Potentially habitable flow-like features from Martian dry ice geyser dune spots: Difference between revisions
Potentially habitable flow-like features from Martian dry ice geyser dune spots (edit)
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[[File:Flow-like-features.gif|thumb|Flow-like-features|Larger region of the Richardson crater dune field showing the dark dune spots and flow-like features. ]][[File:Flow-like-features detail.gif|thumb|Flow-like-features detail|Detailed zoom into the flow-like features around a small cluster of the spots on the dunes in Richardson Crater, Mars [http://www.google.co.uk/mars/#q=Richardson%20crater&zoom=2 (Richardson crater in Google Mars)]. These dark dune spots are thought to be the debris of the hypothesized [[Geyser (Mars)|Martian Geysers]] and the fingers of the flow like features extend later in the year. The dark material at the end of the flows moves at between 0.1 and 1.4 m/day in late spring / summer on Mars. This example moves approximately 39 meters in 26 days between the last two frames.<br><br>The two main models involve liquid water - either interfacial layers, or else layers of water created through the solid state greenhouse effect. <ref name="MartínezRenno2013DarkDuneSpots"/><ref name=Kereszturi2008>Kereszturi, A., et al. [http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1555.pdf "Analysis of possible interfacial water driven seepages on Mars"], Lunar and Planetary Science Conference. Vol. 39. 2008.</ref><br><br>Animation centered on {{coord|72.02|S|179.408|E|globe:Mars}} [http://www.google.co.uk/mars/#lat=-72.02&lon=179.408&zoom=7 (location in Google Mars)]. Displayed region 188.5 meters by 172 meters. Dates of sequence: 19 January (sol 396), 24 January (sol 401), 29 January (sol 406), 10 February (sol 418), and 09 March (sol 444), all in 2009. All taken between 4.10 pm and 4.28 pm in Mars local time.]]
These features near the Martian southern polar region are associated with the [[Geyser (Mars)|Martian Geysers]]. Before these geysers were well understood, there was a lot of speculation about what they might be. The seasonal patterns they form resemble trees and vegetation, and in 2001 looking at the Mars Global Surveyor images, Arthur C. Clarke called them "Banyan trees"<ref name=Foulke2001>Nicole Foulke, [https://www.popsci.com/military-aviation-space/article/2001-12/banyan-trees-mars The Banyan trees of Mars], Popular science e-mail interview with Arthur C. Clarke, December 17, 2001</ref>, saying, only half joking "I'm now convinced that Mars is inhabited by a race of demented landscape gardeners,"<ref name=ClarkeSmithsonian2001>Arthur C. Clarke, speaking by teleophone for the [http://www.martianspiders.com/Sir%20Arthur%20C_%20Clarke%20at%20the%20Smithsonian,%20June%202001.htm Wernher von Braun Memorial Lecture], Smithsonian institute's National Air and Space Museum, June 6, 2001 - reported by John C. Sherwood</ref>
Most of
{{quote|There is mounting evidence that while dark spots and FLF form by “dry” gas venting, liquid brines form temporarily on them.}}
However, later in the spring, the dark streaks from the geysers begin to extend further down the slopes, sometimes at a rate of meters per day. This is the part of the process that may be associated with liquid brines. There are streaks in both hemispheres but the details of how they form differ.▼
▲
