THE SERQET-TO-SETH MATCHES (This is the third section of the sub series leading to proof of the head lobe stretching prior to shearing from the body)
Yellow, green and red lines- these denote the head rim and the body shear line where the head rim detached. The red line is for orientation only. It’s where the Part 17 matches take over from this post’s matches at the end of the green line. Other than that it’s irrelevant to this post. The green line dips inwards behind the yellow and red lines on both sides. This denotes a matching structure that is assumed to have run between both lobes when they were seated together. It’s more visible in the unannotated version, below. It’s coloured green to distinguish it as a feature but its front end runs along the head rim and shear line.
Two larger green dots on head and body- section along the perimeter of the structure mentioned above, which is easy to match (see the close up photos below). These two dots were already shown in Part 23 and when seated together they constituted the ‘three-way junction’ described in that part.
Yellow line- this line denotes the rest of the head rim and shear line for this part. It’s yellow because the prominent triangle and its set of concertinaed protrusions are in the middle and they have always been annotated in yellow.
Two larger yellow dots on the head and body- these denote the tip of the very obvious triangle on the head rim and its seating position, presented accurately here for the first time.
Two orange dots- a match within the yellow line. The body dot is set back from the yellow line but the head dot isn’t, even though there’s a distinct v-shape on the head rim too (see below). This is because the head tipped forward, away from us, before stretching upwards. This means that in this photo the head rim is presented much nearer to a side-on position like angling a plate so that its rim is viewed nearer to side-on. Indeed this trait is discernible for the entire run of both lines, head rim and body shear line: the body line is fatter, so to speak, and more curved because we’re looking down more from above to where the head rim ‘plate’ once sat on the body. This trait of complex perspectives creeping naturally into the match lines, as they are gradually plotted out, is a sign of the matches themselves being genuine. It’s a completely unpredictable and unavoidable artefact that becomes apparent only after the plot is complete. If random, pseudo matches were being made all over the comet, it would be impossible to do that while keeping the perspective from messing things up for you on the second or third match.
Two mauve dots- another match mentioned in Part 23, also in Part 22. The close ups in this post will now show it in more detail.
Light blue line- on the prominent yellow triangle. This is a crevice matching the edge of the block that the triangle detached from.
Some readers may detect some drifting up the head lobe to fudge a match near the mauve dot. There’s a reason for this being legitimate and that will become clear in the post after next.
This is a view from the middle distance before we dwell on the close ups. Everything is the same as in the key above. Zooming is needed as the dots are small so as not to obscure detail. This is as close as we can get while showing head rim and shear line matching in the same photo. It’s not the best of vantage points due to the head rim being even more edge-on than in the header. Toggling up and down between the two is recommended although it may be more instructive to see the close ups before really scrutinising this one. The only addition here is the imprint of the double ridge running away from the orange dot on the body. It’s running across the dust of Hapi towards the neck. This imprint matches the double ridge running up the head lobe from its respective orange dot thus proving that this structure ran through both the head lobe and the body lobe before separation. In other words it was a large, single, solid structure like the green formation described above. Indeed, both the head lobe and body lobe counterparts of the green formation and the blue formation above the orange dot, curve round parallel to each other as if loosely related.
This is a simple post concerned only with matches. It’s done in the usual style, with the corresponding head lobe and body lobe features demarcated in the same coloured dots. As usual, all scenarios are stated as fact so as to avoid endless qualifying of statements. Of course, the hypothesised scenarios may be wrong. However, this blanket qualification that’s made in each post is looking increasingly perfunctory due to the increasing availability of NAVCAM photos and the mounting evidence for stretch that they show. Apologies for what appears to be superfluous repetition in some places. It’s done to avoid the minefield of potential ambiguities when describing matches.
The prospect of more matches probably seems rather boring now, after 24 posts, but these ones aren’t boring at all. In the post after next, the fifth section of the sub series, all the evidence from the other four sections will be brought together. These four ordinary looking matches are key, not only to the process of head lobe stretch, but also the massive outgassing at the shear line (Part 7) the Hathor dykes (Part 8) and the removal of slabs A and E (Parts 9 and 23). It will also give a clue to the unique ‘dry mix concrete’ appearance of the neck at Anuket and the sudden demarcation line between that morphology and the completely different appearance of Hathor. So, having a good knowledge of these matches will help greatly in understanding the next two posts. The four matches will be referred to continually in several more posts after that, which address all the above issues as well as implications for Hatmehit and its missing slab.
