View source for Astronomy:Colonization of Mars

{{Short description|Proposed concepts for human settlements on Mars}}
[[File: Martian habitat with colonists.jpg|upright=1.5|alt=An astronaut fixing machine on Mars and another heading back to the base|thumb|Artist conception of [[Astronaut|astronaut]]s working outside, near a large modular habitat]]
'''Colonization''' or '''settlement of Mars''' is the theoretical human migration to and establishment of long-term human presence on [[Astronomy:Mars|Mars]]. The prospect has garnered interest from public space agencies and private corporations and has been extensively explored in science fiction writing, film, and art. Organizations have proposed plans for a [[Astronomy:Human mission to Mars|human mission to Mars]], the first step towards any colonization effort, but thus far no person has set foot on the planet, and there have been no return missions. However, landers and [[Astronomy:Mars rover|rovers]] have successfully explored the planetary surface and delivered information about conditions on the ground.

Mars' orbit is close to [[Astronomy:Earth's orbit|Earth's orbit]] and the [[Astronomy:Asteroid belt|asteroid belt]]. While [[Astronomy:Mars sol|Mars' day]] and [[Chemistry:Composition of Mars|general composition]] are similar to Earth, the planet is hostile to life. Mars has an [[Astronomy:Atmosphere of Mars|unbreathable atmosphere]], thin enough that its [[Astronomy:Climate of Mars#Temperature|temperature]] on average fluctuates between {{Cvt|-70 and 0|C|F}}, yet thick enough to cause [[Astronomy:Dust storms on Mars|planet-wide dust storms]]. The barren [[Astronomy:Geology of Mars|landscape on Mars]] is covered by fine, toxic dust and intense [[Physics:Ionizing radiation|ionizing radiation]]. Mars has in-situ resources, such as [[Astronomy:Water on Mars|underground water]], [[Astronomy:Martian soil|Martian soil]], and [[Astronomy:Ore resources on Mars|ore]], which could be used by colonists. Opportunities to generate electricity via wind, [[Engineering:Solar power|solar]], and [[Physics:Nuclear power|nuclear power]] using resources on Mars are poor.

Justifications and motivations for colonizing Mars include curiosity, the potential for humans to provide more in-depth observational research than uncrewed rovers, an economic interest in its resources, and the possibility that the settlement of other planets could decrease the probability of [[Unsolved:Human extinction|human extinction]]. Difficulties and hazards include [[Physics:Radiation exposure|radiation exposure]] during a trip to Mars and on its surface, [[Astronomy:Martian soil#Toxicity|toxic soil]], low gravity, the isolation that accompanies Mars' distance from Earth, a lack of water, and cold temperatures.

Commitments to researching permanent settlement have been made by public space agencies—[[Organization:NASA|NASA]], ESA, [[Company:Roscosmos|Roscosmos]], [[Astronomy:Indian Space Research Organisation|ISRO]], the [[Organization:China National Space Administration|CNSA]], among others—and private organizations—[[Company:SpaceX|SpaceX]], [[Company:Lockheed Martin|Lockheed Martin]], and [[Company:Boeing|Boeing]].

==Mission concepts and timelines==
Since the 20th century, there have been several proposed human missions to Mars both by government agencies and private companies.{{vague|date=March 2020}}

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 [[Organization:NASA|NASA]], 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 [[Astronomy:Mars Direct|Mars Direct]] and the [[Astronomy:Mars Direct#Revisions|Semi-Direct]] concepts, advocated by [[Biography:Robert Zubrin|Robert Zubrin]], an advocate of the colonization of Mars.<ref name="zubrin1996" />

At the February 2017 World Government Summit, the [[Place:United Arab Emirates|United Arab Emirates]] announced a plan to establish a settlement on Mars by 2117, led by the [[Engineering:Mohammed bin Rashid Space Centre|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"
|+ [[Physics:Atmospheric pressure|Atmospheric pressure]] comparison
! scope="col" | Location
! scope="col" | Pressure
|-
! scope="row" | [[Astronomy:Olympus Mons|Olympus Mons]] summit
| {{Convert|72|Pa|abbr=on|lk=on}} (0.0007 [[Physics:Atmosphere (unit)|atm]])
|-
! scope="row" | [[Astronomy:Atmosphere of Mars|Mars average]]
| {{Convert|610|Pa|abbr=on}} (0.006 atm)
|-
! scope="row" | [[Astronomy:Hellas Planitia|Hellas Planitia]] bottom
| {{Convert|1.16|kPa|abbr=on}} (0.0114 atm)
|-
! scope="row" | [[Astronomy:Armstrong limit|Armstrong limit]]
| {{Convert|6.25|kPa|abbr=on}} (0.0617 atm)
|-
! scope="row" | [[Earth:Mount Everest|Mount Everest]] summit<ref>{{cite journal|doi=10.1152/jappl.1999.86.3.1062|pmid=10066724|title=Barometric pressures on Mt. Everest: New data and physiological significance|journal=Journal of Applied Physiology|volume=86|issue=3|pages=1062–1066|year=1999|last1=West|first1=John B.|s2cid=27875962 }}</ref>
| {{Convert|33.7|kPa|abbr=on}} (0.3326 atm)
|-
! scope="row" | Earth sea level
| {{Convert|101.3|kPa|abbr=on}} (1 atm)
|}

===Gravity and size===

The surface [[Physics:Gravity of Mars|gravity of Mars]] is just 38% that of Earth. Although microgravity is known to cause health problems such as [[Physics: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 |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 [[Astronomy:Mars Gravity Biosatellite|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 [[Astronomy:Magnetosphere|magnetosphere]], [[Astronomy:Solar particle event|solar particle event]]s and [[Astronomy:Cosmic ray|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===
[[Physics:Atmospheric pressure|Atmospheric pressure]] on Mars is far below the [[Astronomy:Armstrong limit|Armstrong limit]] at which people can survive without [[Engineering:Pressure suit|pressure suit]]s. Since [[Astronomy:Terraforming of Mars|terraforming]] cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with [[Physics:Pressure vessel|pressure vessel]]s similar to spacecraft, capable of containing a pressure between 30 and 100&nbsp;kPa. The atmosphere is also toxic as most of it consists of [[Chemistry:Carbon dioxide|carbon dioxide]] (95%&nbsp;[[Chemistry:Carbon dioxide|carbon dioxide]], 3%&nbsp;nitrogen, 1.6%&nbsp;argon, and traces totaling less than 0.4% of other gases, including oxygen).

