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{{Short description|Proposed concepts for human settlements on Mars}}
{{redirect|Occupy Mars|SpaceX's program|SpaceX Mars colonization program}}
{{Use American English|date=November 2020}}
{{Use mdy dates|date=November 2020}}
[[File:Interplanetary Transport System (29343823914).jpg|thumb|upright=1.3|A rendering of the [[Interplanetary Transport System]] approaching Mars, a concept colonyship of the in-development [[SpaceX Mars Colonization Program]]]]
The '''colonization of Mars''' is the proposed process of establishing permanent [[human settlement]]s on the planet [[Mars]].<ref name="h987">{{cite web | last=Wall | first=Mike | title=Bill Nye: It's Space Settlement, Not Colonization | website=Space.com | date=2019-10-25 | url=https://www.space.com/bill-nye-space-settlement-not-colonization.html | access-date=2024-07-13}}</ref> Most colonization concepts focus on settling, but [[colonization]] is a broader ethical concept,<ref name="Space Policy">{{cite journal | last1=Puumala | first1=Mikko M. | last2=Sivula | first2=Oskari | last3=Lehto | first3=Kirsi | title=Moving to Mars: The Feasibility and Desirability of Mars Settlements | journal=Space Policy | volume=66 | date=2023 | doi=10.1016/j.spacepol.2023.101590 | article-number=101590| doi-access=free | bibcode=2023SpPol..6601590P }}</ref> which international [[space law]] has limited,<ref name="v667">{{cite journal | last=Eijk | first=Cristian van | title=Sorry, Elon: Mars is not a legal vacuum – and it's not yours, either | journal=Völkerrechtsblog | date=2020 | publisher=Fachinformationsdienst für internationale und interdisziplinäre Rechtsforschung | doi=10.17176/20210107-183703-0 | url=https://intr2dok.vifa-recht.de/receive/mir_mods_00009795 | access-date=2024-07-13 | page=}}</ref> and national space programs have avoided,<ref name="u584">{{cite web | last=Bartels | first=Meghan | title=Should We Colonize Space or Decolonize It? | website=Newsweek | date=2018-05-25 | url=https://www.newsweek.com/should-we-colonize-space-some-people-argue-we-need-decolonize-it-instead-945130 | access-date=2024-07-13}}</ref> instead focusing on [[human mission to Mars]] for [[Mars exploration|exploring the planet]]. The settlement of Mars would require the migration of humans to the planet, the establishment of a permanent human presence, and the exploitation of local resources.
No crewed missions to Mars have occurred, although there have been successful robotic [[List of missions to Mars|missions to the planet]]. Public space agencies (including [[NASA]], [[ESA]], [[Roscosmos]], [[Indian Space Research Organisation|ISRO]], the [[China National Space Administration|CNSA]], among others) have explored colonization concepts, but have primarily focused on further robotic exploration of Mars and the possibility of crewed landings. Some [[space advocacy]] groups, such as the [[Mars Society]] and the [[National Space Society]],<ref name="t667">{{cite web | title=The Case for Colonizing Mars, by Robert Zubrin | website=NSS | date=2017-08-03 | url=https://nss.org/the-case-for-colonizing-mars-by-robert-zubrin/ | access-date=2024-09-16}}</ref> as well as some private organizations, such as [[SpaceX]], have promoted the idea of colonization. The prospect of settling Mars has been explored extensively in [[Mars in fiction#Colonization|science fiction writing, film, and art]].
Challenges to settlement include the intense [[ionizing radiation]] that impacts the Martian surface, and the fine, toxic dust that covers the planet. Mars [[Atmosphere of Mars|has an atmosphere]], but it is unbreathable and thin. [[Climate of Mars#Temperature|Surface temperatures]] fluctuate widely, between {{Cvt|-70 and 0|C|F}}. While Mars has [[Water on Mars|underground water]] and [[Ore resources on Mars|other resources]], conditions do not favor power production using [[Wind power|wind]] and [[Solar power|solar]]; similarly, the planet has few resources for [[nuclear power]]. [[Mars's orbit|Mars' orbit]] is the third closest to [[Earth's orbit]], though far enough from Earth that the distance would present a serious obstacle to the movement of [[materiel]] and settlers. Justifications and motivations for colonizing Mars include technological curiosity, the opportunity to conduct in-depth observational research, the possibility that the settlement of other planets could decrease the probability of [[human extinction]], the interest in establishing a colony independent of Earth, and the potential benefits of economic exploitation of the planet's resources.
==Background==
===Terminology===
[[Colonization]] of Mars differs from the [[Human mission to Mars|crewed Mars exploration]] missions currently pursued by public space agencies, as they aim to land humans for [[exploration]].<ref name="f823">{{cite web | title=Why go to Mars? | website=ESA | url=https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/Why_go_to_Mars | access-date=September 17, 2024}}</ref><ref name="b015">{{cite web | title=Humans to Mars | website=NASA | date=March 10, 2023 | url=https://www.nasa.gov/humans-in-space/humans-to-mars/ | access-date=September 17, 2024}}</ref>
The terminology used to refer a potential human presence on Mars has been scrutinized since at least the 2010s,<ref name="u584">{{cite web | last=Bartels | first=Meghan | title=Should We Colonize Space or Decolonize It? | website=Newsweek | date=2018-05-25 | url=https://www.newsweek.com/should-we-colonize-space-some-people-argue-we-need-decolonize-it-instead-945130 | access-date=2024-07-13}}</ref> with [[space colonization]] in general since the 1977, as by [[Carl Sagan]], who preferred to refer to [[settlements in space]] as cities, instead of [[colonies]] because of the implied [[colonialism]]; the US State Department had already made clear to avoid the use of the term because of the colonialist meaning.{{when|date=November 2024}}<ref name="x516">{{cite journal | last=Scharmen | first=Fred | title=Highest and Best Use: Subjectivity and Climates Off and After Earth | journal=Journal of Architectural Education | volume=71 | issue=2 | date=2017-07-03 | issn=1046-4883 | doi=10.1080/10464883.2017.1340775 | pages=184–196}}</ref> Today "settlement" is preferred out of similar reasons, trying to avoid the broad<ref name="Space Policy">{{cite journal | last1=Puumala | first1=Mikko M. | last2=Sivula | first2=Oskari | last3=Lehto | first3=Kirsi | title=Moving to Mars: The Feasibility and Desirability of Mars Settlements | journal=Space Policy | volume=66 | date=2023 | doi=10.1016/j.spacepol.2023.101590 | article-number=101590| doi-access=free | bibcode=2023SpPol..6601590P }}</ref> sociopolitical connotations of colonization.<ref name="h987">{{cite web | last=Wall | first=Mike | title=Bill Nye: It's Space Settlement, Not Colonization | website=Space.com | date=2019-10-25 | url=https://www.space.com/bill-nye-space-settlement-not-colonization.html | access-date=2024-07-13}}</ref>
Today the term is most prominently used by [[Robert Zubrin]] and the [[SpaceX Mars colonization program]], with the term ''Occupy Mars'' also being used,<ref name="k411">{{cite web | last=Wattles | first=Jackie | title=Colonizing Mars could be dangerous and ridiculously expensive. Elon Musk wants to do it anyway | website=CNN | date=2020-09-08 | url=https://edition.cnn.com/2020/09/08/tech/spacex-mars-profit-scn/index.html | access-date=2024-09-16}}</ref> aspiring for an [[independence|independent]] Mars colony, despite limiting international [[space law]].<ref name="v667">{{cite journal | last=Eijk | first=Cristian van | title=Sorry, Elon: Mars is not a legal vacuum – and it's not yours, either | journal=Völkerrechtsblog | date=2020 | publisher=Fachinformationsdienst für internationale und interdisziplinäre Rechtsforschung | doi=10.17176/20210107-183703-0 | url=https://intr2dok.vifa-recht.de/receive/mir_mods_00009795 | access-date=2024-07-13 | page=}}</ref>
===Mission concepts===
Landers and [[Mars rover|rovers]] have successfully explored the surface of Mars and delivered information about conditions on the ground. The first successful lander, the ''[[Viking_1#Lander|Viking 1]]'' lander, touched down on the planet in 1976.<ref>{{cite journal |author=Mutch |first=T. A. |display-authors=etal |date=August 1976 |title=The Surface of Mars: The View from the Viking 1 Lander |journal=Science |series=New Series |volume=193 |issue=4255 |pages=791–801 |bibcode=1976Sci...193..791M |doi=10.1126/science.193.4255.791 |jstor=1742881 |pmid=17747782 |s2cid=42661323}}<!--|access-date= 2008-01-17 --></ref>
Crewed missions to Mars have been proposed,<ref>{{cite news |title=China plans its first crewed mission to Mars in 2033 |url=https://www.reuters.com/business/aerospace-defense/china-plans-its-first-crewed-mission-mars-2033-2021-06-24/ |access-date=18 July 2024 |work=Reuters |date=24 June 2021}}</ref> but no person has attempted to travel to the planet, and there have been no return missions. Most of the human mission concepts as currently conceived by national governmental space programs would not be direct precursors to colonization. Programs such as those being tentatively planned by [[NASA]], [[Russian Federal Space Agency|Roscosmos]], and [[ESA]] are intended solely as exploration missions, with the establishment of a permanent base possible but not yet the main goal.{{Citation needed|date=March 2020}} Colonization requires the establishment of permanent habitats that have the potential for self-expansion and self-sustenance. Two early proposals for building habitats on Mars are the [[Mars Direct]] and the [[Mars Direct#Revisions|Semi-Direct]] concepts, advocated by [[Robert Zubrin]], an advocate of the colonization of Mars.<ref name="zubrin1996" />
At the February 2017 World Government Summit, the [[United Arab Emirates]] announced a plan to establish a settlement on Mars by 2117, led by the [[Mohammed bin Rashid Space Centre]].<ref>{{cite web|url=https://www.khaleejtimes.com/news/general/uaes-mars-2117-is-put-in-action |title=UAE's Mars 2117 is put in action|date=February 22, 2017|archive-url=https://web.archive.org/web/20210716192426/https://www.khaleejtimes.com/news/general/uaes-mars-2117-is-put-in-action |archive-date=July 16, 2021 }}</ref><ref>{{Cite web |url=https://mars2117.worldgovernmentsummit.org/ |title=Mars 2117 |access-date=July 16, 2021 |archive-date=July 16, 2021 |archive-url=https://web.archive.org/web/20210716192428/https://mars2117.worldgovernmentsummit.org/ |url-status=live }}</ref>
==Comparisons between Earth and Mars==
{| class="wikitable plainrowheaders" style="float:right; margin-right:20px"
|+ [[Atmospheric pressure]] comparison
! scope="col" | Location
! scope="col" | Pressure
|-
! scope="row" | [[Olympus Mons]] summit
| {{Convert|
|-
! scope="row" | [[Atmosphere of Mars|Mars average]]
| {{Convert|
|-
! scope="row" | [[Hellas Planitia]] bottom
| {{Convert|1.16|kPa|
|-
! scope="row" | [[Armstrong limit]]
| {{Convert|6.25|kPa|
|-
! scope="row" | [[Mount Everest]] summit<ref>{{cite
| {{Convert|33.7|kPa|
|-
! scope="row" | Earth sea level
| {{Convert|101.3|kPa|abbr=on}} (1 atm)
|}
===Gravity and size===
The surface [[gravity of Mars]] is just 38% that of Earth. Although [[microgravity]] is known to cause health problems such as [[Weightlessness#Human health effects|muscle loss and bone demineralization]],<ref name="WIRED-20140212">{{cite magazine |last=Fong, MD |first=Kevin |title=The Strange, Deadly Effects Mars Would Have on Your Body |url=https://www.wired.com/opinion/2014/02/happens-body-mars/ |date=12 February 2014 |magazine=[[Wired (magazine)|Wired]] |access-date=2014-02-12 |archive-date=March 25, 2014 |archive-url=https://web.archive.org/web/20140325002634/http://www.wired.com/opinion/2014/02/happens-body-mars/ |url-status=live }}</ref><ref>{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ |title=Gravity Hurts (so Good) |publisher=NASA |year=2001 |access-date=July 12, 2017 |archive-date=May 28, 2017 |archive-url=https://web.archive.org/web/20170528223301/https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ |url-status=live }}</ref> it is not known if Martian gravity would have a similar effect. The [[Mars Gravity Biosatellite]] was a proposed project designed to learn more about what effect Mars' lower surface gravity would have on humans, but it was cancelled due to a lack of funding.<ref>{{cite web |title=Mars Mice |url=https://science.nasa.gov/science-news/science-at-nasa/2004/20jan_marsmice/ |work=science.nasa.gov |year=2004 |access-date=July 12, 2017 |archive-date=May 16, 2017 |archive-url=https://web.archive.org/web/20170516234651/https://science.nasa.gov/science-news/science-at-nasa/2004/20jan_marsmice |url-status=live }}</ref>
Mars has a surface area that is 28.4% of Earth's, which is only slightly less than the amount of dry land on Earth (which is 29.2% of Earth's surface). Mars has half the radius of Earth and only one-tenth the mass. This means that it has a smaller volume (≈15%) and lower average density than Earth.
===Magnetosphere===
Due to the lack of a [[magnetosphere]], [[solar particle event]]s and [[cosmic ray]]s can easily reach the Martian surface.<ref name="solar wind at Mars">{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ |title=The Solar Wind at Mars |date=January 31, 2001 |first=Tony |last=Phillips |publisher=NASA |access-date=July 12, 2017 |archive-date=August 18, 2011 |archive-url=https://web.archive.org/web/20110818180040/https://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ |url-status=live }}</ref><ref name="hostile to life">{{cite news | title=What makes Mars so hostile to life? | date=January 7, 2013 | url=http://www.bbc.co.uk/science/0/20915340 | work=BBC News | access-date=October 5, 2016 | archive-date=August 30, 2013 | archive-url=https://web.archive.org/web/20130830081628/http://www.bbc.co.uk/science/0/20915340 | url-status=live }}</ref><ref>{{cite journal | title=The impact of Mars geological evolution in high energy ionizing radiation environment through time | journal=Planetary and Space Science – Eslevier | date=November 2012 | first1=A. | last1=Keating | first2=P. | last2=Goncalves | volume=72 | issue=1 | pages=70–77 | doi=10.1016/j.pss.2012.04.009 | bibcode=2012P&SS...72...70K }}</ref>
===Atmosphere===
[[Atmospheric pressure]] on Mars is far below the [[Armstrong limit]] at which people can survive without [[pressure suit]]s. Since [[terraforming of Mars|terraforming]] cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with [[pressure vessel]]s similar to spacecraft, capable of containing a pressure between 30 and 100 kPa. The atmosphere is also toxic as most of it consists of [[carbon dioxide]] (95% [[carbon dioxide]], 3% nitrogen, 1.6% argon, and traces totaling less than 0.4% of other gases, including oxygen).
