {{chem|C|O|2}} atmosphere has about 1% the pressure of the Earth's at sea level. It is estimated that there is sufficient {{chem|C|O|2}} ice in the [[regolith]] and the south polar cap to form a {{convert|30|to|60|kPa|psi|abbr=~|lk=in}} atmosphere if it is released by planetary warming.<ref name="Requirements">{{cite web| url=http://www.users.globalnet.co.uk/~mfogg/zubrin.htm| title=Technological Requirements for Terraforming Mars| author=Robert M. Zubrin (Pioneer Astronautics), Christopher P. McKay. [[NASA Ames Research Center]]| date=c. 1993| access-date=August 10, 2006| archive-date=February 1, 2016| archive-url=https://web.archive.org/web/20160201124311/http://www.users.globalnet.co.uk/~mfogg/zubrin.htm| url-status=live}}</ref> The reappearance of liquid water on the Martian surface would add to the warming effects and atmospheric density,<ref name="Requirements"/> but the lower [[gravity of Mars]] requires 2.6 times Earth's column airmass to obtain the optimum {{convert|100|kPa|psi|abbr=on}} pressure at the surface.<ref name=Gasses/> Additional volatiles to increase the atmosphere's density must be supplied from an external source, such as redirecting several massive asteroids (40–400&nbsp;billion tonnes total) containing [[ammonia]] ({{chem|N|H|3}}) as a source of [[nitrogen]].<ref name="Requirements"/>

=== Breathing on Mars ===
Current conditions in the Martian atmosphere, at less than {{convert|1|kPa|psi|abbr=on}} of atmospheric pressure, are significantly below the [[Armstrong limit]] of {{convert|6|kPa|psi|abbr=on}} where very low pressure causes exposed bodily liquids such as saliva, tears, and the liquids wetting the alveoli within the lungs to boil away. Without a [[pressure suit]], no amount of breathable [[oxygen]] delivered by any means will sustain oxygen-breathing life for more than a few minutes.<ref name="Landis">{{cite web |author=Geoffrey A. Landis |url= http://www.geoffreylandis.com/vacuum.html |title=Human Exposure to Vacuum |publisher=Geoffrey A. Landis |access-date=March 21, 2016 |archive-date=July 21, 2009 |archive-url=https://web.archive.org/web/20090721182306/http://www.geoffreylandis.com/vacuum.html |url-status=live}}</ref><ref name="nasa" /> In the [[NASA]] technical report ''Rapid (Explosive) Decompression Emergencies in Pressure-Suited Subjects'', after exposure to pressure below the Armstrong limit, a survivor reported that his "last conscious memory was of the water on his [[tongue]] beginning to boil".<ref name="nasa">{{cite web |url= http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html |archive-url= https://web.archive.org/web/20141014072430/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html |title=Human Body in a Vacuum |archive-date=October 14, 2014}}</ref> In these conditions humans die within minutes unless a pressure suit provides life support.

If Mars' atmospheric pressure could rise above {{convert|19|kPa|psi|abbr=on}}, then a pressure suit would not be required. Visitors would only need to wear a mask that supplied 100% oxygen under positive pressure. A further increase to {{convert|24|kPa|psi|abbr=on}} of atmospheric pressure would allow a simple mask supplying pure oxygen.<ref>{{cite web |url= http://www.nasa.gov/centers/dryden/research/AirSci/ER-2/pshis.html |title=NASA – Airborne Science – ER-2 History of the Pressure Suit |access-date=March 22, 2016 |archive-url=https://web.archive.org/web/20160325173807/http://www.nasa.gov/centers/dryden/research/AirSci/ER-2/pshis.html |archive-date=March 25, 2016 |df=mdy-all}}</ref>{{clarify|Humans do not need 19kPa partial pressure of oxygen; at least high-altitude mountain village inhabitants can do with about half as much permanently|date=August 2018}} This might look similar to mountain climbers who venture into pressures below {{convert|37|kPa|psi|abbr=on}}, also called the [[Effects of high altitude on humans#Death zone|death zone]], where an insufficient amount of bottled oxygen has often resulted in [[Hypoxic hypoxia|hypoxia]] with fatalities.<ref name=Grocott>{{cite journal |journal=N Engl J Med |year=2009 |volume=360 |pages=140–9 |title=Arterial Blood Gases and Oxygen Content in Climbers on Mount Everest |first1=Michael P.W.|last1=Grocott |first2=Daniel S.|last2=Martin |first3=Denny Z.H.|last3=Levett |first4=Roger|last4=McMorrow |first5=Jeremy|last5=Windsor |first6=Hugh E.|last6=Montgomery |doi=10.1056/NEJMoa0801581 |pmid=19129527 |issue=2 |url= https://research.brighton.ac.uk/en/publications/ba1483ec-4ad4-47c2-b504-57529d1fed8e |access-date=September 22, 2021|archive-date=October 1, 2021 |archive-url= https://web.archive.org/web/20211001060305/https://research.brighton.ac.uk/en/publications/arterial-blood-gases-and-oxygen-content-in-climbers-on-mount-ever |url-status=live |doi-access=free}}</ref> However, if the increase in atmospheric pressure was achieved by increasing CO<sub>2</sub> (or other toxic gas) the mask would have to ensure the external atmosphere did not enter the breathing apparatus. CO<sub>2</sub> concentrations as low as 1% cause drowsiness in humans. Concentrations of 7% to 10% may cause suffocation, even in the presence of sufficient oxygen. (See [[Carbon dioxide#Toxicity|Carbon dioxide toxicity]].)

In 2021, the NASA Mars rover [[Perseverance (rover)|Perseverance]] was able to make oxygen on Mars. However, the process is complex and takes a considerable amount of time to produce a small amount of oxygen.<ref>{{cite web | url=https://www.fox29.com/news/nasas-perseverance-rover-produces-oxygen-on-mars-in-historic-first-water-could-be-next-scientists-say | title=NASA's Perseverance rover produces oxygen on Mars in historic first — water could be next, scientists say | date=April 22, 2021 }}</ref>

== Advantages ==
{{Further|Atmosphere of Mars}}

[[File:TerraformedMars.jpg|thumb|Hypothetical terraformed Mars]]

Mars exists on the outer edge of the [[habitable zone]], a region of the Solar System where liquid water on the surface may be supported if concentrated greenhouse gases could increase the atmospheric pressure.<ref name="Requirements"/> The lack of both a [[magnetic field]] and geologic activity on Mars may be a result of its relatively small size, which allowed the interior to cool more quickly than Earth's, although the details of such a process are still not well understood.<ref name="magnetosphere">{{cite web|date=November 9, 2006|title=Magnetic Fields and Mars|publisher=Mars Global Surveyor @ NASA|author=Valentine, Theresa|author2=Amde, Lishan|url=http://mgs-mager.gsfc.nasa.gov/Kids/magfield.html|access-date=July 17, 2009|archive-date=September 14, 2012|archive-url=https://archive.today/20120914152639/http://mgs-mager.gsfc.nasa.gov/Kids/magfield.html|url-status=live}}</ref><ref>{{cite magazine|url=https://www.wired.com/2011/01/mars-dynamo-death/|title=Multiple Asteroid Strikes May Have Killed Mars's Magnetic Field – WIRED|date=January 20, 2011|magazine=WIRED|access-date=June 2, 2015|archive-date=June 26, 2015|archive-url=https://web.archive.org/web/20150626220935/http://www.wired.com/2011/01/mars-dynamo-death/|url-status=live}}</ref>