This thin atmosphere does not filter out [[Chemistry: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&nbsp;°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===
[[Astronomy:Water on Mars|Water on Mars]] is scarce, with rovers ''[[Engineering:Spirit (rover)|Spirit]]'' and ''[[Engineering:Opportunity (rover)|Opportunity]]'' finding less than there is 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=[[Organization:NASA|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 [[Astronomy: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 [[Earth:Extremes on Earth|lowest temperature ever recorded on Earth]] was 184 K (−89.2&nbsp;°C) in [[Earth:Antarctica|Antarctica]].

Because Mars is about 52% farther from the [[Astronomy:Sun|Sun]], the amount of [[Physics:Solar energy|solar energy]] entering its upper atmosphere per unit area (the [[Astronomy:Solar constant|solar constant]]) is only 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 [[Astronomy:Solar irradiance|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 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 [[Astronomy:Climate of Mars#Dust storms|dust storms]]). This means solar panels can always operate at maximum efficiency on dust-free days.

[[Astronomy: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=Viorel Badescu| title=Mars: Prospective Energy and Material Resources| url=https://books.google.com/books?id=BnPE37Ms5awC&pg=PA83| year=2009| publisher=Springer Science & Business Media| isbn=978-3-642-03629-3| page=83| access-date=December 28, 2018| archive-date=December 21, 2019| archive-url=https://web.archive.org/web/20191221172930/https://books.google.com/books?id=BnPE37Ms5awC&pg=PA83| 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&nbsp;°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 | 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&nbsp;°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 [[Astronomy:Axial tilt|axial tilt]] of 25.19°, similar to Earth's 23.44°. As a result, Mars has [[Physics:Season|season]]s much like Earth, though on average they last nearly twice as long because the Martian year is about 1.88&nbsp;Earth years, despite having a similar rotational period (known as a sol) to an Eartian day (see below). 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 [[Astronomy: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 ''[[Biology:Debaryomyces hansenii|Debaryomyces hansenii]]'' exposed in lab experiments to increasing [[Chemistry: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 }}</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 [[Earth:Extremophile|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 [[Astronomy: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 [[Astronomy: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%&nbsp;oxygen.

In 2012, it was reported that some [[Biology:Lichen|lichen]] and [[Biology:Cyanobacteria|cyanobacteria]] survived and showed remarkable [[Social:Adaptive capacity|adaptation capacity]] for [[Earth:Photosynthesis|photosynthesis]] after 34&nbsp;days in [[Simulation|simulated]] Martian conditions in the Mars Simulation Laboratory (MSL) maintained by the [[Organization:German Aerospace Center|German Aerospace Center]] (DLR).<ref name="Skymania-20120426">{{cite web |last=Baldwin |first=Emily |title=Lichen survives harsh Mars environment |url=http://www.skymania.com/wp/2012/04/lichen-survives-harsh-martian-setting.html |date=26 April 2012 |publisher=Skymania News |access-date=2012-04-27 |archive-url=https://web.archive.org/web/20120528145425/http://www.skymania.com/wp/2012/04/lichen-survives-harsh-martian-setting.html/ |archive-date=28 May 2012 |url-status=dead }}</ref><ref name="EGU-20120426">{{cite journal |last1=de Vera |first1=J.-P. |last2=Kohler |first2=Ulrich |title=The adaptation potential of extremophiles to Martian surface conditions and its implication for the habitability of Mars |journal=EGU General Assembly Conference Abstracts |volume=14 |pages=2113 |url=http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |date=26 April 2012 |publisher=[[Organization:European Geosciences Union|European Geosciences Union]] |access-date=2012-04-27 |url-status=dead |archive-url=https://web.archive.org/web/20120504224706/http://media.egu2012.eu/media/filer_public/2012/04/05/10_solarsystem_devera.pdf |archive-date=4 May 2012 |bibcode=2012EGUGA..14.2113D }}</ref><ref name="dlr">{{cite web |url=http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10081/151_read-3409/ | archive-url=https://web.archive.org/web/20180323053655/http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10081/151_read-3409/#/gallery/5671 | archive-date=2018-03-23 | title=Surviving the conditions on Mars |publisher=DLR }}</ref> Some scientists think that cyanobacteria could play a role in the development of self-sustainable crewed outposts on Mars.<ref name="Verseux2015">{{cite journal |title=Sustainable life support on Mars – the potential roles of cyanobacteria |journal=International Journal of Astrobiology |volume=15 |issue=1 |pages=65–92 |date=3 August 2015 |last1=Verseux |first1=Cyprien |last2=Baqué |first2=Mickael |last3=Lehto |first3=Kirsi |last4=de Vera |first4=Jean-Pierre P. |doi=10.1017/S147355041500021X |display-authors=0|bibcode=2016IJAsB..15...65V |doi-access=free }}</ref> They propose that cyanobacteria could be used directly for various applications, including the production of food, fuel and oxygen, but also indirectly: products from their culture could support the growth of other organisms, opening the way to a wide range of life-support biological processes based on Martian resources.<ref name="Verseux2015"/>

