Potentially habitable flow-like features from Martian dry ice geyser dune spots: Difference between revisions
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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=" |
[[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">{{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|url=https://link.springer.com/article/10.1007/s11214-012-9956-3|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><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.]] |
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These features near the Martian polar regions 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>, and a team of Hungarian scientists proposed that they might be the result of spreading colonies of overwintering photosynthetic microbial life. <ref name=Andras/> |
These features near the Martian polar regions 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>, and a team of Hungarian scientists proposed that they might be the result of spreading colonies of overwintering photosynthetic microbial life. <ref name=Andras/> |
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However, later in the year dark streaks gradually extend down the slopes from the dark spots, sometimes at a rate of meters per day. These are the "flow-like features" that may be associated with liquid brines. There are streaks in both hemispheres but the details of how they form differ. |
However, later in the year dark streaks gradually extend down the slopes from the dark spots, sometimes at a rate of meters per day. These are the "flow-like features" that may be associated with liquid brines. There are streaks in both hemispheres but the details of how they form differ. |
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In the Southern hemisphere, both of the current models for this part of the process involve liquid water. In one of these models the features from initially as fresh water at 0 °C below clear ice in a solid state greenhouse effects. The other model involves thin layers of ULI water (undercooled liquid water) 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, 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 fresh water at 0 °C below clear ice in a solid state greenhouse effects. The other model involves thin layers of ULI water (undercooled liquid water) 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. |
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The northern hemisphere flow like features form at much lower surface temperatures and if they involve brines the temperatures are around -90 °C, too low in temperature to be habitable for Earth life, at least. Also, though most of the models for the northern hemisphere features involve water, they can also be explained with dry ice and cascading dust. |
The northern hemisphere flow like features form at much lower surface temperatures and if they involve brines the temperatures are around -90 °C, too low in temperature to be habitable for Earth life, at least. Also, though most of the models for the northern hemisphere features involve water, they can also be explained with dry ice and cascading dust. |
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The debris from these geysers form the dark spots, and the "flow like features". |
The debris from these geysers form the dark spots, and the "flow like features". |
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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=" |
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=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|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> |
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A different mechanism is proposed for them in the Northern and in the Southern hemispheres. |
A different mechanism is proposed for them in the Northern and in the Southern hemispheres. |
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===Interfacial liquid layers model=== |
===Interfacial liquid layers model=== |
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Another model for these southern hemisphere features involves ULI water (undercooled liquid water) which forms as a thin layer over surfaces and can melt at well below the usual melting point of ice. In Mohlmann's sandwich model, then the interfacial water layer forms on the surfaces of solar heated grains in the ice, which then flows together down the slope. Calculations of downward flow of water shows that several litres a day of water could be supplied to the seepage flows in this way.<ref name="MartínezRenno2013DarkDuneSpots">{{cite journal|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><ref name=Kereszturi2008/> |
Another model for these southern hemisphere features involves ULI water (undercooled liquid water) which forms as a thin layer over surfaces and can melt at well below the usual melting point of ice. In Mohlmann's sandwich model, then the interfacial water layer forms on the surfaces of solar heated grains in the ice, which then flows together down the slope. Calculations of downward flow of water shows that several litres a day of water could be supplied to the seepage flows in this way.<ref name="MartínezRenno2013DarkDuneSpots">{{cite journal|last1=Martínez|first1=G. M.|last2=Renno|first2=N. O.|title=Water and Brines on Mars: Current Evidence and Implications for MSL - section 3.1.2 Dune Dark Spots and Flow-like Features|url=https://link.springer.com/article/10.1007%2Fs11214-012-9956-3#Sec12|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><ref name=Kereszturi2008/> |
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The idea then is that this ULI water would be the water source for liquid brines which then flow down the surface to form the features. |
The idea then is that this ULI water would be the water source for liquid brines which then flow down the surface to form the features. |
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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. |
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. |
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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=" |
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="MartínezRenno2013"/> |
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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="MartínezRenno2013DarkDuneSpots"/> |
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="MartínezRenno2013DarkDuneSpots"/> |
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