This thin atmosphere does not filter out [[Health effects of sunlight exposure|ultraviolet sunlight]], which causes instability in the molecular bonds between atoms. For example, ammonia (NH<sub>3</sub>) is not stable in the Martian atmosphere and breaks down 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> Also due to the thinness of the atmosphere, the temperature difference between day and night is much larger than on Earth, typically around 70 °C.<ref name="REMS-2015">{{cite web |url=http://cab.inta-csic.es/rems/index.htm |title=Mars Weather |publisher=Centro de Astrobiología |date=2015 |access-date=May 31, 2015 |url-status=dead |archive-url=https://archive.today/20151025050810/http://cab.inta-csic.es/rems/index.htm |archive-date=October 25, 2015 |df=mdy-all }}</ref> However, the day/night temperature variation is much lower during dust storms when very little light gets through to the surface even during the day, and instead warms the middle atmosphere.<ref name="Opportunity Hunkers Down During Dust Storm"/>
===Water and climate===
[[Water on Mars]] is scarce, with rovers ''[[Spirit (rover)|Spirit]]'' and ''[[Opportunity (rover)|Opportunity]]'' finding less than in Earth's driest desert.<ref name="Why is Mars So Dry">{{cite web |title=Why is Mars So Dry? |url=https://www.universetoday.com/9303/why-is-mars-so-dry/ |website=Universe Today |date=16 February 2004 |access-date=26 November 2018 |archive-date=November 27, 2018 |archive-url=https://web.archive.org/web/20181127022501/https://www.universetoday.com/9303/why-is-mars-so-dry/ |url-status=live }}</ref><ref>{{cite journal |last=Hecht |first=M. H. |year=2002 |title=Metastability of Liquid Water on Mars |journal=Icarus |volume=156 |issue=2 |pages=373–386 |doi=10.1006/icar.2001.6794|bibcode = 2002Icar..156..373H }}</ref><ref name="NASA-20131210">{{cite web |last1=Webster |first1=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Spacecraft Reveals a More Dynamic Red Planet |url=http://www.jpl.nasa.gov/news/news.php?release=2013-361&1#1 |date=10 December 2013 |work=[[NASA]] |access-date=2014-03-02 |archive-date=December 14, 2013 |archive-url=https://web.archive.org/web/20131214013848/http://www.jpl.nasa.gov/news/news.php?release=2013-361&1#1 |url-status=live }}</ref>
The [[Climate of Mars|climate]] is much colder than Earth, with mean surface temperatures between {{convert|186|and|268|K|C|abbr=on}} (depending on the season and latitude).<ref>{{cite web |last=Hamilton |first=Calvin |title=Mars Introduction |url=http://www.solarviews.com/eng/mars.htm |access-date=March 8, 2013 |archive-date=August 16, 2013 |archive-url=https://web.archive.org/web/20130816032516/http://www.solarviews.com/eng/mars.htm |url-status=live }}</ref><ref>{{cite web |last=Elert |first=Glenn |title=Temperature on the Surface of Mars |url=http://hypertextbook.com/facts/2001/AlbertEydelman.shtml |access-date=March 8, 2013 |archive-date=November 24, 2013 |archive-url=https://web.archive.org/web/20131124235435/http://hypertextbook.com/facts/2001/AlbertEydelman.shtml |url-status=live }}</ref> The [[Extremes on Earth|lowest temperature ever recorded on Earth]] was 184 K (−89.2 °C) in [[Antarctica]].
Because Mars is about 52% farther from the [[Sun]], the amount of [[solar energy]] entering its upper atmosphere per unit area (the [[solar constant]]) is around 43.3% of what reaches the Earth's upper atmosphere.<ref>{{cite journal|url=http://discovermagazine.com/1992/sep/marsinearthsimag105|title=Mars, in Earth's Image|volume=13|issue=9|pages=70|journal=Discover Magazine|access-date=12 June 2015|bibcode=1992Disc...13...70K|last1=Kluger|first1=J.|year=1992|archive-date=April 27, 2012|archive-url=https://web.archive.org/web/20120427061015/http://discovermagazine.com/1992/sep/marsinearthsimag105|url-status=live}}</ref> However, due to the much thinner atmosphere, a higher fraction of the solar energy reaches the surface as radiation.<ref>{{cite book |url=http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources30.pdf |title=Atmospheric Effects on the Utility of Solar Power on Mars| url-status=dead|archive-url=https://web.archive.org/web/20160305054458/http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources30.pdf| archive-date=2016-03-05| bibcode=1993rnes.book..845H| year=1993| last1=Haberle| first1=R. M.| last2=McKay| first2=C. P.| last3=Pollack| first3=J. B.|last4=Gwynne| first4=O. E.|last5=Atkinson|first5=D. H.|author6-link=Joseph Appelbaum |last6=Appelbaum| first6=J.|author7-link=Geoffrey A. Landis|last7=Landis| first7=G. A.|last8=Zurek| first8=R. W. |last9=Flood| first9=D. J.}}</ref><ref>{{Cite journal|bibcode=1957SvA.....1..547S|title=1957SvA.....1..547S Page 547| volume=1 |pages=547 |journal=Harvard.edu |last1=Sharonov| first1=V. V. |year=1957}}</ref> The maximum [[solar irradiance]] on Mars is about 590 W/m<sup>2</sup> compared to about 1000 W/m<sup>2</sup> at the Earth's surface; optimal conditions on the Martian equator can be compared to those on [[Devon Island]] in the Canadian Arctic in June.<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> Mars' orbit is more [[eccentricity (orbit)|eccentric]] than Earth's, increasing temperature and solar constant variations over the course of the Martian year.{{citation needed|date=February 2021}} Mars has no rain and virtually no clouds,{{citation needed|date=February 2021}} so although cold, it is permanently sunny (apart from during [[Climate of Mars#Dust storms|dust storms]]). This means solar panels can always operate at maximum efficiency on dust-free days.
[[Climate of Mars#Effect of dust storms|Global dust storms]] are common throughout the year and can cover the entire planet for weeks, blocking sunlight from reaching the surface.<ref>{{cite book |author=Badescu |first=Viorel |url=https://books.google.com/books?id=BnPE37Ms5awC&pg=PA83 |title=Mars: Prospective Energy and Material Resources |publisher=Springer Science & Business Media |year=2009 |isbn=978-3-642-03629-3 |page=83 |access-date=December 28, 2018 |archive-url=https://web.archive.org/web/20191221172930/https://books.google.com/books?id=BnPE37Ms5awC&pg=PA83 |archive-date=December 21, 2019 |url-status=live}}</ref><ref>{{cite web| url=http://tomatosphere.org/teachers/guide/grades-8-10/mars-agriculture|title=Teachers guide – Sunlight on mars – Tomatosphere|author=Tomatosphere|work=tomatosphere.org|access-date=12 June 2015|url-status=dead| archive-url=https://web.archive.org/web/20150623152330/http://tomatosphere.org/teachers/guide/grades-8-10/mars-agriculture| archive-date=23 June 2015}}</ref> This has been observed to cause temperature drops of 4 °C for several months after the storm.<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 | url-status=dead | 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> In contrast, the only comparable events on Earth are infrequent large volcanic eruptions such as the [[Krakatoa]] event which threw large amounts of ash into the atmosphere in 1883, causing a global temperature drop of around 1 °C. These dust storms would affect electricity production from solar panels for long periods, and interfere with communications with Earth.<ref name="Opportunity Hunkers Down During Dust Storm">{{cite web |title=Opportunity Hunkers Down During Dust Storm |url=https://www.nasa.gov/feature/jpl/opportunity-hunkers-down-during-dust-storm |website=NASA |date=8 June 2018 |access-date=26 November 2018 |archive-date=December 5, 2018 |archive-url=https://web.archive.org/web/20181205120746/https://www.nasa.gov/feature/jpl/opportunity-hunkers-down-during-dust-storm/ |url-status=live }}</ref>
====Temperature and seasons====
Mars has an [[axial tilt]] of 25.19°, similar to Earth's 23.44°. As a result, Mars has [[season]]s much like Earth, though on average they last nearly twice as long because the Martian year is about 1.88 Earth years. Mars' temperature regime is more similar to Earth's than to any other planet's in the [[Solar System]]. While generally colder than Earth, Mars can have Earth-like temperatures in some areas and at certain times.
===Soil===
The [[Martian soil#Toxicity|Martian soil is toxic]] due to relatively high concentrations of chlorine and associated compounds, such as perchlorates, which are hazardous to all known forms of life,<ref name="toxicsoil1">{{cite web |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 |website=The Guardian |date=July 6, 2017 |access-date=26 November 2018 |archive-date=February 18, 2021 |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 |url-status=live }}</ref><ref name="toxicmars">{{cite web |title=Toxic Mars: Astronauts Must Deal with Perchlorate on the Red Planet |url=https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html |website=space.com |date=June 13, 2013 |access-date=26 November 2018 |archive-date=November 20, 2020 |archive-url=https://web.archive.org/web/20201120151522/https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html |url-status=live }}</ref> even though some halotolerant microorganisms might be able to cope with enhanced perchlorate concentrations by drawing on physiological adaptations similar to those observed in the yeast ''[[Debaryomyces hansenii]]'' exposed in lab experiments to increasing [[Sodium perchlorate|NaClO<sub>4</sub>]] concentrations.<ref>{{Cite journal |last1=Heinz |first1=Jacob |last2=Doellinger |first2=Joerg |last3=Maus |first3=Deborah |last4=Schneider |first4=Andy |last5=Lasch |first5=Peter |last6=Grossart |first6=Hans-Peter |last7=Schulze-Makuch |first7=Dirk |date=2022-08-10 |title=Perchlorate-specific proteomic stress responses of Debaryomyces hansenii could enable microbial survival in Martian brines |journal=Environmental Microbiology |volume=24 |issue=11 |language=en |pages=1462–2920.16152 |doi=10.1111/1462-2920.16152 |pmid=35920032 |issn=1462-2912|doi-access=free |bibcode=2022EnvMi..24.5051H }}</ref>
The presence of perchlorates may form a key component of solid rocket propellant, combining with other materials via resonant acoustic mixing.<ref>{{Cite journal |last1=Hoganson |first1=Alexander C. C. |last2=Afriat |first2=Aaron |last3=Wernex |first3=Chase M. |last4=Ferguson |first4=Robert E. |last5=Rathore |first5=Hetal |last6=Patel |first6=Dhruval N. |last7=Tappan |first7=Bryce |last8=Son |first8=Steven F. |date=May 2024 |title=Novel Solid Propellants Enabled Through In Situ Martian Perchlorates |url=https://arc.aiaa.org/doi/10.2514/1.B39269 |journal=Journal of Propulsion and Power |volume=40 |issue=3 |pages=388–396 |doi=10.2514/1.B39269 |issn=0748-4658|url-access=subscription }}</ref>
===Survivability===
Plants and animals cannot survive the ambient conditions on the surface of Mars.<ref>{{cite web |url=http://library.thinkquest.org/12145/lifeon.htm |title= Can Life exist on Mars? |work= Mars Academy |publisher=ORACLE-ThinkQuest | archive-url = https://web.archive.org/web/20010222154617/http://library.thinkquest.org/12145/lifeon.htm | archive-date = February 22, 2001}}</ref> However, some [[extremophile]] organisms that survive in hostile conditions on Earth have endured periods of exposure to environments that approximate some of the conditions found on Mars.
===Length of day===
The Martian day (or [[Sol (day on Mars)|sol]]) is very close in duration to Earth's. A [[solar day]] on Mars is 24 hours, 39 minutes and 35.244 seconds.<ref>{{cite book |title=Mars: Prospective Energy and Material Resources |edition=illustrated |first1=Viorel |last1=Badescu |publisher=Springer Science & Business Media |year=2009 |isbn=978-3-642-03629-3 |page=600 |url=https://books.google.com/books?id=BnPE37Ms5awC |access-date=May 20, 2016 |archive-date=December 25, 2019 |archive-url=https://web.archive.org/web/20191225021702/https://books.google.com/books?id=BnPE37Ms5awC |url-status=live }} [https://books.google.com/books?id=BnPE37Ms5awC&pg=PA600 Extract of page 600] {{Webarchive|url=https://web.archive.org/web/20170416140128/https://books.google.com/books?id=BnPE37Ms5awC&pg=PA600 |date=April 16, 2017 }}</ref>
==Conditions for human habitation==
[[File:Project Deimos - Mars Surface Base.jpg|thumb|An expedition-style crewed mission would operate on the surface, but for limited amounts of time.]]
[[File:Mars-human-exploration-art-astronauts-vehicle-dust-full.jpg|thumb|[[Dust]] is one concern for Mars missions.]]
Conditions on the surface of Mars are closer to the conditions on Earth in terms of temperature and sunlight than on any other planet or moon, except for the [[Colonization of Venus#Aerostat habitats and floating cities|cloud tops of Venus]].<ref>{{cite web |url=http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211467.pdf |title= Atmospheric Flight on Venus |publisher= Glenn Research Center, National Aeronautics and Space Administration|date= June 2002 | number = NASA/TM–2002–211467 | first1 = Geoffrey A. | last1 = Landis | first2 = Anthony | last2 = Colozza | first3 = Christopher M. | last3 = LaMarre |url-status=dead | archive-url = https://web.archive.org/web/20111016143148/http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211467.pdf | archive-date=October 16, 2011}}</ref> However, the surface is not hospitable to humans or most known life forms due to the radiation, greatly reduced air pressure, and an atmosphere with only 0.16% oxygen.