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 [[Earth:Antarctica|Antarctica]].<ref>{{cite web|url= http://marsrover.nasa.gov/spotlight/20070612.html|title= Extreme Planet Takes Its Toll|work= Mars Exploration Rovers|publisher= Jet Propulsion Laboratory, California Institute of Technology|date= June 12, 2007|access-date= March 12, 2014|archive-url= https://web.archive.org/web/20131102112312/http://marsrover.nasa.gov/spotlight/20070612.html|archive-date= November 2, 2013|url-status= dead}}</ref> The atmospheric pressure at the highest altitudes reached by piloted balloon ascents (35&nbsp;km (114,000 feet) in 1961,<ref>{{cite web |url=http://www.centennialofflight.gov/essay/Lighter_than_air/20th_cent_records-2/LTA12.htm |title= Higher, Farther, and Longer — Record Balloon Flights in the Second Part of the Twentieth Century|publisher=U.S. Centennial Of Flight Commission| archive-url = https://web.archive.org/web/20030430070850/http://www.centennialofflight.gov/essay/Lighter_than_air/20th_cent_records-2/LTA12.htm | archive-date = April 30, 2003 | access-date = September 22, 2014}}</ref> 38&nbsp;km in 2012) is similar to that on the surface of Mars. However, the pilots were not exposed to the extremely low pressure, as it would have killed them, but seated in a pressurized capsule.<ref>{{cite web|url=http://www.sablesys.com/baro-altitude.html|title=Barometric Pressure vs. Altitude Table|publisher=Sable Systems International|date=2014|url-status=dead|archive-url=https://web.archive.org/web/20071025050551/http://www.sablesys.com/baro-altitude.html|archive-date=2007-10-25}}</ref>

Human survival on Mars would require living in artificial [[Astronomy:Mars habitat|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 a 10% decrease physical and mental impairment (See [[Medicine:Dehydration|Dehydration]]). A person in the UK uses 70–140&nbsp;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 [[Engineering: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), 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|Astronomy: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 consecutive space flight is 438&nbsp;days by cosmonaut [[Biography:Valeri Polyakov|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 878&nbsp;days by Gennady Padalka.<ref name="Record Breaking">{{cite news 
 |last1=Cheng 
 |first1=Kenneth 
 |title=Breaking Space Records 
 |url=https://www.nytimes.com/live/international-space-station-launch/breaking-space-records 
 |access-date=28 June 2015 
 |work=The New York Times 
 |date=27 March 2015 
 |archive-url=https://web.archive.org/web/20150405145407/http://www.nytimes.com/live/international-space-station-launch/breaking-space-records/ 
 |archive-date=5 April 2015 
 |url-status=dead 
 }}</ref> The longest time spent outside the protection of the Earth's [[Astronomy:Van Allen radiation belt|Van Allen radiation belt]] is about 12&nbsp;days for the [[Engineering:Apollo 17|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 colonies. 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, [[Astronomy: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 [[Biology:Bone|bone]]s and [[Biology:Muscle|muscle]]s. There is also risk of [[Medicine:Osteoporosis|osteoporosis]] and [[Biology:Circulatory system|cardiovascular]] problems. Current rotations on the [[Astronomy:International Space Station|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 [[Biology:Erythropoietin|erythropoietin]] secretion.<ref>Aubert AE, 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 our body's 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 WH. Space motion sickness: Incidence, etiology, and countermeasures. Autonomic Neuroscience 2006;129(1):77-79.</ref> Returning astronauts also felt disoriented. Journeys to and from Mars being six months is the average time spent at the ISS. 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====
Dangerous amounts of radiation reach Mars' surface despite it being much further from the Sun compared to Earth. Mars has lost its inner [[Physics:Dynamo theory|dynamo]] giving it a weaker global [[Astronomy:Magnetosphere|magnetosphere]] than Earth does. Combined with a thin atmosphere, this permits a significant amount of [[Physics:Ionizing radiation|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>
{{Further|Astronomy:Health threat from cosmic rays}}
The [[Astronomy:2001 Mars Odyssey|Mars Odyssey]] spacecraft carries an instrument, the [[Astronomy:Mars Radiation Environment Experiment|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 [[Astronomy:International Space Station|International Space Station]]. The average daily dose was about {{convert|220|uGy|mrad|abbr=on}}—equivalent to 0.08&nbsp;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 events (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 [[Astronomy:Aurora|aurora]] 25-times brighter than any observed earlier, due to a massive, and unexpected, [[Astronomy: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 [[Astronomy:Martian lava tube|Martian lava tube]]s) would significantly lower the colonists' exposure to radiation.

[[File:PIA17601-Comparisons-RadiationExposure-MarsTrip-20131209.png|thumb|left|Comparison of radiation doses—includes the amount detected on the trip from Earth to Mars by the [[Astronomy:Radiation assessment detector|RAD]] on the 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 |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 |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. | display-authors=8 |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 [[Organization:NASA Space Radiation Laboratory|NASA Space Radiation Laboratory]], at [[Organization:Brookhaven National Laboratory|Brookhaven National Laboratory]], that employs [[Physics:Particle accelerator|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 quite as dangerous as once thought; and that [[Biology:Radiation hormesis|radiation hormesis]] occurs.<ref name="zubrin1996b">{{cite book |last=Zubrin |first=Robert |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 [[Biology:DNA|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 shields 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===
[[Image:MarsTransitionV.jpg|thumb|right|Artist's conception of the process of terraforming Mars as discussed in some works of science fiction]]

{{Main|Astronomy:Terraforming of Mars}}

Various works of fiction put forward the idea of terraforming Mars to allow a wide variety of life forms, including humans, to survive unaided on Mars' surface. Some ideas of possible technologies that may be able to contribute to the [[Astronomy:Terraforming of Mars|terraforming of Mars]] have been conjectured, but none would be able to bring the entire planet into the Earth-like habitat pictured in science fiction.<ref>{{cite web | url = http://www.users.globalnet.co.uk/~mfogg/zubrin.htm | title = Technological Requirements for Terraforming Mars | first1 = Robert M. | last1 = Zubrin | first2 = Christopher P. | last2 = McKay | access-date = November 1, 2006 | archive-date = February 1, 2016 | archive-url = https://web.archive.org/web/20160201124311/http://www.users.globalnet.co.uk/~mfogg/zubrin.htm | url-status = live }}</ref>

===Minimum size of a colony===

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 |page=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, 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.

As the number of individuals grows, both activities and objects can be shared between them. Growth also will offset the risks of collapse of the society, caused by sudden deaths, accidents, infertility or inbreeding. But this may not prevent mortal combat between different groups of individuals, or the loss of efficiency due to inappropriate social organization.

