Difference between revisions 799453806 and 813268024 on enwiki

{{AFC submission|d|essay|u=Robertinventor|ns=118|decliner=Tokyogirl79|declinets=20150702083850|ts=20150609204825}} <!-- Do not remove this line! -->

{{AFC comment|1=Fix reference errors. [[User:Robert McClenon|Robert McClenon]] ([[User talk:Robert McClenon|talk]]) 02:52, 21 April 2016 (UTC)}}

{{AFC comment|1=This is well written as a journal article or essay, but it's not really a Wikipedia article. There's too much OR in this article to make it a good fit for Wikipedia. It also doesn't help that there's already a section on this very topic at [[Life_on_Mars#Habitability]] that already gives a pretty good overview. There's also an issue of timeliness, since this is the type of thing that could be forever changing. 

In any case, I think that this goes into far more detail than is really appropriate for Wikipedia, where we're basically only supposed to go into a more general overview of the subject. I'd recommend that you look to see if any of this can be merged into the pre-existing section on this topic. [[User:Tokyogirl79|Tokyogirl79]][[User talk:Tokyogirl79|'''<span style="color:#19197; background:#fff;"> (｡◕‿◕｡)</span>''']] 08:38, 2 July 2015 (UTC)}}

{{AFC comment|1=And just as I thought, it paraphrases https://link.springer.com/article/10.1007%2Fs11214-012-9956-3/fulltext.html [[User:FoCuSandLeArN|FoCuSandLeArN]] ([[User talk:FoCuSandLeArN|talk]]) 15:59, 30 June 2015 (UTC)}}

{{AFC comment|1=This seems like [[WP:OR|OR]]. [[User:FoCuSandLeArN|FoCuSandLeArN]] ([[User talk:FoCuSandLeArN|talk]]) 15:57, 30 June 2015 (UTC)}}

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: I've replied to these comments [[Draft_talk:Present_day_habitability_of_Mars#Reply_to_comments | Reply to comments]] on the talk page.

(contracted; show full)t;/ref><ref>[http://www.pnas.org/content/103/44/16089.full The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results] vol. 103 no. 44 > Rafael Navarro-González, Proceedings of the National Academy of Sciences of the United States of America 16089–16094, doi: 10.1073/pnas.0604210103</ref>. Though other scientists have suggested that they could have detected low levels of organics....<ref>[http
s://www.ncbi.nlm.nih.gov/pmc/articles/PMC1965509/ The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results] Rafael Navarro-González, Karina F. Navarro, José de la Rosa, Enrique Iñiguez, Paola Molina, Luis D. Miranda, Pedro Morales, Edith Cienfuegos, Patrice Coll, François Raulin, Ricardo Amils, and Christopher P. McKay, Proc Natl Acad Sci U S A. 2007 Jun 19; 104(25): 10310–10313.
(contracted; show full)

===Droplets on the Phoenix legs===

Until 2008, most scientists thought that there was no possibility of liquid water on Mars for any length of time in the current conditions there. However, in 2008 through to 2009, droplets were observed on the landing legs of Phoenix. 

[[File:Mars-water-droplets-phoenix-2008-bg.gif|Mars-water-droplets-phoenix-2008-bg]]

Unfortunately, it wasn't equipped to analyse them but the leading theory is that these were droplets of salty water. <ref>[http
s://www.newscientist.com/article/dn16620-first-liquid-water-may-have-been-spotted-on-mars.html?full=true#.VRReJ_msV8E First liquid water may have been spotted on Mars], New Scientist, February 2009 by David Shiga</ref> They were observed to grow, merge, and then disappear, presumably as a result of falling off the legs.