There are strong indications that Mars once had an atmosphere as thick as Earth's during an earlier stage in its development, and that its pressure supported abundant liquid [[Water on Mars|water at the surface]].<ref>{{cite web | url = https://science.nasa.gov/headlines/y2008/21nov_plasmoids.htm?list59243 | title = Solar Wind Rips Up Martian Atmosphere | publisher = NASA | author = Dr. Tony Phillips | date = November 21, 2008 | access-date = April 1, 2015 | archive-url = https://web.archive.org/web/20090217212646/http://science.nasa.gov/headlines/y2008/21nov_plasmoids.htm?list59243 | archive-date = February 17, 2009 }}</ref> Although water appears to have once been present on the Martian surface, ground ice currently exists from mid-latitudes to the poles.<ref name='exposed ice 2018'>[https://www.jpl.nasa.gov/news/news.php?feature=7038 Steep Slopes on Mars Reveal Structure of Buried Ice] {{Webarchive|url=https://web.archive.org/web/20190617060621/https://www.jpl.nasa.gov/news/news.php?feature=7038 |date=June 17, 2019 }}. NASA Press Release. January 11, 2018.</ref><ref>[https://www.science.org/content/article/ice-cliffs-spotted-mars Ice cliffs spotted on Mars] {{Webarchive|url=https://web.archive.org/web/20180128062432/http://www.sciencemag.org/news/2018/01/ice-cliffs-spotted-mars |date=January 28, 2018 }}. ''Science News''. Paul Voosen. January 11, 2018.</ref> The [[Martian soil|soil]] and [[atmosphere of Mars]] contain many of the main elements crucial to life, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.<ref>{{cite web | url = http://www.jpl.nasa.gov/news/news.php?release=2013-092#1 | title = NASA Rover Finds Conditions Once Suited for Ancient Life on Mars | author = Dwayne Brown | website = [[Jet Propulsion Laboratory]] | date = March 12, 2013 | access-date = September 2, 2014 | archive-date = January 5, 2019 | archive-url = https://web.archive.org/web/20190105080402/https://www.jpl.nasa.gov/news/news.php?release=2013-092#1 | url-status = live }}</ref>

Any climate change induced in the near term is likely to be driven by greenhouse warming produced by an increase in atmospheric [[carbon dioxide]] ({{chem|C|O|2}}) and a consequent increase in atmospheric water vapor. These two gases are the only likely sources of greenhouse warming that are available in large quantities in Mars' environment.<ref name=JakoskyLPS>[https://www.hou.usra.edu/meetings/lpsc2017/pdf/1193.pdf Can Mars be Terraformed?] {{Webarchive|url=https://web.archive.org/web/20170906225637/https://www.hou.usra.edu/meetings/lpsc2017/pdf/1193.pdf |date=September 6, 2017 }} (PDF) B. M. Jakosky and C. S. Edwards.  Lunar and Planetary Science XLVIII, 2017</ref> Large amounts of [[Ice|water ice]] exist below the Martian surface, as well as on the surface at the poles, where it is mixed with [[dry ice]], frozen {{CO2}}. Significant amounts of water are located at the south pole of Mars, which, if melted, would correspond to a planetwide ocean 5–11 meters deep.<ref>{{Cite journal
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 | url-status=live
 | url-access=subscription
 }}{{subscription required}}</ref><ref>{{cite web | url = http://www.space.com/17048-water-on-mars.html | title = Water on Mars: Exploration & Evidence | website = [[Space.com]] | date = October 7, 2015 | access-date = May 8, 2016 | archive-date = May 12, 2016 | archive-url = https://web.archive.org/web/20160512225805/http://www.space.com/17048-water-on-mars.html | url-status = live }}</ref> Frozen [[carbon dioxide]] ({{CO2}}) at the poles [[sublimation (phase transition)|sublimes]] into the atmosphere during the Martian summers, and small amounts of water residue are left behind, which fast winds sweep off the poles at speeds approaching {{convert|400|km/h|mph|abbr=on}}.{{Citation needed|date=December 2012}}{{Original research inline|date=March 2016}} This seasonal occurrence transports large amounts of [[dust]] and [[Ice|water ice]] into the atmosphere, forming Earth-like [[ice]] clouds.<ref>{{cite web|title=Water Clouds on Mars|url=http://www.nasa.gov/mission_pages/phoenix/images/press/16145-animated.html|access-date=August 1, 2014|archive-date=June 2, 2016|archive-url=https://web.archive.org/web/20160602213811/http://www.nasa.gov/mission_pages/phoenix/images/press/16145-animated.html|url-status=live}}</ref><ref>{{Cite web|url=https://science.nasa.gov/blog/cloudy-sols-are-here-again/|title=Cloudy Sols Are Here Again - NASA Science|date=February 3, 2023}}</ref>

Most of the oxygen in the Martian atmosphere is present as carbon dioxide ({{CO2}}), the main atmospheric component. Molecular [[oxygen]] (O<sub>2</sub>) only exists in trace amounts. Large amounts of oxygen can be also found in [[iron oxide|metal oxide]]s on the Martian surface, and in the soil, in the form of [[nitrate|per-nitrates]].<ref name="Lovelock">{{Cite book |last1=Lovelock |first1=James |last2=Allaby |first2=James |title=The Greening of Mars |date=1984| publisher=St. Martin's Press| isbn=978-0-312-35024-6}}</ref> An analysis of soil samples taken by the [[Phoenix lander]] indicated the presence of [[perchlorate]], which has been used to liberate oxygen in [[chemical oxygen generators]].<ref>{{cite journal|last=Hecht|display-authors=etal|title=Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site|journal=Science|year=2009|volume=325|issue=5936|pages=64–7|url=https://www.science.org/doi/abs/10.1126/science.1172466|publisher=Science Magazine|doi=10.1126/science.1172466|pmid=19574385|bibcode=2009Sci...325...64H|s2cid=24299495|access-date=January 13, 2014|archive-date=July 18, 2014|archive-url=https://web.archive.org/web/20140718184655/http://www.sciencemag.org/content/325/5936/64.abstract|url-status=live|url-access=subscription}}</ref> [[Electrolysis]] could be employed to separate water on Mars into oxygen and [[hydrogen]] if sufficient liquid water and electricity were available. However, if vented into the atmosphere it would escape into space.