The four matches were found by using the last available matches on either side along the head rim and measuring along the rim from them to these new specific points; then, the same distance was measured along the body. The last available points are very specific places on the shear line, not general areas. One is the top end of the so-called hollow block wall described in Part 18. It abuts the seating position for rock B in Part 14. The other is the end point of the red line matches in Part 17. Measuring forward from the hollow block wall and backwards from the red line served as a double-check, constraining the four new match points to the exact positions we see in the header photo. This means that these points were absolutely constrained by the previous matches hemming them in from both sides. There was simply no wiggle room to go trekking off across the comet looking for random, pseudo matches in any one of countless thousands of places where some vague similarity might be found. Instead, there was only one possible candidate location for each of the four matches. That means if the head lobe hadn’t detached from the body then the chances of finding small-scale matches when zooming into these completely constrained points would be effectively zero. So if we zoomed in and found no small scale matches to confirm our initial positioning, we couldn’t shift the entire shear line over to a new position where we might have found something that vaguely matched. If there were no small-scale matches, this run of the shear line would remain unmatched, casting some doubt on stretch theory. But of course, the expected small-scale matches were there.
As mentioned above, there are four definitive matches between the slab A extension (Part 22) and the three-way junction (Part 23). The two matches at either end were roughly annotated in the previous two parts but they’ll be firmed up in detail here. The two in the middle are the yellow-dotted head rim triangle, which hasn’t been given a proper body seating position before now, and one other wholly new match. In the higher resolution photos below, you can see that the matches aren’t single points but short lengths along the shear line with several mini matches within each one. The centre points of each short section have a large dot in their respective colour, larger than the ones forming the line they are part of. The main reason for dwelling on these central sections of each match and marking them with a larger dot is that they are all on or very near solid, rocky structures that are sticking out of the body at the shear line. Moreover, their head counterparts extend right through the head rim to its top side. This fact will become more significant in the next few posts.
The orange match is part of the yellow line because it wasn’t recognised as a strong match and part of a structure until much of the annotating was done. Otherwise it might have been set within its own orange stretch. Similarly, its two ridges are marked blue according to annotation precedent. They should really be orange, like the green structure, to show that the orange match is a structure that ran from head to body.
The whole section in the middle, between the yellow and orange matches has so many small-scale matches, often dubbed ‘mini matches’, that it is essentially one long match of about 500m. The stretches on either side (mauve to yellow and orange to dark green) are so constrained that the only viable runs they could make are along lines already scored out on the body that are very likely the imprint of the head lobe rim. The head rim has the same shape above these points, after all. There are a few tentative mini matches along these lines too but they aren’t as strong as the rest. Large chunks at either end have mini matches too so these small stretches in between actually constitute a third or less of the whole line in this post.
So it’s pretty safe to say that the middle half is definitively matched, along with the two end pieces, and that the whole line is or soon will be fully matched for the entire 1km-plus length. This section abuts the Part 17 red matches, making a roughly 2km line from the slab A extension (at the mauve match) to the south pole turn. There are matches along the south pole too but thus far the released photos allow only for large-scale matches. In fact, this post completes the matches all the way round the 67P shear line except for the section across the ‘amphitheatre’, officially known as Landing Site A, which has no solid matches due to missing slab A.
The whole shear line along the body for the four matches is shown below, including the two short sections with scored lines but no definitive mini matches. Much of this line has scree on one side of it and striations or scouring on the other side, which is aligned with scouring on the underside of the head rim rebate, above. That’s a clue in itself.
The following set of close up photos from different angles should make everything clear. They have the same basic key as the header photo and any additional information in their respective narrative keys.
Photo 4- shear line.
Mauve dots- in the distance at the end of the yellow line. These constitute the the mauve body match. The area enclosed by these dots is about the size of the single dot used in the low resolution photo above so this is much more detailed.
