- Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
Long comment follows. Since this was my attempt at visualising the minutiae of matching 3d surfaces from a written explanation from A Cooper, and his scute blog has done that rigorously, this is the explanations from the original ESA comment, that has been already expanded on. Short of ESA releasing names for all these features, we are stuck with wordy descriptions, coloured points and numbers.
Here are all the things that I've been meaning to say for the last few days. I should've copied the original comment and reposted but this comment has more thoughts and questions anyway so here goes.
The numbered line you have (1-10) is pretty accurate. The only place it went off slightly is in places where I'd made a mistake myself or it was not explained very well. I shall adjust them one by one below with my reasoning. Most are correct or very close.
3) correct - spot on. The other side of the lump it's next to is where the last dot of the line in my Part 2 is positioned, the fuchsia dot.
6) not quite. My fault. I can see you are following the nicely demarcated apparent shear line as I did. Although it was where the real rupturing happened, it took the adjoining rectangle with it. The perimeter of this rectangle is:
from the correctly positioned '5' hug your way round the mound next to it with the two pimples as far as the longest prong of the three-pronged fork. Travel straight up the fork. Follow the wavy line above it into the shadow. Just as a check- part of that wavy line looks, by coincidence, like a faded '5' just to the right of the pointed shadow. The left hand edge of that faded 5 is one tip of the seagull wing and the '6' is over the other tip. So 6 is on the line after all but only by chance and out of sequence.
7) needs to be shunted over to a point in line between the 6 and the 8.
8) correct. The 8 is actually positioned on the very edge of the head in the foreground but the shear line does run under the head at that point from this camera position's point of view.
9) correct. But I'm now wondering if this should be a bit further up the little ridge. I can match those little dips in the ridge to the line of dips at the right of the cove in the head but the head ones go further and tip over. Then I realised that the two strange curved rocks sitting on site A had almost certainly come from the continuation of that ridge just off frame to right. One appears to fit into a divot in the side of the ridge and is in keeping with the shape of other formations on the ridge as seen from above. Once in place though, I'm not sure it stretches far enough into this photo to marry to the ridge above. Of course, this is all fine detail. The two ridges almost match and this area around the 9 is getting close to where things get very unclear because just beyond it there should be no matches if a giant slab went missing. Before this point the matches are so evident that the missing slabs they were married to must have been thin. Site A looks deeper and much more catastrophic which is why....
10) I don't think the head sat quite here. Although this edge that the 10 marks is clearly a shear line, I think the head sat in a line that would mean shoving the 10 to the left till it's just under the actual head in this image. So if the 10 is marking an obvious shear line but isn't where the head sat it means that the giant slab took with it part of the material from this section of the trench, attached to its underside (that's if you buy into the slab theory. I don't expect you to but I seem to remember some positive feedback).
I may be wrong about the 10. But from most angles I can't quite stretch the head rim back to the crater rim in my minds eye so as to seat it down. It always comes up short, cutting across the low trench of the neck before meeting the ridge by the craters for its next likely match. This of course is evidence for a thick missing slab. All the matches are on another chunk flying round on the same orbit! Then again, your picture with the yellow line looks plausible at this point on the perimeter.
I think the yellow line is perfect where it zigzags at the right. At the left end where it almost appears to kiss the head, it needs to be erased a short distance to where the curve starts and turned to run along the dark strip to the end. Then sharp right at the end of the dark strip, over another dark strip and out of view.
The yellow line goes through the rectangle but your yellow dots straddle it at an angle and end up in the trench. If you look at the picture in my Part 5 that puts a green dot on each corner, you should be able to relate it to your picture because the lighting and distance is similar (although it's viewed from a different point.
The green line is in the trench. You may be thinking of the scalloped triangle edge which would be where the gull wing profile is. That is to be found under the end of the longer yellow line in the yellow V. This denotes one end of tbe rectangle.
You can see the two semicircular formations peeping out from under the yellow line, which sit against each gull wing. I believe this is dried slurry that was being forced through the stratum layer and pushed up the gull wings. They obviously continue underneath if they fit perfectly at the exit aperture.
In fact, I believe that all those lines that form the V and the rectangle and the s shape up to your first yellow dot are slurry residue from the exit fissures along a slab that is long gone. This is because they all resemble the one along the back of the rectangle which has very good evidence of being a slurry residue line (it pushed up the frilly edge of the cliff).
Also, I noticed that the only real sublimation activity on the head seems to be in the five craters just above this point. I'm wondering whether this was where the shearing started and the tear worked its way round the perimeter from here. This is typical of many failures like exploding gas canisters. They tear more than explode like a bomb. But there is a momentary explosive rupture before the tear starts. This is what we may be seeing here in this small area.
I left a comment on the 14th December Rosetta post in reply to Robin Sherman regarding all this. I was suggesting a scenario involving explosive sublimation but seeing as I know nothing about sublimation explosive or otherwise, feel free to take a look and correct me!
Seeing as I've nearly got as far round as site A, have you got any ideas why it's so flat? I know one can say it's thicker dust or if there was a slab there then it was fracked by gases underneath and it's a smooth stratum. But it's so absolutely flat it puzzles me especially when there's evidence of chaos all around it.
I'm sure there's evidence staring right at us and we're staring right at it and yet not seeing it. It took me 3 months to realise the gull wings were pushed up but I'd puzzled over those two little semicircular splodges every time I passed over them on my way somewhere else. Same thing with the rocks on site A and the boulder at the back. Now that I fully accept the lobes were joined I'm seeing more things which follow from that, things which you couldn't notice if you were stuck in contact binary mode.
I tweeted Phil Plait the 'Bad Astronomer' blogger. He sounded very interested but has now gone silent.