Planet Four Talk

Black Deposits

  • gerbs236 by gerbs236

    I'm wondering what all these black deposits on the surface are. They seem to be some sort of powdery mineral that gets blown by the wind. What are your thoughts?

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  • p.titchin by p.titchin in response to gerbs236's comment.

    Hi, here is the short version!!- hope it helps! These are the vented deposits that form the 'fans' and 'blotches' we are asked to mark. These are 'fans' and at this density we call this a 'fan field'. If you look at where they start you will see that they arise on narrow white channels we call 'spider channels'. (this image from 2007 shows a largely defrosted surface so the frost left in the channels shows them up as white) .In Winter the surface is covered in CO2 ice and as the sunlight passes through this in Spring it heats the darker surface subliming the CO2 and building up pressure which then vents forcibly through weaknesses in the ice layer.The force of this scours the surface and the dark surface material is vented with the CO2 gas. The removal of this material forms the spider channels and the 'grust' (rusty looking dust/grit) falls to the surface as a 'blotch (if no wind) or a fan (if blown along in a wind). You can read loads more in the past P4 blogs on talk/blogs but hope this summary helps. Good to see you on the discussion boards~ pete.

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  • mschwamb by mschwamb scientist, translator in response to gerbs236's comment.

    Hi,

    Exactly. Pete gives a great summary. You can also find more details on our about page and blog.

    Cheers,
    ~Meg

    Posted