By mathematical modelling of the time spent by people on these issues and by keeping things simple, Salotti concludes 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 [[Astronomy:Proxima Centauri b|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>

==Transportation==

===Interplanetary spaceflight===
[[File:Mars orbit rendez vous S95 01407.jpg|thumb|Rendezvous, an interplanetary stage and lander stage come together over Mars]]
[[File:Mars Valles Marineris.jpeg|thumb|left|Mars (''[[Astronomy:Viking 1|Viking 1]]'', 1980)]]
Mars requires less energy per unit mass (delta V) to reach from Earth than any planet except [[Astronomy:Venus|Venus]]. Using a [[Astronomy:Hohmann transfer orbit|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 down 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 [[Astronomy:Delta-v|delta-v]] and an increasing amount of fuel, and is difficult with chemical rockets. It could be feasible with advanced [[Astronomy:Spacecraft propulsion|spacecraft propulsion]] technologies, some of which have already been tested to varying levels, such as [[Physics:Variable Specific Impulse Magnetoplasma Rocket|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 rockets. 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 |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 down 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 [[Physics:Radiation|radiation]], which would require a means to protect them. Cosmic radiation and [[Astronomy:Solar wind|solar wind]] cause DNA damage, which increases the risk of cancer significantly. 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===
[[File:Mars Lander by Brian McMullin, 1986.jpg|thumb|Painting of a landing on Mars (1986)]]
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 [[Engineering:Apollo Lunar Module#Operational profile|Apollo Moon landings]], yet the atmosphere is too thin for aerodynamic effects to be of much help in [[Astronomy:Aerobraking|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|GPa}} then a [[Astronomy:Space elevator|space elevator]] could be built to land people and material on Mars.<ref>{{cite web |title=The Space Elevator – Chapters 2 & 7 |archive-url= https://web.archive.org/web/20050603001216/http://www.isr.us/Downloads/niac_pdf/chapter2.html |archive-date=2005-06-03 | url-status= dead |url=http://www.isr.us/Downloads/niac_pdf/chapter2.html }}</ref> A space elevator on [[Astronomy:Phobos (moon)|Phobos]] (a Martian moon) has also been proposed.<ref name = chapter>{{cite conference |chapter-url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030065879_2003074809.pdf |chapter=Space Colonization Using Space-Elevators from Phobos |conference=Space Technology and Applications International Forum - Staif 2003 |volume=654 |pages=1227–1235 |first=Leonard M. |last=Weinstein |title=AIP Conference Proceedings |bibcode=2003AIPC..654.1227W |year=2003 |doi=10.1063/1.1541423 |hdl=2060/20030065879 |hdl-access=free |access-date=July 7, 2017 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927193413/http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030065879_2003074809.pdf |url-status=live }}</ref>

====Phobos as a space elevator for Mars====
[[File:Space elevator Phobos.jpg|thumb|300px|[[Astronomy:Space elevator|Space elevator]] Phobos]]
[[File:Earth vs Mars gravity at elevation.webp|thumb|300px|[[Physics:Gravity of Earth|Earth]] vs Mars vs Moon gravity at [[Elevation|elevation]]]]
[[Astronomy:Phobos (moon)|Phobos]] is [[Astronomy:Tidal locking|synchronously]] orbiting [[Astronomy:Mars|Mars]], where the same face stays facing the planet at ~6,028 [[Kilometre|km]] above the [[Astronomy:Martian surface|Martian surface]]. A [[Astronomy:Space elevator|space elevator]] could extend down from Phobos to Mars 6,000 km, about 28 kilometers from the surface, and just out of the [[Astronomy:Atmosphere of Mars|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 [[Astronomy:Areostationary orbit|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 [[Astronomy:Delta-v|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==
Colonization of Mars would require a wide variety of equipment—both equipment to directly provide services to humans and [[Finance: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 ([[Chemistry:Oxygen|oxygen]], [[Engineering:Electricity generation|power]], [[Social:Communications system|local communications]], waste disposal, [[Engineering:Sanitation|sanitation]] and [[Earth:Reclaimed water#Reuse in space stations|water recycling]])
*[[Astronomy:Mars habitat|Habitats]]
*Storage facilities
*Workspaces
*Airlock, for pressurization and dust management
*Resource extraction equipment—initially for [[Astronomy:Chronology of discoveries of water on Mars|water]] and oxygen, later for a wider cross section of minerals, building materials, etc.
*Equipment for energy production and [[Engineering:Energy storage|energy storage]], some [[Physics:Solar panels on spacecraft|solar]] and perhaps [[Physics:Nuclear power in space|nuclear]] as well
[[File:Mars Greenhouse.jpg|thumb|Mars greenhouses feature in many colonization designs, especially for food production and other purposes.]]
[[File:Possible_exploration_of_the_surface_of_Mars.jpg|thumb|Various technologies and devices for Mars are shown in the illustration of a Mars base.]]
*Food production spaces and equipment.<ref name="NYT-20231127">{{cite news |last=Scoles 
|first=Sarah |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  |date=27 November 2023 |work={{wipe|The New York Times}} |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 }}</ref>
*Propellant production equipment, generally thought to be hydrogen and methane through the [[Chemistry:Sabatier reaction|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 [[Physics:Liquid oxygen|oxygen]] oxidizer—for chemical rocket engines
*Fuels or other energy source for use with surface transportation. [[Chemistry:Carbon monoxide|Carbon monoxide]]/[[Chemistry:Oxygen|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 [[Chemistry:Zirconium dioxide|zirconium dioxide]] [[Chemistry:Electrolysis|electrolysis]] from the Martian atmosphere without requiring use of any of the Martian water resources to obtain hydrogen.<ref name="landis2001">{{cite journal |last=Landis |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—[[Astronomy:Mars suit|Mars suit]], [[Astronomy:Crewed Mars rover|crewed rovers]] and possibly even [[Astronomy:Mars aircraft|Mars aircraft]].

=== Basic utilities ===
In order to function at all 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 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 when Earth is above the Martian horizon. NASA and ESA included communications relay equipment in several of the Mars orbiters, so Mars already has [[Astronomy:Communications satellite|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 [[Physics:Speed of light|speed of light]] ranges from about 3 minutes at closest approach (approximated by perihelion of Mars minus aphelion of Earth) to 22&nbsp;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 [[Astronomy:Sun|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 [[Astronomy:Lagrangian point|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 [[Astronomy:STEREO|STEREO]] probes passed through the L4 and L5 regions without damage in late 2009.