(contracted; show full)
Methane was detected in the Mars atmosphere for the first time in 2004. This stimulated follow up measurements, and research into possible biological or geological origins for methane on Mars. <ref>[http
s://www.newscientist.com/article/dn4827-methane-on-mars-could-signal-life.html#.VRci_fmsV8E Methane on Mars could signal life], Anil Ananthaswamy, New Scientist, March 2004</ref>.<ref>{{cite web|url=http://dsc.discovery.com/news/2009/08/12/mars-life.html |title=Martian Life Appears Less Likely : Discovery News |publisher=Dsc.discovery.com |date=August 12, 2009 |accessdate=December 19, 2010}}</ref>. 

(contracted; show full)methanogens (methane producing bacteria).''''' These are [[Autotroph|autotrophs]] which require little more than hydrogen and carbon dioxide to metabolize. For the hydrogen source they could use a geothermal source of hydrogen, possibly due to volcanic or hydrothermal activity, or they could use the reaction of basalt and water. Methanogens have been found to be able to grow in Mars soil simulant in these conditions of water, CO<sub>2</sub> and hydrogen.<ref>[http
s://www.ncbi.nlm.nih.gov/pubmed/15570711 Growth of methanogens on a Mars soil simulant] Orig Life Evol Biosph. 2004 Dec;34(6):615-26.</ref>, and to be able to withstand the Martian freeze / thaw cycles.<ref>[http://www.sciencedaily.com/releases/2014/05/140519114248.htm Earth organisms survive under Martian conditions: Methanogens stay alive in extreme heat and cold] Science Daily, May 19, 2014,  University of Arkansas, Fayetteville</ref>
(contracted; show full)

This process has been been observed in Antarctica. On Mars, there could be enough water to create conditions for physical, chemical, and biological processes.<ref>[http
s://www.newscientist.com/article/mg20427373.700 Watery niche may foster life on Mars] "According to Möhlmann, the heat from sunlight penetrating into ice or snow should get absorbed by any embedded dust grains, warming the dust and the surrounding ice. This heat mostly gets trapped because ice absorbs infrared radiation." {{Subscription required|date=August 2011}}</ref><ref>{{cite web|author=Tudor Vieru |url=http://news.softpedia.com/news/Greenhouse-Effect-on-Mars-May-Be-Allowing-for-Li(contracted; show full)

Then, as local summer approaches, the flow like features start to extend down the slope. These are small features only a few tens of meters in scale, and grow at a rate of a meter or a few meters per Martian sol through the late Martian spring and summer. This is the part of the process that is thought to be due to liquid water, in nearly all the models proposed for them so far.<ref name=Kereszturi2008/><ref name="MartínezRenno2013">{{cite journal|url=http
s://link.springer.com/article/10.1007%2Fs11214-012-9956-3/fulltext.html|last1=Martínez|first1=G. M.|last2=Renno|first2=N. O.|title=Water and Brines on Mars: Current Evidence and Implications for MSL|journal=Space Science Reviews|volume=175|issue=1-4|year=2013|pages=29–51|issn=0038-6308|doi=10.1007/s11214-012-9956-3|bibcode = 2013SSRv..175...29M }}</ref>

A different mechanism is proposed for them in the Northern and in the Southern hemispheres.

===Southern hemisphere flow like features===

(contracted; show full)

The flow like features in the northern hemisphere polar ice cap form at average surface temperatures of around 150°K - 180°K, i.e. up to -90°C approximately. 

The flows start as wind-blown features but then are followed by seepage features which increase at between 0.3 meters and 7 meters a day.<ref name="MartínezRenno2013"/><ref name=Kereszturi>Kereszturi, A., et al. [http
s://www.researchgate.net/profile/Szaniszlo_Berczi/publication/222062822_Indications_of_brine_related_local_seepage_phenomena_on_the_northern_hemisphere_of_Mars/links/0fcfd509b9bbd37ff0000000.pdf  "Indications of brine related local seepage phenomena on the northern hemisphere of Mars."] Icarus 207.1 (2010): 149-164.</ref>

(contracted; show full)

Then, as with the model for the Martian geysers, shortwave radiation can penetrate translucent CO<sub>2</sub> ice layer, and heat the subsurface through the solid state greenhouse effect. 

