Planet Four Talk

Bright fans

  • michaelaye by michaelaye scientist

    Hi guys,
    this beauty has several scenarios possible. The most favorite is the CO2 frost falling down after the compressed CO2 gas erupts from the vent that is located near the very dark spot source. But as it turns out, the models don't make it look very easy to actually create CO2 frost, so we are always considering other alternatives as well for bright fans.
    One other possibility that certainly happens at some places is a weird cleaning effect of the ice, most like created by the dark fan deposits! We believe that the increased solar absorption can make some of the dark dust sink through the ice, and while doing so, reshaping the ice crystals in a way that makes them much more reflective for sunlight. So that's another one.
    But even without sinking into the ice, one could just imagine a slight thaw by the dark dust on the ice followed by some stronger winds to remove a previous fan. The thaw again reshaped the ice to potentially make it brighter. One difficulty in all these interpretations is that CO2 ice is not yet completely understand, partially because it is not easy to create under the Martian climate conditions which are: 6 mBar pressure. So one needs a vacuum chamber to really recreate the conditions on the Mars' surface.
    Thanks for all your enthusiasm and for your help in getting us further in understanding the crazy poles of Mars!
    Cheers,
    Michael

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  • michaelaye by michaelaye scientist

    Oh, and btw the potential shadow of an currently ongoing geyser or jet while illuminated from a low sun also always gets me visually, but there are 2 to 3 reasons why this is, alas, unlikely to happen (but not excluded!): 1. the observations are all very strictly from above (within a certain precision of course), so no angles whatsoever can cause any appearances. The next reason is that our current models show that it is more likely that these jets occur very fast and don't last long, which reduces strongly the probability of catching one while flying over its head. The last point is that the same models also predict that those jets most likely occur in the mornings, while the HiRISE camera on the MRO satellite mostly observes data on the local early afternoon (ruled by orbital mechanics).
    But please, that should not stop you from looking out for active jets. THAT would most certainly be one of the highlights of this project if we could identify with certainty an active jet, but don't get too disappointed if we tell you it's not. As I said, it's quite unlikely.
    For low angles sun and their shadows we can check by the way, as we know where the sun was at the time of the image and we certainly will do that for the weirdest fan candidates that somehow look suspiciously active.
    Thanks again, and happy classifying!

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  • jules by jules in response to michaelaye's comment.

    Cool that this got a mention on BBC's Stargazing Live!

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  • JellyMonster by JellyMonster

    The wiggly veins in some images are meant to be channels. Rotating the image through 180° corrects this. Small pits/craters become rocks/boulders... try it and see.

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  • Hakaeh by Hakaeh in response to JellyMonster's comment.

    interesting, my brain just switches between positive and negative as it pleases... not much i can do to influence this.

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  • Hakaeh by Hakaeh in response to michaelaye's comment.

    Image APF0000wxx

    this one looks like a cast shadow of an ongoing eruption, but I guess it's not.. could be that wind has changed and so has the material which has been dispersed?

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  • JellyMonster by JellyMonster

    Hakaeh, can you see both positive and negative images from a photograph that has not been rotated? Try it on spiders (veins) as they are meant to be depressions.

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  • Hakaeh by Hakaeh in response to JellyMonster's comment.

    JellyMonster,
    that works on almost all pictures with good light in them.. especially the ones with boulders. Most spiders i have seen are quite dark, so don't have it there so much... But it is very weird to see ridges/boulders one moment and after blinking with the eye they have become dents/holes..=] Especially after hours of classifying...I should go to bed

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  • JellyMonster by JellyMonster

    I made up a few examples here, just scroll down to Mars mission... http://the-orangery.weebly.com/

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  • Hakaeh by Hakaeh in response to JellyMonster's comment.

    they are all positive and negative, but I do have to look at them a few times. Exception is the white one, I cannot switch once one has become positive or negative. Have to close the window or look at something else! =]

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  • JellyMonster by JellyMonster

    Thanks for looking. I think the first picture (with lots of fans) is the best example. It turns something that looks like a sponge into something more credible.

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  • AlbionStarDestroyer by AlbionStarDestroyer

    See, i had my suspision that "frost" was actually copper sulphate

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  • rowbumby by rowbumby in response to michaelaye's comment.

    would you be able to give us a example image of a active jet please

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  • Portyankina by Portyankina scientist in response to rowbumby's comment.

    Hi!

    I can answer the last question instead of Michael: no, we can not 😦 We never got one. There are many reasons that can explain this: they activity time might be very short, like minutes and we never hit it. Or they are always go off in the early morning, while our spacecraft is locked in 2-3 pm orbir (i.e. place we are flying over is always at afternoon local time). Or they are too diffuse to be detectable with visual camera and we need some kind of laser instrument to detect them.

    Anya

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  • Portyankina by Portyankina scientist in response to rowbumby's comment.

    Oh, just to add: we are still trying to get them. We sometimes do imaging with stereo on consequent orbits (i.e. several hours apart by tilting the spacecraft strongly). We can not dot his very often, it's a complicated move for the team to plan it, and so far we have got no success to argue to repeat it often.

    Anya

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  • Hakaeh by Hakaeh in response to michaelaye's comment.

    Hi Michael,
    I have Been constantly mulling about the bright fans and where they come from/how they develop. Looking back through some collected images, I believe that the white fans occur after dust fans. An example: Image APF0000obl
    It looks like the white fan is overlapping the dark fan.
    I think that if a vent has blown out the gas/dust mixture then clogged up the vent ( not entirely sure how maybe re freeze ) and the sublimation starts again creating the gas to rise pressure and open up the vent a second time. BUT this time the gas did not mix with any dust as it has been blown out previously?

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