In 2012, it was reported that some [[lichen]] and [[cyanobacteria]] survived and showed remarkable [[adaptive capacity|adaptation capacity]] for [[photosynthesis]] after 34
Humans have explored parts of Earth that match some conditions on Mars. Based on NASA rover data, temperatures on Mars (at low latitudes) are similar to those in [[Antarctica]].<ref>{{cite web
Human survival on Mars would require living in artificial [[Mars habitat]]s with complex life-support systems. One key aspect of this would be water processing systems. Being made mainly of water, a human being would die in a matter of days without it. Even a 5–8% decrease in total body water causes fatigue and dizziness, and with a 10% decrease comes physical and mental impairment (See [[Dehydration]]). A person in the [[UK]] uses 70–140 litres of water per day on average.<ref name="average-water-usage">{{cite web |title=How much water does an average person use? |url=https://www.southwestwater.co.uk/frequently-asked-questions/saving-water/how-much-water-does-an-average-person-use/ |website=South West Water |access-date=26 November 2018 |archive-date=April 7, 2019 |archive-url=https://web.archive.org/web/20190407061411/https://www.southwestwater.co.uk/frequently-asked-questions/saving-water/how-much-water-does-an-average-person-use/ |url-status=live }}</ref> Through experience and training, astronauts on the ISS have shown it is possible to use far less, and that around 70% of what is used can be recycled using the [[ISS ECLSS#Water recovery systems|ISS water recovery systems]]. (For instance, half of all water is used during showers.<ref>Mui, K. W.; Wong, L. T.; & Law, L. Y. (2007). Domestic water consumption benchmark development for Hong Kong. Building Services Engineering Research & Technology, 28(4), p. 329.</ref>) Similar systems would be needed on Mars but would need to be much more efficient, since regular robotic deliveries of water to Mars would be prohibitively expensive (the ISS is supplied with water four times per year). Potential access to on-site water (frozen or otherwise) via drilling has been investigated by NASA.<ref>{{Cite news|url=https://www.nasa.gov/feature/langley/students-work-to-find-ways-to-drill-for-water-on-mars|title=Students Work to Find Ways to Drill for Water on Mars|last=Gillard|first=Eric|date=2016-12-09|work=NASA|access-date=2018-01-21|language=en|archive-date=June 17, 2019|archive-url=https://web.archive.org/web/20190617075048/https://www.nasa.gov/feature/langley/students-work-to-find-ways-to-drill-for-water-on-mars/|url-status=live}}</ref>
=== Effects on human health ===
{{main|Effect of spaceflight on the human body}}
Mars presents a hostile environment for human habitation. Different technologies have been developed to assist long-term space exploration and may be adapted for habitation on Mars. The existing record for the longest continuous space flight is 438 days by cosmonaut [[Valeri Polyakov]],<ref name="nytimes">{{cite news|last=Schwirtz|first=Michael|title=Staying Put on Earth, Taking a Step to Mars|url=https://www.nytimes.com/2009/03/31/science/space/31mars.html|access-date=15 May 2010|newspaper=The New York Times|date=30 March 2009|archive-date=July 7, 2018|archive-url=https://web.archive.org/web/20180707011946/https://www.nytimes.com/2009/03/31/science/space/31mars.html|url-status=live}}</ref> and the most accrued time in space is 1,111 days by [[Oleg Kononenko]]. The longest time spent outside the protection of the Earth's [[Van Allen radiation belt]] is about 12 days for the [[Apollo 17]] Moon landing. This is minor in comparison to the 1100-day journey to Mars and back<ref>{{Cite web|url=https://www.nasa.gov/sites/default/files/atoms/files/journey-to-mars-next-steps-20151008_508.pdf|title=NASA's Journey to Mars – Pioneering Next Steps in Space Exploration|date=October 2015|website=NASA|access-date=2017-03-19|archive-date=August 10, 2019|archive-url=https://web.archive.org/web/20190810150733/https://www.nasa.gov/sites/default/files/atoms/files/journey-to-mars-next-steps-20151008_508.pdf|url-status=live}}</ref> envisioned by NASA for possibly as early as the year 2028. Scientists have also hypothesized that many different biological functions can be negatively affected by the environment of Mars. Due to higher levels of radiation, there are a multitude of physical side-effects that must be mitigated.<ref>{{Cite news|url=http://nsbri.org/researches/speech-monitoring-of-cognitive-deficits-and-stress/|title=Speech Monitoring of Cognitive Deficits and Stress – NSBRI|work=NSBRI|access-date=2017-03-18|language=en-US|archive-date=March 27, 2017|archive-url=https://web.archive.org/web/20170327171207/http://nsbri.org/researches/speech-monitoring-of-cognitive-deficits-and-stress/|url-status=live}}</ref> In addition, [[Martian soil#Toxicity|Martian soil]] contains high levels of toxins which are hazardous to human health.
==== Physical effects ====
The difference in gravity may negatively affect human health by weakening [[bone]]s and [[muscle]]s. There is also risk of [[osteoporosis]] and [[Circulatory system|cardiovascular]] problems. Current rotations on the [[International Space Station]] put astronauts in zero gravity for six months, a comparable length of time to a one-way trip to Mars. This gives researchers the ability to better understand the physical state that astronauts going to Mars would arrive in. Once on Mars, surface gravity is only 38% of that on Earth. Microgravity affects the cardiovascular, musculoskeletal and neurovestibular (central nervous) systems. The cardiovascular effects are complex. On Earth, blood within the body stays 70% below the heart, but in microgravity this is not the case due to nothing pulling the blood down. This can have several negative effects. Once entering into microgravity, the blood pressure in the lower body and legs is significantly reduced.<ref>{{cite journal|first1=Nguyen |last1=Nguyen |first2=Gyutae |last2=Kim |first3=Kyu-Sung |last3=Kim|date=2020|title=Effects of Microgravity on Human Physiology |journal=Korean Journal of Aerospace & Environmental Medicine |volume=30|issue=1 |pages=25–29|doi=10.46246/KJAsEM.30.1.25 |s2cid=225893986 |doi-access=free }}</ref> This causes legs to become weak through loss of muscle and bone mass. Astronauts show signs of a puffy face and chicken legs syndrome. After the first day of reentry back to Earth, blood samples showed a 17% loss of blood plasma, which contributed to a decline of [[erythropoietin]] secretion.<ref>Aubert, A. E.; Beckers, F.; Verheyden, B. Cardiovascular function and basics of physiology in microgravity. Acta Cardiologica 2005; 60(2): 129–151.</ref><ref>Williams, D.; Kuipers. A.; Mukai, C.; Thirsk, R. Acclimation during space flight: effects on human physiology. CMAJ: Canadian Medical Association journal = journal de l’Association medicale canadienne 2009; 180(13): 1317–1323.</ref> On the skeletal system which is important to support body posture, long space flight and exposure to microgravity cause demineralization and atrophy of muscles. During re-acclimation, astronauts were observed to have a myriad of symptoms including cold sweats, nausea, vomiting and motion sickness.<ref>Heer, M.; Paloski, W. H. Space motion sickness: Incidence, etiology, and countermeasures. Autonomic Neuroscience 2006; 129(1): 77–79.</ref> Returning astronauts also felt disoriented. Once on Mars with its lesser surface gravity (38% percent of Earth's), these health effects would be a serious concern.<ref>{{Cite news|url=http://www.spacesafetymagazine.com/space-exploration/mars-mission/earthlings-martians-living-red-planet-affect-human-bodies/|title=How Will Living On Mars Affects Our Human Body?|date=2014-02-11|work=Space Safety Magazine|access-date=2017-03-19|language=en-US|archive-date=March 27, 2017|archive-url=https://web.archive.org/web/20170327170248/http://www.spacesafetymagazine.com/space-exploration/mars-mission/earthlings-martians-living-red-planet-affect-human-bodies/|url-status=live}}</ref> Upon return to Earth, recovery from bone loss and atrophy is a long process and the effects of microgravity may never fully reverse.{{Citation needed|date=October 2019}}
====Radiation====
{{Further|Health threat from cosmic rays}}
Dangerous amounts of radiation reach Mars' surface despite it being much further from the Sun compared to Earth. Mars has lost its inner [[Dynamo theory|dynamo]] giving it a weaker global [[magnetosphere]] than Earth. Combined with a thin atmosphere, this permits a significant amount of [[ionizing radiation]] to reach the Martian surface. There are two main types of radiation risks to traveling outside the protection of Earth's atmosphere and magnetosphere: galactic cosmic rays (GCR) and solar energetic particles (SEP). Earth's magnetosphere protects from charged particles from the Sun, and the atmosphere protects against uncharged and highly energetic GCRs. There are ways to mitigate solar radiation, but without much of an atmosphere, the only solution to the GCR flux is heavy shielding amounting to roughly 15 centimeters of steel, 1 meter of rock, or 3 meters of water, limiting human colonists to living underground most of the time.<ref>{{Cite web |url=https://ntrs.nasa.gov/search.jsp?R=19910008686 |title=NASA.gov |date=February 1991 |access-date=August 6, 2020 |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112024851/https://ntrs.nasa.gov/search.jsp?R=19910008686 |url-status=live |last1=Simonsen |first1=Lisa C. |last2=Nealy |first2=John E. }}</ref>
The [[2001 Mars Odyssey|Mars Odyssey]] spacecraft carries an instrument, the [[Mars Radiation Environment Experiment]] (MARIE), to measure the radiation. MARIE found that radiation levels in orbit above Mars are 2.5 times higher than at the [[International Space Station]], or much higher than the combined [[global fallout]] of the thousands of [[nuclear weapons testing]]. The average daily dose was about {{convert|220|uGy|mrad|abbr=on}}—equivalent to 0.08 Gy per year.<ref>{{cite web |url=http://hacd.jsc.nasa.gov/projects/space_radiation_marie_references.cfm |title= References & Documents | publisher= Human Adaptation and Countermeasures Division, Johnson Space Center, NASA |url-status=dead | archive-url = https://web.archive.org/web/20100530060723/http://hacd.jsc.nasa.gov/projects/space_radiation_marie_references.cfm | archive-date = May 30, 2010}}</ref> A three-year exposure to such levels would exceed the safety limits currently adopted by NASA,<ref>[https://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars Real Martians: How to Protect Astronauts from Space Radiation on Mars.] {{Webarchive|url=https://web.archive.org/web/20190925202707/https://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars/ |date=September 25, 2019 }} ''Moon To Mars''. NASA. 30 September 2015. Quote: "[...] a trip to interplanetary space carries more radiation risk than working in low-Earth orbit, said Jonathan Pellish, a space radiation engineer at Goddard."</ref> and the risk of developing cancer due to radiation exposure after a Mars mission could be two times greater than what scientists previously thought.<ref>[https://www.unlv.edu/news/release/study-significant-collateral-damage-cosmic-rays-increases-cancer-risks-mars-astronauts Study: Collateral Damage from Cosmic Rays Increases Cancer Risk for Mars Astronauts] {{Webarchive|url=https://web.archive.org/web/20191014002551/https://www.unlv.edu/news/release/study-significant-collateral-damage-cosmic-rays-increases-cancer-risks-mars-astronauts |date=October 14, 2019 }}. University of Nevada, Las Vegas (UNLV). May 2017.</ref><ref>"Non-Targeted Effects Models Predict Significantly Higher Mars Mission Cancer Risk than Targeted Effects Models." Francis A. Cucinotta, and Eliedonna Cacao. ''Nature'', Scientific Reports, volume 7, Article number: 1832. 12 May 2017. {{doi|10.1016/j.lssr.2015.04.002}}.</ref> Occasional [[solar proton event]]s (SPEs) produce much higher doses, as observed in September 2017, when NASA reported radiation levels on the surface of Mars were temporarily [[Orders of magnitude (radiation)|doubled]], and were associated with an [[aurora]] 25-times brighter than any observed earlier, due to a massive, and unexpected, [[Coronal mass ejection|solar storm]].<ref name="PHYS-20170930">{{cite web |last=Scott |first=Jim |title=Large solar storm sparks global aurora and doubles radiation levels on the martian surface |url=https://phys.org/news/2017-09-large-solar-storm-global-aurora.html |date=30 September 2017 |work=[[Phys.org]] |access-date=30 September 2017 |archive-date=September 30, 2017 |archive-url=https://web.archive.org/web/20170930222447/https://phys.org/news/2017-09-large-solar-storm-global-aurora.html |url-status=live }}</ref> Building living quarters underground (possibly in [[Martian lava tube]]s) would significantly lower the colonists' exposure to radiation.