The models suggest that subsurface melt water layers, and interfacial water could form with surface temperatures as low as 180°K (-90°C). Salts in contact with them could then form liquid brines.<ref name=Kereszturi/><ref name="MartínezRenno2013b">{{cite journal|url=http
s://link.springer.com/article/10.1007%2Fs11214-012-9956-3/fulltext.html|last1=Martínez|first1=G. M.|last2=Renno|first2=N. O.|title=Water and Brines on Mars: Current Evidence and Implications for MSL|journal=Space Science Reviews|volume=175|issue=1-4|year=2013|pages=29–51|issn=0038-6308|doi=10.1007/s11214-012-9956-3|quote='''"Martinez et al. (2012) show that the formation of brines is consistent with the low temperatures measured by TES and THEMIS when they form (≤180 K), if the spatial re(contracted; show full)

An alternative mechanism for the Northern hemisphere involves dry ice and sand cascading down the slope but most of the models involve liquid brines for the seepage stages of the features. .<ref name="MartínezRenno2013"/>

For details see the Dark Dune Spots section of Nilton Renno's paper [http
s://link.springer.com/article/10.1007%2Fs11214-012-9956-3/fulltext.html Water and Brines on Mars: Current Evidence and Implications for MSL] which also has images of the two types of feature as they progress through the season.

==Life able to take up water from the 100% night time humidity of the Mars atmosphere==

(contracted; show full)gives them enough protection to tolerate the light levels in conditions of partial shade in the simulation chambers and make use of the light to photosynthesize. Indeed UV protection pigments have been suggested as potential biomarkers to search for on Mars.<ref>"Solar radiation is the primary energy source for surface planetary life, so that pigments are fundamental components of any surface-dwelling organism. They may therefore have evolved in some form on Mars as they did on Earth."[http
s://www.researchgate.net/publication/231828252_Pigmentation_as_a_survival_strategy_for_ancient_and_modern_photosynthetic_microbes_under_high_ultraviolet_stress_on_planetary_surfaces Pigmentation as a survival strategy for ancient and modern photosynthetic microbes under high ultraviolet stress on planetary surfaces] D.D. Wynn-Williams, H.G.M. Edwards, E.M. Newton and J.M. Holder, International Journal of Astrobiology 12/2001; 1(01):39 - 49. DOI: 10.1017/S1473550402001039</ref>

(contracted; show full) correlated with the beginning and the end of the simulated Martian day. Those are times when atmospheric water vapour could condense on the soil and be absorbed by it, and could probably also form cold brines with the salts in the simulated martian regolith. The pressure used for the experiment was 700 - 800 Pa, above the triple point of pure water at 600 Pa and consistent with the conditions measured by Curiosity in Gale crater.<ref name="de VeraSchulze-Makuch2014">{{cite journal|url=http
s://www.researchgate.net/profile/Jean-Pierre_de_Vera/publication/258227207_Adaptation_of_an_Antarctic_lichen_to_Martian_niche_conditions_can_occur_within_34_days/links/00b4952e11f3088291000000.pdf|last1=de Vera|first1=Jean-Pierre|last2=Schulze-Makuch|first2=Dirk|last3=Khan|first3=Afshin|last4=Lorek|first4=Andreas|last5=Koncz|first5=Alexander|last6=Möhlmann|first6=Diedrich|last7=Spohn|first7=Tilman|title=Adaptation of an Antarctic lichen to Martian niche conditions can occur within 34 days|journal=Planetary a(contracted; show full)sed medium to support growth of the archaeon Halobacterium salinarum. These findings show that presence of perchlorate among the salts on Mars does not preclude the possibility of halophilic life. If indeed the liquid brines that may exist on Mars are inhabited by salt-requiring or salt-tolerant microorganisms similar to the halophiles on Earth, presence of perchlorate may even be stimulatory when it can serve as an electron acceptor for respiratory activity in the anaerobic Martian environment."[http
s://www.ncbi.nlm.nih.gov/pubmed/24150694 Perchlorate and halophilic prokaryotes: implications for possible halophilic life on Mars] Oren A1, Elevi Bardavid R, Mana L.. Water Sci Technol. 2009;60(7):1745-56. doi: 10.2166/wst.2009.635.</ref>. 