Recent work by the [[Organization:University of Strathclyde|University of Strathclyde]]'s Advanced Space Concepts Laboratory, in collaboration with the [[Organization:European Space Agency|European Space Agency]], has suggested an alternative relay architecture based on highly non-[[Astronomy: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 [[Physics:Solar sail|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:Astronauts approach Viking 2.jpg|thumb|left|Astronauts approach ''[[Astronomy:Viking 2|Viking 2]]'' lander probe]]

The path to a human colony could be prepared by [[Engineering:Robotic spacecraft|robotic]] systems such as the [[Astronomy:Mars Exploration Rover|Mars Exploration Rover]]s ''Spirit'', ''Opportunity'', ''Curiosity'' and ''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.

[[Astronomy:Mars Surveyor 2001 Lander|Mars Surveyor 2001 Lander]] MIP (Mars ISPP Precursor) was to demonstrate manufacture of oxygen from the [[Astronomy:Atmosphere of Mars|atmosphere of Mars]],<ref>{{cite journal |first=D. |last=Kaplan |url=http://www.lpi.usra.edu/meetings/marsmiss99/pdf/2503.pdf |title=The Mars In-Situ-Propellant-Production Precursor (MIP) Flight Demonstration |journal=Workshop on Mars 2001: Integrated Science in Preparation for Sample Return and Human Exploration |issue=991 |pages=54 |display-authors=0 |bibcode=1999misp.conf...54K |year=1999 |access-date=August 30, 2012 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927132905/http://www.lpi.usra.edu/meetings/marsmiss99/pdf/2503.pdf |url-status=live }} Paper presented at ''Mars 2001: Integrated Science in Preparation for Sample Return and Human Exploration'', Lunar and Planetary Institute, Oct. 2–4 1999, Houston, TX.</ref> and test solar cell technologies and methods of mitigating the effect of Martian dust on the power systems.<ref>{{cite web |first1=G. A. |last1=Landis |first2=P. |last2=Jenkins |first3=D. |last3=Scheiman |first4=C. |last4=Baraona |url=http://www.lpi.usra.edu/meetings/robomars/pdf/6136.pdf |title=MATE and DART: An Instrument Package for Characterizing Solar Energy and Atmospheric Dust on Mars |access-date=August 30, 2012 |archive-date=September 27, 2013 |archive-url=https://web.archive.org/web/20130927132807/http://www.lpi.usra.edu/meetings/robomars/pdf/6136.pdf |url-status=live }} Presented at ''Concepts and Approaches for Mars Exploration'', July 18–20, 2000 Houston, Texas.</ref>{{update after|2014|4|17}}<!-- So what happened with these "plans"? How did they work out? -->

Before any people are transported to Mars on the notional 2020s [[Astronomy:SpaceX Mars transportation infrastructure|Mars transportation infrastructure]] envisioned by [[Company:SpaceX|SpaceX]], a number of robotic cargo missions would be undertaken first in order to transport the requisite equipment, [[Astronomy:Mars habitat|habitats]] and supplies.<ref name=tss20140321gs>{{cite AV media |people=Gwynne Shotwell |date=2014-03-21 |title=Broadcast 2212: Special Edition, interview with Gwynne Shotwell |medium=audio file |url=http://archived.thespaceshow.com/shows/2212-BWB-2014-03-21.mp3 |access-date=2014-03-22 |archive-url=https://web.archive.org/web/20140322013556/http://archived.thespaceshow.com/shows/2212-BWB-2014-03-21.mp3 |archive-date=2014-03-22 |format=mp3 |time=29:45–30:40 |publisher=The Space Show |id=2212 |quote=''would have to throw a bunch of stuff before you start putting people there. ... It is a transportation system between Earth and Mars.'' |url-status=dead }}</ref>
Equipment that would be necessary would include "machines to produce fertilizer, methane and oxygen from Mars' atmospheric nitrogen and carbon dioxide and the planet's subsurface water ice" as well as construction materials to build transparent domes for initial agricultural areas.<ref name=dn20121213>{{cite news |url=http://news.discovery.com/space/alien-life-exoplanets/mars-colony-spacex-121126.htm |title=Huge Mars Colony Eyed by SpaceX Founder |date=2012-12-13 |access-date=2014-03-14 |publisher=Discovery News |archive-date=November 15, 2014 |archive-url=https://web.archive.org/web/20141115083758/http://news.discovery.com/space/alien-life-exoplanets/mars-colony-spacex-121126.htm |url-status=live }}</ref>

==Economics==
[[File:PIA07269-Mars Rover Opportunity-Iron Meteorite.jpg|thumb|right|Iron–nickel meteorite found on Mars' surface ([[Astronomy:Heat Shield Rock|Heat Shield Rock]])]]
As with early colonies in the [[Earth:New World|New World]], economics would be a crucial aspect to a colony's success. The reduced [[Physics:Gravity well|gravity well]] of Mars and its position in the Solar System may facilitate Mars–Earth trade and may provide an economic rationale for continued settlement of the planet. Given its size and resources, this might eventually be a place to grow food and produce equipment to [[Astronomy:Asteroid mining|mine the asteroid belt]].

Some early Mars colonies might specialize in developing local resources for Martian consumption, such as water and/or ice. 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 [[Astronomy:Ore resources on Mars|Martian ore]] currently known to be available is metallic iron in the form of nickel–iron [[Astronomy:Meteorite|meteorite]]s. Iron in this form is more easily extracted than from the iron oxides that cover the planet.

Another main inter-Martian trade good during early colonization could be manure.<ref>Lovelock, James and Allaby, Michael, "''The Greening of Mars''" 1984</ref> Assuming that life does not exist on Mars, the [[Astronomy:Martian soil|soil]] is going to be very poor for growing plants, so [[Chemistry:Manure|manure]] and other fertilizers will be valued highly in any [[Astronomy:Martian|Martian]] civilization until the planet changes enough chemically to support growing vegetation on its own.