[[File:PIA17601-Comparisons-RadiationExposure-MarsTrip-20131209.png|thumb|upright=1.2|left|Comparison of radiation doses—includes the amount detected on the trip from Earth to Mars by the [[Radiation assessment detector|RAD]] on the [[Mars Science Laboratory|MSL]] (2011–2013).<ref name="SCI-20130531a">{{cite journal |last=Kerr |first=Richard |title=Radiation Will Make Astronauts' Trip to Mars Even Riskier |date=31 May 2013 |journal=[[Science (journal)|Science]] |volume=340 |page=1031 |doi=10.1126/science.340.6136.1031 |pmid=23723213 |issue=6136 |bibcode=2013Sci...340.1031K }}</ref><ref name="SCI-20130531b">{{cite journal |title=Measurements of Energetic Particle Radiation in Transit to Mars on the Mars Science Laboratory |journal=[[Science (journal)|Science]] |date=31 May 2013 |volume=340 |pages=1080–1084 |doi=10.1126/science.1235989 |pmid=23723233 |author=Zeitlin, C. |issue=6136 |last2=Hassler |first2=D. M. |last3=Cucinotta |first3=F. A. |last4=Ehresmann |first4=B. |last5=Wimmer-Schweingruber |first5=R. F. |last6=Brinza |first6=D. E. |last7=Kang |first7=S. |last8=Weigle |first8=G. |last9=Bottcher |first9=S. |bibcode = 2013Sci...340.1080Z |s2cid=604569 }}</ref><ref name="NYT-20130530">{{cite news |last=Chang |first=Kenneth |title=Data Point to Radiation Risk for Travelers to Mars |url=https://www.nytimes.com/2013/05/31/science/space/data-show-higher-cancer-risk-for-mars-astronauts.html |date=30 May 2013 |work=The New York Times |access-date=31 May 2013 |archive-date=May 31, 2013 |archive-url=https://web.archive.org/web/20130531031329/http://www.nytimes.com/2013/05/31/science/space/data-show-higher-cancer-risk-for-mars-astronauts.html |url-status=live }}</ref>]]
Much remains to be learned about space radiation. In 2003, NASA's [[Lyndon B. Johnson Space Center]] opened a facility, the [[NASA Space Radiation Laboratory]], at [[Brookhaven National Laboratory]], that employs [[particle accelerator]]s to simulate space radiation. The facility studies its effects on living organisms, as well as experimenting with shielding techniques.<ref>{{cite web|url= http://www.bnl.gov/medical/NASA/LTSF.asp|title= Space Radiobiology|work= NASA/BNL Space Radiation Program|publisher= NASA Space Radiation Laboratory|date= November 1, 2011|access-date= September 16, 2007|archive-date= September 24, 2013|archive-url= https://web.archive.org/web/20130924040250/http://www.bnl.gov/medical/NASA/LTSF.asp|url-status= live}}</ref> Initially, there was some evidence that this kind of low level, chronic radiation is not as dangerous as once thought; and that [[radiation hormesis]] occurs.<ref name="zubrin1996b">{{cite book |last=Zubrin |first=Robert |author-link=Robert Zubrin |title=The Case for Mars: The Plan to Settle the Red Planet and Why We Must |publisher=Touchstone |year=1996 |isbn=978-0-684-83550-1 |pages=[https://archive.org/details/caseformarsplant00zubr/page/114 114–116] |url=https://archive.org/details/caseformarsplant00zubr/page/114 }}</ref> However, results from a 2006 study indicated that protons from cosmic radiation may cause twice as much serious damage to [[DNA]] as previously estimated, exposing astronauts to greater risk of cancer and other diseases.<ref name="spaceRdiation">{{cite web |url=http://www.findingdulcinea.com/news/science/2009/september/Space-Radiation-Hinders-NASA-s-Mars-Ambitions-.html |title=Space Radiation Hinders NASA's Mars Ambitions |publisher=Finding Dulcinea |date=September 17, 2009 |first=Anita |last=Gutierrez-Folch |access-date=April 27, 2012 |archive-date=September 28, 2013 |archive-url=https://web.archive.org/web/20130928013958/http://www.findingdulcinea.com/news/science/2009/september/Space-Radiation-Hinders-NASA-s-Mars-Ambitions-.html |url-status=live }}</ref> As a result of the higher radiation in the Martian environment, the summary report of the [[Review of U.S. Human Space Flight Plans Committee]] released in 2009 reported that "Mars is not an easy place to visit with existing technology and without a substantial investment of resources."<ref name="spaceRdiation" /> NASA is exploring a variety of alternative techniques and technologies such as [[deflector shield]]s of plasma to protect astronauts and spacecraft from radiation.<ref name="spaceRdiation" />
==== Psychological effects ====
Due to the communication delays, new protocols need to be developed in order to assess crew members' psychological health. Researchers have developed a Martian simulation called [[HI-SEAS]] (Hawaii Space Exploration Analog and Simulation) that places scientists in a simulated Martian laboratory to study the psychological effects of isolation, repetitive tasks, and living in close-quarters with other scientists for up to a year at a time. Computer programs are being developed to assist crews with personal and interpersonal issues in absence of direct communication with professionals on Earth.<ref>{{Cite web|url=http://www.apa.org/monitor/julaug04/mental.aspx|title=Mental preparation for Mars|publisher=American Psychological Association|language=en|access-date=2017-03-19|archive-date=March 27, 2017|archive-url=https://web.archive.org/web/20170327170949/http://www.apa.org/monitor/julaug04/mental.aspx|url-status=live}}</ref>
===Terraforming===
[[
{{Main|Terraforming of Mars}}
{{See also|Oxygen evolution}}
===Minimum size of a colony===
No consensus exists about the minimum viable size of a colony required to ensure that inbreeding would not occur.<ref name=city_on_mars>{{cite book |last1=Weinersmith |first1=Kelly |last2=Weinersmith |first2=Zach |title=A City on Mars: Can we settle space, should we settle space, and have we really thought this through? |date=7 November 2023 |publisher=Penguin |isbn=978-1-9848-8173-1 |url=https://books.google.com/books?id=ImmvEAAAQBAJ&q=a+city+on+mars |access-date=17 July 2024 |language=en}}</ref> Through mathematical modelling of the time spent by people on work in a colony, Jean-Marc Salotti concluded that the minimum number for a colony on Mars is 110.<ref name="Salotti" /> This is close to other studies of the genetic problems involved in the longer journey to [[Proxima Centauri b]] (6,000+ years).<ref>{{cite journal |last1=Smith |first1=Cameron M. |title=Estimation of a genetically viable population for multigenerational interstellar voyaging: Review and data for project Hyperion |journal=Acta Astronautica |date=2014 |volume=97 |pages=16–29 |doi=10.1016/j.actaastro.2013.12.013 |bibcode=2014AcAau..97...16S |url=https://www.academia.edu/5506161 |access-date=1 April 2022 |archive-date=April 1, 2022 |archive-url=https://web.archive.org/web/20220401150138/https://www.academia.edu/5506161 |url-status=live }}</ref> Other studies, focused on interstellar settlement, have concluded that minimum viable populations or a desirable number of colonists range from 198 to as high as 10,000.<ref name=city_on_mars/><ref>{{cite journal |last1=Smith |first1=Cameron M. |title=Estimation of a genetically viable population for multigenerational interstellar voyaging: Review and data for project Hyperion |journal=Acta Astronautica |date=April 2014 |volume=97 |pages=16–29 |doi=10.1016/j.actaastro.2013.12.013 |bibcode=2014AcAau..97...16S }}</ref>
To be self-sustaining, a colony would have to be large enough to provide all the necessary living services. These include:<ref name="Salotti">{{cite journal |last1=Salotti |first1=Jean-Marc |title=Minimum number of Settlers for Survival on Another planet |journal=Nature |date=2020 |volume=Scientific Reports |issue=1 |article-number=9700 |doi=10.1038/s41598-020-66740-0 |pmid=32546782 |pmc=7297723 |bibcode=2020NatSR..10.9700S }}</ref>
* '''Ecosystem management''': producing appropriate gases, controlling air composition pressure and temperature, collecting and producing water, growing food and processing organic wastes.
* '''Energy production''': this includes extracting methane for vehicles and, if photovoltaic cells are used to produce energy, this would include the extraction and processing of silicates, to augment or replace any original equipment.
* '''Industry''': extracting and processing appropriate ores, manufacturing tools and other objects; producing clothes, medicine, glass, ceramics, and plastics.
* '''Building''': even if the base is constructed before arrival, it will need frequent adaptation according to the evolution of the settlement as well as inevitable replacement.
* '''Social activities''': this includes raising children and educating them, health care, preparing meals, cleaning, washing, organizing the work and making decisions. Time for sport, culture and entertainment can be minimized but not eliminated.
==Transportation==
===Interplanetary spaceflight===
{{Main |Interplanetary spaceflight}}
[[File:Mars orbit rendez vous S95 01407.jpg|thumb|Rendezvous, an interplanetary stage and lander stage come together over Mars (artist conception)]]
Mars requires less energy per unit mass ([[delta V]]) to reach from Earth than any planet except [[Venus]]. Using a [[Hohmann transfer orbit]], a trip to Mars requires approximately nine months in space.<ref>{{cite web |url=http://www.phy6.org/stargaze/Smars1.htm |title=#21b, Flight to Mars: How Long? Along what Path? |publisher=Phy6.org |date=2004-12-12 |access-date=2013-08-01 |first=David P. |last=Stern |work=From Stargazers to Starships |archive-date=September 13, 2012 |archive-url=https://web.archive.org/web/20120913081839/http://www.phy6.org/stargaze/Smars1.htm |url-status=live }}</ref> Modified transfer trajectories that cut the travel time to four to seven months in space are possible with incrementally higher amounts of energy and fuel compared to a Hohmann transfer orbit, and are in standard use for robotic Mars missions. Shortening the travel time below about six months requires higher [[delta-v]] and an increasing amount of fuel, and is difficult with [[chemical rocket]]s. It could be feasible with advanced [[spacecraft propulsion]] technologies, some of which have already been tested to varying levels, such as [[Variable Specific Impulse Magnetoplasma Rocket]],<ref>{{cite web |url=http://www.techbriefs.com/content/view/1768/32/ |publisher=NASA |work=Tech Briefs |title=Variable-Specific-Impulse Magnetoplasma Rocket |date=September 2001 |access-date=March 26, 2008 |archive-date=December 11, 2008 |archive-url=https://web.archive.org/web/20081211065353/http://www.techbriefs.com/content/view/1768/32/ |url-status=live }}</ref> and [[nuclear rocket]]s. In the former case, a trip time of forty days could be attainable,<ref name="ns.dn17476">{{cite web |url=https://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true |title=Ion engine could one day power 39-day trips to Mars |work=New Scientist |access-date=August 25, 2017 |archive-date=March 13, 2015 |archive-url=https://web.archive.org/web/20150313224849/http://www.newscientist.com/article/dn17476-ion-engine-could-one-day-power-39day-trips-to-mars.html?full=true |url-status=live }}</ref> and in the latter, a trip time down to about two weeks.<ref name="zubrin1996">{{cite book |last=Zubrin |first=Robert |author-link=Robert Zubrin |title=The Case for Mars: The Plan to Settle the Red Planet and Why We Must |publisher=Touchstone |year=1996 |isbn=978-0-684-83550-1 |url-access=registration |url=https://archive.org/details/caseformarsplant00zubr }}</ref> In 2016, a University of California, Santa Barbara scientist said they could further reduce travel time for a small robotic probe to Mars to "as little as 72 hours" with the use of a laser propelled sail (directed photonic propulsion) system instead of the fuel-based rocket propulsion system.<ref>{{Cite web
| url = https://www.usatoday.com/story/tech/2016/02/26/nasa-scientist-can-get-humans-mars-month/80980218/
| title = NASA Scientist: I can get humans to Mars in a month
| website = USA TODAY
| access-date = 2016-03-01
| archive-date = January 12, 2017
| archive-url = https://web.archive.org/web/20170112050838/http://www.usatoday.com/story/tech/2016/02/26/nasa-scientist-can-get-humans-mars-month/80980218/
| url-status = live
}}</ref><ref>[https://www.deepspace.ucsb.edu/projects/starlight Starlight: Directed Energy for Relativistic Interstellar Missions.] {{Webarchive|url=https://web.archive.org/web/20191109072355/https://www.deepspace.ucsb.edu/projects/starlight |date=November 9, 2019 }} UCSB Experimental Cosmology Group. Accessed on 9 November 2019.</ref>
During the journey, the astronauts would be subject to [[radiation]], which would require a means to protect them. [[Cosmic radiation]] and [[solar wind]] cause DNA damage, which significantly increases the risk of cancer. The effect of long-term travel in interplanetary space is unknown, but scientists estimate an ''added'' risk of between 1% and 19% (one estimate is 3.4%) for males to die of cancer because of the radiation during the journey to Mars and back to Earth. For females the probability is higher due to generally larger glandular tissues.<ref>{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2004/17feb_radiation |publisher=NASA |title=Space radiation between Earth and Mars poses a hazard to astronauts. |access-date=September 6, 2017 |archive-date=June 7, 2017 |archive-url=https://web.archive.org/web/20170607184206/https://science.nasa.gov/science-news/science-at-nasa/2004/17feb_radiation/ |url-status=live }}</ref>
===Landing on Mars===
{{Main |Mars landing}}
[[File:SpaceX Dragon Capsule on Mars (18053607180).jpg|thumb|Artist's conception of two ''Red Dragon'' capsules on Mars, next to an outpost]]
Mars has a surface gravity 0.38 times that of Earth, and the density of its atmosphere is about 0.6% of that on Earth.<ref name="Dr. David R. Williams">{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html |title=Mars Fact Sheet |access-date=2007-09-18 |first=Dr. David R. |last=Williams |date=2004-09-01 |publisher=NASA Goddard Space Flight Center |archive-date=June 12, 2010 |archive-url=https://web.archive.org/web/20100612092806/http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html |url-status=live }}</ref> The relatively strong gravity and the presence of aerodynamic effects make it difficult to land heavy, crewed spacecraft with thrusters only, as was done with the [[Apollo Lunar Module#Operational profile|Apollo Moon landings]], yet the atmosphere is too thin for aerodynamic effects to be of much help in [[aerobraking]] and landing a large vehicle. Landing piloted missions on Mars would require braking and landing systems different from anything used to land crewed spacecraft on the Moon or robotic missions on Mars.<ref name="Nancy Atkinson">{{cite web |url=http://www.universetoday.com/2007/07/17/the-mars-landing-approach-getting-large-payloads-to-the-surface-of-the-red-planet |title=The Mars Landing Approach: Getting Large Payloads to the Surface of the Red Planet |first=Nancy |last=Atkinson |date=2007-07-17 |access-date=2007-09-18 |archive-date=April 30, 2010 |archive-url=https://web.archive.org/web/20100430183743/http://www.universetoday.com/2007/07/17/the-mars-landing-approach-getting-large-payloads-to-the-surface-of-the-red-planet/ |url-status=live }}</ref>
If one assumes carbon nanotube construction material will be available with a strength of {{cvt|130
====Phobos as a space elevator for Mars====
[[Phobos (moon)|Phobos]] is [[Tidal locking|synchronously]] orbiting [[Mars]], where the same face stays facing the planet at ~6,028 [[Kilometre |km]] above the [[Martian surface]]. A [[space elevator]] could extend down from Phobos to Mars 6,000 km, about 28 kilometers from the surface, and just out of the [[atmosphere of Mars]]. A similar space elevator cable could extend out 6,000 km the opposite direction that would [[counterbalance]] Phobos. In total the space elevator would extend out over 12,000 km which would be below [[Areostationary orbit]] of Mars (17,032 km). A rocket launch would still be needed to get the rocket and cargo to the beginning of the space elevator 28 km above the surface. The surface of Mars is rotating at 0.25 [[km/s]] at the equator and the bottom of the space elevator would be rotating around Mars at 0.77 km/s, so only 0.52 km/s of [[Delta-v]] would be needed to get to the space elevator. Phobos orbits at 2.15 km/s and the outer most part of the space elevator would rotate around Mars at 3.52 km/s.<ref name = chapter/>
==Equipment needed for colonization==
[[File:Possible_exploration_of_the_surface_of_Mars.jpg|thumb|upright=1.2|Various technologies and devices for Mars are shown in the conceptual illustration of a Mars base.]]
Colonization of Mars would require a wide variety of equipment—both equipment to directly provide services to humans and [[Capital (economics)|production equipment]] used to produce food, propellant, water, energy and breathable oxygen—in order to support human colonization efforts. Required equipment will include:<ref name="zubrin1996" />
*Basic [[utilities]] ([[oxygen]], [[Electricity generation|power]], [[Communications system|local communications]], [[waste disposal]], [[sanitation]] and [[Reclaimed water#Reuse in space stations|water recycling]])
*[[Mars habitat|Habitats]]
*Storage facilities
*Workspaces
*Airlock, for pressurization and dust management
*[[In-situ resource utilization|Resource extraction equipment]]—initially for [[Chronology of discoveries of water on Mars|water]] and oxygen, later for a wider cross section of minerals, building materials, etc.
*
[[File:Mars Greenhouse.jpg|thumb|upright=1.2|Mars greenhouses feature in many colonization designs, especially for food production and other purposes.]]
