Editing Space colonization (section)

====Planetary protection and risk of contamination====

{{see also|Planetary protection}}
Agencies conducting interplanetary missions are guided by [[Committee on Space Research|COSPAR]]'s planetary protection policies, to have at most 300,000 spores on the exterior of the craft—and more thoroughly sterilized if they contact "special regions" containing water, or it could contaminate life-detection experiments or the planet itself.<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/20181119091228/https://www.bbc.co.uk/news/uk-northern-ireland-27526981 |date=19 November 2018}} "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>[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=6 March 2013}} (20 October 2002; As Amended to 24 March 2011).</ref>

It is impossible to sterilize human missions to this level, as humans are host to typically a hundred trillion [[microorganism]]s of thousands of species of the [[human microbiome]], and these cannot be removed while preserving the life of the human. Containment seems the only option, but it is a major challenge in the event of a hard landing (i.e. crash).<ref name=biospherescollide>{{cite web|url=https://www.nasa.gov/history/history-publications-and-resources/nasa-history-series/when-biospheres-collide/#.U_uVh_mwJcQ |title=When Biospheres Collide – a History of NASA's Planetary Protection Programs |archive-url=https://web.archive.org/web/20190714112103/https://www.nasa.gov/connect/ebooks/when_biospheres_collide_detail.html#.U_uVh_mwJcQ |archive-date=14 July 2019 |first=Michael |last=Meltzer |date=31 May 2012 |quote=see Chapter 7, Return to Mars – final section: Should we do away with human missions to sensitive targets|access-date=18 April 2025}}</ref> There have been several planetary workshops on this issue, but with no final guidelines yet for a way forward.<ref>Johnson, James E. [http://www.hou.usra.edu/meetings/ppw2015/pdf/1010.pdf "Planetary Protection Knowledge Gaps for Human Extraterrestrial Missions: Goals and Scope." (2015)] {{Webarchive|url=https://web.archive.org/web/20191026125720/https://www.hou.usra.edu/meetings/ppw2015/pdf/1010.pdf |date=26 October 2019 }}</ref> Human explorers could also inadvertently contaminate Earth if they return to the planet while carrying extraterrestrial microorganisms.<ref>{{cite book |title=Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface |date=2002 |url=https://nap.nationalacademies.org/catalog/10360/safe-on-mars-precursor-measurements-necessary-to-support-human-operations |chapter=Potential Hazards of the Biological Environment (Chapter 5) |publisher=National Academies Press |location=Washington, DC |access-date=19 April 2025 |quote=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>