Light blue- same ridge and crevice as before but there is an additional line annotated in very small dots inside the dark green formation, behind the shear line. This will be shown on the head lobe close up photo too. The tiny isolated dot to the left of this ridge marks a rounded dip that is also replicated in the head close up. Zooming is required to see these- when dots are small it’s done so as not to obscure detail. There’s also a stubby pair of light blue lines beyond the shear line by the orange-dotted match. These correspond to a double ridge running up the head lobe from its respective orange dot (see photo 6).
Parts of the large yellow triangle are highly foreshortened due to the viewing angle but also due to the block of material sticking up with its top face running almost along our sight line. It’s worth toggling with other photos to resolve this issue. The 3D nature of this rising block appears to upset the neat 2D match as seen from the header photo. The paradox is explained by the fact that the large triangular protrusion that’s embedded in the neck below the head rim triangle, once sat abutting this block on its left side as we view it, forming a flat platform for the flat underside of the head triangle we see today. More on this in the next post.
In another apparent anomaly, the yellow line staggers to the left as it approaches us (between the larger yellow dot and the orange dot). That’s because it disappears from view for a bit before climbing up and onto the terrace that hosts the stubby pair of ridge ends and the orange match.
The stubby ridges match a slender, curved, double ridge on the head that will be seen in photo 6. They are dotted both blue and yellow. This is because the small triangle where they join is replicated on the head rim above it so that triangle constitutes part of the shear line and is dotted yellow. Beyond the triangle, the stubby ridges are dotted blue because they are outside the shear line. The ridge pair that matches these two blue lines will be seen on the head as starting ‘too’ high up and tapering together, vertically, to a single point plumb in the bottom of the corresponding v-shape on the head rim. That point is dotted orange in all photos, although the shape of the ‘v’ can change somewhat due to viewing angle. This weird behaviour of the double ridge starting too high up will be resolved in the part after next. It’s to do with the 3D complexity of the shear line at this point. But it’s that very 3D complexity, especially the v-shape, that makes this one of the most compelling matches out of some fifty discovered to date around the shear line.
Photo 5- shear line from a different angle
Photo 5 doesn’t show the green match. Notice the two dark, solid lines at the orange match. These are where the double ridge on the head was seated. You can even see the actual curved base of the double ridge imprinted on the body but it’s rather whited out here. It’s clearer in photos 2 and 3 and is dotted in the summary photo near the bottom. It’s also clearer in some other close ups and suggests the double ridge feature had depth right the way through from this anchor point embedded in the body to the upper surface of the head lobe, above the rim.
The bright green dotted line in photo 5 is not the shear line. It’s a ridge running into Hapi and is a continuation of the very straight perimeter of the slab A extension. It will be discussed later in this post. It’s a sharp dividing line between neat matches this side and mayhem with no matches beyond- or at least up to the other side of the amphitheatre (flat crater with rocks A and B in the middle).
The yellow blob in the middle is a rogue dot. These are sometimes left because re editing can degrade previous annotations.
Photo 6- the head lobe from above.
Notice the very small blue dots showing the ridge and rounded dip within the detailed green match formation as per its twin below on the body.
The pair of blue ridges above the orange dot can now be seen, starting higher than one would expect and tapering together, vertically, to the orange dot in the bottom of the v.
The isolated yellow dot against the black background of space denotes the first and biggest concertinaed protrusion that sits below its partner triangle on the head rim. This is the protrusion that sat against the block on the body shear line to create a flat platform for the yellow triangle. A few other small pieces were also sandwiched in with it and those are now spread out in a line below it, embedded in the neck matrix. They are out of frame.
Notice how high up the head rim one of the green lines goes. This is in keeping with the header photo showing the match to the body formation below it. You may notice, on returning to the header photo, that the green dots on the head trace out a shape that’s more square-on to us than on the body. This, despite saying that the head rim was more edge on. It should be the other way round by that reckoning. However, it will eventually be shown that this head lobe match was tugged down violently, more so than any other part of the head rim in this vicinity, hence just this small section being almost square-on in the header.
Photo 7- head rim from below.
The light blue double ridge can be seen but only from one side. The parallel twin is obscured by the one we see, except for its bottom end-point. That’s marked with a tiny blue dot against the black background, so as not to confuse. Again, the two end-points of the double ridge can be seen to taper to the orange dot in the v-shape on the rim, in a perfect match with its body counterpart.
Photo 8- focus on the mauve match.
