Your attention is drawn to the new “PARTS MENU (quick links)” in the menu bar above. It allows much quicker sequential-number access to the numbered parts than the year/month chronology that’s so favoured by blogging platforms.
Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
The first header is photo 14 reproduced. The second header is unnumbered as it’s a reminder from Part 70 and will be inserted in a few places to save scrolling up and down to the top. Photo 14 is at the end of the post. It shows a summary of the various layer slides and delaminations laid out in this part and Parts 69 and 70. Photo 14 has a description which, along with other preceding photo keys, explains all the slide vectors in the first header.
The other three header photos are designated as being photos 1 to 3. Photo 3’s description is divided into several paragraphs ending with ‘/////’.
It’s advisable to read Part 70 as a primer to this part because it shows two views of the four layers. It’s much shorter than usual, mostly photos.
Your attention is also drawn to Appendix 2, which has a selection of photos showing how the four mauve delaminations each sit on their own respective delaminated layer.
The four mauve dots in the third header are sitting on four similar shapes that once nested together. They have delaminated along with the onion layers they’re sitting on and they’ve delaminated along the long-axis direction of the comet which is consistent with the tensile forces of stretch. This is elaborated on further down. The delamination was rather like the opening up of one side of a cantilever tool box where the trays slide over each other (except the trays are filled to make them solid slabs or layers sliding over each other). We’re looking at four mauve features and each one sat on its own respective tray or layer, making four features on four layers. Each mauve feature is at the northern end of its respective layer and perched on the front lip of that layer. Each front lip is stepped up above the next layer and not very obviously so in the case of the farthest two layers towards Hathor. Each layer is deeper as we progress from the one nearest us, and towards the Hathor cliff (from layer #4 to layer #1 in photo 2). The features are dotted mauve because they were all once nested to the classic mauve anchor (Part 24) which is the third feature on the third layer per photo 2.
This is a close up of the photo above. It shows the exact outlines of the four mauve features and numbers them, #1 to #4, from the Hathor cliff end back towards us. The classic mauve anchor from Part 24 is #3. The blocky rectangle from Part 50 is #4. If you’ve been reading the blog, these features will be familiar and things will make sense more readily. The #1 and #2 mauve features will get their own names in due course because they’ll be referred to a lot for several more parts. Their northern perimeters (left hand perimeters in photo 2) define where the Aswan layers were originally attached before they slid across Hapi (Part 47).
In summarising photos 1 and 2, we have four layers enclosing three delaminations: #2 from #1; #3 from #2; #4 from #3.
The four layers, #1 to #4 shouldn’t be confused with ‘levels 1 to 3’ in Part 39. Those three levels ran along Babi and Aswan. The four delaminated layers in this part are a different set of delaminations subject to wholly different shear force and tensile force vectors. This different force vector set-up is by virtue of their being inside the red triangle, or rather, inside the newly extended red triangle presented further below.
This shows the four delaminations in close-up. It also shows the 1.6km x 200m rift in red (Parts 48 and 49). This rift is key to understanding the shear forces and tensile forces of stretch that caused the mauve delaminations.
Light blue denotes the so-called fracture plane which is in Part 26, signature 2. The fracture plane is now known to comprise exactly one of the delaminations, layer #2, and hosts the #2 mauve feature perched on its front lip, towards the #1 delamination. Its length and width are indicative of the other similarly sized delaminations either side of it which are less obvious until you use this shape as a guide. The fracture plane is therefore the area of one cantilever tool box tray. In reality of course, the layer containing the exposed delamination (fracture plane) extends beneath the other layer towards us i.e. under layer #3 that hosts mauve feature #3 and possibly under layer #4 as well. That’s where the toolbox analogy breaks down, unless it’s conceived as having very wide trays with the exposed delaminations being the first open apertures of each tray appearing.
The four dots, mauve, yellow, orange and dark green are the four coloured anchors first presented in Part 24. Mauve yellow and orange sit along the front lip of the #3 layer. Dark green sits on the #2 layer.
