How old are the spiders

• by wassock moderator

  Have a look at this from the HIRISE site https://dl.dropbox.com/s/tspq3qn1a4gswc7/Spiders.jpg
  I'd have put these as being somewhere on the juvenile spider scale somewhere?

  Posted February 9, 2013 2:06 PM

• by wassock moderator

  OK sorted this embedding stuff out, so we have - Not fully formed spiders?

  

  Posted February 9, 2013 2:09 PM

• by wassock moderator

  Now have a closer look at the crater, top left.

  In general the spider channels tend to run top right to bottom left, and it doesn't take too much to see that there is a channel that would continue across the crater.
  No idea of how old the crater is but it doesn't look all that fresh
  The size of the severed channel is consistent with all the other ones which begs the question, were all the channels already formed when the crater formed? If not have they all continued to grow at the same rate, including the severed one. If we conclude that the channels were already there when the crater formed, and it's been a while since, then we may need a new theory for where the channels come from.

  

  Posted February 9, 2013 2:28 PM

• by wassock moderator

  The area is active with fans - bigger picture of the area the pics above were cropped from.

  

  Posted February 9, 2013 2:31 PM

• by wassock moderator

  There are scale bars on all the above images but they've got chopped off - The crater is about 50 metres across and is more or less central about a fifth of the way up in the big picture

  Posted February 9, 2013 2:35 PM

• by AUricle in response to wassock's comment.

  wassock,

  Where is Paul Johnson when you need 'im! He'll want to see this.

  That's a great shot. My guess on the 'crater' is that it's one of the holes we've been calling Pingo's, and not an impact crater. It is great to be able to look into it and see the entire structure without any shadows or ice mucking up the view. Good find!

  Posted February 9, 2013 4:06 PM

• by Paul_Johnson

  Hey ...? What....Where.....?

  PINGO AHOY!!!

  Posted February 9, 2013 4:09 PM

• by wassock moderator

  There origin of the hole's not the issue only if it post dates the formation of the channel it cuts.

  Posted February 9, 2013 9:26 PM

• by michaelaye scientist

  Craters usually are vastly older than spiders. It has been estimated that spiders are in the area of thousand(s) years old, while this crater, not looking fresh at all, most likely is in the million years category. So, unless I misunderstand your hypothesis, I don't think, the spider model needs an update here. But if I'm missing something here, please explain further your chain of thoughts.

  Posted February 16, 2013 4:23 AM

• by AUricle in response to michaelaye's comment.

  Michael,

  I think the question is really "what came first, the channels or the crater-like pit". Personally, I think the pit probably was a vent site for the channels. In other words, they formed together.

  Off topic,...... but how do you feel about the possibility of liquid CO2 in the channels and percolating into the dust, as opposed to the current gaseous model??

  Posted February 16, 2013 4:37 AM

• by wassock moderator

  The line of enquiry is simply that in a terrain of channels with reasonable consistent orientation and which are fairly continuous we have what looks like one of these channels broken by a crater. The crater itself has a small spider within it, but it's much smaller than the features round-about. This makes it look like the crater was formed after the main channels had formed.

  Posted February 16, 2013 9:35 AM

• by Portyankina scientist

  Hi!

  I wanted to comment, that the crater you are looking at is rather old, its outer rim has completely relaxed into the sub-surface ice. And the spider channel runs right where the outer rim might have been long ago. So, the crater came first.
  With polar craters is hard to estimate their age, it depends on the exact percentage of water ice to regolith in the subsurface. Which is hardly known for most of the places.

  Anya

  Posted March 5, 2013 3:07 AM

• by wassock moderator

  Anya, I had the crater down as old, I just think there's something to be learned here somewhere maybe from the answers to the following:

  If the crater predates the surface channels/spiders why are the spiders in the crater so much smaller than those around it? - This could be as simple as the surface at the bottom of the crater is just harder.

  Why do the channels either side of the crater just stop there? There doesn't seem to be any evidence of erosion/gas flow from the crater to the channel - does that fit with the formation of spiders model?

  This is an area featuring series of channels which are formed with a fairly consistent orientation and a degree of continuity. What is it about the way they form which means they don't care if there's a big hole in the way. More examples of the same needed to see if this happens often.

  Just to ask the obvious idiot question - have you actually got any evidence to show that the CO2 venting is growing spiders, like a new channel that wasn't there last year? Has the possibility been looked at that the spiders are actually ancient? Perhaps caused by water action (melt water?) in the very distant past, which is what they look like, and that the vents are just exploiting a feature that has 'always' been there?

  Posted March 5, 2013 12:58 PM

• by Kitharode moderator

  Wassock. In your third post (page 1) where we "have a closer look at the crater" you say "In general the spider channels tend to run top right to bottom left". I'd have said they run the other way, from top left to bottom right. Is this a glitch on your behalf, a flip of the image, or I'm seeing it wrong?

  I've tried hard to 'see' an old crater, but for the life of me I can only feel comfortable with a 'collapsed surface' - a sinkhole, I guess. Absolutely no evidence to support this view, but whereas I can visualise a spidery suface sinking to form the image you showed us, I can't visualise an old crater ending up looking the same. I'm happy to be proved wrong.

  Re your 'idiot question'. I'm sure that was answered elsewhere recently and I'll post it if I find it again. If memory serves, there is no real evidence yet that spiders are growing now (therefore could be ancient) but over time, with more images(?), it's expected that the evidence for growth will emerge. That's not a quote, but I think I'm close enough.

  Good subject and I hope you get more answers.

  Posted March 8, 2013 7:14 PM

• by wassock moderator

  Kith you have it right, case of not knowing A from elbow. I've started a whole new thread on the idiot question, see Heresy

  Posted March 8, 2013 8:58 PM

• by hnavas88

  This crater are believe that they have formed as ancient rivers transported water and sediments to the central pit. how did they get a water source? well it is still under investigation but probably one of the reason was precipitation as a significant contributor. this website has a good source of information about the crater like pit:
  https://planetarygeomorphology.wordpress.com/2014/01/01/fluvial-channels-in-central-pit-craters/
  How old are spiders?
  It seems that becouse of sublimation of Mar's seasonal CO2 ice cap and a distinct seasonal evolution, I provided this article if you want to check it out:
  http://ashimaresearch.com/wp-content/uploads/papers/Piqueux_JGR2002JE002007.pdf

  Posted January 19, 2015 12:31 AM

• by wassock moderator

  Welcome hnavas, I suspect you may draw more questions than you can handle 😃

  This bit is from the 2nd paper

  [19] Notably, all occurrences of spiders fall on areas
  historically mapped as polar layered deposits [Tanaka and
  Scott, 1987]. No instances are observed on the residual cap
  or in the surrounding cratered highlands.

  We've been looking a lot at Inca City recently which we'd been thinking was not on the layered deposits - plenty of spiders there though. (I realise the paper is a dozen years old now).

  Posted January 19, 2015 11:00 AM