(contracted; show full)
[[File:Salt Pillars - Atacama Desert.jpg|thumb|400 px|'The Atacama desert hosts the closest analogue of what a real, live Martian might be like', in its salt rock formations.<ref>{{cite web|last1=Davies|first1=Paul|title=The key to life on Mars may well be found in Chile|url=http
s://www.theguardian.com/commentisfree/2012/aug/03/life-mars-chile|website=The Guardian|date=Aug 3, 2012}}</ref>]]
Micro-environmental data measured simultaneously outside and inside halite pinnacles in the Yungay region (table 2 from <ref name="WierzchosDavila2012"/>)

{| class="wikitable"
|-
!Variable !! Halite exterior !! Halite interior
|-
| Mean annual RH, % || 34.75 || 54.74
(contracted; show full) (CaSO<sub>4</sub>.2H<sub>2</sub>O), however Gypsum doesn't deliquesce. Researchers found that the regions of the desert that had microbial colonies within the gypsum correlated with regions with over 60% relative humidity for a significant part of the year. They also found that the microbes imbibed water whenever the humidity increased above 60% and gradually became desiccated when it was below that figure.<ref name="WierzchosCámara2011">{{cite journal|url=http
s://www.researchgate.net/profile/Alfonso_Davila/publication/45797377_Microbial_colonization_of_Ca-sulfate_crusts_in_the_hyperarid_core_of_the_Atacama_Desert_implications_for_the_search_for_life_on_Mars/links/0912f50e37831ae515000000.pdf|last1=Wierzchos|first1=J.|last2=Cámara|first2=B.|last3=De Los Ríos|first3=A.|last4=Davila|first4=A. F.|last5=Sánchez Almazo|first5=I. M.|last6=Artieda|first6=O.|last7=Wierzchos|first7=K.|last8=Gómez-Silva|first8=B.|last9=Mckay|first9=C.|last10=Ascaso|first10=C.|title=Microbia(contracted; show full)

He made the widely reported statement<ref>[http://rt.com/news/171300-mars-bacteria-salt-ice/ ‘Swimming pool for bacteria’: There could be life on Mars today - new study] - RT News</ref><ref>[http
s://www.independent.co.uk/news/science/is-there-life-on-mars-water-can-and-does-exist-on-the-planet-says-new-research-9591187.html 'Is there life on Mars?': Water can and does exist on the planet says new research] - the Independent</ref><ref> [http://www.ns.umich.edu/new/releases/22274-martian-salts-must-touch-ice-to-make-liquid-water-study-shows Martian salts must touch ice to make liquid water, study shows] - Michigan News (the research was by a team of researchers at the University of Michigan)</ref> about "swimming pools for bacteria" on Mars. <ref>"Based on the results of our experiment, we expect this soft ice that can liquify perhaps a few days per year, perhaps a few hours a day, almost anywhere on Mars. --- This is a small amount of liquid water. But for a bacteria, that would be a huge swimming pool  ... So, a small amount of water is '''''enough for you to be able to create conditions for Mars to be habitable today. And we believe this is possible in the shallow subsurface, and even the surface of the Mars polar region for a few hours per day during the spring.''''''"<br>(transcript from 2 minutes into the video onwards, from [https://www.youtube.com/watch?v=iLWv9UGwjdE#t=135 Nilton Renno video (youtube)]</ref>

