Planet Four Talk

Please explain

  • ronsim by ronsim

    Just joined Zooniverse today. Please tell me why we have pics with different colours when Mars is called the red planet. Why are not all the pics red like on tv. In fact i hardly see any red pics.

    Posted

  • AUricle by AUricle

    There is plenty of (rust) red to be found. Our images are from the South polar region, and so the 'surface' you often see is the seasonal carbon dioxide ice sheet which "melts" to CO2 gas in the late Martian spring and summer (each Martain 'season' is about twice the length of a similar 'Earth' season.

    Generally speaking, depending on the lighting angle of the sun, the white is the ice-sheet, bluish to white could be a fresh layer of CO2 frost or snow, and the gamut of orange-to-brown and black is the surface dust or dirt (called regolith).

    The image at left here is a vent in the CO2 ice-sheet (black hole) The CO2 gas builds pressure under the ice, because the ice is 70% transparent, and the solar energy received on the surface warms the underside of the ice-sheet and the surface, which "thaws" (actually 'sublimates' is the correct term) which becomes CO2 gas. This creates pressure which seeks a weak spot in the ice. The vent is the point where the gas breaks into the atmosphere. This gas often carries loose regolith up with it and this dust( orange-to-black) is what defines the fans and blotches. The blue-ish stuff is the gas that re-freezes when it his the 'air'. It falls back to the surface of the ice-sheet as CO2 frost or snow. Because it is lighter than the dust, it often 'out-flanks' the fan or blotch creating a sort of 'outline' to the feature. Include this in your marking dimension.

    Now for the kick in the teeth.😉 ....... Almost every image you see is lit from the lower right (opposite of what our brains are accustomed to seeing) so when you think you see a bump or raised feature, it's really a depression or hole. Sometimes you'll see what look like raised 'veins', but they're really channels cut into the surface. Somrtimes you could be staring at the image, and it will 'flip', so that you see it as it really is, and then if you move your eyes over the image, it'll flip back to the 'wrong' view. It's really wild!

    To see most images 'right' you can download the image into a simple photo editor and rotate the image 180 degrees and voila!... the image is "right". This sounds dis-concerting, and it is, but you can mark the fans and blotches in the wrong orientation without fear. They won't change, regardless of how your eyes percieve the topography. Whew! That got long-winded!

    Anyway, the short story on the image at left is; a long dark central fan of dust (most likely wind-blown) surrounded by a broader but shorter fan of frost, on top of the ice sheet.

    Posted

  • AUricle by AUricle in response to ronsim's comment.

    ronsim,

    If you've survived my tirade, visit the Planet Four blog here; http://blog.planetfour.org/ and just read what the scientists have written. It will explain alot about what they think is happening in the region of our images.....and they're not as 'windy' as I was 😉

    Posted

  • wassock by wassock moderator

    Plus the images have I think been fiddled with a bit to enhance the contrast of the fans so wht you are seeing isnt always 'true colour'. The cameras work through 3 different colour filter sand some images have one or more filters absent, sometimes by design and sometimes due to a glitch.
    Theres a surprising amount of green about as well as the blue, but also quite a lot in various shades of red

    Posted

  • Portyankina by Portyankina scientist

    Hi there!

    Looks like especially for you today: http://blog.planetfour.org/2013/03/05/lets-talk-about-color/ - we wrote an explanation why our images are so colorful. Enjoy!

    Anya

    Posted