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'{{speculation|date=October 2013}} [[Image:MarsTransitionV.jpg|thumb|320px|right|Artist's conception of the process of terraforming Mars.]] send gummi to space and let him fart all over mars The '''terraforming of Mars''' is the hypothetical process by which [[Climate of Mars|Martian climate]], surface, and known properties would be deliberately changed with the goal of making large areas of the environment more hospitable to human habitation, thus making [[Colonization of Mars|human colonization]] much safer and more sustainable. The concept relies on the assumption that the environment of a planet can be [[terraforming|altered through artificial means]]. In addition, the feasibility of creating a planetary [[biosphere]] on [[Mars]] is undetermined. There are several proposed methods, some of which present prohibitive economic and natural resource costs, and others that may be currently technologically achievable.<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]]|year=1993?}}</ref> == Motivation and ethics == {{See also|Ethics of terraforming}} Future population growth and demand for resources may necessitate human colonization of objects other than [[Earth]], such as [[Mars]], the [[Moon]], and nearby planets. [[Space colonization]] will facilitate harvesting the [[Solar System]]'s energy and material resources.<ref name="MTS-1994">{{cite web |last=Savage |first=Marshall T. |title=The Millennial Project: Colonizing the Galaxy in Eight Easy Steps |url=http://www.amazon.com/The-Millennial-Project-Colonizing-Galaxy/dp/0316771635 |publisher=[[Little, Brown and Company]] (Amazon.com) |year=1994 |asin=0316771635 |accessdate=September 28, 2013 }}</ref> In many respects, Mars is the most Earth-like of all the other planets in the Solar System. It is thought<ref name="Space-20130408">{{cite web |last=Wall |first=Mike |title=Most of Mars' Atmosphere Is Lost in Space |url=http://www.space.com/20560-mars-atmosphere-lost-curiosity-rover.html |date=April 8, 2013 |work=[[Space.com]] |accessdate=April 9, 2013 }}</ref> that Mars once did have a more Earth-like environment early in [[geological history of Mars|its history]], with a thicker [[atmosphere]] and abundant water that was [[Atmospheric escape#Comparison of non-thermal loss processes based on planet and particle mass|lost over the course of hundreds of millions of years]]. Given the foundations of similarity and proximity, Mars would make one of the most efficient and effective terraforming targets in the Solar System. Ethical considerations of terraforming include the potential displacement or destruction of [[Life on Mars|indigenous life]], even if microbial, if such life exists.{{citation needed|date=July 2014}} == Challenges and limitations == {{See also|Colonization of Mars}} The Martian environment presents several terraforming challenges to overcome and the extent of terraforming may be limited by certain key environmental factors. === Low gravity === {{see also|Effects of low gravity on humans}} 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>[http://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ Gravity Hurts (so Good)] - NASA 2001</ref> Additionally, the low gravity (and thus low [[escape velocity]]) of Mars may render it more difficult for it to retain an atmosphere when compared to the more massive Earth and [[Venus]].<ref name="Ludin & Barabash">{{cite journal|last=Lundin|first=Rickard|author2=Stanislav Barabash |title=Evolution of the Martian atmosphere and hydrosphere: Solar wind erosion studied by ASPERA-3 on Mars Express|journal=Planetary and Space Science|year=2004|volume=52|issue=11|pages=1059–71|doi=10.1016/j.pss.2004.07.020|url=http://www.sciencedirect.com/science/article/pii/S0032063304000832|accessdate=3 May 2013}}</ref> Earth and Venus are both able to sustain thick atmospheres, even though they experience more of the solar wind that is believed to strip away planetary volatiles. Continuing sources of atmospheric gases on Mars might therefore be required to ensure that an atmosphere sufficiently dense for humans is sustained in the long term. === Countering the effects of space weather === {{See also|Health threat from cosmic rays}} Mars lacks a [[magnetosphere]], which poses challenges for mitigating solar radiation and retaining atmosphere. It is believed that fields detected on Mars are remnants of a magnetosphere that collapsed early in its history. The lack of a magnetosphere is thought to be one reason for Mars's thin atmosphere. [[Solar wind|Solar-wind]]-induced ejection of Martian atmospheric atoms has been detected by Mars-orbiting