In the academic paper about this research he writes:<ref name="FischerMartínez2014">{{cite journal|url=http://onlinelibrary.wiley.com/doi/10.1002/2014GL060302/full|last1=Fischer|first1=Erik|last2=Martínez|first2=Germán M.|last3=Elliott|first3=Harvey M.|last4=Rennó|first4=Nilton O.|title=Experimental evidence for the formation of liquid saline water on Mars|journal=Geophysical Research Letters|year=2014|pa(contracted; show full)pact 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/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, Journal of Geophysical Research: Planets (1991–2012) Volume 101, Issue E6, pages 14951–14955, 25 June 1996 DOI: 10.1029/96JE01139</ref><ref>[http
s://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)is evidence is in the form of hydrogen / deuterium isotope ratios in Martian meteorites, which give indirect evidence that Mars must have a subsurface reservoir of water, most likely in the form of ice.<ref>{{cite web|last1=NASA|title=NASA, Planetary Scientists Find Meteoritic Evidence of Mars Water Reservoir|url=http://mars.jpl.nasa.gov/news/whatsnew/index.cfm?FuseAction=ShowNews&NewsID=1768|date=December 19, 2014}}</ref><ref name="UsuiAlexander2015">{{cite journal|url=http
s://www.researchgate.net/profile/Justin_Simon2/publication/269393996_Meteoritic_evidence_for_a_previously_unrecognized_hydrogen_reservoir_on_Mars/links/54887e000cf268d28f08f75c.pdf|last1=Usui|first1=Tomohiro|last2=Alexander|first2=Conel M. O'D.|last3=Wang|first3=Jianhua|last4=Simon|first4=Justin I.|last5=Jones|first5=John H.|title=Meteoritic evidence for a previously unrecognized hydrogen reservoir on Mars|journal=Earth and Planetary Science Letters|volume=410|year=2015|pages=140–151|issn=0012821X|doi=1(contracted; show full)

===Atacama Desert Core - Maria Elena South===

This site is even drier than the Yungay area. It was found through a systematic search for drier regions than Yungay in the Atacama desert. 

In a paper about the results published in March 2015 they report <ref name="Azua-BustosCaro-Lara2015">{{cite journal|url=http
s://www.researchgate.net/profile/Armando_Azua/publication/270052971_Discovery_and_microbial_content_of_the_driest_site_of_the_hyperarid_Atacama_Desert_Chile/links/54ecd6210cf2465f5330490e.pdf|last1=Azua-Bustos|first1=Armando|last2=Caro-Lara|first2=Luis|last3=Vicuña|first3=Rafael|title=Discovery and microbial content of the driest site of the hyperarid Atacama Desert, Chile|journal=Environmental Microbiology Reports|year=2015|pages=n/a–n/a|issn=17582229|doi=10.1111/1758-2229.12261}}</ref> an average atm(contracted; show full)

{{quote|"At these sites permafrost, frigid winter temperatures, and arid atmospheric conditions approximate conditions of present-day, as well as past, Mars. Mineralogy of the three springs is dominated by halite (NaCl), calcite (CaCO3), gypsum (CaSO4·2H2O), thenardite (Na2SO4), mirabilite (Na2SO4·10H2O), and elemental sulfur (S°).<ref name="BattlerOsinski2013">{{cite journal|url=http
s://www.researchgate.net/publication/256719821_Mineralogy_of_saline_perennial_cold_springs_on_Axel_Heiberg_Island_Nunavut_Canada_and_implications_for_spring_deposits_on_Mars |last1=Battler|first1=Melissa M.|last2=Osinski|first2=Gordon R.|last3=Banerjee|first3=Neil R.|title=Mineralogy of saline perennial cold springs on Axel Heiberg Island, Nunavut, Canada and implications for spring deposits on Mars|journal=Icarus|volume=224|issue=2|year=2013|pages=364–381|issn=00191035|doi=10.1016/j.icarus.2012.08.031|bibco(contracted; show full)
Opportunity found evidence for magnesium sulfates on Mars (one form of it is epsomite, or "Epsom salts"), in 2004. <ref>{{cite web|last1=Bortman|first1=Henry|title=Evidence of Water Found on Mars|url=http://www.astrobio.net/news-exclusive/evidence-of-water-found-on-mars/|website=Astrobiology Magazine (NASA)|date=Mar 3, 2004}}</ref> Curiosity has detected calcium sulfates on Mars<ref name="NachonClegg2014">{{cite journal|url=http
s://www.researchgate.net/profile/Cecile_Fabre2/publication/260020935_Calcium_sulfate_veins_characterized_by_ChemCam_Curiosity_at_Gale_Crater_Mars/links/5411d7cb0cf2788c4b354db9.pdf|last1=Nachon|first1=M.|last2=Clegg|first2=S. M.|last3=Mangold|first3=N.|last4=Schröder|first4=S.|last5=Kah|first5=L. C.|last6=Dromart|first6=G.|last7=Ollila|first7=A.|last8=Johnson|first8=J. R.|last9=Oehler|first9=D. Z.|last10=Bridges|first10=J. C.|last11=Le Mouélic|first11=S.|last12=Forni|first12=O.|last13=Wiens|first13=R.C.|last(contracted; show full)