*[[Plants in space|Food]] [[Space farming|production]] spaces and equipment<ref name="NYT-20231127">{{cite news |last=Scoles |first=Sarah |date=27 November 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 |archiveurl=https://archive.today/20231128053332/https://www.nytimes.com/2023/11/27/science/mars-needs-insects.html |archivedate=28 November 2023 |accessdate=28 November 2023 |work=[[The New York Times]]}}</ref>
*[[In-situ resource utilization#Rocket propellant|Propellant production equipment]], generally thought to be [[Hydrogen rocket fuel|hydrogen]] and [[liquid methane|methane]] through the [[Sabatier reaction]]<ref name="nsf20140307">{{cite news |last=Belluscio |first=Alejandro G. |title=SpaceX advances drive for Mars rocket via Raptor power |url=http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/ |work=NASAspaceflight.com |date=7 March 2014 |access-date=2014-03-14 |archive-date=September 11, 2015 |archive-url=https://web.archive.org/web/20150911235533/http://www.nasaspaceflight.com/2014/03/spacex-advances-drive-mars-rocket-raptor-power/ |url-status=live }}</ref> for fuel—with [[liquid oxygen|oxygen]] oxidizer—for chemical rocket engines
*Fuels or other energy source for use with surface transportation; such as [[Methanol fuel|Methanol]]<ref>{{cite report|url=https://www.researchgate.net/publication/289163413 |title=Methanol: A fuel for earth and mars |date=January 2000 |first=K.R. |last=McMillen |access-date=26 April 2025}}</ref> or [[carbon monoxide]]/[[oxygen]] (CO/O<sub>2</sub>) engines have been suggested for early surface transportation use as both carbon monoxide and oxygen can be straightforwardly produced by [[zirconium dioxide]] [[electrolysis]] from the [[Martian atmosphere]] without requiring use of any of the Martian water resources to obtain hydrogen<ref name="landis2001">{{cite journal |last1=Landis |first1=Geoffrey A. |first2=Diane L. |last2=Linne|title=Mars Rocket Vehicle Using In Situ Propellants |journal=Journal of Spacecraft and Rockets |year=2001 |volume=38 |issue=5 |pages=730–735 |doi=10.2514/2.3739 |bibcode = 2001JSpRo..38..730L }}</ref>
*Off-planet communication equipment
*Equipment for moving over the surface—[[Mars suit]], [[Crewed Mars rover|crewed rovers]] and possibly [[Mars aircraft]].
===
In order to function, the colony would need the basic utilities to support human civilization. These would need to be designed to handle the harsh Martian environment and would either have to be serviceable while wearing an EVA (extra vehicular activity) suit or housed inside a human habitable environment. For example, if electricity generation systems rely on solar power, large energy storage facilities will also be needed to cover the periods when dust storms block out the sun, and automatic dust removal systems may be needed to avoid human exposure to conditions on the surface.<ref name=Fenton/> If the colony is to scale beyond a few people, systems will also need to maximise use of local resources to reduce the need for resupply from Earth, for example by recycling water and oxygen and being adapted to be able to use any water found on Mars, whatever form it is in.
===Communication with Earth===
Communications with Earth are relatively straightforward during the half-[[Sol (day of Mars)|sol]] when Earth is above the Martian horizon. NASA and ESA included communications relay equipment in several of the Mars orbiters, so Mars already has [[communications satellite]]s. While these will eventually wear out, additional orbiters with communication relay capability are likely to be launched before any colonization expeditions are mounted.
The one-way communication delay due to the [[speed of light]] ranges from about 3 minutes at closest approach (approximated by perihelion of Mars minus aphelion of Earth) to 22 minutes at the largest possible superior conjunction (approximated by aphelion of Mars plus aphelion of Earth). Real-time communication, such as telephone conversations or [[Internet Relay Chat]], between Earth and Mars would be highly impractical due to the long time lags involved. NASA has found that direct communication can be blocked for about two weeks every [[synodic period]], around the time of [[superior conjunction]] when the [[Sun]] is directly between Mars and Earth,<ref>{{cite web |url=http://marsrovers.jpl.nasa.gov/spotlight/20061020.html |title=During Solar Conjunction, Mars Spacecraft Will Be on Autopilot |work=Spotlight |publisher=JPL, NASA |date=October 20, 2006 |access-date=October 31, 2006 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927193237/http://marsrovers.jpl.nasa.gov/spotlight/20061020.html |url-status=dead }}</ref> although the actual duration of the communications blackout varies from mission to mission depending on various factors—such as the amount of link margin designed into the communications system, and the minimum data rate that is acceptable from a mission standpoint. In reality most missions at Mars have had communications blackout periods of the order of a month.<ref>{{cite journal |doi=10.1196/annals.1370.007 |title=MarsSat: Assured Communication with Mars |year=2005 |last=Gangale |first=T. |journal=Annals of the New York Academy of Sciences |volume=1065 |pages=296–310 |pmid=16510416 |bibcode=2005NYASA1065..296G |s2cid=22087209 }}</ref>
A satellite at the {{L4}} or {{L5}} Earth–Sun [[Lagrangian point]] could serve as a relay during this period to solve the problem; even a constellation of communications satellites would be a minor expense in the context of a full colonization program. However, the size and power of the equipment needed for these distances make the L4 and L5 locations unrealistic for relay stations, and the inherent stability of these regions, although beneficial in terms of station-keeping, also attracts dust and asteroids, which could pose a risk.<ref>{{cite web |url=http://www.stk.com/downloads/resources/user-resources/downloads/whitepapers/0201_sun_mars_lib_pts.pdf |title=Sun-Mars Libration Points and Mars Mission Simulations |publisher=Stk.com |access-date=2013-10-06 |url-status=dead |archive-url=https://web.archive.org/web/20130927055355/http://www.stk.com/downloads/resources/user-resources/downloads/whitepapers/0201_sun_mars_lib_pts.pdf |archive-date=2013-09-27 }}</ref> Despite that concern, the [[STEREO]] probes passed through the L4 and L5 regions without damage in late 2009.
Recent work by the [[University of Strathclyde]]'s Advanced Space Concepts Laboratory, in collaboration with the [[European Space Agency]], has suggested an alternative relay architecture based on highly non-[[Kepler orbit|Keplerian orbits]]. These are a special kind of orbit produced when continuous low-thrust propulsion, such as that produced from an ion engine or [[solar sail]], modifies the natural trajectory of a spacecraft. Such an orbit would enable continuous communications during solar conjunction by allowing a relay spacecraft to "hover" above Mars, out of the orbital plane of the two planets.<ref>{{cite web |url=http://strathprints.strath.ac.uk/25836/2/Macdonald_M_-_strathprints_-_A_novel_interplanetary_communications_relay_Aug_2010.pdf |title=A Novel Interplanetary Communications Relay |date=August 2010 |access-date=2011-02-14 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927194004/http://strathprints.strath.ac.uk/25836/2/Macdonald_M_-_strathprints_-_A_novel_interplanetary_communications_relay_Aug_2010.pdf |url-status=live }}</ref> Such a relay avoids the problems of satellites stationed at either L4 or L5 by being significantly closer to the surface of Mars while still maintaining continuous communication between the two planets.
==Robotic precursors==
[[File:Mars orbital command module.webp|thumb|[[Mars Piloted Orbital Station|Mars orbital command module]]; [[Human spaceflight|crewed module]] to control [[Mars rover|robots]] and [[Mars aircraft]] without the [[Latency (engineering)|latency]] of controlling it from Earth<ref>{{Cite web |title=Marpost |url=http://www.astronautix.com/m/marpost.html |access-date=2024-07-12 |website=www.astronautix.com}}</ref>]]
The path to a human colony could be prepared by [[robotic spacecraft|robotic]] systems such as the [[Mars Exploration Rover]]s ''[[Spirit rover|Spirit]]'', ''[[Opportunity rover|Opportunity]]'', ''[[Curiosity rover|Curiosity]]'' and ''[[Perseverance rover|Perseverance]]''. These systems could help locate resources, such as ground water or ice, that would help a colony grow and thrive. The lifetimes of these systems would be years and even decades, and as recent developments in [[commercial spaceflight]] have shown, it may be that these systems will involve private as well as government ownership. These robotic systems also have a reduced cost compared with early crewed operations, and have less political risk.
Wired systems might lay the groundwork for early crewed landings and bases, by producing various consumables including fuel, oxidizers, water, and construction materials. Establishing power, communications, shelter, heating, and manufacturing basics can begin with robotic systems, if only as a prelude to crewed operations.
[[Mars Surveyor 2001 Lander]] MIP (Mars ISPP Precursor) was to demonstrate manufacture of oxygen from the [[atmosphere of Mars]],<ref>{{cite
Before any people are transported to Mars on the notional
==Stages==
In the literature there has been a differentiation of the different stages Mars settlement would encompass:
# Pre-settlement: small outpost (near-term future)
# In-settlement: permanent settlement (medium-term future)
# Post-settlement: self-sufficient society (long-term future)<ref name="l907">{{cite journal | last1=Puumala | first1=Mikko M. | last2=Sivula | first2=Oskari | last3=Lehto | first3=Kirsi | title=Moving to Mars: The Feasibility and Desirability of Mars Settlements | journal=Space Policy | volume=66 | date=2023 | issn=0265-9646 | doi=10.1016/j.spacepol.2023.101590 | article-number=101590| doi-access=free | bibcode=2023SpPol..6601590P }}</ref>
==Economics==
===Economic drivers and prerequisites===
The rise of [[Reusable launch vehicle|reusable launch vehicles]] in the 2020s has substantially reduced the cost of access to space. With a published price of {{USD|62 million}} per launch of up to {{convert|22800|kg|abbr=on}} payload to [[low Earth orbit]] or {{convert|4020|kg|abbr=on}} to Mars,<ref name="sxCapabilitiesSvcs20131211">{{cite web |title=SpaceX Capabilities and Services |url=http://www.spacex.com/about/capabilities |year=2017<!-- copyright date; no other date provided --> |publisher=SpaceX |access-date=2017-03-12 |url-status=dead |archive-url=https://web.archive.org/web/20131007205105/http://www.spacex.com/about/capabilities |archive-date=2013-10-07 }} <!-- SpaceX refers to these prices as the "PAID IN FULL STANDARD LAUNCH PRICES (2013)" --></ref> [[SpaceX]] [[Falcon 9]] rockets are already the "cheapest in the industry".<ref name=fp20131209>{{cite news |last=Belfiore |first=Michael |title=The Rocketeer |url=https://foreignpolicy.com/articles/2013/12/02/the_rocketeer_elon_musk |newspaper=Foreign Policy |date=2013-12-09 |access-date=2013-12-11 |archive-date=December 10, 2013 |archive-url=https://web.archive.org/web/20131210233009/http://www.foreignpolicy.com/articles/2013/12/02/the_rocketeer_elon_musk |url-status=live }}</ref> SpaceX's reusability includes the [[Falcon Heavy]] and future [[Liquid methane rocket fuel|methane-based]] launch vehicles including the [[SpaceX Starship|Starship]]. SpaceX was successful in developing the reusable technology with Falcon 9 and Falcon Heavy and as of April 2024, it was rapidly advancing towards reusability of Starship. This is expected to "have a major impact on the cost of access to space", and change the increasingly [[competition (economics)|competitive market]] in space launch services.<ref name="bbc20130930">{{cite news |url=https://www.bbc.co.uk/news/science-environment-24331860 |title=Recycled rockets: SpaceX calls time on expendable launch vehicles |work=BBC News |last=Amos |first=Jonathan |date=30 September 2013 |access-date=2013-10-02 |archive-date=October 3, 2013 |archive-url=https://web.archive.org/web/20131003085420/http://www.bbc.co.uk/news/science-environment-24331860 |url-status=live }}</ref><ref>{{Cite web |last=kentnstxl |date=2024-02-12 |title=Reducing the Cost of Space Travel with Reusable Launch Vehicles |url=https://nstxl.org/reducing-the-cost-of-space-travel-with-reusable-launch-vehicles/ |access-date=2024-04-08 |website=NSTXL |language=en-US}}</ref>
Alternative funding approaches might include the creation of [[Inducement prize contest|inducement prizes]]. For example, the 2004 [[President's Commission on Implementation of United States Space Exploration Policy]] suggested that an inducement prize contest should be established, perhaps by government, for the achievement of space colonization. One example provided was offering a prize to the first organization to place humans on the Moon and sustain them for a fixed period before they return to Earth.<ref>{{cite web |url=http://www.nasa.gov/pdf/60736main_M2M_report_small.pdf |title=A Journey to Inspire, Innovate, and Discover |work=Report of the [[President's Commission on Implementation of United States Space Exploration Policy]] |date=June 2004 |access-date=December 14, 2013 |archive-date=October 10, 2012 |archive-url=https://web.archive.org/web/20121010151959/http://www.nasa.gov/pdf/60736main_M2M_report_small.pdf |url-status=live }}</ref>
===Local resource extraction and trade with Earth===
No evidence of abundant resources on Mars with value to Earth has been collected.<ref name=city_on_mars/> The distance between Mars and Earth would present a considerable challenge to potential trade between the planets.<ref name=city_on_mars/>
===Local trade===
[[File:PIA07269-Mars Rover Opportunity-Iron Meteorite.jpg|thumb|right|Iron–nickel meteorite found on Mars' surface ([[Heat Shield Rock]])]]
Some early Mars colonies might specialize in developing local resources for Martian consumption, such as water and/or ice.{{Citation needed|date=July 2024}} Local resources can also be used in infrastructure construction.<ref name="Landis, Geoffrey A.">{{cite journal |doi=10.1016/j.actaastro.2008.07.011 |title=Meteoritic steel as a construction resource on Mars |year=2009 |last1=Landis |first1=Geoffrey A. |journal=Acta Astronautica |volume=64 |issue=2–3 |page=183|bibcode = 2009AcAau..64..183L }}</ref> One source of [[Ore resources on Mars|Martian ore]] currently known to be available is metallic iron in the form of nickel–iron [[meteorite]]s. Iron in this form is more easily extracted than from the iron oxides that cover the planet.
Another inter-Martian trade good during colonization could be manure,<ref>{{cite book|last1=Lovelock |first1=James |last2=Allaby |first2=Michael |title=The Greening of Mars |date=1984 |url=https://books.google.com/books?id=j612QgAACAAJ|publisher=St. Martin's Press|isbn=978-0-312-35024-6 |access-date=26 April 2025}}</ref> as [[Martian soil|soil]] will be very poor for growing plants.
