Difference between revisions 796703208 and 798705639 on enwiki

[[File:Phoenix landing2.jpg|thumb|300 px|Artist's impression  of the Phoenix Lander landing on Mars.<br><br>Phoenix's atmospheric measurements of isotope ratios of carbon and oxygen gave evidence for liquid water on the surface now or in the recent geological past.<ref name=phoenixisotope/> Also its 2008 observations of possible droplets on its legs suggested new ways that water could be stable temporarily on Mars.<ref name=phoenix_droplets_2009/> These observations lead ma(contracted; show full) colour graphics])</ref><ref>[https://scholar.google.com/scholar_url?url=http://online.liebertpub.com/doi/abs/10.1089/153110701750137459&hl=en&sa=T&oi=gsb&ct=res&cd=0&ei=sjMsVaPNFMHG0gGDkIBI&scisig=AAGBfm3UJr_PERdljYeIO3Ri9uWItz6ZgQ Location and Sampling of Aqueous and Hydrothermal Deposits in Martian Impact Craters] Horton E. Newsom, Justin J. Hagerty, and Ivan E. Thorsos. Astrobiology. March 2001, 1(1): 71-88. doi:10.1089/153110701750137459.]</ref><ref>
[http://onlinelibrary.wiley.com/{{cite journal|doi/=10.1029/96JE01139/abstract Impact crater lakes on Mars], Horton E. Newsom, Gregory E. Brittelle, Charles A. Hibbitts, Laura J. Crossey, Albert M. Kudo,  | bibcode=1996JGR...10114951N | volume=101 | title=Impact crater lakes on Mars | year=1996 | journal=Journal of Geophysical Research: Planets (1991–2012) Volume 101, Issue E6,| pages  =14951–14955, 25 June 1996 DOI: 10.1029/96JE01139 | last1 = Newsom | first1 = Horton E.}}</ref><ref>[http://books.google.co.uk/books/about/Lakes_on_Mars.html?id=2hNsJTfUsmMC Lakes on Mars (Google eBook)],  Nathalie A. Cabrol, Edmond A. Grin, Elsevier, 15 Sep 2010</ref>

==Temporary lakes resulting from volcanic activity==

(contracted; show full);/ref><ref>Michael T. Mellon  [https://science.nasa.gov/media/medialibrary/2011/06/29/Mellon_Water_PPS_May2011_-_TAGGED.pdf Subsurface Ice at Mars: A review of ice and water in the equatorial regions] University of Colorado 10 May 2011 Planetary Protection Subcommittee Meeting</ref><ref>Robert Roy Britt [http://www.space.com/812-ice-packs-methane-mars-suggest-present-life.html Ice Packs and Methane on Mars Suggest Present Life Possible] space.com 22 February 2005</ref><ref>
Mellon, M. T., B. M. Jakosky, and S{{cite journal | last1 = Mellon | first1 = M. T. | last2 = Jakosky | first2 = B. EM. Postawko (1997)[http://onlinelibrary.wiley.com/doi/10.1029/97JE01346/ The persistence of equatorial ground ice on Mars], J. Geophys. Res., 102(E8),| last3 = Postawko | first3 = S. E. | year = 1997 | title = The persistence of equatorial ground ice on Mars | url = http://onlinelibrary.wiley.com/doi/10.1029/97JE01346/ | journal = J. Geophys. Res. | volume = 102 | issue = E8| pages = 19357–19369, | doi: = 10.1029/97JE01346. }}</ref>

==Hydrosphere - possible layer of liquid water several kilometers below the surface==

Deep rock habitats on Earth are inhabited by life so may also be on Mars. However they need liquid water to survive, which may possibly exist below the cyrosphere.

(contracted; show full)UV-B or a blue-light screening pigment in the lichen Xanthoria parietina?]Yngvar Gauslaa and Elin Margrete Ustvedt, Photochem. Photobiol. Sci., 2003, 2, 424–432</ref><ref>[http://link.springer.com/article/10.1007/s00442-004-1583-6 The lichens Xanthoria elegans and Cetraria islandica maintain a high protection against UV-B radiation in Arctic habitats] Line Nybakken, Knut Asbjørn Solhaug, Wolfgang Bilger, Yngvar Gauslaa, Oecologia July 2004, Volume 140, Issue 2, pp 211-216</ref><ref>
[http://onlinelibrary.wiley.com/{{cite journal|doi/=10.1046/j.1469-8137.2003.00708.x/full  | volume=158 | title=UV-induction of sun-screening pigments in lichens] Knut Asbjørn Solhaug, Yngvar Gauslaa, Line Nybakken and Wolfgang Bilger, New Phytologist
Volume 158, Issue 1, | year=2003 | journal=New Phytologist | pages  =91–100, April 2003 DOI: 10.1046/j.1469-8137.2003.00708.x | last1 = Asbjorn Solhaug | first1 = Knut}}</ref>
* '''''Low pressures (hypobaria)''''' at 1–14 mbar
* '''''Anoxic CO<sub>2</sub>-enriched atmosphere'''''. All the habitats suggested so far require [[anaerobes]] - lifeforms that don't require oxygen.
(contracted; show full)n it first formed in the early solar system, it was too hot for life, and so was uninhabitable. Then there are various trajectories it could follow after that, starting from the early Mars. In his paper "Trajectories of Martian Habitability" he identifies six main possible trajectories. T<ref>{{cite journal | pmc= 3929387 | pmid=24506485 | doi=10.1089/ast.2013.1106 | volume=14 | title=Trajectories of martian habitability | journal=Astrobiology | pages=182–203 | last1 = Cockell | first1 = CS
 | year=2014}}</ref>

* "Trajectory 1. Mars is and was always uninhabitable."
* "Trajectory 2. Uninhabited Mars has hosted uninhabited habitats transiently or continuously during its history."
* "Trajectory 3. Uninhabited Mars was habitable and possessed uninhabited habitats but is now uninhabitable."
* "Trajectory 4. Mars is and was inhabited."
* "Trajectory 5. Mars was inhabited, life became extinct, but uninhabited habitats remain on Mars."
(contracted; show full)
==External links==
* Three days long conference on the subject in 2013 [http://planets.ucla.edu/meetings/past-meetings/mars-habitability-2013/program/ The Present-Day Habitability of Mars 2013] under the auspices of the UCLA Institute for Planets and Exoplanets - with video archived for all the talks.

==References==
{{reflist|30em}}

[[Category:Mars]]