In high alpine and polar regions, lichens have to cope with conditions of high UV fluxes low temperatures and arid environments. This is especially so when the two factors, polar regions and high altitudes are combined. These conditions occur in the high mountains of Antarctica, where lichens grow at altitudes up to 2,000 meters with no liquid water, just snow and ice. Researchers described this as the most Mars-like environment on the Earth.<ref>{{cite journal|url=http
s://www.researchgate.net/profile/Jean-Pierre_de_Vera/publication/258227207_Adaptation_of_an_Antarctic_lichen_to_Martian_niche_conditions_can_occur_within_34_days/links/00b4952e11f3088291000000.pdf|last1=de Vera|first1=Jean-Pierre|last2=Schulze-Makuch|first2=Dirk|last3=Khan|first3=Afshin|last4=Lorek|first4=Andreas|last5=Koncz|first5=Alexander|last6=Möhlmann|first6=Diedrich|last7=Spohn|first7=Tilman|title=Adaptation of an Antarctic lichen to Martian niche conditions can occur within 34 days|journal=Planetary a(contracted; show full)nd to alpine sites of the Central European Alps. Populations from the Alps receive 3–5 times higher UV-B irradiance than their Arctic counterparts from Svalbard because of latitudinal and altitudinal gradients in UV-B irradiance.... This implies that Arctic populations maintain a high level of screening pigments in spite of low ambient UV-B, and that the studied lichen species presumably may tolerate an increase in UV-B radiation due to the predicted thinning of the ozone layer over polar areas" [http
s://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
(contracted; show full)

# Uninhabitable - doesn't have the conditions for life
# Has habitats but they are all uninhabited
# Has at least some habitats with life

As Mars evolved, initially when 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>[http
s://www.ncbi.nlm.nih.gov/pmc/articles/PMC3929387/ Trajectories of Martian Habitability], Charles S. Cockell, Astrobiology. 2014 Feb 1; 14(2): 182–203.
doi:  10.1089/ast.2013.1106</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."
(contracted; show full)reading seems to relate to a type of fatty acid molecule. These are important for life because organisms use them to build cell membranes, but they could have a non-biological origin.<br><br> Glavin also confirmed previous hints from SAM of an organic compound called chlorobenzene. Again, this might not be a sign of life, but it suggests that complex organic molecules can survive on the surface of Mars, upping the chances of future missions finding microbes if they are there."}} from [http
s://www.newscientist.com/article/mg22530143.200-nasas-curiosity-rover-finds-fatty-acids-on-mars.html#.VSUy3vnF98F NASA's Curiosity rover finds fatty acids on Mars], New Scientist, 25 March 2015</ref>

==Planned and proposed missions to search for present day life on Mars==

===Past missions===

Viking 1 and 2 are the only successful missions to Mars to date designed to search for present day life.

(contracted; show full)==See also==
* [[Life on Mars]]

==References==
{{reflist}}

==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.