[[Engineering:Solar power|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]]. But the 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>

===Economic drivers===
Space colonization on Mars can roughly be said to be possible when the necessary methods of space colonization become cheap enough (such as space access by cheaper launch systems) to meet the cumulative funds that have been gathered for the purpose.

Although there are no immediate prospects for the large amounts of money required for any space colonization to be available given traditional launch costs,<ref>{{cite web |url=https://space.nss.org/settlement/nasa/Basics/wwwwh.html |title=Space Settlement Basics |first=Al |last=Globus |publisher=NASA Ames Research Center |website=nss.org |date=2 February 2012 |access-date=January 20, 2023 |archive-date=January 20, 2023 |archive-url=https://web.archive.org/web/20230120225059/https://space.nss.org/settlement/nasa/Basics/wwwwh.html |url-status=live }}</ref> there is some prospect of a radical reduction to launch costs in the 2020s, which would consequently lessen the cost of any efforts in that direction. With a published price of {{USD|62 million}} per launch of up to {{convert|22800|kg|abbr=on}} payload to [[Astronomy:Low Earth orbit|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> [[Company:SpaceX|SpaceX]] [[Engineering:Falcon 9|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 reusable plans include [[Engineering:Falcon Heavy|Falcon Heavy]] and future methane-based launch vehicles including the [[Engineering:SpaceX Starship|Starship]]. If SpaceX is successful in developing the reusable technology, it would be expected to "have a major impact on the cost of access to space", and change the increasingly [[Finance: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>

Alternative funding approaches might include the creation of 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>

====Mining the asteroid belts from Mars====
[[Image:InnerSolarSystem-en.png|300px|thumb|The asteroids of the inner Solar System and Jupiter: The belt is located between the orbits of Jupiter and Mars.
{| style="width:100%;"
|-
| valign=top|
{{legend2|#FFFF00|border=1px solid #B3B300|[[Astronomy:Sun|Sun]]}}<br />
{{legend2|#6ad768|border=1px solid #2B9929|[[Astronomy:Jupiter trojan|Jupiter trojan]]s}}<br />
{{legend-line|#007DD6 solid 2px|[[Physics:Orbit|Orbit]]s of [[Astronomy:Planet|planet]]s}}
| valign=top|
{{legend2|#e9e9e9|border=1px solid #999999|[[Astronomy:Asteroid belt|Asteroid belt]]}}<br />
{{legend2|#d39300|border=1px solid #855D00|Hilda asteroids {{small|(Hildas)}}}}<br />
{{legend2|#c90000|border=1px solid #940000|[[Astronomy:Near-Earth object|Near-Earth object]]s {{small|(selection)}}}}
|}
]]
[[File:Main Asteroid Belt Asteroids.jpg|thumb|300px|Main Asteroid Belt 42 largest asteroids
{{legend-line|#14A80F solid 3px|[[Astronomy:Amor asteroid|Amor asteroid belt]]}}
{{legend-line|#CC0000 solid 3px|[[Astronomy:Apollo asteroid|Apollo asteroid belt]]}}
{{legend-line|#F8DC2C solid 3px|[[Astronomy:Aten asteroid|Aten asteroid belt]]}}
Since [[Astronomy:Mars|Mars]] is much closer to the [[Astronomy:Asteroid belt|asteroid belt]] than [[Astronomy:Earth|Earth]] is, it would take less [[Astronomy:Delta-v|Delta-v]] to get to the Asteroid belt and return [[Earth:Mineral|minerals]] to Mars. One hypothesis is that the [[Astronomy:Moons of Mars|Moons of Mars]] ([[Astronomy:Phobos (moon)|Phobos]] and [[Astronomy:Deimos (moon)|Deimos]]) are actually [[Astronomy:Asteroid capture|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> [[Astronomy:16 Psyche|16 Psyche]] in the main belt could have over $10,000 [[Names of large numbers|Quadrillion]] {{wipe|United States dollar}} worth of minerals. On October 13, 2023, 

[[Organization:NASA|NASlaunchedAthe]]   [[Engineering:Psyche (spacecraft)|Psyche o]]<nowiki/>iter, which is set to reach the asteroid d by August 20dy.<ref>{{cite web | url=https://www.jpl.nasa.gov/news/nasa-continues-psyche-asteroid-mission | title=NASA Continues Psyche Asteroid Mission | website=[[Organization:Jet Propulsion Laboratory|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> [[Astronomy:511 Davida|511 Davida]] could have $27 quadrillion Dollars 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 [[Astronomy: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 | page=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={{wipe|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={{wipe|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={{wipe|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 locations for settlements==
[[File:Pavonis Mons lava tube skylight crop.jpg|thumb|280px|Cropped version of a HiRISE image of a lava tube skylight entrance on the Martian volcano Pavonis Mons]]

=== 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 ===
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 [[Astronomy: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 ===
Several possible [[Astronomy:Martian lava tube|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=Wynne1 |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 ===
[[Astronomy:Hellas Planitia|Hellas Planitia]] is the lowest lying plain below the Martian geodetic datum. The atmospheric pressure is relatively higher in this place when compared to the rest of Mars.

==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 [[Biology:Microorganism|microorganism]]s of thousands of species of the [[Biology:Human microbiome|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, but with no final guidelines for a way forward yet.<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>

== Ethical, political and legal challenges ==
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. In the 1967 United Nations [[Engineering:Outer Space Treaty|Outer Space Treaty]], it was determined that no country may take claim to space or its inhabitants. 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 very 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> NASA had to deal with several cuts in funding. During the presidency of [[Biography:Barack Obama|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 [[Astronomy:Space Launch System|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 |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>

