Planet Four Talk

havin the darnedest time

  • Mote by Mote

    If the light source is from the bottom right, then that's a good lookin' boulder. Its' shadow matches the miniscule crater at the very bottom of the image, just left of center. To start, I am seeing three distinct areas of color variance in this image, the right side is red, the left is grey, the center seems to have a white plume dusting from the boulder to the bottom. 1) Which of these three parts is the surface that is dusted with another material, and 2) which is the surface material being exposed through erosion? 3) Why does the rest of the image appear to have an opposite light source of the boulder, i.e. no other shadows 4) If the light source is bottom right then the other dark-as-shadow spots are either exhaust plume (blotch), or dust that has blown from the bottom center, correct? 5) The top left quarter of image has a light colored thin line with darker sides oriented at a diagonal from top left to bottom right, is this feature a channel, a ridge, a subsurface gas tube, or a surface discoloration? 6) Intersecting this linear feature is what appears to be a darker trough with light edges, being that there are no shadows past the boulder, what are the dimensions of the surface on the left side of the image, i.e. how deep is that trough? 7) What luminescent effects are possible in the material in this image (fractoluminescence, phosphorescence)? 8) Is the rock actually the brightest reflector in this image ( I cannot judge by eye if the other, smaller bright spots have the same brightness)? 9) Which is shadow and which is plume, comparing the boulder with any of its' apparent opposites? Finally 10) I would love to do this all day for the rest of my life, is there a way to get trained then paid to identify these images now? 11) What major should I study to be able to answer all of these wonderful questions?

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  • wassock by wassock moderator

    Oh want a lot of questions, will see what I can doo:

    1 & 2) All of then to a certain degree and there's something like a meter of CO2 ice on top of the 'bedrock'

    1. you are looking at a landscape which contains a series of ridges, with the sun in a place that your brain isn't used to. To get a better idea of what is going on take a look at the Hi-rise images (click the link below the image here) - the grey scale non map .jpg is probably the best one to start with. The difference in shading is mostly down to shadows.

    2. ..................or they are actually depressions

    3. difficult to tell, can be that way some times, which is why it sometimes helps tohave a look at the larger picture from hi-rise

    4. The image scale is 25cm per pixel, which comes out at the smallest thing you can see on the image is about 70 cm. We used to work on the ‘an image is about the size of a football field type of scale. Most of the spiders are thought to be less than 2 meters deep.

    5. Good question – no idea I’m afraid

    6. solid ice which catches the light in just the right way tends to be the brightest thing in the image, but you have to remember that there’s a degree, of fiddling with the image gone on before you get to see it, to enhance the features we’re looking at.

    7. Shadows will usually be a lot darker than fan, Plume would be the column of ejecting material (if you can find one of those you’re on a winner). And I wouldn’t mark anything in the image as fan or blotch, think it’s all shadow.

    10), when you find out let me know so that I can sign up. I think that even the professionals involved in this project spend time on this when they can get time away from the day job.

    1. who knows – seems to me that there are more unanswered questions than otherwise at the moment, which is what makes it all so very interesting

    Welcome aboard

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

    Hi, Mote, I can add a little to Wassock's comments. Your image (as I'm sure you know, if you clicked on and looked at the HiRISE image for the clip) comes from Inca city. I think I've located this one to the lower end of a long ridge running from top to bottom of the image in the lower third of the HiRISE RGB colour strip. This means that objects to the left of your image will be on the downslope of a ridge, and will not be directly lit by the sun. Those on the crest, and to the right are directly llt and so show an apparrent higher albedo. Several boulders towards the crest show distinct shadows, and the hummocks on top of the ridge give shadows that can look like vented deposits, or hollows on the 'lee side' of the ridge. The ridge runs from just right of centre at the top of the image to left of centre at the bottom edge, and gives rise to the colour change, and suggestion of a longtitudinal hollow on the left. It is the unlit downside of the ridge. Hope this helps your image interpretation. 😃 Remember that the light comes from lower right, and our brains interpret light shining from above.~Pete

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  • Mote by Mote

    Thank you both very much. Your care inspires. On to the next!

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  • Kitharode by Kitharode moderator

    Apologies for late reply. Major broadband problems here in the hills of Todmorden. 😦

    With so many Inca City images coming through at the moment, I thought I'd mention my mini-paper on the region. There are lots of great images in the paper and I think it gives a good feel for the area. Cheers, Kith. http://talk.planetfour.org/#/boards/BPF0000008/discussions/DPF0000fj8

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  • Mote by Mote in response to Kitharode's comment.

    An exhilarating and much needed perspective has been provided by your hard work! Thank You Kitharode! (good luck with those hills, they look a bit taller than ours here in Fayetteville, Ar 😃 )

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