If you’re schooled in the Part 24 narrative, it will come as a surprise that the dark green anchor isn’t on the same layer as the other three because the head lobe shear line is supposed to run through all four. It does run through all four but the simple fact is that orange delaminated from dark green while the head lobe was still attached to the body. This happened as the #3 layer delaminated from the #2 layer. This delamination of orange from dark green was tweeted with photos long ago but is still awaiting its own blog post. The mirror image of the body delamination is even discernible on the head rim underside. They’re both in the same tweet:
WordPress has reproduced this as a tweet stream (with missing tweets) instead of just the link I typed so apologies to Dr. Nick Attree for being dragged in to this blog post. You can click on it to see the relevant tweet he’s quoting. The photos and their originals (which are more compelling) are reproduced at the bottom as a mini-appendix.
As if this isn’t enough proof, this same delamination is betrayed even on the upper side of the head rim, that is, the flared, upper side of the rim at Serqet. It’s the two curved, blue ridges in Part 24. Those two ridges are situated directly on the other side of the rim from the ‘underside’ tweet photo. They used to be nested. 67P simply couldn’t be trying any harder to let us know it stretched.
The tweet photos prove that the dark green-to-orange delamination took place before the head lobe actually lifted off the body. The head had to be clamped to the body for them to exhibit the same mirrored features let alone the same sliding signature. And since the head must therefore have been attached to the body during the delamination, and it also involves a whole layer delaminating by 300 metres along the comet’s long axis, it represents ongoing stretch of the single body due to spin-up. That would therefore be proof of 67P stretching even before the head sheared.
The reason this delamination can be extrapolated to a whole layer is because the mauve and yellow anchors moved back on the same front lip of the layer with the orange anchor. That brings us back to where we were: the #3 layer delaminated from the #2 layer, taking the mauve, yellow and orange anchors with it. Meanwhile, the green anchor remained on the #2 layer as the vestige of the progenitor to the orange anchor. Much more evidence of stretch before head lobe shear is available in Parts 26 to 29.
THE MAUVE DELAMINATIONS
Below is a description of the mauve delaminations. More photos follow, further down.
This part is important in its own right but it’s also placed here in preparation for explaining the Aswan/Hapi layer slides. Those slides happened right next door to the line of mauve delaminations in this part. They went off in a different direction. This part and the next few parts will explain why the mauve delaminations behaved so differently from the Aswan/Babi slides even though all the layers concerned were joined together before they were torn apart, slid and delaminated. They were joined as continuous layers running across that very straight line we see running down the northern side of the mauve delaminations. That would be the straight line kissing this side of all four mauve features in the header photos. It is the southern perimeter of the 1.6km x 200m rift.
So far, only one of the Aswan/Babi slides has been explained. It was the Aswan layer slide in Part 69. The southern perimeter of the 1.6 km x 200m rift is crucial to understanding why the Aswan layer and the one below it broke away from where they did and why they slid in the direction they did. They broke away from the southern rift perimeter line and went in one particular direction, 90°, from it. Meanwhile the four mauve delaminations shown in the headers slid along the other side of the southern perimeter. They slid along it, kissing it all the way, and didn’t move away from it at 90° at all. This is completely different behaviour for the two sections of crust that were once joined and then momentarily kissing each other on being sheared from each other. This seemingly bizarre behaviour is easily explained when viewed from the perspective of a stretching comet as will be gradually laid out in this part and the ones following it.
The 1.6 km x 200m rift was annotated in part 69 and invoked for explaining the main Aswan terrace slide. However, the exact mechanism for how the rift sheared along today’s southern perimeter and opened up has not been fully explained before, not even in Parts 48/49. This also implies that Part 69 isn’t the whole story and that the supposedly immobile, lower layer in that part also slid from the southern rift perimeter. It will be shown to have done so in a future part but you don’t have to wait for that part. All the matches are there, it just requires looking at a few photos from different angles to see them. The photos are all in Part 69 and this part.
It has been hinted at before that the southern rift perimeter line was very important and that the comet’s morphology differs greatly on either side of it but this part starts to unravel why the line is such a strong demarcation line between two distinct areas. It won’t be the full explanation but the photos below make a start in showing how the mauve delaminations were concertinaed out along this line, hugging it all the way.
The fact that the mauve delaminations extend right into Hapi from the classic mauve anchor (Part 24) means that we can now extend the northern long side of the red triangle as far as the furthest delamination (#1). That’s almost as far as the Hathor cliff. It also implies that the other long side of the red triangle, the southern side can be extended in a similar manner. The northern extension is shown in photo 5, below, and it shows the southern extension in the background.