probes. Venus, however, clearly demonstrates that the lack of a magnetosphere does not preclude a dense atmosphere. Earth abounds with water because its ionosphere is permeated with a magnetosphere. The hydrogen ions present in its ionosphere move very fast due to their small mass, but they cannot escape to outer space because their trajectories are deflected by the magnetic field. Venus has a dense atmosphere, but only traces of water vapor (20 ppm) because it has no magnetic field. The Martian atmosphere also loses water to space. Earth's ozone layer provides additional protection. Ultraviolet light is blocked before it can dissociate water into hydrogen and oxygen. Because little water vapor rises above the troposphere and the ozone layer is in the upper stratosphere, little water is dissociated into hydrogen and oxygen. The Earth's magnetic field is 31 [[Tesla (unit)|µT]]. Mars would require a similar magnetic-field intensity to similarly offset the effects of the solar wind at its distance further from the Sun. The technology for inducing a planetary-scale [[magnetic field]] does not currently exist. The importance of magnetosphere has been brought into question. In the past, Earth has regularly had periods where the magnetosphere [[Geomagnetic reversal|changed direction]],<ref>{{cite web|url=http://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield/|title=Earth's Inconstant Magnetic Field|work=Science@Nasa|last=Phillips|first=Tony|date=December 29, 2003|accessdate=March 17, 2012}}</ref> yet life has continued to survive. A thick atmosphere similar to Earth's could also provide protection against solar radiation in the absence of a magnetosphere.<ref>{{cite web|url=http://www.phy6.org/earthmag/magnQ&A1.htm#q6}}</ref> == Advantages == {{See also|Atmosphere of Mars}} {{Refimprove section|date=February 2013}} [[File:TerraformedMarsGlobeRealistic.jpg|thumb|Hypothetical terraformed Mars]] According to modern theorists, Mars exists on the outer edge of the [[habitable zone]], a region of the Solar System where life can exist. Mars is on the border of a region known as the extended habitable zone where concentrated greenhouse gases could support the liquid water on the surface at sufficient atmospheric pressure. Therefore, Mars has the potential to support a hydrosphere and biosphere.{{citation needed|date=February 2013}} 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, though the details of such a process are still not well understood. It has been suggested that Mars once had an environment relatively similar to that of Earth during an earlier stage in its development.<ref> {{cite web| url = http://science.nasa.gov/headlines/y2008/21nov_plasmoids.htm?list59243 | title = Solar Wind Rips Up Martian Atmosphere | publisher = NASA | author = Dr. Tony Phillips | date = 21 November 2008 }}</ref> Although water appears to have once been present on the Martian surface, water appears to exist at the poles just below the planetary surface as [[permafrost]]. On September 26, 2013, NASA scientists reported the [[Mars]] [[Curiosity (rover)|Curiosity rover]] detected "abundant, easily accessible" [[Water on Mars|water]] (1.5 to 3 weight percent) in [[Martian soil|soil samples]] at the [[Rocknest (Mars)|Rocknest region]] of [[Aeolis Palus]] in [[Gale Crater]].<ref name="ST-20130926">{{cite web |last=Lieberman |first=Josh |title=Mars Water Found: Curiosity Rover Uncovers 'Abundant, Easily Accessible' Water In Martian Soil |url=http://www.isciencetimes.com/articles/6131/20130926/mars-water-soil-nasa-curiosity-rover-martian.htm |date=September 26, 2013 |work=iSciencetimes |accessdate=September 26, 2013 }}</ref><ref name="Science-20130926a">{{cite journal |author=Leshin, L. A. et al |title=Volatile, Isotope, and Organic Analysis of Martian Fines with the Mars Curiosity Rover |url=http://www.sciencemag.org/content/341/6153/1238937 |date=September 27, 2013 |journal=[[Science (journal)]] |volume=341 |number=6153 |doi=10.1126/science.1238937 |accessdate=September 26, 2013 }}</ref><ref name="Science-20130926">{{cite journal |last=Grotzinger |first=John |title=Introduction To Special Issue: Analysis of Surface Materials by the Curiosity Mars Rover |url=http://www.sciencemag.org/content/341/6153/1475.full |date=September 26, 2013 |journal=[[Science (journal)]] |volume=341 |number=6153 |page=1475 |doi=10.1126/science.1244258 |accessdate=September 27, 2013 }}</ref><ref name="NASA-20130926a">{{cite web |last1=Neal-Jones |first1=Nancy |last2=Zubritsky |first2=Elizabeth |last3=Webster |first3=Guy |last4=Martialay |first4=Mary |title=Curiosity's SAM Instrument Finds Water and More in Surface Sample |url=http://www.nasa.gov/content/goddard/curiositys-sam-instrument-finds-water-and-more-in-surface-sample/ |date=September 26, 2013 |work=[[NASA]] |accessdate=September 27, 2013 }}</ref><ref name="NASA-20130926b">{{cite web |last1=Webster |first1=Guy |last2=Brown |first2=Dwayne |title=Science Gains From Diverse Landing Area of Curiosity |url=http://www.nasa.gov/mission_pages/msl/news/msl20130926.html |date=September 26, 2013 |work=[[NASA]] |accessdate=September 27, 2013 }}</ref> The [[soil]] and [[atmosphere of Mars]] contain many of the main elements{{which|date=December 2012}} needed for life.