== Proposed methods and strategies ==
{{See also|Oxygen evolution}}
{| class="wikitable floatright"
|+ '''Comparison of dry atmosphere'''
! Atmospheric<br />property
! [[Atmosphere of Mars|Mars]]
! [[Atmosphere of Earth|Earth]]
|-
| Pressure || {{convert|0.61|kPa|abbr=on}} || {{convert|101.3|kPa|abbr=on}}
|-
| [[Carbon dioxide]] ({{CO2}}) || 96.0% || 0.04%
|-
| [[Argon]] (Ar) || 2.1% || 0.93%
|-
| [[Nitrogen]] (N<sub>2</sub>) || 1.9% || 78.08%
|-
| [[Oxygen]] (O<sub>2</sub>) || 0.145% || 20.94%
|}

Terraforming Mars would entail three major interlaced changes: building up the magnetosphere, building up the atmosphere, and raising the temperature. The atmosphere of Mars is relatively thin and has a very low surface pressure. Because its atmosphere consists mainly of {{CO2}}, a known [[greenhouse gas]], once Mars begins to heat, the {{CO2}} may help to keep [[thermal energy]] near the surface. Moreover, as it heats, more {{CO2}} should enter the atmosphere from the frozen reserves on the poles, enhancing the [[greenhouse effect]]. This means that the two processes of building the atmosphere and heating it would augment each other, favoring terraforming. However, it would be difficult to keep the atmosphere together because of the lack of a protective global magnetic field against erosion by the [[solar wind]].<ref name="NYT-20151105">{{cite news |last=Chang |first=Kenneth |title=Solar Storms Strip Air From Mars, NASA Says |url=https://www.nytimes.com/2015/11/06/science/space/mars-atmosphere-stripped-away-by-solar-storms-nasa-says.html |date=5 November 2015 |work=The New York Times |access-date=5 November 2015 |archive-date=August 25, 2019 |archive-url=https://web.archive.org/web/20190825051437/https://www.nytimes.com/2015/11/06/science/space/mars-atmosphere-stripped-away-by-solar-storms-nasa-says.html |url-status=live }}</ref><ref name="YT-20151105">{{cite web |author=Staff |title=VIDEO (51:58) – MAVEN – Measuring Mars' Atmospheric Loss |url=https://www.youtube.com/watch?v=Y4vVFetfSF8 |date=5 November 2015 |work=[[NASA]] |access-date=5 November 2015 |archive-date=August 25, 2017 |archive-url=https://web.archive.org/web/20170825181526/https://www.youtube.com/watch?v=Y4vVFetfSF8 |url-status=live }}</ref><ref name="NASA-15217">{{cite web |last=Northon |first=Karen |title=NASA Mission Reveals Speed of Solar Wind Stripping Martian Atmosphere |url=http://www.nasa.gov/press-release/nasa-mission-reveals-speed-of-solar-wind-stripping-martian-atmosphere |date=5 November 2015 |work=[[NASA]] |access-date=5 November 2015 |archive-date=January 12, 2019 |archive-url=https://web.archive.org/web/20190112134100/https://www.nasa.gov/press-release/nasa-mission-reveals-speed-of-solar-wind-stripping-martian-atmosphere |url-status=live }}</ref><ref>{{cite web |last=Wall |first=Mike |title=Mars Lost Atmosphere to Space as Life Took Hold on Earth |url=http://www.space.com/31031-mars-atmosphere-discovery-nasa-maven.html?adbid=662349226177761280&adbpl=tw&adbpr=15431856 |date=5 November 2015 |work=[[Space.com]] |access-date=6 November 2015 |archive-date=July 18, 2018 |archive-url=https://web.archive.org/web/20180718001346/https://www.space.com/31031-mars-atmosphere-discovery-nasa-maven.html?adbid=662349226177761280&adbpl=tw&adbpr=15431856 |url-status=live }}</ref>

=== Importing ammonia ===
One method of augmenting the Martian atmosphere is to introduce [[ammonia]] (NH<sub>3</sub>). Large amounts of ammonia are likely to exist in frozen form on minor planets orbiting in the [[outer Solar System]]. It might be possible to redirect the orbits of these or smaller ammonia-rich objects so that they collide with Mars, thereby transferring the ammonia into the Martian atmosphere.<ref name="ColeCox1964">{{Cite book |author1=Dandridge M. Cole |author1-link=Dandridge M. Cole |author2=Donald William Cox |title=Islands in Space: The Challenge of the Planetoids |date=1964 |publisher=Chilton Books |pages=126–127}}</ref><ref name="Requirements"/> Ammonia is not stable in the Martian atmosphere, however. It breaks down into (diatomic) nitrogen and hydrogen after a few hours.<ref name="davidw">{{cite news |last=Whitehouse |first=David |date=July 15, 2004 |url=http://news.bbc.co.uk/2/hi/3896335.stm |title=Dr. David Whitehouse – Ammonia on Mars could mean life |work=BBC News |access-date=August 14, 2012 |archive-date=October 31, 2012 |archive-url=https://web.archive.org/web/20121031013215/http://news.bbc.co.uk/2/hi/3896335.stm |url-status=live }}</ref> Thus, though ammonia is a powerful [[greenhouse gas]], it is unlikely to generate much planetary warming.

=== Importing hydrocarbons ===
Another way to create a Martian atmosphere would be to import [[methane]] (CH<sub>4</sub>) or other [[hydrocarbon]]s,<ref name="aboutmyplanet.com">{{cite web |author=Mat Conway |url=http://www.aboutmyplanet.com/science-technology/now-were-there-terraforming-mars/ |title=Now We're There: Terraforming Mars |publisher=Aboutmyplanet.com |date=February 27, 2007 |access-date=2011-08-20 |archive-url=https://web.archive.org/web/20110723231654/http://www.aboutmyplanet.com/science-technology/now-were-there-terraforming-mars/ |archive-date=July 23, 2011 |df=mdy-all }}</ref><ref name="BIOL0602_Lecture_2012">{{Cite web |url=http://www.webdesignasia.com/extremophiles/pdfs/BIOL0602_Lecture%2012.pdf |title=Terraforming – Can we create a habitable planet? |access-date=January 16, 2010 |archive-date=April 20, 2018 |archive-url=https://web.archive.org/web/20180420074037/http://www.webdesignasia.com/extremophiles/pdfs/BIOL0602_Lecture%2012.pdf |url-status=live }}</ref> which are common in [[Titan (moon)|Titan's]] atmosphere and on its [[Lakes of Titan|surface]]; the methane could be vented into the atmosphere where it would act to compound the greenhouse effect.<ref>{{cite web|url=https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane|website=epa.gov|publisher=United States Government EPA|title=Overview of Greenhouse Gases|date=December 23, 2015 |access-date=2016-10-24|archive-date=August 12, 2016|archive-url=https://web.archive.org/web/20160812082641/https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane|url-status=live}}</ref> However, like ammonia (NH<sub>3</sub>), methane (CH<sub>4</sub>) is a relatively light gas. It is in fact even less dense than ammonia and so would similarly be lost into space if it was introduced, and at a faster rate than ammonia. Even if a method could be found to prevent it escaping into space, methane can exist in the Martian atmosphere for only a limited period before it is destroyed. Estimates of its lifetime range from 0.6–4 years.<ref name="plumes">{{cite journal |title=Strong Release of Methane on Mars in Northern Summer 2003 |journal=Science |date=February 20, 2009 |first=Michael J. |last=Mumma |volume=323 |issue=5917 |pages=1041–1045 |doi=10.1126/science.1165243 |url=http://images.spaceref.com/news/2009/Mumma_et_al_Methane_Mars_wSOM_accepted2.pdf |pmid=19150811 |bibcode=2009Sci...323.1041M |s2cid=25083438 |display-authors=etal |access-date=November 26, 2018 }}</ref><ref name="nature460">{{cite journal |title=Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics |journal=Nature |date=August 6, 2009 |first=Lefèvre |last=Franck |author2=Forget, François |volume=460 |pages=720–723 |doi=10.1038/nature08228 |pmid=19661912 |issue=7256 |bibcode=2009Natur.460..720L|s2cid=4355576 }}</ref>

