Planet Four Talk

At the edge of the ice

  • wassock by wassock moderator

    If I'm reading the HiRise description right ( http://www.uahirise.org/ESP_039538_1005 ) and interpreting the image correctly then this spider is right against the (receding) edge of the permanent ice cap.

    North is at around 10:30 and the sun at ~ 8:00 (ish) (225 and 159 degrees respectively, from 3:00) and we're at a longitude of -79

    enter image description here

    At first I assumed that the 'tongue' was the ice cap (as it's south of the smooth bit) and the smooth surroundings the ground. Looking closer it appears it's the other way round - smooth = ice and rough = ground

    enter image description here

    The ice (smooth) shows some blotchy fans and some polygonal cracking but no real spiders (that I could find)

    enter image description here

    So if I have the reading of this right the large spider underneath this dark blotch has formed in the time that the cap has taken to recede the 150 meters or so that it covers. How longs that Meg? (unless it was there all the time and has been revealed by the receding ice)

    Posted

  • wassock by wassock moderator

    Oh and I found this dinky little crater (~8meters) on the ice

    enter image description here

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Hi,

    Anya, Michael, and Candy would know better, but I can take a stab. I'm trying to follow the conversation, so forgive me if this isn't discussing the right thing. There is still black blotches in the images. The contract comes because of the semi-translucent ice sheet being present. When other areas are defrosted you don't see the black anymore. That's why it's though the material making the fans is the regolith right under the fans. In the spider you show, it's all covered in black, so to me it looks like it is ice covered.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator

    Hi Meg. I'm reading what is writ. The image shows the edge of the , permanent , ice cap. And the blotches are on the regolith, formerly covered by the permanent cap, which now gets a seasonal ice layer through which the blotch forms, making a spider in the process. If the permenent cap is receeding, and we know how fast then we know how long this spider took to form. So wgat I'I'm trying to get from HiRise is confirmation that I am looking at what I think I am wrt the permanent cap.

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Hey Wassock,

    I don't know, but I'll see if I can get someone else on the science team to answer that question.

    Cheers,

    ~Meg

    Posted