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{{Life in the Universe}}
 
The possibility of '''life on [[Mars]]''' is a subject of significant interest to [[astrobiology]] due to the planet's proximity and similarities to [[Earth]]. To date no proof has been found of past or present life on Mars. However, cumulative evidencethere is nowstrong buildingevidence that the ancient surface environment of Mars had seas in the northern hemmisphere, and abundant liquid water and may have been [[Planetary habitability|habitable]] for microorganisms. Since 2008 then evidence has also been building for the presence of traces of thin filims of liquid water in near surface layers/ Most of it is expected to be very salty, and including more reactive cholorates, perchlorates and sulfates instead of the chlorides and sulfides of Earth, but some of it may possibly be habiable for microbes and lichens in microhabitats. The atmosphere also may have enough humidity at times for lichens to survive in semi-shade on the surface according to some experiments at DLR. The existence of habitable conditions does not necessarily indicate the presence of life.
 
Scientific searches for evidence of life began in the 19th century, and they continue today via telescopic investigations and landed missions. While early work focused on phenomenology and bordered on fantasy, modern [[Models of scientific inquiry|scientific inquiry]] has emphasized the search for [[Water on Mars|water]], chemical [[biosignature]]s in the soil and rocks at the planet's surface, and [[biomarker]] gases in the atmosphere.<ref>{{cite conference|url=https://ntrs.nasa.gov/search.jsp?R=20120003707 |title=The Search for Life on Mars |last=Mumma |first=Michael J. |date=January 8, 2012 |conference=Origin of Life Gordon Research Conference |location=Galveston, TX |deadurl=no |archiveurl=https://web.archive.org/web/20160604111239/https://ntrs.nasa.gov/search.jsp?R=20120003707 |archivedate=June 4, 2016 }}</ref><ref name="NYT-20160912">{{cite news|last=Chang |first=Kenneth |title=Visions of Life on Mars in Earth’s Depths |url=https://www.nytimes.com/2016/09/13/science/south-african-mine-life-on-mars.html |date=September 12, 2016 |work=[[New York Times]] |accessdate=September 12, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20160912225220/http://www.nytimes.com/2016/09/13/science/south-african-mine-life-on-mars.html |archivedate=September 12, 2016 }}</ref> On November 22, 2016, NASA reported finding a large amount of [[Water on Mars|underground ice]] in the [[Utopia Planitia]] region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in [[Lake Superior]].<ref name="NASA-20161122">{{cite web|author=Staff |title=Scalloped Terrain Led to Finding of Buried Ice on Mars |url=http://photojournal.jpl.nasa.gov/catalog/PIA21136 |date=November 22, 2016 |work=[[NASA]] |accessdate=November 23, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20161124094205/http://photojournal.jpl.nasa.gov/catalog/PIA21136 |archivedate=November 24, 2016 }}</ref><ref name="Register-2016">{{cite web|url=https://www.theregister.co.uk/2016/11/22/nasa_finds_ice_under_martian_surface/ |title=Lake of frozen water the size of New Mexico found on Mars – NASA |publisher=The Register |date=November 22, 2016 |accessdate=November 23, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20161123120850/http://www.theregister.co.uk/2016/11/22/nasa_finds_ice_under_martian_surface/ |archivedate=November 23, 2016 }}</ref><ref name="NASA-20161122jpl">{{cite web|url=http://www.jpl.nasa.gov/news/news.php?release=2016-299 |title=Mars Ice Deposit Holds as Much Water as Lake Superior |publisher=NASA |date=November 22, 2016 |accessdate=November 23, 2016 |deadurl=no |archiveurl=https://web.archive.org/web/20161123145052/http://www.jpl.nasa.gov/news/news.php?release=2016-299 |archivedate=November 23, 2016 }}</ref>
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This includes the search for evidence of [[Planetary habitability|habitability]], [[taphonomy]] (related to [[fossils]]), and [[organic carbon]] on the planet [[Mars]].<ref name="SCI-20140124a" />
 
In July 2017, researchers reported that the surface on the planet Mars may be more toxic to [[microorganism]]s, especially a common terrestrial type, ''[[Bacillus subtilis]]'', than thought earlier. This is based on studies with [[perchlorates]], common on Mars, in a simulated Martian [[ultraviolet]] atmosphere.<ref name="SM-20170706">{{cite news |last=Daley |first=Jason |title=Mars Surface May Be Too Toxic for Microbial Life - The combination of UV radiation and perchlorates common on Mars could be deadly for bacteria |url=http://www.smithsonianmag.com/smart-news/mars-surface-may-be-toxic-bacteria-180963966/ |date=6 July 2017 |work=[[Smithsonian (magazine)|Smithsonian]] |accessdate=8 July 2017 }}</ref><ref name="NAT-20170706">{{cite journal|last1=Wadsworth |first1=Jennifer |last2=Cockell |first2=Charles S. |title=Perchlorates on Mars enhance the bacteriocidal effects of UV light |url=https://www.nature.com/articles/s41598-017-04910-3 |date=6 July 2017 |work=[[Scientific Reports]] |volume=7 |number=4662 |doi=10.1038/s41598-017-04910-3 |accessdate=8 July 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20170706185518/http://www.nature.com/articles/s41598-017-04910-3 |archivedate=July 6, 2017 |bibcode = 2017NatSR...7.4662W }}</ref>
 
On September 5, 2017, scientists reported that the [[Curiosity (rover)|''Curiosity'' rover]] detected [[boron]], an essential ingredient for [[life]] on [[Earth]], on Mars. Such a finding, along with previous discoveries that water may have been present on ancient Mars, further supports the possible early habitability of [[Gale (crater)|Gale Crater]] on Mars.<ref name="GPL-20170905">{{cite journal |author=Gasda, Patrick J. et al. |title=In situ detection of boron by ChemCam on Mars |url=http://onlinelibrary.wiley.com/doi/10.1002/2017GL074480/full |date=September 5, 2017 |journal=[[Geophysical Research Letters]] |doi=10.1002/2017GL074480 |accessdate=September 6, 2017 }}</ref><ref name="GZ-20170906">{{cite news |last=Paoletta |first=Rae |title=Curiosity Has Discovered Something That Raises More Questions About Life on Mars |url=https://gizmodo.com/curiosity-has-discovered-something-that-raises-more-que-1800879035 |date=September 6, 2017 |work=[[Gizmodo]] |accessdate=September 6, 2017 }}</ref>
 
== Early speculation ==
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