This is a completely different approach for verifying the mauve match. The bright green line on the body is the right hand perimeter of the slab A extension as you look down on the body (slab A extension, Part 22). The bright green line on the head follows a distinctive cliff line along the border of Ma’at. If you sat the head back down on the body, these two lines would join and continue in a straight line, one to the other. The mauve match would be sandwiched at the join of the two lines. Moreover, the bright green line on the body follows a ridge that extends beyond the mauve body match, dropping down into the smooth, dusty Hapi region. It represents a linear outcrop of ‘rock’ continuing along in the same direction. That outcrop is almost exactly the same length and is in the same orientation as the cliff line perimeter on Ma’at, above it. So if you sat the head lobe down, the cliff line would appear to be the same structure emerging from the head lobe. There is more evidence for this, which will be put forward in the next two posts. This continuity from lobe to lobe would be akin to the dark green, three-way junction structure that extends from the body into the head and is visible on its surface well above its rim. The orange match seems to exhibit this trait too, as mentioned above. This means that the cliff-to-linear-outcrop was also likely to have been one robust monolithic lump joining the two lobes when the head was seated.
Everything to the right of the bright green line on the body is undisturbed i.e. the triangle of untrammelled craters, marked red in the two most recent posts. Everything to the left, i.e. the slab A extension, is disturbed. The cliff line in the head lobe also extends a long way up, just like the three-way junction structure, the two parallel blue ridge lines above the orange match and, to a lesser extent, the yellow triangle.
Photos 9 and 10- focus on the yellow and orange matches.
Photo 9 is a view of the head rim, which is presented more square-on (i.e. more from above) than it is in photo 10. This is shown simply as preparation for photo 10 because it shows the two obvious curves in the rim between the tip of the yellow triangle and the orange match (curves are dotted yellow). Photo 10 also shows these two curves on the body shear line but the head rim is slightly side-on in that photo so the two curves aren’t obvious at all. Photo 9 allows us to see they are indeed there. Just the two curves, the orange match and the single blue ridge/crevice on the yellow triangle are annotated.
Photo 10 shows the top side of the head lobe rim and the body lobe in one shot. It’s a pity the whole yellow triangle isn’t shown in the head rim part. However, the perimeter runs just a tad off the top of frame and parallel to it, so it is all there for our purposes.
This photo captures the yellow and orange matches on both lobes. There are some extra blue ridges too. The fuchsia dots are one-off annotations just for orientation of all the matches here. They’re more faithful because they both adjoin the two parallel mini lines or ridges.
The curved blue ridge line on the head running from the fuchsia dot to the orange match, corresponds to the very finely dotted line on the body, the one nearest to the two yellow perimeter curves. The body version is very finely dotted because the line is almost indiscernible. But it does get a match to the underside of the rim in photo 12, below, so it’s probably more important than it looks. It also looks too close to the perimeter to match the stated head lobe curve. It could possibly correspond to the slightly less obvious head lobe curve nearer the head rim perimeter. However, the body match is on a moderate slope (see photo 4) so the distance between line and perimeter is foreshortened.
The more obvious curve on the body can’t be the exact match to the one on the head because the triangular protrusion embedded in the neck beneath the head rim triangle used to sit here (its upper, long side may have actually left the very lightly dotted blue line- see photo 12).
Incidentally, the lightly dotted blue line isn’t visible in photo 4. But it’s telling that in that photo there are lines running down the slope from this point- either slurry dykes or scoring as the head rim and its sandwiched triangle slid forward together. The head rim is thin and frilly beyond this line (similar to elsewhere, Part 5) so it bears the hallmark of gases and slurry escaping from under the rim of the triangular section, when it was seated on the body, only to find themselves trapped under this very last section of floppy head perimeter (when it too was seated on the body). So they pushed up that last section to create the frilly rim. In that case, they are more likely to be dykes like the dozen or so identified elsewhere along the shear line.
