Possible present day habitats for life on Mars (Including potential Mars special regions): Difference between revisions
Possible present day habitats for life on Mars (Including potential Mars special regions) (edit)
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The [[Viking program#Viking landers|Viking landers]] (operating on Mars from 1976-1982), are the only spacecraft so far to search directly for life on Mars. They landed in the equatorial regions of Mars. With our modern understanding of Mars, this would be a surprising location to find life, as the soil there is thought to be completely ice free to a depth of at least hundred meters, and possibly for a kilometer or more. It is not totally impossible though, as some scientists have suggested ways that life could exist even in such arid conditions, using the night time humidity of the atmosphere, and possibly in some way utilizing the frosts that form frequently in the mornings in equatorial regions.<ref name=LevinMarsLifeIdea/><ref name=sanddunesbioreactor/><ref name=LevinMarsLifeIdea>[http://www.astrobio.net/news-exclusive/the-viking-files/ The Viking Files] Astrobiology Magazine (NASA) - May 29, 2003, astrobio.net (summary of scientific research)</ref>
The Viking results were intriguing, and inconclusive.<ref name="Levin 1976 1322–1329">{{cite journal |doi=10.1126/science.194.4271.1322 |pages=1322–1329 |title=Viking Labeled Release Biology Experiment: Interim Results |date=1976 |last=Levin |first=G. V. |last2=Straat |first2=P. A. |journal=Science |volume=194 |issue=4271 |pmid=17797094 |bibcode=1976Sci...194.1322L }}</ref> There has been much debate since then between a small number of scientists who think that the Viking missions did detect life,<ref name=VikingGasChromatograph/><ref name=JosephMiller/><ref name="Bianciardi-2012"/><ref name=Levin2016>Levin, G.V. and Straat, P.A., 2016. The case for extant life on Mars and its possible detection by the Viking labeled release experiment. Astrobiology, 16(10), pp.798-810.
{{quote|"'''''It is concluded that extant life is a strong possibility, that abiotic interpretations of the LR data are not conclusive, and that, even setting our conclusion aside, biology should still be considered as an explanation for the LR experiment. Because of possible contamination of Mars by terrestrial microbes after Viking, we note that the LR data are the only data we will ever have on biologically pristine martian samples'''''"}}
</ref> and the majority of scientists who think that it did not.<ref name="PlaxcoGross2011_2"/><ref name=Quine2013/>
The Viking lander had three main biological experiments, but only one of these experiments produced positive results.<ref>[http://www.astrobio.net/news-exclusive/the-viking-files/ The Viking Files, Astrobiology Magazine (NASA) - May 29, 2003]</ref>
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* '''''Unlikely''''' - these authors cite the inability of microbes to survive dormancy on the surface between periods when the atmosphere is thicker, due to ionizing radiation, the ephemeral nature of surface habitats, low temperatures, or low relative humidity, and the difficulty of colonization in surface conditions of high UV...<ref name=Morais>[https://books.google.com/books?id=TZKeBQAAQBAJ&pg=PA153 Planetary Exploration and Science: Recent Results and Advances], Antonio de Morais M. Teles, page 153, 27 Nov 2014</ref><ref name="PlaxcoGross2011_2"/><ref name=Quine2013/>
* '''''Possible, recolonized from below''''', these point out the ability of micro-organisms to repair damage by ionizing radiation and capability to remain dormant for up to several million years in the deep subsurface, suggesting that these short lived surface habitats, such as the Recurring Slope Lineae, could be recolonized from the subsurface.<ref name=Westall>[https://books.google.com/books?id=VYjEBAAAQBAJ&pg=PA192 Habitability of other planets and satellites - Habitability and Survival], Francis Westall, page 192, 30 Jul 2013
{{quote|'''''"This presupposes that the ephemeral surface habitats could be colonized by viable life forms, that is, that a subsurface reservoir exists in which microbes could continue to metabolize and that, as noted above, the viable microbes could be transported into the short-lived habitat.... Although there are a large number of constraints on the continued survival of life in the subsurface of Mars, the astonishing biomass in the subsurface of Earth suggests that this scenario as a real possibility."'''''}}
</ref>
* '''''Possible, open question if it occurs on the surface''''' these are investigating the possibility with experiments in simulated Mars conditions, theoretical models and study of the observations from Mars, and treat it as an open question for now, whether the present day surface and near sub surface is habitable.