=== Use of fluorine compounds ===
Especially powerful greenhouse gases, such as [[sulfur hexafluoride]], [[chlorofluorocarbon]]s (CFCs), or [[perfluorocarbon]]s (PFCs), have been suggested both as a means of initially warming Mars and of maintaining long-term climate stability.<ref name="Requirements"/><ref name=Gasses>{{Cite journal
| last1 = Gerstell | first1 = M. F.
| last2 = Francisco |first2 = J. S.
| last3 = Yung |first3 = Y. L.
| last4 = Boxe |first4 = C.
| last5 = Aaltonee |first5 = E. T.
| title = Keeping Mars warm with new super greenhouse gases
| doi = 10.1073/pnas.051511598
| journal = Proceedings of the National Academy of Sciences
| volume = 98
| issue = 5
| pages = 2154–2157
| date = 2001
| pmid=11226208 | pmc=30108
| bibcode = 2001PNAS...98.2154G| doi-access = free
}}</ref><ref name=MarsAstrobiology>{{Cite journal
| last1 = Teles | first1 = A. M. M.
| editor3-first = Wing-Huen
| editor3-last = Ip
| editor3-link= Ip Wing-huen
| editor2-first = Nader
| editor2-last = Haghighipour
| editor1-first = Shuanggen
| editor1-last = Jin
| title = Mars Astrobiology: Recent Status and Progress
| doi = 10.1007/978-3-662-45052-9
| journal = Planetary Exploration and Science: Recent Results and Advances
| pages = 147–245
| date = 2015
| isbn = 978-3-662-45051-2
| s2cid = 125651936
}}</ref><ref name=JakoskyLPS/> These gases are proposed for introduction because they generate a greenhouse effect thousands of times stronger than that of {{CO2}}. Fluorine-based compounds such as sulphur hexafluoride and perfluorocarbons are preferable to chlorine-based ones as the latter destroys [[ozone]]. It has been estimated that approximately 0.3 microbars of CFCs would need to be introduced into Mars' atmosphere to sublimate the south polar {{CO2}} glaciers.<ref name=MarsAstrobiology/> This is equivalent to a mass of approximately 39 million tonnes, that is, about three times the amount of CFCs manufactured on Earth from 1972 to 1992 (when CFC production was banned by international treaty).<ref name=MarsAstrobiology/> Maintaining the temperature would require continual production of such compounds as they are destroyed due to photolysis. It has been estimated that introducing 170 kilotons of optimal greenhouse compounds (CF<sub>3</sub>CF<sub>2</sub>CF<sub>3</sub>, CF<sub>3</sub>SCF<sub>2</sub>CF<sub>3</sub>, SF<sub>6</sub>, SF<sub>5</sub>CF<sub>3</sub>, SF<sub>4</sub>(CF<sub>3</sub>)<sub>2</sub>) annually would be sufficient to maintain a 70-K greenhouse effect given a terraformed atmosphere with earth-like pressure and composition.<ref name=Gasses/>

Typical proposals envision producing the gases on Mars using locally extracted materials, nuclear power, and a significant industrial effort. The potential for mining fluorine-containing minerals to obtain the raw material necessary for the production of CFCs and PFCs is supported by mineralogical surveys of Mars that estimate the elemental presence of fluorine in the bulk composition of Mars at 32 ppm by mass (as compared to 19.4 ppm for the Earth).<ref name="Gasses"/>

Alternatively, CFCs might be introduced by sending rockets with payloads of compressed CFCs on collision courses with Mars.<ref name=Lovelock/> When the rockets crashed into the surface they would release their payloads into the atmosphere. A steady barrage of these "CFC rockets" would need to be sustained for a little over a decade while Mars is changed chemically and becomes warmer.

=== Use of conductive nanorods ===
A 2024 study proposed using [[nanorod]]s consisting of a conductive material, such as aluminum or iron, made by processing Martian minerals. These nanorods would scatter and absorb the thermal infrared upwelling from the surface, thus warming the planet. This process is claimed to be over 5,000 times more effective (in terms of warming per unit mass) than warming using fluorine compounds.<ref>{{Cite journal |last1=Ansari |first1=Samaneh |last2=Kite |first2=Edwin S. |last3=Ramirez |first3=Ramses |last4=Steele |first4=Liam J. |last5=Mohseni |first5=Hooman |date=2024-08-09 |title=Feasibility of keeping Mars warm with nanoparticles |journal=Science Advances |language=en |volume=10 |issue=32 |pages=eadn4650 |doi=10.1126/sciadv.adn4650 |issn=2375-2548 |pmc=11305381 |pmid=39110809|arxiv=2409.03925 |bibcode=2024SciA...10N4650A }}</ref><ref>{{Cite web |last=Whitwam |first=Ryan |date=August 8, 2024 |title=Terraforming Mars Might Be Simpler Than Anyone Expected: Study |url=https://www.extremetech.com/science/terraforming-mars-might-be-simpler-than-anyone-expected-study |website=ExtremeTech}}</ref>

===Use of orbital mirrors===
Mirrors made of thin aluminized [[PET film (biaxially oriented)|PET film]] could be placed in orbit around Mars to increase the total [[insolation]] it receives.<ref name="Requirements"/> This would direct the sunlight onto the surface and could increase Mars's surface temperature directly. The 125 km radius mirror could be positioned as a [[statite]], using its effectiveness as a [[solar sail]] to orbit in a stationary position relative to Mars, near the poles, to sublimate the {{chem|C|O|2}} ice sheet and contribute to the warming greenhouse effect. However, certain problems have been found with this. The main concern is the difficulty of launching large mirrors from Earth.<ref name="Requirements"/>