In the Southern hemisphere, they form in the debris of the geysers, and both of the current models for this part of the process involve liquid water<ref name="MartínezRenno2013DarkDuneSpots"/>. In one of these models the features from initially as subsurface melt water, fresh water that forms at 0 °C below snow-ice packs, in solid state greenhouse effects - they are optically thin in visible light but opaque to thermal infrared, so trapping heat in a solid state greenhouse effect familiar in similar situations in Antarctica<ref name="MartínezRenno2013SubsurfaceMeltWater>{{cite journal|url=https://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 section 2.2.2 Subsurface Melt Water|url=https://link.springer.com/article/10.1007%2Fs11214-012-9956-3#Sec6|journal=Space Science Reviews|volume=175|issue=1-4|year=2013|pages=29–51|issn=0038-6308|doi=10.1007/s11214-012-9956-3}}</ref>. The other model involves thin layers of ULI water (undercooled liquid water)<ref name="MartínezRenno2013ULIWater>{{cite journal|url=https://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 section 2.2.1 Undercooled Liquid Interfacial Water|url=https://link.springer.com/article/10.1007%2Fs11214-012-9956-3#Sec5|journal=Space Science Reviews|volume=175|issue=1-4|year=2013|pages=29–51|issn=0038-6308|doi=10.1007/s11214-012-9956-3}}</ref> which form on the surface of solar heated grains, then flows downwards, supplying several litres of water per day to the features. In both cases they then pick out salts which let them remain liquid in the cold near surface conditions as they flow down the slopes.▼
▲In the Southern hemisphere, they form in the debris of the geysers, and both of the current models for this part of the process involve liquid water<ref name="MartínezRenno2013DarkDuneSpots"/>. In one of these
The northern hemisphere flow like features form at much lower surface temperatures, and they begin as wind-blown features on steep slopes, and start to extend similarly to the southern hemisphere features. However, if they involve brines, the temperatures are far lower, with surface temperatures around -90 °C, though the brines themselves would be warmer than that. Also, though most of the models for the northern hemisphere features involve water, they can also be explained with dry ice and cascading dust. <ref name="MartínezRenno2013DarkDuneSpots"/>▼
▲The northern hemisphere flow like features
The southern hemisphere Richardson crater flow-like features are the ones of most interest for brines at temperatures within the range of habitability for Earth life (life based on novel biochemistry based on perchlorates or hydrogen peroxide in the place of the chloride salts of Earth life might tolerate or prefer lower temperatures<ref name=xerophilic>Schulze-Makuch, D. and Houtkooper, J.M., 2010. [https://meetingorganizer.copernicus.org/EPSC2010/EPSC2010-308.pdf A perchlorate strategy for extreme xerophilic life on Mars]. EPSC Abstracts, 5, pp.EPSC2010-308.</ref>.).
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===Solid state greenhouse effect model===
Möhlmann uses a solid state greenhouse effect in his model, similarly to the process that forms the geysers, but with translucent ice or snow-ice packs, rather than dry ice as the solid state greenhouse layer.<ref name="LiquidWaterSnowIce">{{cite journal|url=http://www.sciencedirect.com/science/article/pii/S0019103509004539|last1=Möhlmann|first1=Diedrich T.F.|title=Temporary liquid water in upper snow/ice sub-surfaces on Mars?|journal=Icarus|volume=207|issue=1|year=2010|pages=140–148|issn=0019-1035|doi=10.1016/j.icarus.2009.11.013|bibcode=2010Icar..207..140M}}</ref>
[[File:JoekullsarlonBlueBlockOfIce.jpg|thumb|JoekullsarlonBlueBlockOfIce|
In his model, first the ice forms a translucent layer - then as summer approaches, the solid state greenhouse effect raises the temperature of a layer below the surface to 0 °C, so melting it. This is a process familiar on the Earth for instance in Antarctica. On Earth, in similar conditions, the surface ice remains frozen, but a layer of liquid water forms from 0.1 to 1 meters below the surface. It forms preferentially in "blue ice".<ref>Nl, K., and T. SAND. [http://www.igsoc.org:8080/journal/42/141/igs_journal_vol42_issue141_pg271-278.pdf "Melting, runoff and the formation of frozen lakes in a mixed snow and blue-ice field in Dronning Maud Land, Antarctica."], Journal of Glaciology, T'ol. 42, .\"0.141, 1996</ref>
