Is it just an Ilusion
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by
wassock
moderator
THis is from a HiRise image that most will be familiar with - It's where a lot of the Blue Fans come from:
Its a merged RGBimage, the strip down the center is the rgb bit and you can see the edge of the area running across the image. Within the area we have blue fans outside just black/grey fans where, presumably, there are also blue bits occupying the same positions on the other fans. But in the non-RGB bits there's nothing really there to suggest there's anything out of the ordinary (Blue). So is the blue really there or is it just some sort of camera illusion?Note also that there are some fans associated with the fledgling spiders but many more spiders and fans which are not so associated.
URL for the image is http://hirise-pds.lpl.arizona.edu/PDS/EXTRAS/RDR/ESP/ORB_020500_020599/ESP_020597_0925/ESP_020597_0925_RGB.NOMAP.browse.jpg
Posted
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wassock
moderator
As is usual when one starts looking closer at these images,one question leads to another take a look at the parallel line running up the image above - so a bit lower down we have this area:
Which has 2 different types of crack formation, one which has fairly well defined rectagonal features which extend up into the first image and a second polygonal crack system, with associated fans which overlies the rectagons
Posted
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Kitharode
moderator
With so many blue fans being seen in so many images I can't see them being a camera illusion. My thinking is that if they were, then surely by now the science team would have let us know (?).
'Rectagonal' - Is that a real word? If not, it should be. I've got the rectagons as surface features, with ice-polygons on top.
Yep. Spiders/fans, spiders/no fans, fans/no spiders. Hmmm .. I'll pass for now. ** 😃 **
Posted
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p.titchin
in response to wassock's comment.
another thing that has puzzled me in the images of this area are the 'sink hole' like features on the RGB strip. They are not associated with either the 'rectangular' lines, or the polygonal cracks, and I can't see any associated venting. Any thoughts? ~Pete
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Kitharode
moderator
in response to p.titchin's comment.
I'm guessing your 'sink-holes' equate to my 'mites' discussed elsewhere (?) Currently I'm into a bit of landscape study on Mars, early days and no conclusions yet, but I'm beginning to think that these 'mite-like' objects are only to be found in very smooth areas. To put it another way, I'm finding it hard to find mites that are not on smooth ground.
I now look forward to an avalanche of images showing mites on bumpy ground. ** 😛 **
Posted
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mschwamb
scientist, translator
The blue is real though (as Anya and Michael have mentioned color isn't quite the color we would see if we were looking at the surface of Mars when looking at RGB HiRISE images). Also I think the exact color might change depending on some imaging parameters and other things. It's one of the reasons it is not a task in the decision tree to spot blue fans/blotches. It is going to show up in the grey scale images but we just as a grey or lighter black which it looks like to me, but yes hard to distinguish them from the dark black features if there are no color images.
Cheers,
~Meg
Posted
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wassock
moderator
Meg
Underlying issue with the blue images is that they are almost all from December 2010 (9th and 18th mostly) and I have seen very few from other years and even fewer that are as 'good' as the 2010 ones. I'd like to understand why that is and also what we are actually looking at when we see the blue colouration (which is purple in the IRB renderings of the same images) If it is ice why do the blue bits look exactly the same as the black/grey bits in a non rgb image.
We've been here before I think but the question remains,what is causing the blue colouration?
This all ties into the white fan thread running elsewhere.Posted
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p.titchin
in response to wassock's comment.
Seconded. Im getting more and more concerned by the relevance given to colours, when we know they are manipulated. We all probably remember the old mistake because the sky was expected to be blue, not pink.. 😃. I'm looking at the 'greyscale' more and more.~ pete
Posted
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mschwamb
scientist, translator
in response to wassock's comment.
It's likely one or two things. It's frost/ "light snow" from the geyser at some point or what we're also seeing is that it is the particles in the fans sinking into the ice, changing the ice. The ice recystralizes differently and that's what is producing the color difference. So definitely for fans and blotches with lighter halos that are lighter (not always blue -I think the color may change with observing angle) we think it's the older particles sinking into the ice. Likely both mechanisms are happening on the surface is my bet (though probably not on the same fan/blotch).
This one (APF00001qc) has blue and is from 2009 - there is blue at other times.
Also the strength may change from season to season. The seasons likely have different ice sheet thicknesses. There was a dust storm in between season 1 and season 2. So it may not be so surprising that there is more blue frost features one spring/summer than another. I'm not sure if someone has looked at that.
Cheers,
~Meg
Posted
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wassock
moderator
in response to mschwamb's comment.
That one has blue halos not the clearly defined blue fans that we get in the 2010 images. What are we actually looking at? Are there actually big blue areas on the surface or is it some sort of texture/refraction/reflection effect that we can turn blue by 'turning up the gain' on the camera filters?
Think this is linked to the formation of white fans, see here http://talk.planetfour.org/#/boards/BPF0000001/discussions/DPF0000fzvPosted
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p.titchin
in response to wassock's comment.
You are expressing my concerns. Shouldn't be a problem to give an answer between the parameters of ' current thought.-- don't know--Looking at it-'
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