Liquid water still possible for the cause of the Martian "spiders".

[exoscientist]

The news release from the AGU conference argues that the Mars "spider"<br />features at the south pole are due to gas release:<br /><br />HiRISE | Isolated Araneiform Topography (PSP_003087_0930).<br />http://hirise.lpl.arizona.edu/PSP_003087_0930<br /><br />Spring at the South Pole of Mars.<br />AGU Press Conference<br />C. J. Hansen, A. McEwen and the HiRISE Team.<br />December 2007<br />http://hirise.lpl.arizona.edu/pdf/agu_press_conf_dec07.pdf<br /><br />However, this report shows temperatures above 250K can be reached<br />seasonally even as far south as the Mars spiders:<br /><br />Astrobiology<br />Spiders: Water-Driven Erosive Structures in the Southern Hemisphere of<br />Mars.<br />Aug 2006, Vol. 6, No. 4: 651-667<br />http://www.liebertonline.com/doi/abs/10.1089/ast.2006.6.651 [abstract]<br /><br />This is within the temperature range of calcium chloride liquid water<br />brines.<br />Evidence for a liquid water origin is the dendritic pattern shown by<br />the spider "legs". On Earth this is taken for evidence of channels cut<br />by liquid water.<br />The news release argues that the channels are cut by gas because some<br />channels travel uphill. But of course water can also travel uphill for<br />short distances under pressure or simply because it is traveling<br />quickly as in a flood.<br /><br />A related possibility is that the origin of the spiders is due to the<br />transition of CO2-water clathrates to liquid water brines. This report<br />shows this could occur on heating and would result in explosive gas<br />release:<br /><br />PTX PHASE EQUILIBRIA IN THE H2O-CO2-SALT SYSTEM AT MARS NEAR-SURFACE<br />CONDITIONS.<br />R.J. Bodnar1, 1Fluids Research Laboratory, Department of Geological<br />Sciences, Virginia Tech, Blacksburg, VA 24061 e <div class="Discussion_UserSignature"> </div>

 

[3488]

Thanks Bob,<br /><br />Very interesting indeed.<br /><br />I expect that you have seen this one Aranieform, due to repeated erosion & redeposition?<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[alokmohan]

What is AGU?

 

[Swampcat]

<font color="yellow">"What is AGU?"</font><br /><br /><font color="yellow"><b>A</b></font>erican <font color="yellow"><b>G</b></font>ophysical <font color="yellow"><b>U</b></font>ion. <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[exoscientist]

I looked again at the Astrobiology paper "Spiders: Water-Driven Erosive Structures in the Southern Hemisphere of Mars" and found the temperatures as far south as 81 S latitude where the spiders are found can reach 268 K, only 5 degrees C below freezing. <br /> Also, this report from experiments showed liquid water carved channels could occur under current Mars conditions:<br /><br />Martian Outflow Channel Formation by Water Erosion Under<br />Nonequilibrium Conditions.<br />Abstracts of the Lunar and Planetary Science Conference, volume 20,<br />page 666, (1989).<br />"An experimental study was carried out in a 2.4m by 4.9m cylindrical<br />vacuum chamber in order to investigate the possibility that martian<br />outflow channels were formed by the melting of ground ice. Frozen<br />soils that were subjected to an increased geothermal gradient at<br />temperatures about 273K and at an average pressure of 8.38 mbar,<br />melted and formed water-filled depressions and outflow channels. The<br />depressions formed as a subsurface ice layer thawed. Water initially<br />appeared at the surface either during gradual collapse of the surface<br />material or as geysers. The mode of appearance of water at the surface<br />was a function primarily of the strength of the ice and the<br />temperature of the water vapor."<br />http://adsabs.harvard.edu/cgi-bin/bib_query?1989LPI....20..666M<br />[full text] <br /><br /> In regards to the south polar "spiders" and the deposited fans, what is interesting is that the experiments showed geysers could result as well from ice turning to liquid and gas under an ice cover. Whether the result of the subsurface melting was channels or geysers depended on the strength of the ice and the temperature of the water vapor.<br /> In the case of channel formation, the report's description of how they formed suggests this could be similar to how the south polar "spiders" form: <div class="Discussion_UserSignature"> </div>

 

[exoscientist]

Andrew, by using the IAS viewer I used to be able to look at a full resolution HIRISE image even if it was gigabyte size by the viewer just streaming the image, i.e., by its only downloading that part I was looking at at the time. However, this streaming feature doesn't seem to be working now. I would have to download the whole hundreds of megabytes to gigabyte size image, which I can not do because of lack of space on my hard drive.<br /> Are you able to stream the full resolution images or download the full resolution images? <br /><br /><br /> Bob Clark <div class="Discussion_UserSignature"> </div>

 

[arkady]

Same problem for me. <img src="/images/icons/frown.gif" /> <div class="Discussion_UserSignature"> "<font color="#0000ff"><em>The choice is the Universe, or nothing</em> ... </font>" - H.G Wells </div>