===Colonialism===
Space colonization in general has been discussed as continuation of [[Social:Imperialism|imperialism]] and [[Social:Colonialism|colonialism]],<ref>{{cite news|title=How imperialism shaped the race to the moon|url=https://www.washingtonpost.com/outlook/2019/07/22/how-imperialism-shaped-race-moon/|newspaper={{wipe|The Washington Post}}|access-date=19 September 2019|date=22 July 2019|author=Gabrielle Cornish|language=en|archive-date=July 23, 2019|archive-url=https://web.archive.org/web/20190723032005/https://www.washingtonpost.com/outlook/2019/07/22/how-imperialism-shaped-race-moon/|url-status=live}}</ref> especially regarding Mars colonial decision making and reasons for colonial labor<ref>{{cite web|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/|website=Salon.com|access-date=20 September 2019|date=8 October 2017|author=Keith A. Spencer|language=en|archive-date=September 19, 2019|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/|url-status=live}}</ref> and land exploitation have been questioned with [[Philosophy:Postcolonialism|postcolonial]] critique. Seeing the need for inclusive<ref>{{cite web|title=Rethinking the Narrative of Mars Colonisation|url=https://othersociologist.com/2015/03/26/rethinking-the-narrative-of-mars-colonisation/|website=Other Sociologist|access-date=20 September 2019|date=26 March 2015|author=Zuleyka Zevallos|language=en|archive-date=December 11, 2019|archive-url=https://web.archive.org/web/20191211122431/https://othersociologist.com/2015/03/26/rethinking-the-narrative-of-mars-colonisation/|url-status=live}}</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|title=Keep the Red Planet Red|url=https://www.jacobinmag.com/2017/02/mars-elon-musk-space-exploration-nasa-colonization|website=Jacobin|access-date=20 September 2019|date=2 May 2017|author=Keith A. Spencer|language=en|archive-date=November 3, 2019|archive-url=https://web.archive.org/web/20191103165331/https://jacobinmag.com/2017/02/mars-elon-musk-space-exploration-nasa-colonization|url-status=live}}</ref>

The narrative of space exploration as a "New Frontier" has been criticized as unreflected continuation of [[Social:Settler colonialism|settler colonialism]] and manifest destiny, continuing the narrative of colonial exploration as fundamental to the assumed [[Philosophy:Human nature|human nature]].<ref>{{cite web|title=The racist language of space exploration|url=https://theoutline.com/post/5809/the-racist-language-of-space-exploration|website=The Outline|access-date=20 September 2019|date=14 August 2018|author=Caroline Haskins|language=en|archive-date=October 16, 2019|archive-url=https://web.archive.org/web/20191016235916/https://theoutline.com/post/5809/the-racist-language-of-space-exploration|url-status=live}}</ref><ref>{{cite web|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/|website=Scientific American|access-date=20 September 2019|date=26 March 2015|author=DNLee|language=en|archive-date=September 14, 2019|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/|url-status=live}}</ref><ref>{{cite web|date=2018-11-09|title=We need to change the way we talk about space exploration|first=Nadia|last=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 opposed to 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|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/|newspaper=Visionlearning Blog|access-date=20 September 2019|date=14 March 2017|author=David Warmflash|language=en|archive-date=December 11, 2019|archive-url=https://web.archive.org/web/20191211122431/https://www.visionlearning.com/blog/2017/03/14/colonization-venusian-clouds-surfacism-clouding-judgement/|url-status=live}}</ref>

[[Image:NASA Artemis Gateway logo.png|The logo and name of the [[Astronomy:Lunar Gateway|Lunar Gateway]] references the St. Louis Gateway Arch, associating Mars with the American frontier.<ref>{{cite web|url=https://www.space.com/nasa-lunar-gateway-moon-station-logo.html|title=NASA Reveals New Gateway Logo for Artemis Lunar Orbit Way Station|website=Space.com|date=September 18, 2019|access-date=2020-06-28|author=Robert Z. Pearlman|archive-date=June 28, 2020|archive-url=https://web.archive.org/web/20200628112732/https://www.space.com/nasa-lunar-gateway-moon-station-logo.html|url-status=live}}</ref>|thumb|left]]

===Dangers to pregnancy===
One possible ethical challenge that space travelers might face is that of [[Medicine:Pregnancy|pregnancy]] during the trip. According to NASA's policies, it is forbidden for members of the crew to engage in [[Astronomy:Sex in space|sex in space]]. NASA wants its crew members to treat each other like coworkers would in a professional environment. A pregnant member on a spacecraft is dangerous to all those 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 Feb. 2011. Web. 09 Dec. 2016.</ref> During a long trip to Mars, it is likely that members of 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:Buzz Aldrin.jpg|thumb|Buzz Aldrin, the Apollo 11 astronaut and second person to set foot on the Moon, has recommended human Mars missions.]]
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 [[Organization:Mars Society|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. [[Astronomy:Mars to Stay|Mars to Stay]] advocates recycling emergency return vehicles into permanent settlements as soon as initial explorers determine permanent habitation is possible.

[[Biography:Elon Musk|Elon Musk]] founded [[Company:SpaceX|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|url=https://www.forbes.com/sites/alexknapp/2012/11/27/spacex-billionaire-elon-musk-wants-a-martian-colony-of-80000-people/|title=SpaceX Billionaire Elon Musk Wants A Martian Colony Of 80,000 People|author=Alex Knapp|date=27 November 2012|work=Forbes|access-date=12 June 2015|archive-date=August 15, 2017|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/|url-status=live}}</ref> [[Biography:Richard Branson|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 ''[[Astronomy: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, [[Biography:Buzz Aldrin|Buzz Aldrin]], {{wipe|United States}} [[Engineering:Engineer|engineer]] and former [[Astronaut|astronaut]], and the [[Engineering:Apollo 11#Lunar surface operations|second person to walk on the Moon]], wrote an opinion, published in ''{{wipe|The New York Times}}'', supporting a [[Astronomy:Human mission to Mars|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 [[Organization:Florida Institute of Technology|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 still 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 completely new kind of civilization with distinct goals, values, fears and desires.