[[Solar power]] is a candidate for power for a Martian colony. [[Solar insolation]] (the amount of solar radiation that reaches Mars) is about 42% of that on Earth, since Mars is about 52% farther from the Sun and insolation [[inverse-square law|falls off as the square of distance]]. However, Mars' thin atmosphere would allow almost all of that energy to reach the surface as compared to Earth, where the atmosphere absorbs roughly a quarter of the solar radiation. Sunlight on the surface of Mars would be much like a moderately cloudy day on Earth.<ref>{{cite web |url=http://www.ftexploring.com/solar-energy/clouds-and-pollution.htm |title=Effect of Clouds and Pollution on Insolation |access-date=2012-10-04 |archive-date=March 5, 2012 |archive-url=https://web.archive.org/web/20120305180029/http://www.ftexploring.com/solar-energy/clouds-and-pollution.htm |url-status=live }}</ref>
====Mining the asteroid belts from Mars====
{{see also|Category:Main-belt asteroids|Amor asteroids|Apollo asteroids}}
Since [[Mars]] is much closer to the [[asteroid belt]] than [[Earth]], it would take less [[Delta-v]] to get to the Asteroid belt and return [[Mineral|minerals]] to Mars. One hypothesis is that the [[Moons of Mars]] ([[Phobos (moon)|Phobos]] and [[Deimos (moon)|Deimos]]) are actually [[asteroid capture]]s from the Asteroid belt.<ref>{{cite web | url=https://www.space.com/24285-mars-moon-phobos-captured-asteroid.html | title=Potato-Shaped Mars Moon Phobos May be a Captured Asteroid | website=[[Space.com]] | date=January 15, 2014 | access-date=November 30, 2022 | archive-date=November 30, 2022 | archive-url=https://web.archive.org/web/20221130022417/https://www.space.com/24285-mars-moon-phobos-captured-asteroid.html | url-status=live }}</ref>
[[16 Psyche]] in the main belt could have over 10,000 [[Names of large numbers|quadrillion]] [[United States dollar|dollars]] worth of minerals. On October 13, 2023, [[NASA]] launched the [[Psyche (spacecraft)|Psyche]] orbiter, which is set to reach the asteroid by August 2029.<ref>{{cite web | url=https://www.jpl.nasa.gov/news/nasa-continues-psyche-asteroid-mission | title=NASA Continues Psyche Asteroid Mission | website=[[Jet Propulsion Laboratory]] | access-date=November 30, 2022 | archive-date=November 8, 2022 | archive-url=https://web.archive.org/web/20221108030113/https://www.jpl.nasa.gov/news/nasa-continues-psyche-asteroid-mission | url-status=live }}</ref>
[[511 Davida]] could have $27 quadrillion worth of minerals and resources.<ref>{{cite web | url=https://www.universetoday.com/156335/could-we-use-mars-as-a-base-for-asteroid-mining/ | title=Could We Use Mars as a Base for Asteroid Mining? | date=June 21, 2022 | access-date=November 30, 2022 | archive-date=November 30, 2022 | archive-url=https://web.archive.org/web/20221130022419/https://www.universetoday.com/156335/could-we-use-mars-as-a-base-for-asteroid-mining/ | url-status=live }}</ref> Using the moon [[Phobos (moon)|Phobos]] to launch spacecraft is energetically favorable and a useful ___location from which to dispatch missions to main belt asteroids.<ref>{{cite journal | doi=10.1016/j.pss.2022.105450 | title=Phobos and Mars orbit as a base for asteroid exploration and mining | year=2022 | last1=Taylor | first1=Anthony J. | last2=McDowell | first2=Jonathan C. | last3=Elvis | first3=Martin | journal=Planetary and Space Science | volume=214 | article-number=105450 | bibcode=2022P&SS..21405450T | s2cid=247275237 | doi-access=free }}</ref>
Mining the asteroid belt from Mars and its moons could help in the colonization of Mars.<ref>{{cite web | url=https://www.forbes.com/sites/jamiecartereurope/2021/10/19/the-age-of-space-mining-just-got-closer-as-scientists-discover-two-asteroids-whose-precious-metals-would-exceed-global-reserves/?sh=6525e439713b | title=Space Mining: Scientists Discover Two Asteroids Whose Precious Metals Would Exceed Global Reserves | website=[[Forbes]] | access-date=November 30, 2022 | archive-date=November 30, 2022 | archive-url=https://web.archive.org/web/20221130022420/https://www.forbes.com/sites/jamiecartereurope/2021/10/19/the-age-of-space-mining-just-got-closer-as-scientists-discover-two-asteroids-whose-precious-metals-would-exceed-global-reserves/?sh=6525e439713b | url-status=live }}</ref><ref>{{cite web | url=https://www.forbes.com/sites/jamiecartereurope/2020/10/26/hubble-views-massive-asteroid-called-psyche-that-could-worth-more-than-our-global-economy/?sh=e85d6d9515a5 | title=Hubble Examines Massive Metal Asteroid Called 'Psyche' That's Worth Way More Than Our Global Economy | website=[[Forbes]] | access-date=November 30, 2022 | archive-date=November 30, 2022 | archive-url=https://web.archive.org/web/20221130022415/https://www.forbes.com/sites/jamiecartereurope/2020/10/26/hubble-views-massive-asteroid-called-psyche-that-could-worth-more-than-our-global-economy/?sh=e85d6d9515a5 | url-status=live }}</ref><ref>{{cite web | url=https://www.forbes.com/sites/jamiecartereurope/2019/06/12/nasa-heads-for-psyche-a-giant-mysterious-metallic-asteroid-that-could-be-a-dead-planets-heart/?sh=2a6ef5a665b8 | title=NASA Heads for 'Psyche,' A Mysterious Metallic Asteroid That Could be the Heart of a Dead Planet | website=[[Forbes]] | access-date=November 30, 2022 | archive-date=November 30, 2022 | archive-url=https://web.archive.org/web/20221130022417/https://www.forbes.com/sites/jamiecartereurope/2019/06/12/nasa-heads-for-psyche-a-giant-mysterious-metallic-asteroid-that-could-be-a-dead-planets-heart/?sh=2a6ef5a665b8 | url-status=live }}</ref>
==Possible settlement locations==
=== Poles ===
It has been proposed to set up a first base at a Martian pole, which would allow access to water.<ref name="Rüede Ivanov Leonardi Volkova 2019 pp. 234–249">{{cite journal | last1=Rüede | first1=Anne-Marlene | last2=Ivanov | first2=Anton | last3=Leonardi | first3=Claudio | last4=Volkova | first4=Tatiana | title=Systems engineering and design of a Mars Polar Research Base with a human crew | journal=Acta Astronautica | publisher=Elsevier BV | volume=156 | year=2019 | issn=0094-5765 | doi=10.1016/j.actaastro.2018.06.051 | pages=234–249| bibcode=2019AcAau.156..234R | s2cid=85551985 | url=http://infoscience.epfl.ch/record/264096 }}</ref>
=== Caves ===
{{See also|Caves of Mars Project}}
Caves would naturally provide a degree of insulation from Martian hazards for humans on the planet.<ref name=nytcaves>{{cite news |last1=Kornei |first1=Katherine |title=House-Hunting on Mars Has Already Started |url=https://www.nytimes.com/2022/10/29/science/mars-caves-astronauts.html |access-date=1 November 2022 |work=The New York Times |date=29 October 2022 |archive-date=November 1, 2022 |archive-url=https://web.archive.org/web/20221101142340/https://www.nytimes.com/2022/10/29/science/mars-caves-astronauts.html |url-status=live }}</ref> These hazards include radiation, impactor events, and the wide range in temperatures on the surface.<ref name=nytcaves/>
[[Mars Odyssey]] found what appear to be natural caves near the volcano [[Arsia Mons#Possible cave entrances|Arsia Mons]]. It has been speculated that settlers could benefit from the shelter that these or similar structures could provide from radiation and micrometeoroids. Geothermal energy is also suspected in the equatorial regions.<ref>{{cite journal |bibcode=1997JBIS...50..187F |url=http://www.users.globalnet.co.uk/~mfogg/fogg1996.pdf |first1=Martyn J. |last1=Fogg |year=1997 |title=The utility of geothermal energy on Mars |journal=Journal of the British Interplanetary Society |volume=49 |pages=403–22 |access-date=August 12, 2009 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927111139/http://www.users.globalnet.co.uk/~mfogg/fogg1996.pdf |url-status=live }}</ref>
A team of researchers which presented at Geological Society of America Connects 2022 identified some 139 caves worth exploring as potential shelters.<ref name=nytcaves/> Each was within {{convert|60|miles|km|-1}} of a ___location ideal for use as a landing site and had been imaged in high-resolution by [[HiRISE]].<ref name=nytcaves/>
=== Lava tubes ===
[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|Cropped version of a [[HiRISE]] image of a lava tube skylight entrance on the Martian volcano [[Pavonis Mons]]]]
Several possible [[Martian lava tube]] skylights have been located on the flanks of Arsia Mons. Earth based examples indicate that some should have lengthy passages offering complete protection from radiation and be relatively easy to seal using on-site materials, especially in small subsections.<ref>{{cite web |url=http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1371.pdf |title=THEMIS Observes Possible Cave Skylights on Mars |first1=G. E. |last1=Cushing |first2=T. N. |last2=Titus |first3=J. J. |last3=Wynne |first4=P. R. |last4=Christensen |access-date=2010-06-18 |archive-date=September 15, 2011 |archive-url=https://web.archive.org/web/20110915195653/http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1371.pdf |url-status=live }}</ref>
=== Hellas Planitia ===
[[Hellas Planitia]] is the lowest lying plain below the Martian [[Datum (geodesy)|geodetic datum]]. The atmospheric pressure is relatively higher in this place when compared to the rest of Mars.
==Impact of human presence==
There has been a lively discussion about how human presence on Mars would relate to possible indigenous life on Mars. More fundamentally even the very understanding of human life and in relation to extraterrestrial life, and their different worths have been discussed.<ref name="i232">{{cite journal | last=Valentine | first=David | title=Gravity fixes: Habituating to the human on Mars and Island Three | journal=HAU: Journal of Ethnographic Theory | publisher=University of Chicago Press | volume=7 | issue=3 | date=1 December 2017 | issn=2575-1433 | doi=10.14318/hau7.3.012 | pages=185–209}}</ref>
===Planetary protection===
{{see also|Planetary protection}}
Robotic spacecraft to Mars are required to be sterilized, to have at most 300,000 spores on the exterior of the craft—and more thoroughly sterilized if they contact "special regions" containing water,<ref name=groundwatercontamination>[https://www.bbc.co.uk/news/uk-northern-ireland-27526981 Queens University Belfast scientist helps NASA Mars project] {{Webarchive|url=https://web.archive.org/web/20191026125803/https://www.bbc.co.uk/news/uk-northern-ireland-27526981 |date=October 26, 2019 }} "No-one has yet proved that there is deep groundwater on Mars, but it is plausible as there is certainly surface ice and atmospheric water vapour, so we wouldn't want to contaminate it and make it unusable by the introduction of micro-organisms."</ref><ref name="COSPAR PLANETARY PROTECTION POLICY">[https://science.nasa.gov/media/medialibrary/2012/05/04/COSPAR_Planetary_Protection_Policy_v3-24-11.pdf COSPAR PLANETARY PROTECTION POLICY] {{webarchive|url=https://web.archive.org/web/20130306111646/https://science.nasa.gov/media/medialibrary/2012/05/04/COSPAR_Planetary_Protection_Policy_v3-24-11.pdf |date=2013-03-06 }} (20 October 2002; As Amended to 24 March 2011)</ref> otherwise there is a risk of contaminating not only the life-detection experiments but possibly the planet itself.
It is impossible to sterilize human missions to this level, as humans are host to typically a hundred trillion [[microorganism]]s of thousands of species of the [[human microbiome]], and these cannot be removed while preserving the life of the human. Containment seems the only option, but it is a major challenge in the event of a hard landing (i.e. crash).<ref name=biospherescollide>[http://www.nasa.gov/connect/ebooks/when_biospheres_collide_detail.html#.U_uVh_mwJcQ When Biospheres Collide – a history of NASA's Planetary Protection Programs] {{Webarchive|url=https://web.archive.org/web/20190714112103/https://www.nasa.gov/connect/ebooks/when_biospheres_collide_detail.html#.U_uVh_mwJcQ |date=July 14, 2019 }}, Michael Meltzer, May 31, 2012, see Chapter 7, Return to Mars – final section: "Should we do away with human missions to sensitive targets"</ref> There have been several planetary workshops on this issue, yet no final guidelines for a way forward.<ref>Johnson, James E. [http://www.hou.usra.edu/meetings/ppw2015/pdf/1010.pdf "Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions: Goals and Scope." (2015)] {{Webarchive|url=https://web.archive.org/web/20191026125720/https://www.hou.usra.edu/meetings/ppw2015/pdf/1010.pdf |date=October 26, 2019 }}</ref> Human explorers would also be vulnerable to back contamination to Earth if they become carriers of microorganisms should Mars have life.<ref>[http://www.nap.edu/openbook.php?record_id=10360&page=37 Safe on Mars page 37] {{Webarchive|url=https://web.archive.org/web/20150906050040/http://www.nap.edu/openbook.php?record_id=10360&page=37 |date=September 6, 2015 }} "Martian biological contamination may occur if astronauts breathe contaminated dust or if they contact material that is introduced into their habitat. If an astronaut becomes contaminated or infected, it is conceivable that he or she could transmit Martian biological entities or even disease to fellow astronauts, or introduce such entities into the biosphere upon returning to Earth. A contaminated vehicle or item of equipment returned to Earth could also be a source of contamination."</ref>
== Political and legal context ==
In the 1967 United Nations [[Outer Space Treaty]], it was determined that no country may take claim to space or its inhabitants. Many articles of the Outer Space Treaty prevent the legal colonization of outer space.<ref>{{Cite web |last=Parkita |first=Piotr Filip |date=2025-04-11 |title=Tomorrow for which we are not prepared. Why is the Outer Space Treaty opposed to the idea of colonizing Mars? |url=https://journals.law.harvard.edu/ilj/2025/04/tomorrow-for-which-we-are-not-prepared-why-is-the-outer-space-treaty-opposed-to-the-idea-of-colonizing-mars/ |access-date=2025-04-16 |website=Harvard International Law Journal |language=en-US}}</ref>
NASA had to deal with several cuts in funding. During the presidency of [[Barack Obama]], the objective for NASA to reach Mars was pushed to the background.<ref>{{Cite web |url=https://www.space.com/35394-president-obama-spaceflight-exploration-legacy.html |title=President Obama's Space Legacy: Mars, Private Spaceflight and More |website=[[Space.com]] |date=January 20, 2017 |access-date=April 5, 2018 |archive-date=April 6, 2018 |archive-url=https://web.archive.org/web/20180406040542/https://www.space.com/35394-president-obama-spaceflight-exploration-legacy.html |url-status=live }}</ref> In 2017, president [[Donald Trump]] promised to return humans to the Moon and eventually Mars,<ref>{{Cite web |url=https://www.nasa.gov/press-release/new-space-policy-directive-calls-for-human-expansion-across-solar-system |title=NASA.gov |date=December 11, 2017 |access-date=April 5, 2018 |archive-date=April 28, 2018 |archive-url=https://web.archive.org/web/20180428021245/https://www.nasa.gov/press-release/new-space-policy-directive-calls-for-human-expansion-across-solar-system/ |url-status=live }}</ref> and increased the NASA budget by $1.1 billion,<ref>{{Cite web |url=http://www.sciencemag.org/news/2018/03/updated-us-spending-deal-contains-largest-research-spending-increase-decade |title=Trump, Congress approve largest U.S. Research spending increase in a decade |access-date=April 5, 2018 |archive-date=March 23, 2018 |archive-url=https://web.archive.org/web/20180323235214/http://www.sciencemag.org/news/2018/03/updated-us-spending-deal-contains-largest-research-spending-increase-decade |url-status=live }}</ref> to mostly focus on development of the new [[Space Launch System]].<ref>{{cite web |url=http://www.airspacemag.com/space/bigger-saturn-bound-deep-space-180952802/ |title=Bigger Than Saturn, Bound for Deep Space |first=James R. |last=Chiles |website=Airspacemag.com |access-date=2 January 2018 |archive-date=December 12, 2019 |archive-url=https://web.archive.org/web/20191212201239/https://www.airspacemag.com/space/bigger-saturn-bound-deep-space-180952802/ |url-status=live }}</ref><ref>{{cite web |url=https://arstechnica.com/science/2017/03/for-the-first-time-nasa-has-begun-detailing-its-deep-space-exploration-plans/ |title=Finally, some details about how NASA actually plans to get to Mars |last=Berger|first=Eric|website=Arstechnica.com |date=March 28, 2017 |access-date=2 January 2018 |archive-date=July 13, 2019 |archive-url=https://web.archive.org/web/20190713182116/https://arstechnica.com/science/2017/03/for-the-first-time-nasa-has-begun-detailing-its-deep-space-exploration-plans/ |url-status=live }}</ref>
It is unforeseen how the first human landing on Mars will change the current policies regarding the exploration of space and occupancy of celestial bodies. Since the planet Mars offers a challenging environment and dangerous obstacles for humans to overcome, the laws and culture on the planet will most likely be different from those on Earth.<ref>Szocik, Konrad, Kateryna Lysenko-Ryba, Sylwia Banaś, and Sylwia Mazur. "Political and Legal Challenges in a Mars Colony." ''Space Policy'' (2016): n. pag. Web. 24 Oct. 2016.</ref> With [[Elon Musk]] announcing his plans for travel to Mars, it is uncertain how the dynamic of a private company possibly being the first to put a human on Mars will play out on a national and global scale.<ref name="NYT-20160927" /><ref>''Commercial Space Exploration: Ethics, Policy and Governance'', 2015. Print.