=== Use of nuclear weapons ===
[[Elon Musk]] has proposed terraforming Mars by detonating [[nuclear weapon]]s on the [[Martian polar ice caps]] to vaporize them and release [[carbon dioxide]] and water vapor into the atmosphere. Carbon dioxide and water vapor are [[greenhouse gases]], and the resultant thicker atmosphere would trap heat from the [[Sun]], increasing the planet's temperature. The formation of liquid water could be very favorable for oxygen-producing plants, and thus, human survival.<ref name="spacecom1">{{cite news |author1=Mike Wall |title=Elon Musk Floats 'Nuke Mars' Idea Again (He Has T-Shirts) |url=https://www.space.com/elon-musk-nuke-mars-terraforming.html |access-date=14 May 2024 |work=Space.com |date=17 August 2019 |language=en}}</ref><ref>{{cite news |author1=Mike Wall |title=Looks Like Elon Musk Is Serious About Nuking Mars |url=https://www.space.com/elon-musk-serious-nuke-mars-terraforming.html |access-date=14 May 2024 |work=Space.com |date=21 August 2019 |language=en}}</ref><ref>{{cite news |last1=Herron |first1=Thomas J. |title=Deep Space Thinking: What Elon Musk's Idea to Nuke Mars Teaches Us About Regulating the "Visionaries and Daredevils" of Outer Space |url=https://journals.library.columbia.edu/index.php/cjel/article/view/3728#:~:text=Musk%20believes%20that%20Mars%20has,then%20released%20as%20infrared%20radiation. |access-date=14 May 2024 |work=Columbia Journal of Environmental Law |date=2016 |language=en |doi=10.7916/cjel.v41i3.3728}}</ref><ref>{{cite news |last1=Letenyei |first1=Danielle |title=If We Nuke Mars, Would It Really Become an Earth-Like Planet? |url=https://www.greenmatters.com/technology/nuke-mars#:~:text=Much%20like%20our%20sun%2C%20this,flowing%20water%20and%20blue%20skies. |access-date=14 May 2024 |work=Green Matters |date=1 June 2023}}</ref><ref>{{cite news |title=Elon Musk Wants To Drop Nuclear Bombs on Mars |url=https://www.despatch.com/blog/elon-musk-wants-to-drop-nuclear-bombs-on-mars/#:~:text=Nuclear%20explosion%20will%20warm%20the,Industrial%20Ovens |access-date=14 May 2024 |work=Despatch |date=23 September 2019}}</ref>

Studies suggest that even if all the CO2 trapped in Mars' [[polar ice]] and [[regolith]] were released, it would not be enough to provide significant [[greenhouse warming]] to turn Mars into an Earth-like planet.<ref name="spacecom1" /><ref>{{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 |url=https://www.nature.com/articles/s41550-018-0529-6 |language=en |issn=2397-3366 |access-date=14 May 2024|url-access=subscription }}</ref><ref>{{cite journal |last1=Haberle |first1=Robert M. |last2=Tyler |first2=Daniel |last3=McKay |first3=Christopher P. |last4=Davis |first4=Wanda L. |title=A Model for the Evolution of CO2 on Mars |journal=Icarus |date=May 1994 |volume=109 |issue=1 |pages=102–120 |doi=10.1006/icar.1994.1079 |pmid=11539135 |url=https://www.sciencedirect.com/science/article/abs/pii/S0019103584710797 |access-date=14 May 2024|url-access=subscription }}</ref>
Another criticism is that it would stir up enough dust and particles to block out a significant portion of the incoming sunlight, causing a [[nuclear winter]], the opposite of the goal.<ref name="spacecom1" />

===Albedo reduction===
Reducing the [[albedo]] of the Martian surface would also make more efficient use of incoming sunlight in terms of heat absorption.<ref>{{cite web| url=http://www.nexialquest.com/The%20Terraformation%20of%20Worlds.pdf| title=The Terraformation of Worlds| author=Peter Ahrens| publisher=Nexial Quest| access-date=2007-10-18| archive-date=June 9, 2019| archive-url=https://web.archive.org/web/20190609033202/http://www.nexialquest.com/The%20Terraformation%20of%20Worlds.pdf}}</ref> This could be done by spreading dark dust from Mars's moons, [[Phobos (moon)|Phobos]] and [[Deimos (moon)|Deimos]], which are among the blackest bodies in the Solar System; or by introducing dark [[extremophile]] microbial life forms such as [[lichen]]s, [[algae]] and bacteria.{{Citation needed|date=April 2015}} The ground would then absorb more sunlight, warming the atmosphere. However, Mars is already the second-darkest planet in the solar system, absorbing over 70% of incoming sunlight so the scope for darkening it further is small.

If algae or other green life were established, it would also contribute a small amount of [[oxygen]] to the atmosphere, though not enough to allow humans to breathe. The conversion process to produce oxygen is highly reliant upon water, without which the {{CO2}} is mostly converted to carbohydrates.<ref>{{cite web|url=http://www.howplantswork.com/2009/02/16/plants-dont-convert-co2-into-o2/|title=Plants Don't Convert CO2 into O2 " How Plants Work|work=How Plants Work|date=February 16, 2009 |access-date=June 2, 2015|archive-date=August 22, 2015|archive-url=https://web.archive.org/web/20150822103103/http://www.howplantswork.com/2009/02/16/plants-dont-convert-co2-into-o2/|url-status=live}}</ref> In addition, because on Mars atmospheric oxygen is lost into space (unless an artificial magnetosphere were to be created; see "Protecting the atmosphere" below), such life would need to be cultivated inside a closed system.

On April 26, 2012, scientists reported that [[lichen]] survived and showed remarkable results on the adaptation capacity of photosynthetic activity within the simulation time of 34 days under [[Life on Mars#Survival under simulated Martian conditions|Martian conditions]] in the Mars Simulation Laboratory (MSL) maintained by the [[German Aerospace Center]] (DLR).<ref name="Skymania-20120427">{{cite web |last=Baldwin |first=Emily |title=Lichen survives harsh Mars environment |url=http://www.skymania.com/wp/2012/04/lichen-survives-harsh-martian-setting.html |date=April 26, 2012 |publisher=Skymania |access-date=April 27, 2012 |archive-date=May 28, 2012 |archive-url=https://web.archive.org/web/20120528145425/http://www.skymania.com/wp/2012/04/lichen-survives-harsh-martian-setting.html/ |url-status=live }}</ref><ref name="EGU-20120426">{{cite web |last1=de Vera |first1=J.-P. |last2=Kohler |first2=Ulrich |title=The adaptation potential of extremophiles to Martian surface conditions and its implication for the habitability of Mars |url=http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |date=April 26, 2012 |publisher=[[European Geosciences Union]] |access-date=April 27, 2012 |archive-url=https://web.archive.org/web/20120504224706/http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |archive-date=May 4, 2012 }}</ref>

One final issue with albedo reduction is the common [[Climate of Mars#Effect of dust storms|Martian dust storms]]. These cover the entire planet for weeks, and not only increase the albedo, but block sunlight from reaching the surface. This has been observed to cause a surface temperature drop which the planet takes months to recover from.<ref name=Fenton>{{cite journal | first1=Lori K. | last1=Fenton | first2=Paul E. | last2=Geissler | first3=Robert M. | last3=Haberle | title=Global warming and climate forcing by recent albedo changes on Mars | date=2007 | journal=[[Nature (journal)|Nature]] | volume=446 | doi=10.1038/nature05718 | url=http://humbabe.arc.nasa.gov/~fenton/pdf/fenton/nature05718.pdf | pages=646–649 | pmid=17410170 | issue=7136 | bibcode=2007Natur.446..646F | s2cid=4411643 | archive-url=https://web.archive.org/web/20070708011126/http://humbabe.arc.nasa.gov/~fenton/pdf/fenton/nature05718.pdf | archive-date=July 8, 2007 | df=mdy-all }}</ref> Once the dust settles it then covers whatever it lands on, effectively erasing the albedo reduction material from the view of the [[Sun]].

