Planet Four Talk

Deposits on dunes/in grooves

  • Peek by Peek

    Maybe I'm just stating the obvious here, but I'm guessing that the fan in the upper center part of this image has deposited dust over an area that is full of dunes and grooves. At the edges of the fan, where less dust have reached, the dust have mainly deposited on the ridges of the dunes, or is that the bottom of the grooves?
    The same on a larger scale on the lower part of the image. Looks like the outer parts of a giant fan/blotch that has deposited a thin layer of dust on a network of ridges/grooves.

    Have I understood this correctly, or am I just wildly off?
    Mainly writing this because I'm curious and trying to understand the images. So I guess the whole post is a question, really... 😃

    Posted

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

    Hi Peek,

    Pretty much spot on. For some people it can be hard to tell depressions from ridges because we don't always show the images the way our eyes are used to sun direction coming from so our brains can flip ridge to groove and vice versa (so if you flip the image it might look like grooves. The fans are created by dirt and dust being brought up carbon dioxide geysers to the top of a translucent ice slab that's covering the area. The channels are carved slowly over time by the carbon dioxide gas before it escapes. You can learn more here on your blog.

    Cheers,

    ~Meg

    Posted

  • Peek by Peek

    Thanks for you reply, Meg, and for the link.
    I know about the "flipping" of images that can happen, so I always wonder, when I see images like these, if I'm seeing them the right way or not.
    It's easier when there's an impact crater in the image. If it looks like a dome, then I know I'm seeing it the wrong way. 😃

    Posted

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

    Hi Peek,

    Eventually if we ever get funding to rebuilt the site, we could add the sun direction as a marker, and people have expressed wanting to know the sun direction when classifying. Unfortunately it's not something we can add into the current interface, but if we get developer time for a version 2.0 then maybe it can happen.

    I'm mostly in the percentage of the population that don't see a difference, so it typically looks like troughs or peaks no matter how I rotate the image.

    Cheers,

    ~Meg

    Posted

  • p.titchin by p.titchin

    Hi Peek. if you look under the image we are talking about, you will see that the subsolar azimuth is given (in this case 34.7087 degrees). This indicates the drection of the point on mars where the sun is directly overhead and so effectively gives us the angle the light in this image is comng from .it is measured from '3 o'clock' on the image, and so in this image the light is comng roughly from the lower rght corner (not as we are used to) so we will tend to see ridges as channels (and vice versa) in this image. Hope this is of help.~Pete

    Posted

  • mschwamb by mschwamb scientist, translator

    Thanks for bringing that up Pete. I forgot we had a blog post about sun angle.

    Cheers,

    ~Meg

    Posted

  • Kitharode by Kitharode moderator

    Well done everybody. The blog post mentioned above is also on the FAQ board, in 'Useful Posts on the Planet Four Blog'.

    Forgive me for plugging my own posts, just couldn't resist 😃

    Posted