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==Earlier hypotheses==
[[Image:DDS MSO.jpg|thumb|right
In 2003 a team of Hungarian scientists proposed that the dark dune spots and channels may be colonies of [[photosynthesis|photosynthetic]] Martian microorganisms, which over-winter beneath the ice cap, and as the [[sunlight]] returns to the pole during early spring, light penetrates the ice, the microorganisms photosynthesise and heat their immediate surroundings. A pocket of liquid water, which would normally evaporate instantly in the thin Martian atmosphere, is trapped around them by the overlying ice. As this ice layer thins, the microorganisms show through grey. When it has completely melted, they rapidly desiccate and turn black surrounded by a grey aureole.<ref name=Andras >{{cite journal|title=Probable Evidences of Recent Biological Activity on Mars: Appearance and Growing of Dark Dune Spots in the South Polar Region|journal=32nd Annual Lunar and Planetary Science Conference, Houston, Texas, abstract no.1543|date=12–16 March 2001|first=Tibor|last=Gánti |author2=András Horváth |author3=Szaniszló Bérczi |author4=Albert Gesztesi |author5=Eörs Szathmáry|url=http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1543.pdf|format=PDF|accessdate=20 November 2008}}</ref><ref>{{Cite book| author=Pócs, T. |author2=A. Horváth |author3=T. Gánti |author4=Sz. Bérczi |author5=E. Szathmáry |title=ESA SP-545 - Possible crypto-biotic-crust on Mars?| publisher=European Space Agency| date=2003| url=http://adsabs.harvard.edu/full/2004esasp.545..265p| format=PDF| accessdate=24 November 2008 }}</ref><ref>{{cite journal|title=Dark Dune Spots: Possible Biomarkers on Mars?|journal=Origins of Life and Evolution of Biospheres|date=31 October 2003 |first=Tibor|last=Gánti|author2=András Horváth |author3=Szaniszló Bérczi |author4=Albert Gesztesi |author5=Eörs Szathmáry |volume= 33|issue=s 4–5|pages=515–557|doi=10.1023/A:1025705828948|url=http://www.springerlink.com/content/ut8r78131173254n/|accessdate=18 November 2008 }}</ref><ref>{{Cite journal|author=Pócs, T. |author2=A. Horváth |author3=T. Gánti |author4=S. Bérczi |author5=E. Szathmáry |title=38th Vernadsky-Brown Microsymposium on Comparative Planetology - Are the dark dune spots remnants of the crypto-biotic-crust of Mars? |place=Moscow, Russia |date=27–29 October 2003 |url=http://www.colbud.hu/esa/publications/26MosCBC10color.pdf |format=[[PDF]] |accessdate=7 September 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20110721104952/http://www.colbud.hu/esa/publications/26MosCBC10color.pdf |archivedate=21 July 2011 |df=dmy }}</ref> The Hungarian scientists suggested that that even a complex sublimation process was insufficient to explain the formation and evolution of the dark dune spots in space and time.<ref name=Planetary >{{Cite journal |title=Lunar and Planetary Science XXXIII - Morphological Analysis of the Dark Dune Spots on Mars: New Aspects in Biological Interpretation| editors=A. Horváth, T. Gánti, Sz. Bérczi, A. Gesztesi, E. Szathmáry| date=2002| url=http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1108.pdf| format=PDF| accessdate=24 November 2008 }}</ref><ref>{{cite web|url=http://www.monochrom.at/dark-dune-spots/ |title=Dark Dune Spots – Could it be that it’s alive? |accessdate=4 September 2009 |author=András Sik |author2=Ákos Kereszturi |publisher=Monochrom }} (Audio interview, MP3 6 min.)</ref>
[[File:High resolution image of Arthur C. Clarke's "Banyam tress of Mars".jpg|thumb|In 2001 Arthur C. Clarke speculated that this was Martian vegetation similar to banyan trees. They are now thought to be dust carried in CO2 from dry ice Martian "geysers"]]
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