===Funded research: ecopoiesis===
[[File:Mars Ecopoiesis Test Bed.jpg|thumb|The Mars Ecopoiesis Test Bed showing its transparent dome to allow for solar heat and photosynthesis, and the cork-screw system to collect and seal [[Martian soil]] together with oxygen-producing Earth organisms. Total length is about {{convert|7|cm|in}}.]]
Since 2014, the [[NASA Institute for Advanced Concepts]] (NIAC) program and Techshot Inc have been working together to develop sealed biodomes that would employ colonies of oxygen-producing [[cyanobacteria]] and [[algae]] for the production of molecular oxygen (O<sub>2</sub>) on Martian soil.<ref name="Wentz1">{{cite news |last=Wentz |first=Rachel K. |url=http://www.sciencetimes.com/articles/6407/20150516/nasa-hopes-to-rely-on-algae-and-bacteria-for-oxygen-production-on-mars.htm |title=NASA Hopes to Rely on Algae and Bacteria for Oxygen Production on Mars |work=The Science Times |date=May 16, 2015 |access-date=2015-05-17 |archive-date=May 19, 2015 |archive-url=https://web.archive.org/web/20150519165851/http://www.sciencetimes.com/articles/6407/20150516/nasa-hopes-to-rely-on-algae-and-bacteria-for-oxygen-production-on-mars.htm |url-status=live }}</ref><ref name="Wall2014">{{cite news |last=Wall |first=Mike |url=http://www.space.com/26161-nasa-space-tech-advanced-technology.html |title=NASA Funds 12 Futuristic Space Tech Concepts |work=Space.com |date=June 6, 2014 |access-date=2015-05-17 |archive-date=May 19, 2015 |archive-url=https://web.archive.org/web/20150519234240/http://www.space.com/26161-nasa-space-tech-advanced-technology.html |url-status=live }}</ref><ref name="NIAC2014">{{cite web |url=http://www.nasa.gov/content/mars-ecopoiesis-test-bed/ |title=NIAC 2014 Phase 1 Selections |work=NASA Innovative Advanced Concepts (NIAC) |date=June 5, 2014 |access-date=2015-05-18 |archive-date=March 30, 2015 |archive-url=https://web.archive.org/web/20150330211024/http://www.nasa.gov/content/mars-ecopoiesis-test-bed/ |url-status=live }}</ref> But first they need to test if it works on a small scale on Mars.<ref name="David2015">{{cite journal |title=Terraforming in a Bottle on Mars |journal=Aerospace America Magazine |last=David |first=Leonard |url=http://www.omagdigital.com/publication/index.php?i=-254792&m=7270&l=1&p=10&pre= |access-date=2015-05-17 |quote=Page 8 |archive-date=January 28, 2016 |archive-url=https://web.archive.org/web/20160128065541/http://www.omagdigital.com/publication/index.php?i=-254792&m=7270&l=1&p=10&pre= |url-status=live }}</ref> The proposal is called Mars Ecopoiesis Test Bed.<ref>[http://adsabs.harvard.edu/abs/2016cosp...41E1915T Mars ecopoiesis test bed: on Earth and on the Red Planet] {{Webarchive|url=https://web.archive.org/web/20170704064446/http://adsabs.harvard.edu/abs/2016cosp...41E1915T |date=July 4, 2017 }}. Todd, Paul; Kurk, Michael Andy; Boland, Eugene; Thomas, David; Scherzer, Christopher. Abstract for the 41st COSPAR Scientific Assembly. August 23, 2017</ref> Eugene Boland is the Chief Scientist at Techshot, a company located in Greenville, Indiana.<ref name="Wentz1"/> They intend to send small canisters of [[extremophile]] [[Photosynthesis|photosynthetic]] [[algae]] and [[cyanobacteria]] aboard a future rover mission. The rover would cork-screw the {{convert|7|cm|abbr=on}} canisters into selected sites likely to experience transients of liquid water, drawing some [[Martian soil]] and then release oxygen-producing microorganisms to grow within the sealed soil.<ref name="Wentz1"/><ref name="Burnham2014">{{cite news |last=Burnham |first=R. |url=http://redplanet.asu.edu/?p=7520 |title=Mars 'terraforming' test among NAIC proposals |work=The Red Planet Report |date=June 6, 2014 |access-date=2015-05-17 |archive-date=May 20, 2015 |archive-url=https://web.archive.org/web/20150520092806/http://redplanet.asu.edu/?p=7520 |url-status=live }}</ref> The hardware would use Martian subsurface ice as its phase changes into liquid water.<ref name="David2015"/> The system would then look for oxygen given off as [[Metabolism|metabolic byproduct]] and report results to a Mars-orbiting relay satellite.<ref name="NIAC2014"/><ref name="Burnham2014"/>

If this experiment works on Mars, they will propose to build several large and sealed structures called [[closed ecological system|biodomes]], to produce and harvest oxygen for a future [[human mission to Mars]] life support systems<!--and propellant for their return spacecraft-->.<ref name="Burnham2014"/><ref name="Beach2015">{{cite news |last=Beach |first=Justin |url=http://natmonitor.com/2015/05/17/nasas-plan-to-use-bacteria-to-produce-oxygen-on-mars/ |title=NASA's plan to use bacteria to produce oxygen on Mars |work=National Monitor |date=May 17, 2015 |access-date=2015-05-17 |archive-date=May 20, 2015 |archive-url=https://web.archive.org/web/20150520000821/http://natmonitor.com/2015/05/17/nasas-plan-to-use-bacteria-to-produce-oxygen-on-mars/ |url-status=live }}</ref> Being able to create oxygen there would provide considerable cost-savings to NASA and allow for longer human visits to Mars than would be possible if astronauts have to transport their own heavy oxygen tanks.<ref name="Beach2015"/> This biological process, called ''ecopoiesis'', would be isolated, in contained areas, and is not meant as a type of global [[planetary engineering]] for terraforming of Mars's atmosphere,<ref name="NIAC2014"/><ref name="Beach2015"/> but NASA states that "This will be the first major leap from laboratory studies into the implementation of experimental (as opposed to analytical) planetary ''in situ'' research of greatest interest to planetary biology, ecopoiesis, and terraforming."<ref name="NIAC2014"/>