{{Citation needed|date=December 2012}} 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 stored in the south pole of Mars, which, if melted, would correspond to a planetwide ocean 11 meters deep.<ref>{{Cite journal | author=R.C. | title=Radar Probes Frozen Water at Martian Pole | journal=Science News | volume=171 | issue=13 | page=206 |date=March 2007 | jstor=20055502 | doi=10.1002/scin.2007.5591711315 | url=http://www.sciencenews.org/view/generic/id/8369/title/Radar_probes_frozen_water_at_Martian_pole}}{{subscription required}}</ref> Frozen [[carbon dioxide]] ({{CO2}}) at the poles [[sublimation (phase transition)|sublimate]]s 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}} This seasonal occurrence transports large amounts of [[dust]] and [[water vapor]] into the atmosphere, forming Earth-like clouds.<ref>{{cite web|title=Water Clouds on Mars|url=http://www.nasa.gov/mission_pages/phoenix/images/press/16145-animated.html|accessdate=1 August 2014}}</ref> Most of the oxygen in the Martian atmosphere is present as carbon dioxide ({{CO2}}), the main atmospheric component. Molecular [[oxygen]] (O₂) only exists in trace amounts. Large amounts of elemental 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 |year=1984|publisher=St. Martin's Press|isbn=9780312350246}}</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 web|last=Hecht et al.|title=Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site|url=http://www.sciencemag.org/content/325/5936/64.abstract|publisher=Science Magazine|accessdate=13 January 2014}}</ref> [[Electrolysis]] could be employed to separate water on Mars into oxygen and [[hydrogen]] if sufficient liquid water and electricity were available.{{Citation needed|date=December 2012}} == Proposed methods and strategies == {| class="wikitable" | style="float:right;" |+ '''Comparison of dry atmosphere''' ! ! [[Atmosphere of Mars|Mars]] ! [[Atmosphere of Earth|Earth]] |- ! Pressure || {{convert|0.6|kPa|abbr=on}} || {{convert|101.3|kPa|abbr=on}} |- ! [[Carbon dioxide]] ({{CO2}}) || 96.0% || 0.04% |- ! [[Argon]] (Ar) || 2.1% || 0.93% |- ! [[Nitrogen]] (N₂) || 1.9% || 78.08% |- ! [[Oxygen]] (O₂) || 0.145% || 20.94% |} [[Image:TerraformedMarsTharsis.jpg|thumb|250px|Artist's conception of a terraformed Mars centered on the Tharsis region]] [[Image:TerraformedMars.jpg|thumb|right|250px|Artist's conception of a terraformed Mars. This portrayal is approximately centered on the prime meridian and 30° North latitude, and a hypothesized ocean with a sea level at approximately two kilometers below average surface elevation. The ocean submerges what are now [[Vastitas Borealis]], [[Acidalia Planitia]], [[Chryse Planitia]], and [[Xanthe Terra]]; the visible landmasses are [[Tempe Terra]] at the left, [[Aonia Terra]] at the bottom, [[Terra Meridiani]] at the lower right, and [[Arabia Terra]] at the upper right. Rivers that feed the ocean at the lower right occupy what are now [[Valles Marineris]] and [[Ares Vallis]] and the large lake at the lower right occupies what is now [[Aram Chaos]].]] Terraforming Mars would entail three major interlaced changes: building up the atmosphere, keeping it warm, and keeping the atmosphere from being lost to outer space. 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 one another, favoring terraforming. The tremendous air currents generated by the moving gases would create large, sustained dust storms, which would heat the atmosphere (by absorbing solar radiation).{{citation needed|date=April 2012}} === Carbon dioxide sublimation === There is presently enough carbon dioxide ({{CO2}}) as ice in the Martian south pole and absorbed by regolith (soil) on Mars that, if sublimated to gas by a climate warming of only a few degrees, would increase the atmospheric pressure to {{convert|30|kPa|atm}},<ref name="channel.nationalgeographic.com">{{cite web|author=USA |url=http://channel.nationalgeographic.com/channel/episodes/mars-making-the-new-earth/ <!