There’s an apparent problem with photo 10. All measurements between matches along the shear line and rim show up a roughly 25% disparity, maybe a tad less. The head rim measurements are therefore 25% longer than those on the body. However, this is mostly due to the head tipping towards us at around 35°. Cosine 35°= 0.819 or 81.9%, meaning about 18% of disparity. This would only apply in full if one surface was face on and the other tipped away at 35°. In reality, they are both tipped away somewhat and the head rim is tipped slightly to the right as well. But it gives an indication that most of the measurement disparity is due to the tip. 5% of the discrepancy is explicable via foreshortening: photo taken at 30km; body matches up to 1.5km further away than the head rim matches. Another 3% would be down to either measurement error or the fact that the perspective doesn’t allow the exact match positions to be located e.g. the bottom of the v-shape that defines the orange match on the head has been marked but it’s probably obscured, a bit lower down. That all adds up to 26%, more than the disparity, probably because the whole cosine proportion doesn’t apply.
And the most important thing of all to bear in mind here is that the header photo shows that the yellow and orange matches are definitely the same distance apart on both lobes anyway. There’s no perspective discrepancy in the header because the two matches run across our line of sight and not along it.
Photos 11 and 12 show the head rim underside. 11 is just for orientation and 12 is the close up. Remember this is a mirror image whereas up till now we’ve had the luxury of seeing the matches coming through, unmirrored, into the top side of the head lobe.
The only new annotation is slightly darker blue dots that extend from the main light blue ridge line. That’s the ridge or line that leads through the rim to the wide crevice on its top side and which seated itself along the edge of the protruding block at the yellow match point on the body. And that block is the one with the light blue line along its edge and with the pair of mini lines at the end but still a little way from the perimeter. You can see the match here in photo 12 on the rim underside: two mini lines half way up, on the left of the ridge line.
The reason for the darker blue lines is that, together with the light blue line, they describe a shape that’s similar to one imprinted on the protruding block below (photos 4 and 5). You can even see a small gap between this shape and the two mini lines which is of the same proportions as the one between the shape and the lines on the block below.
You can also see the double ridges emerging below the orange match. These correspond to the imprint on the body in photo 3, except that the triangular block sticking out below it on the neck also has the two lines so that was seated first. This is the triangular protrusion that sat with its other end against the yellow match block on the body. You can now see its shape defined in the head rim above it. It either nestled in against the blue, dotted lines or in the slightly dark triangular section that’s offset a tad down and to the right. It’s probably the latter as that serves to match up the double ridge lines properly. The blue line running parallel to the rim, the hypotenuse of the triangle, is the proposed match for the very lightly dotted line in photo 10. Either that or it’s the hypotenuse of the dark triangle just below.
There appear to be even smaller scale matches in all these photos. They haven’t been annotated due to the resolution. For example, there are mini squares along the two yellow curves on the body (photo 10) which seem to mirror those on the head rim (not the biggish ones in photo 10 but possibly much smaller ones on the very edge of the rim). The body ones are clear but the head rim ones never are, either in photo 10 or others.
Perhaps a summary photo will serve as an apt conclusion. It includes everything from the above photos as well as an additional, long ridge in the Hapi region, dotted in light blue. Its match is also dotted blue on the head. It runs from the double ridge next to the orange match dot, turns left and runs parallel to the rim. The head rim version looks as if it’s too close to the rim but the ‘side-on plate’ perspective issue is mostly if not wholly responsible for this. The ‘take home message’ for this post follows the conclusion photo. Despite being last, it’s an important concept for following the next few posts.
TAKE HOME MESSAGE
All the sub series sections can be viewed as stand-alone posts. But all of them have a take home message, which relates to the information needed to keep in mind for the underlying sub series theme of proving stretch of the head lobe before shearing. The take home message for the necessary points in this post that will be adduced in the next two posts is as follows.
Although most of the perimeter in this area is now matched, there are said to be four specific, coloured match points. All four are defined by apparently resilient ‘rocky’ outcrops on the body and a head lobe match that isn’t just confined to the rim but penetrates deep into the head lobe structure. Furthermore, the four matches, mauve, yellow, orange and dark green are roughly equidistant from each other and exactly define the base of the long, red triangle of relatively undisturbed craters (Part 23).
So, while the slab A extension was being torn to shreds on one flank of the triangle and the Anubis slab was being hurled into deep space from the opposite flank, and the head lobe was being wrenched from its base, the triangle sat in splendid isolation, untrammelled by the chaos unfolding around it. It seems it was somehow protected by these four unusually solid, rocky matches:
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
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All dotted annotations by scute1133.