Research at the [[University of Arkansas]] presented in June 2015 suggested that some [[methanogen]]s could survive in [[Atmosphere of Mars|Mars's low pressure]].<ref name='Mickol'>{{cite news |url=https://www.sciencedaily.com/releases/2015/06/150602125843.htm |title=Earth organisms survive under low-pressure Martian conditions |work=University of Arkansas |date=June 2, 2015 |access-date=2015-06-04 |archive-date=June 4, 2015 |archive-url=https://web.archive.org/web/20150604065906/https://www.sciencedaily.com/releases/2015/06/150602125843.htm |url-status=live }}</ref> Rebecca Mickol found that in her laboratory, four species of methanogens survived low-pressure conditions that were similar to a subsurface liquid [[aquifer]] on Mars. The four species that she tested were ''[[Methanothermobacter]] wolfeii'', ''[[Methanosarcina]] barkeri'', ''[[Methanobacterium]] formicicum'', and ''[[Methanococcus maripaludis]]''.<ref name='Mickol'/> Methanogens do not require oxygen or organic nutrients, are non-photosynthetic, use hydrogen as their energy source and carbon dioxide (CO<sub>2</sub>) as their carbon source, so they could exist in subsurface environments on Mars.<ref name='Mickol'/>

===Protecting the atmosphere===
[[File:PIA18613-MarsMAVEN-Atmosphere-3UV-Views-20141014.jpg|thumb|upright=1.75|[[Atmosphere of Mars|Escaping atmosphere]] on Mars ([[carbon]], [[oxygen]], and [[hydrogen]]) by [[MAVEN]] in [[Ultraviolet–visible spectroscopy|UV]]<ref name="NASA-20141014-NJ">{{cite web |last1=Jones |first1=Nancy |last2=Steigerwald |first2=Bill |last3=Brown |first3=Dwayne |last4=Webster |first4=Guy |title=NASA Mission Provides Its First Look at Martian Upper Atmosphere |url=http://www.jpl.nasa.gov/news/news.php?release=2014-351 |date=October 14, 2014 |publisher=NASA |access-date=October 15, 2014 |archive-date=October 19, 2014 |archive-url=https://web.archive.org/web/20141019184946/http://www.jpl.nasa.gov/news/news.php?release=2014-351 |url-status=live }}</ref>]]

One key aspect of terraforming Mars is to protect the atmosphere (both present and future-built) from being lost into space. Some scientists hypothesize that creating a planet-wide artificial magnetosphere would be helpful in resolving this issue. According to two NIFS Japanese scientists, it is feasible to do that with current technology by building a system of refrigerated latitudinal superconducting rings, each carrying a sufficient amount of [[direct current]].<ref>{{cite web |url=http://www.nifs.ac.jp/report/NIFS-886.pdf |title=Feasibility of Artificial Geomagnetic Field Generation by a Superconducting Ring Network |last1=Motojima |first1=Osamu |last2=Yanagi |first2=Nagato |work=National Institute for Fusion Science (Japan) |date=May 2008 |access-date=2016-06-07 |archive-date=September 10, 2016 |archive-url=https://web.archive.org/web/20160910063154/http://www.nifs.ac.jp/report/NIFS-886.pdf |url-status=live }}</ref>

In the same report, it is claimed that the economic impact of the system can be minimized by using it also as a planetary energy transfer and storage system (SMES).

====Magnetic shield at L<sub>1</sub> orbit====
[[File:Magnetic shield on L1 orbit around Mars.png|thumb|upright=1.3|Magnetic shield on L1 orbit around Mars]]
During the Planetary Science Vision 2050 Workshop<ref name="green2017"/> in late February 2017, NASA scientist Jim Green proposed a concept of placing a [[magnetic dipole]] field between the planet and the Sun to protect it from high-energy solar particles. It would be located at the Mars [[Lagrange point#L1|Lagrange orbit L<sub>1</sub>]] at about 320 R<sub>♂</sub>, creating a partial and distant artificial magnetosphere. The field would need to be "Earth comparable" and sustain {{val|50|u=uT}} as measured at 1 Earth-radius. The paper abstract cites that this could be achieved by a magnet with a strength of {{convert|1|-|2|T|G|abbr=off|lk=on}}.<ref>{{cite web | url = https://livestream.com/viewnow/vision2050/videos/150701155 | title = Policy, Pathways, Techniques, and Capabilities – from NASA Planetary Science: Vision 2050 (Talk: A Future Mars Environment for Science and Exploration) | access-date = March 13, 2017 | archive-date = March 14, 2017 | archive-url = https://web.archive.org/web/20170314063510/https://livestream.com/viewnow/vision2050/videos/150701155 | url-status = live }}{{rp|1:36:00}}</ref> If constructed, the shield may allow the planet to partially restore its atmosphere.<ref>{{cite magazine | url = https://www.wired.co.uk/article/magnetic-shield-mars-habitable | title = NASA wants to put a giant magnetic shield around Mars so humans can live there | magazine = Wired |first=Abigail |last=Beall |date=2017-03-06| access-date = September 15, 2017 | archive-date = September 13, 2017 | archive-url = https://web.archive.org/web/20170913231513/http://www.wired.co.uk/article/magnetic-shield-mars-habitable | url-status = live }}</ref><ref>{{cite web | url = http://www.popularmechanics.com/space/moon-mars/a25493/magnetic-shield-mars-atmosphere/ | title = NASA Considers Magnetic Shield to Help Mars Grow Its Atmosphere | date = March 1, 2017 |first=Jay |last=Bennett | work = Popular Mechanics | access-date = March 13, 2017 | archive-date = March 14, 2017 | archive-url = https://web.archive.org/web/20170314064106/http://www.popularmechanics.com/space/moon-mars/a25493/magnetic-shield-mars-atmosphere/ | url-status = live }}</ref><ref name="green2017"/>

====Plasma torus along the orbit of Phobos====
A plasma torus along the orbit of Phobos by ionizing and accelerating particles from the moon may be sufficient to create a magnetic field strong enough to protect a terraformed Mars.<ref>{{Cite journal |last1=Bamford |first1=R.A. |last2=Kellett |first2=B.J. |last3=Green |first3=J.L. |last4=Dong |first4=C. |last5=Airapetian |first5=V. |last6=Bingham |first6=R. |date=2022 |title=How to create an artificial magnetosphere for Mars |journal=Acta Astronautica |language=en |volume=190 |pages=323–333 |doi=10.1016/j.actaastro.2021.09.023|doi-access=free |arxiv=2111.06887 |bibcode=2022AcAau.190..323B }}</ref><ref>{{cite news |last1=Koberlein |first1=Brian |title=An Absolutely Bonkers Plan to Give Mars an Artificial Magnetosphere |url=https://www.universetoday.com/153368/an-absolutely-bonkers-plan-to-give-mars-an-artificial-magnetosphere/ |access-date=22 November 2021 |work=[[Universe Today]] |date=19 November 2021}}</ref><!-- Needs more research -->