</ref>
==Ethics==
It has been argued that settling Mars may divert attention from solving problems on Earth that may also become problems on Mars,<ref name="j066">{{cite web | last=Bharmal | first=Zahaan | title=The case against Mars colonisation | website=the Guardian | date=2018-08-28 | url=https://www.theguardian.com/science/blog/2018/aug/28/the-case-against-mars-colonisation | access-date=2024-09-14}}</ref> with the reasoning that plans about Mars are always about the plans we have for Earth.<ref name="v547">{{cite web | last=Cisneros | first=Isabella | title=The Space Review: The fault in our Mars settlement plans | website=The Space Review | date=2023-08-21 | url=https://www.thespacereview.com/article/4639/1 | access-date=2024-09-14}}</ref> [[Jeff Bezos]], founder of [[Blue Origin]], [[SpaceX]]'s competitor in [[commercial spaceflight]], has rejected Mars colonization as a mere "Plan B", suggesting instead to preserve Earth through [[space development]] and moving all heavy industrial activity to space.<ref name="f819">{{cite web | title=Jeff Bezos foresees a trillion people living in millions of space colonies. Here's what he's doing to get the ball rolling. | website=NBC News | date=2019-05-15 | url=https://www.nbcnews.com/mach/science/jeff-bezos-foresees-trillion-people-living-millions-space-colonies-here-ncna1006036 | access-date=2024-08-06}}</ref>
It has been pointed out that the impact of human settlement on Mars, with regards to [[planetary protection]], a crucial issue in space exploration, has not been comprehensively answered.<ref name="j066"/>
It has been argued that there are physical and social consequences that need to be addressed with regards to long-term survival on the surface of Mars.<ref name="v547"/> Former President [[Barack Obama]] has characterized Mars as more inhospitable than Earth would be "even after a [[nuclear war]]",<ref name="e729">{{cite web | last=Guenot | first=Marianne | title=Obama takes a shot at the likes of Musk and Bezos, says we must protect Earth before colonizing Mars | website=Business Insider | date=2024-03-14 | url=https://www.businessinsider.com/obama-protect-earth-colonizing-mars-starship-launch-musk-bezos-space-2024-3 | access-date=2024-08-06}}</ref> with others pointing out that Earth and [[nuclear shelter|underground shelters]] on Earth could still provide better conditions and protection for more people from apocalyptic scenarios.<ref name="j066"/> Mars colonization has been called a 'dangerous delusion' by Lord [[Martin Rees]], a British cosmologist/astrophysicist and the [[Astronomer Royal]] of the [[United Kingdom]].<ref>{{Cite web |date=March 15, 2021 |title=Elon Musk's plans for life on Mars are a 'dangerous delusion', says British chief astronomer |url=https://news.sky.com/story/elon-musks-plans-for-life-on-mars-a-dangerous-delusion-12243479 |access-date=August 15, 2024 |website=Sky News}}</ref> Musk has stated that staying on Mars is a life threatening endeavor that needs to be glorious to be worth it.<ref name="CNN23">{{cite web |last=Wattles |first=Jackie |date=December 12, 2023 |title=Colonizing Mars could be dangerous and ridiculously expensive. Elon Musk wants to do it anyway |url=https://www.cnn.com/2020/09/08/tech/spacex-mars-profit-scn/index.html |access-date=August 15, 2024 |website=CNN}}</ref> Exploration of Mars has also been argued to be better left to the already successful robotic missions, with crewed missions simply being too expensive, dangerous and boring.<ref name="j066"/>
===Colonialism===
{{Main|Space colonisation#Colonialism}}[[Image:NASA Artemis Gateway logo.png|thumb|upright=0.8|The logo and name of the [[Lunar Gateway]] references the [[St. Louis]] [[Gateway Arch]], associating Mars with the American [[frontier]].<ref>{{cite web |author=Pearlman |first=Robert Z. |date=September 18, 2019 |title=NASA Reveals New Gateway Logo for Artemis Lunar Orbit Way Station |url=https://www.space.com/nasa-lunar-gateway-moon-station-logo.html |url-status=live |archive-url=https://web.archive.org/web/20200628112732/https://www.space.com/nasa-lunar-gateway-moon-station-logo.html |archive-date=June 28, 2020 |access-date=2020-06-28 |website=Space.com}}</ref>]]Space colonization in general has been discussed as a continuation of [[imperialism]] and [[colonialism]],<ref>{{cite news |author=Cornish |first=Gabrielle |date=22 July 2019 |title=How imperialism shaped the race to the moon |url=https://www.washingtonpost.com/outlook/2019/07/22/how-imperialism-shaped-race-moon/ |url-status=live |archive-url=https://web.archive.org/web/20190723032005/https://www.washingtonpost.com/outlook/2019/07/22/how-imperialism-shaped-race-moon/ |archive-date=July 23, 2019 |access-date=19 September 2019 |newspaper=[[The Washington Post]] |language=en}}</ref> especially regarding Mars colonial decision making, reasons for colonial labor<ref>{{cite web |author=Spencer |first=Keith A. |date=8 October 2017 |title=Against Mars-a-Lago: Why SpaceX's Mars colonization plan should terrify you |url=https://www.salon.com/2017/10/08/against-mars-a-lago-why-spacexs-mars-colonization-plan-should-terrify-you/ |url-status=live |archive-url=https://web.archive.org/web/20190919201220/https://www.salon.com/2017/10/08/against-mars-a-lago-why-spacexs-mars-colonization-plan-should-terrify-you/ |archive-date=September 19, 2019 |access-date=20 September 2019 |website=Salon.com |language=en}}</ref> and land exploitation have been questioned with [[postcolonialism|postcolonial]] critique. Seeing the need for inclusive<ref>{{cite web |author=Zevallos |first=Zuleyka |date=26 March 2015 |title=Rethinking the Narrative of Mars Colonisation |url=https://othersociologist.com/2015/03/26/rethinking-the-narrative-of-mars-colonisation/ |url-status=live |archive-url=https://web.archive.org/web/20191211122431/https://othersociologist.com/2015/03/26/rethinking-the-narrative-of-mars-colonisation/ |archive-date=December 11, 2019 |access-date=20 September 2019 |website=Other Sociologist |language=en}}</ref> and democratic participation and implementation of any space and Mars exploration, infrastructure, or colonialization, many have called for dramatic sociological reforms and guarantees to prevent racism, sexism, and other forms of prejudice.<ref>{{cite web |author=Spencer |first=Keith A. |date=2 May 2017 |title=Keep the Red Planet Red |url=https://www.jacobinmag.com/2017/02/mars-elon-musk-space-exploration-nasa-colonization |url-status=live |archive-url=https://web.archive.org/web/20191103165331/https://jacobinmag.com/2017/02/mars-elon-musk-space-exploration-nasa-colonization |archive-date=November 3, 2019 |access-date=20 September 2019 |website=[[Jacobin (magazine)|Jacobin]] |language=en}}</ref>
The narrative of space exploration as a "[[New Frontier]]" has been criticized as an unreflected continuation of [[settler colonialism]] and [[manifest destiny]], continuing the narrative of colonial exploration as fundamental to the assumed [[human nature]].<ref>{{cite web |author=Haskins |first=Caroline |date=14 August 2018 |title=The racist language of space exploration |url=https://theoutline.com/post/5809/the-racist-language-of-space-exploration |url-status=live |archive-url=https://web.archive.org/web/20191016235916/https://theoutline.com/post/5809/the-racist-language-of-space-exploration |archive-date=October 16, 2019 |access-date=20 September 2019 |website=The Outline |language=en}}</ref><ref>{{cite web |author=Lee |first=D. N. |date=26 March 2015 |title=When discussing Humanity's next move to space, the language we use matters. |url=https://blogs.scientificamerican.com/urban-scientist/when-discussing-humanity-8217-s-next-move-to-space-the-language-we-use-matters/ |url-status=live |archive-url=https://web.archive.org/web/20190914011756/https://blogs.scientificamerican.com/urban-scientist/when-discussing-humanity-8217-s-next-move-to-space-the-language-we-use-matters/ |archive-date=September 14, 2019 |access-date=20 September 2019 |website=[[Scientific American]] |language=en}}</ref><ref>{{cite web|date=2018-11-09|title=We need to change the way we talk about space exploration|first=Nadia|last=Drake|author-link=Nadia Drake|publisher=[[National Geographic]]|access-date=2019-10-19|url=https://www.nationalgeographic.com/science/2018/11/we-need-to-change-way-we-talk-about-space-exploration-mars/|archive-date=October 16, 2019|archive-url=https://web.archive.org/web/20191016235826/https://www.nationalgeographic.com/science/2018/11/we-need-to-change-way-we-talk-about-space-exploration-mars/|url-status=dead}}</ref>
The predominant perspective of territorial colonization in space has been called ''surfacism'', especially comparing advocacy for colonization of [[Mars colonization|Mars]] opposed to [[Venus colonization|Venus]].<ref name="Tickle 2015">{{cite web | last=Tickle | first=Glen | title=A Look Into Whether Humans Should Try to Colonize Venus Instead of Mars | website=Laughing Squid | date=2015-03-05 | url=https://laughingsquid.com/a-look-into-whether-humans-should-try-to-colonize-venus-instead-of-mars/ | access-date=2021-09-01 | archive-date=September 1, 2021 | archive-url=https://web.archive.org/web/20210901191020/https://laughingsquid.com/a-look-into-whether-humans-should-try-to-colonize-venus-instead-of-mars/ | url-status=live }}</ref><ref>{{cite news |author=Warmflash |first=David |date=14 March 2017 |title=Colonization of the Venusian Clouds: Is 'Surfacism' Clouding Our Judgement? |url=https://www.visionlearning.com/blog/2017/03/14/colonization-venusian-clouds-surfacism-clouding-judgement/ |url-status=live |archive-url=https://web.archive.org/web/20191211122431/https://www.visionlearning.com/blog/2017/03/14/colonization-venusian-clouds-surfacism-clouding-judgement/ |archive-date=December 11, 2019 |access-date=20 September 2019 |newspaper=Visionlearning Blog |language=en}}</ref>
===Dangers during pregnancy===
One possible ethical challenge that space travelers might face is that of [[pregnancy]] during the trip. According to NASA's policies, it is forbidden for members of the crew to engage in [[sex in space]], based on the rationale that crew members should treat each other like coworkers would in a professional environment. A pregnant member on a spacecraft would present additional hazards to herself and all others aboard. The pregnant woman and child would need additional nutrition from the rations aboard, as well as special treatment and care. The pregnancy would impinge on the pregnant crew member's duties and abilities. It is still not fully known how the environment in a spacecraft would affect the development of a child aboard. It is known however that a fetus would be more susceptible to solar radiation in space, which would likely have a negative effect on its cells and genetics.<ref>Minkel, JR. "Sex and Pregnancy on Mars: A Risky Proposition." ''Space.com''. Space.com, 11 February 2011. Web. 09 December 2016.</ref> During a long trip to Mars, it is likely that members of a craft may engage in sex due to their stressful and isolated environment.<ref>{{cite journal | doi=10.1186/s40504-016-0043-5 | title=Mars ain't the kind of place to raise your kid: Ethical implications of pregnancy on missions to colonize other planets | year=2016 | last1=Schuster | first1=Haley | last2=Peck | first2=Steven L. | journal=Life Sciences, Society and Policy | volume=12 | issue=1 | page=10 | pmid=27558392 | pmc=4996799 | doi-access=free }}</ref>
==Advocacy==
[[File:Elon_Musk_at_MSC_2006.jpg|alt=Musk standing at a wooden podium talking at the 2006 Mars Society Conference|thumb|[[Elon Musk]] at the 2006 [[Mars Society]] conference, who has briefly joined the Mars Society's board of directors. The society and Musk have been longtime advocates of Mars colonization, with Musk having it set [[SpaceX Mars colonization program|as a goal for his spaceflight company SpaceX]].]]
Mars colonization is advocated by several non-governmental groups for a range of reasons and with varied proposals. One of the oldest groups is the [[Mars Society]] who promote a NASA program to accomplish human exploration of Mars and have set up Mars analog research stations in Canada and the United States. [[Mars to Stay]] advocates recycling emergency return vehicles into permanent settlements as soon as initial explorers determine permanent habitation is possible.