<ref name=Kilmer>{{cite journal|pmc=3989109|last1=Kilmer|first1=Brian R.|last2=Eberl|first2=Timothy C.|last3=Cunderla|first3=Brent|last4=Chen|first4=Fei|last5=Clark|first5=Benton C.|last6=Schneegurt|first6=Mark A.|title=Molecular and phenetic characterization of the bacterial assemblage of Hot Lake, WA, an environment with high concentrations of magnesium sulphate, and its relevance to Mars|journal=International Journal of Astrobiology|volume=13|issue=1|year=2014|pages=69–80|issn=1473-5504|doi=10.1017/S1473550413000268|pmid=24748851|bibcode=2014IJAsB..13...69K}}</ref><ref name=Rummel>Rummel, J.D., Beaty, D.W., Jones, M.A., Bakermans, C., Barlow, N.G., Boston, P.J., Chevrier, V.F., Clark, B.C., de Vera, J.P.P., Gough, R.V. and Hallsworth, J.E., 2014. A new analysis of Mars “special regions”: findings of the second MEPAG Special Regions Science Analysis Group (SR-SAG2).
{{quote|'''''"Claims that reducing planetary protection requirements wouldn't be harmful, because Earth life can't grow on Mars, may be reassuring as opinion, but the facts are that we keep discovering life growing in extreme conditions on Earth that resemble conditions on Mars. We also keep discovering conditions on Mars that are more similar—though perhaps only at microbial scales—to inhabited environments on Earth, which is where the concept of Special Regions initially came from."'''''}}
<ref name=Fairen>Fairén, A.G., Parro, V., Schulze-Makuch, D. and Whyte, L., 2017. [https://www.liebertpub.com/doi/full/10.1089/ast.2017.1703 Searching for life on Mars before it is too late]. Astrobiology, 17(10), pp.962-970.</ref><ref name=RummelConley>Rummel, J. D., Conley C. A, 2017,.[http://online.liebertpub.com/doi/full/10.1089/ast.2017.1749 Four fallacies and an oversight: searching for martian life] Astrobiology, 17(10), pp. 971-974.</ref>▼
</ref><ref name=Davila>Davila, A.F., Skidmore, M., Fairén, A.G., Cockell, C. and Schulze-Makuch, D., 2010. New priorities in the robotic exploration of Mars: the case for in situ search for extant life. Astrobiology, 10(7), pp.705-710.
{{quote|'''''"We argue that the strategy for Mars exploration should center on the search for extant life. By extant life, we mean life that is active today or was active during the recent geological past and is now dormant. As we discuss below, the immediate strategy for Mars exploration cannot focus only on past life based on the result of the Viking missions, particularly given that recent analyses call for a re-evaluation of some of these results. It also cannot be based on the astsumption that the surface of Mars is uniformly prohibitive for extant life, since research contributed in the past 30 years in extreme environments on EArth has shown that life is possible under extremes of cold and dryness."'''''}}}</ref>
▲<ref name=Fairen>Fairén, A.G., Parro, V., Schulze-Makuch, D. and Whyte, L., 2017. [https://www.liebertpub.com/doi/full/10.1089/ast.2017.1703 Searching for life on Mars before it is too late]. Astrobiology, 17(10), pp.962-970.
{{quote|'''''"The case of ExoMars is particularly dramatic as the first priority of the rover is to search for signs of past and present life on Mars ... however, it has been explicitly banned to go to Special Regions because it will not comply with the minimum cleanliness requirements. As a consequence, the billion-dollar life-seeking mission ExoMars will be allowed to search for life everywhere on Mars, except in the very places where we suspect that life may exist."'''''}}</ref><ref name=RummelConley>Rummel, J. D., Conley C. A, 2017,.[http://online.liebertpub.com/doi/full/10.1089/ast.2017.1749 Four fallacies and an oversight: searching for martian life] Astrobiology, 17(10), pp. 971-974.</ref>
and many others. Selected quotes:<ref name="MorozovaMöhlmann2006">{{cite journal|url=http://epic.awi.de/14473/1/Mor2006e.pdf|last1=Morozova|first1=Daria|last2=Möhlmann|first2=Diedrich|last3=Wagner|first3=Dirk|title=Survival of Methanogenic Archaea from Siberian Permafrost under Simulated Martian Thermal Conditions|journal=Origins of Life and Evolution of Biospheres|volume=37|issue=2|year=2006|pages=189–200|issn=0169-6149|doi=10.1007/s11084-006-9024-7|pmid=17160628|quote='''''The observation of high survival rates of methanogens under simulated Martian conditions supports the possibility that microorganisms similar to the isolates from Siberian permafrost could also exist in the Martian permafrost.'''''|bibcode=2007OLEB...37..189M}}</ref>
{{quote|"The observation of high survival rates of methanogens under simulated Martian conditions supports the possibility that microorganisms similar to the isolates from Siberian permafrost could also exist in the Martian permafrost"}}
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