Planet Four Talk

Heresy

  • wassock by wassock moderator

    Is there any observational evidence which supports the theory that the spiders are caused by venting?

    Just to stir the pot a little I would make the following observations/wild speculations:

    Fans appear all over the shop on lots of different types of terrain, some of these terrain types feature spiders and some don't.

    Even in spider country fans often appear not to be associated with a spider.

    Spiders look like they have been formed by flowing liquid. There was surface water a long time ago and other features caused by it are still visible. Can it be shown that they are a fairly new feature or could they be truely ancient, dating from liquid water times?

    There doesn't seem to be any evidence that spiders are growing now.

    Do we need the fans to form the spiders in order to explain how the fans work - would it make any difference if the spiders had just "always" been there?

    Posted

  • Kitharode by Kitharode moderator

    I hadn't realised until now what an interesting, and important question this was. We'll need a scientist to answer it. If there is some evidence or reason that 'proves' the current theory is correct (venting makes spiders) then fine, you'll have your answer.

    But let's say for now that the evidence is lacking and the spiders may well be ancient and 'always there'. Then you've got the makings of an interesting theory I think. If I read you correctly, you're suggesting that 'old spiders make new vents', or something similar(?) You've said elsewhere that existing spider channels could act as 'traps' for windblown dust. We've talked dust elsewhere and there's enough to go round.

    Ok science team - what d'ya have on this question....

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  • wassock by wassock moderator

    More that the vents don't care too much, all they are bothered about is a hole in the ice. You might get a bigger fan ecause theres a lot of gas in the spiders channels, and the spider may even get bigger as a result. But doesn't have to mean that is what made them in the first place.

    Posted

  • wassock by wassock moderator

    At risk of foot shooting I suspect scale may be my biggest problem with this line.

    Posted

  • Kitharode by Kitharode moderator

    Not sure what scale you're shooting your foot with, but getting enough water to do enough eroding to produce a small spider is something of a problem for me. Having said that, there are other ideas available that might work. I'm particularly interested in the reading I've been doing about 'ice wedges' here on Earth.

    I know it's very different on Mars, but many 'linear venting' images fit well with the idea. Check this out and see if you agree: http://www.wiley.com/college/strahler/0471238007/animations/ch15_animations/animation2.html

    Posted

  • AUricle by AUricle

    wassock and Kitharode,

    First lets use wassocks image in the "How Old..." as a reference point. Aside from the 'crater', the landform in general is delineated by a series of 'slumps' or 'scallops'. We don't really have an explanation of either form, so let me further "stir the pot". Note the terrestrial image below:

    enter image description here
    This is called a Thermokarst Failure. It is a slump in the Arctic permafrost caused by a process in which trapped carbon is converted to CO2 gas and released into the atmosphere. The whole ball of yarn is explained here: http://www.redorbit.com/news/science/1112782408/carbon-dioxide-released-by-arctic-permafrost-melt-021213/.

    As you can see from the explanation, water (one key component of permafrost on Earth) is involved in the process. Wassock, this could dove-tail nicely with your most recent "stir" using water to assist in formation of the spider channels. One other key element in the process is organic carbon in the soil, which is converted to CO2 gas.
    Now we're (or I am) getting "out there" with this, but if we believe that Mars was warmer and wetter in the past, maybe, just maybe, a period of time existed when organic material was produced cyclically on Mars,(yes life) setting the stage for a similar process. And perhaps that is responsible for the slumping terrain or the crater in the reference image???

    I'd have to imagine the regolith on Mars to be a very 'spongy' layer, entrained with much CO2 gas ( somewhat a frozen slurry ) so releasing the gas or whatever it is,(*please don't say liquidAUricle) into the atmosphere would provide the necessary space needed to cause the "slump".

    This could occur over time too.It would not have to be a catastrophic one time event. More recent colder temps would hinder the conversion process from happening quickly anyway

    Kiths spider channels could gradually provide the vehicle for sunlight to penetrate deeper and deeper into the substrate, warming ever lower areas, coaxing the release of more gas and furthering the slumping process (after all, this area is marked by a myriad of channels) So what say ye, gents? Has this spider got legs??

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  • Kitharode by Kitharode moderator in response to AUricle's comment.

    Hi AUricle. It'll need some thinking about (and I must eat something) but there's gotta be one leg in it at least. I'll certainly have a read of the article, just for interest if nothing else.

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  • wassock by wassock moderator in response to Kitharode's comment.

    Scale thing relates to the very small but well developed spiders.

    Cant see you link on my tablet, no flash, will look tomorrow

    Posted

  • Portyankina by Portyankina scientist

    Hi!

    There is no definitive proof yet that spiders are modified presently. By venting or otherwise.

    At the northern dunes however we have repeatedly seen creation of tiny channels (furrows) that end at the position where in spring we observed fans. This proved the ability of venting to erode the surface.

    Right at the moment we are executing HiRISE observational campaign to detect changes in spiders. We want to repeat observations from 2007 and compare those to see any changes. It is not that easy: 1) one has to observe spiders during southern summer to eliminate the seasonal effects; from the point of MRO orbit it's slightly harder to do than in spring; 2) the observation geometry must be exactly same as in 2007 images otherwise we will be fooled by shadows; 3) the changes that we are looking for are def. below meter-scale - we know this from furrows, which are typically less than a meter wide, so we need stable spacecraft+ highest resolution + closest point to the surface from orbital point of view + no atmospheric contamination. If we are lucky, we'll have estimates of how efficient the erosion presently is.

    There are some arguments against spiders' formation by liquid water. Even if they are presently stable and old, they are younger than period of warm-wet Mars. Polar areas and esp. polar layer deposits are young surface (you can compare the amount of craters there and anywhere else). Spiders do form on inclined surfaces and even cliffs while water erosion can not work against gravity.

    Anya

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  • wassock by wassock moderator in response to Kitharode's comment.

    AUricle. The slumps are caused by the previously frozen solid soil thawing to become soft, squishy, and more prone to erosion effects that it was when stiil as hard as iron perma frost. The process producing CO2 isnt the cause of this but is a consequence. Soil containing organic matter (including mammoths) is exposed to the air and all the microscopic wee beasties get stuck in for a spot of lunch, producing CO2 as a by product.

    On mars we have a particulate surface mixed up with mostly CO2 ice, even if there were organic carbon in there, you'd still need to find some bacteria to eat it. On mars at the moment, at the surface at least there is no liquid phase of CO2, on on earth for that mattter, so you either have a frozen solid lump or sand, wich may have rock and ice crystals in it. And the transition of a previously frozen solid surface to a heap of sand would provide scope for some slumping, and I read somewhere that Mars may be coming out of an ice age.

    NB I'm not proposing water having any role in spider formation as part of the current situation on Mars.

    Posted