==In fiction==

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'' (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
-->
* ''Away'' (2020), published by [[Company:Netflix|Netflix]]
* ''Climbing Olympus'' (1994), by Kevin J. Anderson
* ''Colony One Mars: A SciFi Thriller'' (2016), by Gerald Kilby 
* ''First Landing'' (2002), by [[Biography:Robert Zubrin|Robert Zubrin]]
* ''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 ''The Martians'' (1999), by [[Biography:Kim Stanley Robinson|Kim Stanley Robinson]]
* ''John Carter'' (2012), by Mark Andrews
* ''Man Plus'' (1976), by Frederik Pohl
* ''The Martian'' (1992) and ''Return to Mars'' (1999), by [[Biography:Ben Bova|Ben Bova]]
* ''Mars'' (2016) by National Geographic
* ''Mars Diaries'' (2000), by Sigmund Brouwer
* ''Mars Underground'' (1997), by William K. Hartmann
* ''[[Software:Martian Gothic: Unification|Martian Gothic]]'' (2000), developed by Creative Reality for [[Software:Microsoft Windows|Microsoft Windows]] and Coyote Developments for [[Engineering:PlayStation (console)|PlayStation]], published by [[Company:TalonSoft|TalonSoft]] for Microsoft Windows and [[Company:Take-Two Interactive|Take-Two Interactive]] for PlayStation
<!-- For possible inclusion – can anyone verify?
* ''Moving Mars'' (1993), by [[Biography:Greg Bear|Greg Bear]]
-->
* ''Mr. Nobody'' (2009), by Jaco Van Dormael
* ''[[Software:Red Faction|Red Faction]]'' (2001), developed by [[Company:Volition|Volition]], published by [[Company:THQ|THQ]]
* ''Red Planet'' (1949), by [[Biography:Robert A. Heinlein|Robert A. Heinlein]]
* ''[[Software:Surviving Mars|Surviving Mars]]'' (2018), developed by [[Company:Haemimont Games|Haemimont Games]], published by [[Company:Paradox Interactive|Paradox Interactive]]
* ''Terra Formars'' (2011)
* ''TerraGenesis'' (2016) developed by Edgeworks Entertainment, published by [[Company:Tilting Point|Tilting Point]]
* ''The Destruction of Faena'' (1974), by [[Biography:Alexander Kazantsev|Alexander Kazantsev]]
* ''The Expanse'' (2016-2021) airing originally on Syfy, then Amazon Prime
* ''The Martian'' (2011), by Andy Weir (and the 2015 film, directed by Ridley Scott)
* ''The Martian Chronicles'' (1950), by [[Biography:Ray Bradbury|Ray Bradbury]]
* ''The Sands of Mars'' (1951), by [[Biography:Arthur C. Clarke|Arthur C. Clarke]]
* ''The Space Between Us'' (2016 film), by Peter Chelsom
* ''Tom and Jerry: Blast Off to Mars'' (2005) animated science fiction comedy film by Warner Bros. Animation and Turner Entertainment
* ''Total Recall'' (1990), by [[Biography:Paul Verhoeven|Paul Verhoeven]]
* ''We Can Remember It for You Wholesale'' (1966), by [[Biography:Philip K. Dick|Philip K. Dick]]

==Interactive Mars map==
{{Mars map}}

==See also==
{{Div col|colwidth=30em}}
* {{annotated link|Biology:Astrobotany}}
* {{annotated link|Astronomy:Climate of Mars}}
* {{annotated link|Astronomy:Colonization of the asteroid belt}}
* {{annotated link|Astronomy:Colonization of the Moon}}
* {{annotated link|Astronomy:Colonization of Venus}}
* {{annotated link|Astronomy:Effect of spaceflight on the human body}}
* {{annotated link|Astronomy:Exploration of Mars}}
* {{annotated link|Astronomy:Health threat from cosmic rays}}
* {{annotated link|Astronomy:Human mission to Mars}}
* {{annotated link|Astronomy:In situ resource utilization}}
* {{annotated link|Engineering:Space architecture}}
* {{annotated link|Astronomy:SpaceX Mars transportation infrastructure}}
* {{annotated link|Astronomy:Life on Mars}}
* [[Astronomy:List of crewed Mars mission plans|List of crewed Mars mission plans]]
* {{annotated link|Astronomy:Mars analog habitat}}
* {{annotated link|Astronomy:Mars habitat}}
* [[Astronomy:Mars Outpost|Mars Outpost]]
* {{annotated link|Astronomy:Mars race}}
* {{annotated link|Astronomy:Martian}}
* {{annotated link|Astronomy:Martian soil}}
* {{annotated link|Astronomy:Vision for Space Exploration}}
* {{annotated link|Company:NewSpace}}
* {{annotated link|Astronomy:Terraforming of Mars}}
* {{annotated link|Astronomy:The Case for Mars|''The Case for Mars''}}
* {{annotated link|Astronomy:Water on Mars}}
{{div col end}}

==References==
{{Reflist|30em}}

==Further reading==
* {{cite book | title=Mission to Mars: My Vision for Space Exploration | publisher=National Geographic Books | author=[[Biography:Buzz Aldrin|Buzz Aldrin]] and Leonard David | year=2013 | isbn=978-1-4262-1017-4| title-link=Mission to Mars: My Vision for Space Exploration }} ([https://buzzaldrin.com/mission-to-mars-my-vision-for-space-exploration/ at BuzzAldrin.com])
* [[Biography:Robert Zubrin|Robert Zubrin]], ''[[Astronomy:The Case for Mars|The Case for Mars: The Plan to Settle the Red Planet and Why We Must]]'', Simon & Schuster/Touchstone, 1996, {{ISBN|0-684-83550-9}}
* [[Biography:Frank Crossman|Frank Crossman]] and Robert Zubrin, editors, ''On to Mars: Colonizing a New World''. Apogee Books Space Series, 2002, {{ISBN|1-896522-90-4}}.
* 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 Sept 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

==External links==
* [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.4frontierscorp.com/ 4Frontiers Corporation]
* [http://www.marshome.org/ The Mars Foundation]
* [https://web.archive.org/web/20100125210332/http://ngm.nationalgeographic.com/big-idea/07/mars Making Mars the New Earth – National Geographic]
* Should we colonize Mars? – Wikidebate in Wikiversity

{{Human missions to Mars}}
{{Mars}}


{{DEFAULTSORT:Colonization Of Mars}}
[[Category:Colonization of Mars| ]]
[[Category:Exploration of Mars]]
[[Category:Human missions to Mars]]

{{Sourceattribution|Colonization of Mars}}