-- DEAD LINK: http://channel.nationalgeographic.com/episode/mars-making-the-new-earth-4588/living-on-mars#tab-living-on-mars/10 --> |title=Mars -- Making the New Earth: Living on Mars |publisher=National Geographic |accessdate=2011-08-20}}</ref> comparable to the altitude of the peak of [[Mount Everest]], where the atmospheric pressure is {{convert|33.7|kPa|atm}}. Although this would not be breathable by humans, it is above the [[Armstrong limit]] and would eliminate the present need for pressure suits. [[Phytoplankton]] can also convert dissolved {{CO2}} into oxygen, which is important because Mars's low temperature will, by [[Henry's law]], lead to a high ratio of dissolved {{CO2}} to atmospheric {{CO2}} in the flooded{{Clarify|date=February 2013}} northern basin. === Importing ammonia === Another more intricate method uses [[ammonia]] as a powerful [[greenhouse gas]]. It is possible that large amounts of it exist in frozen form on minor planets orbiting in the [[outer Solar System]]. It may be possible to move these and send them into Mars's atmosphere.<ref name="ColeCox1964">{{Cite book |author1=[[Dandridge M. Cole]] |author2=Donald William Cox |title=Islands in Space: The Challenge of the Planetoids |year=1964 |publisher=Chilton Books |pages=126–127}}</ref> Because ammonia (NH₃) is mostly [[nitrogen]] by weight, it could also supply the [[buffer gas]] for the atmosphere. Sustained smaller impacts will also contribute to increases in the temperature and mass of the atmosphere. The need for a buffer gas is a challenge that will face any potential atmosphere builders. On [[Earth]], nitrogen is the primary atmospheric component, making up 78% of the atmosphere. Mars would require a similar buffer-gas component although not necessarily as much. Obtaining sufficient quantities of nitrogen, [[argon]] or some other comparatively inert gas is difficult. === Importing hydrocarbons === Another way to create a martian atmosphere would be to import [[methane]] or other [[hydrocarbons]],<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=2007-02-27 |accessdate=2011-08-20}}</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?}}</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. Methane (or other hydrocarbons) could be helpful to increase atmospheric pressure. These gases also can be used to produce water and {{CO2}} for the Martian atmosphere: :[[Methane|CH₄]] + 4 [[Iron(III) oxide|Fe₂O₃]] → [[Carbon dioxide|{{CO2}}]] + 2 [[Water|H₂O]] + 8 [[Iron(II) oxide|FeO]] This reaction could probably be initiated by heat or by Martian solar UV irradiation. Large amounts of the resulting products ({{CO2}} and water) are necessary for photosynthesis, which would be the next step in terraforming. === Importing hydrogen === [[Hydrogen]] could be imported for atmosphere and [[hydrosphere]] engineering.<ref> {{cite web| url = http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ISRU/08Atmos.htm | title = Mars Atmospheric Resources | publisher = [[Johnson Space Center]] | date = 28 September 1998 }}</ref> For example, hydrogen could react with [[iron(III) oxide]] from the [[Martian soil]], which would give water as a product: :[[Hydrogen|H₂]] + [[Iron(III) oxide|Fe₂O₃]] → [[Water|H₂O]] + 2[[Iron(II) oxide|FeO]] Depending on the level of carbon dioxide in the atmosphere, importation and reaction of hydrogen would produce heat, water and [[graphite]] via the [[Bosch reaction]]. Alternatively, reacting [[hydrogen]] with the carbon dioxide atmosphere via the [[Sabatier reaction]] would yield [[methane]] and water. === Use of fluorine compounds === Because long-term climate stability would be required for sustaining a human population, the use of especially powerful fluorine-bearing [[greenhouse gases]], possibly including [[sulfur hexafluoride]] or halocarbons such as [[chlorofluorocarbon]]s (or CFCs) and [[perfluorocarbon]]s (or PFCs), has been suggested.<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 | year = 2001 | url = http://www.pnas.org/content/98/5/2154.full.pdf }}</ref> These gases are the most cited candidates for artificial insertion into the Martian atmosphere because they produce a strong effect as a greenhouse gas, thousands of times stronger than {{CO2}}. This can conceivably be done relatively cheaply by sending rockets with payloads of compressed CFCs on collision courses with Mars.<ref name=Lovelock/> When the rockets crash onto the surface they 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 changes chemically and becomes warmer. In order to sublimate the south polar {{CO2}} glaciers, Mars would require the introduction of approximately 0.3 microbars of CFCs into Mars's atmosphere. This is equivalent to a mass of approximately 39 million metric tons. This is about three times the amount of CFC manufactured on Earth from 1972 to 1992 (when CFC production was banned by international treaty). Mineralogical surveys of Mars estimate the elemental presence of fluorine in the bulk composition of Mars at 32 ppm by mass vs. 19.4 ppm for the Earth.