===Oxygen from electrolysis of water===
{{See also|Mars Oxygen ISRU Experiment|High-temperature electrolysis|High-pressure electrolysis}}
An abundance of [[groundwater on Mars]] was discovered in 2024.<ref>{{cite web | url=https://www.smithsonianmag.com/smart-news/mars-hosts-a-giant-reservoir-of-water-underground-we-just-cant-easily-reach-it-study-finds-180984888/#:~:text=Data%20from%20NASA%27s%20InSight%20lander,7%20and%2013%20miles%20deep | title=Mars Hosts a Giant Reservoir of Water Underground, We Just Can't Easily Reach It, Study Finds }}</ref> It is estimated that 7 [[Zettawatt]]-hours of electricity would need to be produced from [[nuclear fusion]] or [[nuclear fission|fission]] to produce oxygen levels equivalent to [[Atmosphere of Earth|Earth's atmosphere]], by splitting water into hydrogen and oxygen by [[Electrolysis of water|electrolysis]].  120 trillion tons of hydrogen and 880 trillion tons of oxygen would be produced in the process,<ref>{{cite web | url=https://www.thespacereview.com/article/4697/1#:~:text=The%202.1%20tons%20per%20square,304%20trillion%20tons%20of%20oxygen | title=The Space Review: Oxygen for Mars }}</ref> along with [[water vapor]] from the power plants.

===Paraterraforming and GMO designer plants===
{{See also|Climate of Mars|Martian regolith simulant|Superoxide reductase|Horizontal gene transfer|Epigenetics| Deinococcus radiodurans|Gene stacking|Rhizobium|Agrobacterium|Earth BioGenome Project|Bioinformatics|Computational genomics|Finding the Mother Tree}}
{{multiple image
 | align = right
 | total_width = 480
 | image1 = Mars tension fabric greenhouse.webp
 | caption1 = 3D sketch of a Mars [[Tension fabric buildings|tension fabric]] greenhouse with [[genetically modified plant]]s outside, [[Genetic engineering|gene edited]] [[Pine trees]] or [[Conifer]]s<ref>{{Cite web|url=https://www.researchgate.net/publication/336234069_Crop_growth_and_viability_of_seeds_on_Mars_and_Moon_soil_simulants|title=(PDF) Crop growth and viability of seeds on Mars and Moon soil simulants|website=ResearchGate}}</ref><ref>{{cite web | url=https://www.isaaa.org/kc/cropbiotechupdate/article/default.asp?ID=20099 | title=Growing Crops on Mars Possible with Gene Editing }}</ref>
 | image2 = Mars greenhouse inside.webp
 | caption2 = Inside tension fabric greenhouse with [[plant LED incubator]]s and automatic [[irrigation controller|irrigation controlled]] watering on a grow table
}}
Paraterraforming is a concept to build [[Planetary habitability|habitable]] [[greenhouse]]s or [[Closed ecological system|bio-dome]]s to help build [[plant life]] on other planets. NASA's [[NASA Institute for Advanced Concepts|NIAC]] is sponsoring [[North Carolina State University|NC State]] which is working on designer plants/trees or [[Genetically modified plant|genetically modified]] [[vegetation]] that could survive better on Mars. Using [[CRISPR gene editing]] from [[Extremophile]]s on Earth to help withstand the harsh [[Martian regolith]] and [[Atmosphere of Mars|atmosphere]], such as [[ultraviolet radiation]], extreme cold, low [[atmospheric pressure]], [[Perchlorate]]s, and [[drought tolerance]].<ref>{{cite web | url=https://www.nasa.gov/news-release/nasa-designer-plants-on-mars/ | title=NASA - Designer Plants on Mars - NASA }}</ref>  The plants could be tested outdoors to try and start an [[ecosystem]] for the full terraforming of Mars.<ref>{{cite web | url=https://interestingengineering.com/science/making-a-greenhouse-on-another-world-where-can-we-paraterraform-in-our-solar-system | title=Making a Greenhouse on Another World: Where Can We Paraterraform in Our Solar System? }}</ref>

==Thermodynamics of terraforming==
The overall energy required to sublimate the {{CO2}} from the south polar ice cap was modeled by Zubrin and McKay in 1993.<ref name="Requirements"/> If using orbital mirrors, an estimated 120 [[Watt-hour|MW-year]]s of electrical energy would be required to produce mirrors large enough to vaporize the ice caps. This is considered the most effective method, though the least practical. If using powerful halocarbon greenhouse gases, an order of 1,000 MW-years of electrical energy would be required to accomplish this heating. However, if all of this {{CO2}} were put into the atmosphere,
it would only double<ref name=JakoskyLPS/> the current atmospheric pressure from 6 mbar to 12 mbar, amounting to about 1.2% of Earth's mean sea level pressure. The amount of warming that could be produced today by putting even 100 mbar of {{CO2}} into the atmosphere is small, roughly of order {{val|10|u=K}}.<ref name=JakoskyLPS/> Additionally, once in the atmosphere, it likely would be removed quickly, either by diffusion into the subsurface and [[adsorption]] or by re-condensing onto the polar caps.<ref name=JakoskyLPS/>

The surface or atmospheric temperature required to allow liquid water to exist has not been determined, and liquid water
conceivably could exist when atmospheric temperatures are as low as {{convert|245|K|C F}}. However, a warming of {{val|10|u=K}} is much less than thought necessary to produce liquid water.<ref name=JakoskyLPS/>

==See also==
* {{annotated link|Astrobotany}}
* [[Areography]] (geography of Mars)
* {{annotated link|Colonization of Mars}}
* {{annotated link|Human mission to Mars}}
* {{annotated link|Mars habitat}}
* {{Section link|Mars in fiction|Terraforming}}
* {{annotated link|Mars to Stay}}
* {{annotated link|Terraforming of Venus}}
* {{annotated link|Colonization of the Solar System}}
* {{annotated link|Groundwater on Mars}}

==References==
{{reflist}}

==External links==
* {{webarchive |url=https://web.archive.org/web/20070915152013/http://aerospacescholars.jsc.nasa.gov/HAS/cirr/em/10/10.cfm |date=September 15, 2007 |title=NASA – Aerospace Scholars: Terraforming Mars }}
* [https://web.archive.org/web/20081229002652/http://www.spectrum.ieee.org/oct07/5584 Recent Arthur C Clarke interview mentions terraforming]
* [http://www.redcolony.com/ Red Colony]
* [https://web.archive.org/web/20070123205649/http://society.terraformers.ca/ Terraformers Society of Canada]
* [http://www.users.globalnet.co.uk/~mfogg/zubrin.htm Research Paper: Technological Requirements for Terraforming Mars]
* [http://www.nexialquest.com/The%20Terraformation%20of%20Worlds.pdf Peter Ahrens The Terraformation of Worlds]

{{Human missions to Mars}}
{{Mars}}
{{Space colonization}}
{{Portal bar|Science|Solar System|Technology}}

{{DEFAULTSORT:Terraforming Of Mars}}
[[Category:Climate of Mars]]
[[Category:Exploration of Mars]]
[[Category:Science fiction]]
[[Category:Terraforming|Mars]]