Elon Musk founded SpaceX with the long-term goal of developing the technologies that will enable a self-sustaining human colony on Mars.<ref name="NYT-20160927">{{cite news |last=Chang |first=Kenneth |title=Elon Musk's Plan: Get Humans to Mars, and Beyond |url=https://www.nytimes.com/2016/09/28/science/elon-musk-spacex-mars-exploration.html |date=27 September 2016 |work=The New York Times |access-date=27 September 2016 |archive-date=September 29, 2016 |archive-url=https://web.archive.org/web/20160929095051/http://www.nytimes.com/2016/09/28/science/elon-musk-spacex-mars-exploration.html |url-status=live }}</ref><ref>{{cite web |author=Knapp |first=Alex |date=27 November 2012 |title=SpaceX Billionaire Elon Musk Wants A Martian Colony Of 80,000 People |url=https://www.forbes.com/sites/alexknapp/2012/11/27/spacex-billionaire-elon-musk-wants-a-martian-colony-of-80000-people/ |url-status=live |archive-url=https://web.archive.org/web/20170815194709/https://www.forbes.com/sites/alexknapp/2012/11/27/spacex-billionaire-elon-musk-wants-a-martian-colony-of-80000-people/ |archive-date=August 15, 2017 |access-date=12 June 2015 |work=Forbes}}</ref> [[Richard Branson]], in his lifetime, is "determined to be a part of starting a population on Mars. I think it is absolutely realistic. It will happen... I think over the next 20 years," [from 2012] "we will take literally hundreds of thousands of people to space and that will give us the financial resources to do even bigger things".<ref>{{cite web|url=https://www.cbsnews.com/news/richard-branson-on-space-travel-im-determined-to-start-a-population-on-mars/|title=Richard Branson on space travel: "I'm determined to start a population on Mars"|date=18 September 2012|work=cbsnews.com|access-date=2019-06-15|archive-date=June 16, 2019|archive-url=https://web.archive.org/web/20190616003233/https://www.cbsnews.com/news/richard-branson-on-space-travel-im-determined-to-start-a-population-on-mars/|url-status=live}}</ref>
Author Robert Zubrin has been a major advocate for Mars exploration and colonization for many years. He is a member of the Mars society and has authored several fiction and nonfiction books about the subject. In 1996 he wrote ''[[The Case for Mars|The Case for Mars: The Plan to Settle the Red Planet and Why We Must]].'' He continues to advocate for Mars and space exploration with his most recent book being ''[[The Case for Space: How the Revolution in Spaceflight Opens Up a Future of Limitless Possibility]].''
In June 2013, [[Buzz Aldrin]], [[United States|American]] [[engineer]] and former [[astronaut]], and the [[Apollo 11#Lunar surface operations|second person to walk on the Moon]], wrote an opinion, published in ''[[The New York Times]]'', supporting a [[human mission to Mars]] and viewing the Moon "not as a destination but more a point of departure, one that places humankind on a trajectory to homestead Mars and become a two-planet species".<ref name="NYT-20130613">{{cite news |last=Aldrin |first=Buzz |title=The Call of Mars |url=https://www.nytimes.com/2013/06/14/opinion/global/buzz-aldrin-the-call-of-mars.html |date=13 June 2013 |work=The New York Times |access-date=17 June 2013 |archive-date=July 17, 2019 |archive-url=https://web.archive.org/web/20190717051019/https://www.nytimes.com/2013/06/14/opinion/global/buzz-aldrin-the-call-of-mars.html |url-status=live }}</ref> In August 2015, Aldrin, in association with the [[Florida Institute of Technology]], presented a "master plan", for NASA consideration, for astronauts, with a "tour of duty of ten years", to colonize Mars before the year 2040.<ref name="AP-20150827">{{cite news |last=Dunn |first=Marcia |title=Buzz Aldrin joins university, forming 'master plan' for Mars |url=http://apnews.excite.com/article/20150827/us-sci-buzz-aldrin-c7bc5ba293.html |date=27 August 2015 |work=[[AP News]] |access-date=30 August 2015 |archive-url=https://web.archive.org/web/20150904072417/http://apnews.excite.com/article/20150827/us-sci-buzz-aldrin-c7bc5ba293.html |archive-date=4 September 2015 |url-status=dead }}</ref>
There are critics of the project of Mars colonization. American political scientist [[Daniel Deudney]] has argued that a fully developed Mars colony represents an existential threat to humans remaining on Earth. His book, ''Dark Skies: Space Expansionism, Planetary Geopolitics, and the Ends of Humanity'', challenges the widespread view among advocates that a Mars colony would be friendly to the interests of humans on Earth.<ref>{{Cite book |last=Deudney |first=Daniel |url=https://global.oup.com/academic/product/dark-skies-9780190903343?cc=ca&lang=en& |title=Dark Skies: Space Expansionism, Planetary Geopolitics, and the Ends of Humanity |date=2020-03-02 |publisher=Oxford University Press |isbn=978-0-19-090334-3 |___location=Oxford, New York}}</ref> According to Deudney, this is merely an assumption based on the largely unexamined claim that a future Mars colony will be a straightforward extension of civilization on Earth, rather than a new kind of civilization with distinct goals, values, fears and desires.
==In fiction==
{{Main|Mars in fiction#Colonization}}
A few instances in fiction provide detailed descriptions of Mars colonization.<!-- This does not include depictions that don't describe the colonization process, or depictions of the exploration of Mars without colonization. --> They include:
* ''[[Aria (manga)|Aria]]'' (2002–2008), by [[Kozue Amano]]
<!-- Ditto...
* ''[[As It Is On Mars]]'' (2001), ''[[Give Us This Mars]]'' (2003), and ''[[Glory Be To Mars]]'' (2005), by [[William Thomas Cronin]]
* ''[[Doctor Who]]'' episode "[[The Waters of Mars]]" (2009) by Russell T Davies
-->
* ''[[
* ''[[Climbing Olympus]]'' (1994), by [[Kevin J. Anderson]]
* ''[[
* ''[[For All Mankind (TV series)|For All Mankind]]'' (2019), airing originally on [[Apple TV+]], from Series 3 onwards
* ''[[Icehenge]]'' (1985), the [[Mars trilogy]] (''Red Mars'', ''Green Mars'', ''Blue Mars'', 1992–1996), and ''[[Mars trilogy|The Martians]]'' (1999), by [[Kim Stanley Robinson]]
* ''[[John Carter (film)|John Carter]]'' (2012), by [[Mark Andrews (filmmaker)|Mark Andrews]]
* ''[[Man Plus]]'' (1976), by [[Frederik Pohl]]
* ''[[Mars (Bova novel)|The Martian]]'' (1992) and ''[[Return to Mars]]'' (1999), by [[Ben Bova]]
* ''[[Mars (miniseries)|Mars]]'' (2016), by [[National Geographic (U.S. TV channel)|National Geographic]]
* ''[[Mars Diaries]]'' (2000), by [[Sigmund Brouwer]]
* ''[[Mars Underground]]'' (1997), by [[William K. Hartmann]]
* ''[[Martian Gothic: Unification]]'' (2000), developed by Creative Reality for [[Microsoft Windows]] and Coyote Developments for [[PlayStation (console)|PlayStation]], published by [[TalonSoft]] for Microsoft Windows and [[Take-Two Interactive]] for PlayStation
<!-- For possible inclusion – can anyone verify?
* ''[[Moving Mars]]'' (1993), by [[Greg Bear]]
-->
* ''[[Mr. Nobody (film)|Mr. Nobody]]'' (2009), by [[Jaco Van Dormael]]
* ''[[Red Faction]]'' (2001), developed by [[Volition (company)|Volition]], published by [[THQ]]
* ''[[Red Planet (novel)|Red Planet]]'' (1949), by [[Robert A. Heinlein]]
* ''[[Surviving Mars]]'' (2018), developed by [[Haemimont Games]], published by [[Paradox Interactive]]
* ''[[Terra Formars]]'' (2011)
* ''[[Alexander Winn#TerraGenesis|TerraGenesis]]'' (2016), developed by [[Edgeworks Entertainment]], published by [[Tilting Point]]
* ''[[The Expanse (TV series)|The Expanse]]'' (2016–2021), airing originally on [[Syfy]], then [[Amazon Prime]]
* ''[[The Martian (Weir novel)|The Martian]]'' (2011), by Andy Weir (and the [[The Martian (film)|2015 film]], directed by [[Ridley Scott]])
* ''[[The Martian Chronicles]]'' (1950), by [[Ray Bradbury]]
* ''[[The Sands of Mars]]'' (1951), by [[Arthur C. Clarke]]
* ''[[The Space Between Us (film)|The Space Between Us]]'' (2016 film), by [[Peter Chelsom]]
* ''[[Tom and Jerry: Blast Off to Mars]]'' (2005), [[Animated film|animated]] [[science fiction comedy]] film by [[Warner Bros. Animation]] and [[Turner Entertainment]]
* ''[[Total Recall (1990 film)|Total Recall]]'' (1990), by [[Paul Verhoeven]]
* ''[[
==See also==
{{
* {{annotated link|Astrobotany}}
* {{annotated link|Climate of Mars}}
* {{annotated link|Colonization of the asteroid belt}}
* {{annotated link|Colonization of the Moon}}
* {{annotated link|Colonization of Venus}}
* {{annotated link|Effect of spaceflight on the human body}}
* {{annotated link|Exploration of Mars}}
* {{annotated link|Health threat from cosmic rays}}
* {{annotated link|Human mission to Mars}}
* {{annotated link|Human outpost}}
* {{annotated link|In situ resource utilization}}
* {{annotated link|Inspiration Mars}}
* {{annotated link|Space architecture}}
* {{annotated link|SpaceX Mars transportation infrastructure}}
* {{annotated link|Life on Mars}}
* [[List of crewed Mars
* {{annotated link|Mars analog habitat}}
* {{annotated link|Mars Desert Research Station}}
* {{annotated link|Mars habitat}}
* [[Mars Outpost]]
* {{annotated link|Mars race}}
* [[
* {{annotated link|Martian}}
* {{annotated link|Martian soil}}
* {{annotated link|Vision for Space Exploration}}
* {{annotated link|NewSpace}}
* {{annotated link|Terraforming of Mars}}
* {{annotated link|The Case for Mars|''The Case for Mars''}}
* {{annotated link|Water on Mars}}
{{div col end}}
==References==
{{Reflist|
==Further reading==
* {{cite book |author-link1= |title=Mission to Mars: My Vision for Space Exploration |publisher=[[National Geographic Books]] |author=Aldrin |first1=Buzz |year=2013 |isbn=978-1-4262-1017-4 |title-link=Mission to Mars: My Vision for Space Exploration |last2=David |first2=Leonard}} ([https://buzzaldrin.com/mission-to-mars-my-vision-for-space-exploration/ at BuzzAldrin.com])
*
* [[Frank Crossman]] and Robert Zubrin, editors, ''On to Mars
* Frank Crossman and Robert Zubrin, editors, ''On to Mars 2: Exploring and Settling a New World''. Apogee Books Space Series, 2005, {{ISBN|978-1-894959-30-8}}
* [http://docs.google.com/viewer?a=v&q=cache:BoCLnaClDwIJ:www.spacegeneration.org/files/images/MMWFILES/ISRU_presentation.pdf+human+outpost&hl=en&gl=ca&sig=AHIEtbR531BikZhNPCsx08s2KFYV1WbArg Resource Utilization Concepts for MoonMars]; By Iris Fleischer, Olivia Haider, Morten W. Hansen, Robert Peckyno, Daniel Rosenberg and Robert E. Guinness; 30 September 2003; IAC Bremen, 2003 (29 Sept–03 Oct 2003) and MoonMars Workshop (26–28 September 2003, Bremen). Accessed on 18 January 2010
* [http://www.praxis-publishing.co.uk/9780387981901.htm ''MARTIAN OUTPOST: The Challenges of Establishing a Human Settlement on Mars''] {{Webarchive|url=https://web.archive.org/web/20160603215417/http://www.praxis-publishing.co.uk/9780387981901.htm |date=June 3, 2016 }}; by Erik Seedhouse; Praxis Publishing; 2009; {{ISBN|978-0-387-98190-1}}. Also see [https://www.springer.com/astronomy/space+exploration/book/978-0-387-98190-1], [https://www.amazon.com/Martian-Outpost-Challenges-Establishing-Exploration/dp/038798190X]
* [https://web.archive.org/web/20170208034458/http://news.idg.no/cw/art.cfm?id=CB21C80A-17A4-0F78-3174039834A1E181 Ice, mineral-rich soil could support human outpost on Mars]; by Sharon Gaudin; 27 June 2008; [[IDG News Service]]
* {{cite journal |last1=Puumala |first1=Mikko M. |last2=Sivula |first2=Oskari |last3=Lehto |first3=Kirsi |title=Moving to Mars: The Feasibility and Desirability of Mars Settlements |journal=Space Policy |date=2023 |volume=66 |article-number=101590 |doi=10.1016/j.spacepol.2023.101590 |doi-access=free|bibcode=2023SpPol..6601590P }}
* {{cite journal |last1=Woo |first1=Carlton Yuan Bo |title=Review of the technologies and preparations required for Mars colonization |journal=Theoretical and Natural Science |date=2023 |volume=13 |pages=245–250 |doi=10.54254/2753-8818/13/20240854 |doi-access=free}}
* {{cite journal |last1=Neukart |first1=Florian |title=Towards sustainable horizons: A comprehensive blueprint for Mars colonization |journal=[[Heliyon]] |date=2024 |volume=10 |issue=4 |article-number=e26180 |doi=10.1016/j.heliyon.2024.e26180 |doi-access=free|pmid=38404830 |pmc=10884476 |arxiv=2309.16806 |bibcode=2024Heliy..1026180N }}
==External links==
{{Commons category|Colonization of Mars}}
{{Wikibooks|Colonising Mars}}
{{wikiversity|Should we colonize Mars?}}
{{Spoken Wikipedia|date=2021-04-08|En-Colonization of Mars-article.ogg}}
* [http://www.marssociety.org/ Mars Society]
* [http://mmp.planetary.org/index.html The Planetary Society: Mars Millennium Project]
* [https://web.archive.org/web/20180917143417/http://www.
* [http://www.marshome.org/ The Mars Foundation] – {{Webarchive|url=https://web.archive.org/web/20120301104324/http://www.marshome.org/ |date=March 1, 2012 }}
* [https://web.archive.org/web/20100125210332/http://ngm.nationalgeographic.com/big-idea/07/mars Making Mars the New Earth
* [[v:Should we colonize Mars?|Should we colonize Mars?]] – Wikidebate in Wikiversity
{{Human missions to Mars}}
{{Mars}}
{{Space colonization}}
{{Portal bar|Astronomy|Solar System|Science}}
{{Use American English|date=January 2014}}
{{DEFAULTSORT:Colonization Of Mars}}
[[Category:Colonization of Mars| ]]
[[Category:Exploration of Mars]]
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[[Category:Space colonization|*Mars]]
[[Category:Mars Society]]
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