<ref name="Gasses"/> A proposal to mine fluorine-containing minerals as a source of CFCs and PFCs is supported by the belief that because these minerals are expected to be at least as common on Mars as on Earth, this process could sustain the production of sufficient quantities of optimal greenhouse compounds (CF₃SCF₃, CF₃OCF₂OCF₃, CF₃SCF₂SCF₃, CF₃OCF₂NFCF₃, C₁₂F₂₇N) to maintain Mars at 'comfortable' temperatures, as a method of maintaining an Earth-like atmosphere produced previously by some other means.<ref name=Gasses/> === 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 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 {{CO2}} ice sheet and contribute to the warming greenhouse effect. === Albedo reduction === Reducing the [[albedo]] of the Martian surface would also make more efficient use of incoming sunlight.<ref>{{cite web| url=http://www.nexialquest.com/The%20Terraformation%20of%20Worlds.pdf| title=The Terraformation of Worlds| author=Peter Ahrens| publisher= Nexial Quest| format=PDF| accessdate=2007-10-18}}</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]]. The ground would then absorb more sunlight, warming the atmosphere. 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. The {{CO2}} is mostly converted to carbohydrates.<ref>http://www.howplantswork.com/2009/02/16/plants-dont-convert-co2-into-o2/</ref> On 26 April 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#Life 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=26 April 2012 |publisher=Skymania |accessdate=27 April 2012 }}</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=26 April 2012 |publisher=[[European Geosciences Union]] |accessdate=27 April 2012 }}</ref> === Asteroid impact === Another way to increase the [[temperature]] could be to direct small [[asteroids]] onto the Martian surface. This could be achieved through use of spaceborne lasers to alter trajectories or other methods proposed for [[asteroid impact avoidance]]. The impact energy would be released as heat. This heat could sublimate {{CO2}} or, if there is liquid water present at this stage of the terraforming process, could vaporize it to steam, which is also a [[greenhouse gas]]. Asteroids could also be chosen for their composition, such as [[ammonia]], which would then disperse into the atmosphere on impact, adding greenhouse gases to the [[atmosphere]]. Lightning may have built up nitrate beds in Mars's soil.<ref name="channel.nationalgeographic.com"/> Impacting asteroids on these nitrate beds would release additional nitrogen and oxygen into the atmosphere. ==Thermodynamics of terraforming== The overall energy required to sublimate the {{CO2}} from the south polar ice cap is modeled by Zubrin and McKay.<ref name="Requirements"/> Raising temperature of the poles by four kelvin would be necessary in order to trigger a runaway greenhouse effect. If using orbital mirrors, an estimated 120 MWe-years would be required in order 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 1000 MWe-years would be required to accomplish this heating. Although ineffectual in comparison, it is considered the most practical method. Impacting an asteroid, which is often considered a synergistic effect, would require approximately four 10-billion-tonne ammonia-rich asteroids to trigger the runaway greenhouse effect, totaling an eight degree increase in temperature. ==See also== * [[Colonization of Ceres]] * [[Colonization of Mars]] * [[Mars to Stay]] * [[Terraforming of Europa]] * [[Terraforming of Venus]] ==References== <!--Please use this reference generator: http://toolserver.org/~magnus/makeref.php --> {{Reflist|30em}} ==External links== *{{Wayback|url=http://aerospacescholars.jsc.nasa.gov/HAS/cirr/em/10/10.cfm|title=NASA - Aerospace Scholars: Terraforming Mars|date=20070915152013}} *[http://www.spectrum.ieee.org/oct07/5584 Recent Arthur C Clarke interview mentions terraforming] *[http://www.redcolony.com/ Red Colony] *[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] *[http://www.marsdrive.com/ MARSDRIVE: Colonizing Mars]. Red Colony parent organization planning the future exploration and colonization of planet Mars. {{Mars}} {{Manned mission to Mars}} {{Mars spacecraft}} {{portal bar|Mars}} {{DEFAULTSORT:Terraforming Of Mars}} [[Category:Exploration of Mars]] [[Category:Terraforming]] [[es:Terraformación de Marte]]'