The northern long side of the original red triangle is shown running from the sharp, red triangle tip at bottom-right, up to the mauve anchor. The southern long side also runs from the sharp tip and runs to the dark green anchor. The base of this original triangle, also drawn in red, is between the mauve and dark green dots. The new extensions run on past both the mauve and dark green dots. On the mauve side, the extension to the northern long side kisses all four mauve delamination features as it descends into Hapi and ends at a location that’s in line with the strangely squared-off northern end of the Anuket neck. Much the same thing happens for the southern extension but that’s beyond the scope of this post. If we were to join the two ends of the two extensions (not shown) this would be the new, larger red triangle base. It runs under Anuket and along the front lip of layer #1. Thus, the new triangle’s footprint takes in most of the footprint of the Anuket neck’s base. This should come as no surprise for anyone who’s read Part 57. Layer #1 is where the large, flat expanse of Serqet used to sit before tipping up to its current, more vertical position. It tipped up because it was herniating prematurely and through the layer above. That’s why it’s dubbed ‘the vertical wall’ in part 26. Serqet extruded the Anuket neck from the body after the head sheared and rose on the stretching neck. Layer #1 is therefore the base of the Anuket neck by definition. This was even stated as far back as Part 25 (the three-sided box shaping the squared-off form of the Anuket neck through having material extruded from it and through it).
The southern extension doesn’t need to rely on any supposed symmetry with the northern extension to be invoked. It was already implied in Part 57 but wasn’t explicitly pointed out because the northern extension is more obvious and should be aired first. But the southern extension is symmetrical with its northern twin, just like the rest of the isosceles triangle (the red triangle) that the two lines extend from. This is owing to the fact that both the red triangle and its two extensions are straddling the paleo rotation plane (see the ‘Paleo Rotation Plane Adjustment’ page in the menu bar). The paleo rotation plane caused this symmetry when 67P was stretching as a single body. This was before the head lobe sheared and rose on the stretching neck. It’s explained in the page cited above and in Part 26.
The southern red triangle extension line exhibits the same layer delaminations as the ones on which the northern, mauve delaminations sit. In other words, those delaminated layers are strips that run across Hapi or Seth. They run in front of Anuket but in the case of layer #1, its middle section is largely hidden under Anuket. The delaminated layers, #1 to #4, therefore kiss the red-dotted lines at each end. That’s where they were sheared at both ends by the shear gradient running down either long side of the red triangle (Part 26 and upcoming parts). All crust layers outside these two lines were also sheared, by definition, and recoiled from the lines. In the case of the northern line, it was the 1.6km x 200m rift in Parts 48/49. In the the case of the southern line, it was layers at Anubis that recoiled from that exact line (translationally matched to the line in Part 54). Put another way, the flat expanse of Anubis is another large rift. Specifically, it’s the floor of a much wider rift than the 1.6km x 200m rift. This hasn’t been mentioned before and will get its own full post in the future. The northern and southern red lines are of course the long sides of the red triangle including its new extensions.
One of the delaminations runs directly in front of the neck in Hapi (the so-called fracture plane, signature 2 in Part 26). This is layer #2 containing mauve feature #2 on its front lip. And a narrow part of the width of the next layer down, layer #1 is also visible across the front of the base of the Anuket neck but, as mentioned above, a large part of its central portion goes under the neck leaving its full 300-metre width visible only at either end.
It should be mentioned that there is also a supposed layer #0 beyond layer #1. That’s beyond the scope of this post and will be presented later. It’s inferred rather than self-evident and that inference is via the four clear delaminations we see in the headers. Its importance arises from the fact that it runs entirely under the neck behind Anuket and is probably not actually a layer but unlayered (or less obviously layered) core matrix material. It probably therefore also contributed material to the Anuket neck along with layer #1.
All of the four delaminated layers are about 800 metres to a kilometre long and about 300 metres wide. They are successively longer as we move from layer #4, the shortest, to layer #1, the longest. This is owing to them fitting into and across an ever-widening triangle as they progress towards its base along the front lip of layer #1. The layer widths are determined by the distance between the mauve-dotted delaminations shown in this part because each mauve feature sits on the front lip of its respective layer. But the so-called “fracture plane” (layer #2) presents itself in its entirety as being about 800m by 300m and it also contains the #2 delaminated mauve feature. It was called a fracture plane because it wasn’t recognised as a delamination in Part 26. It was only recognised as the top of a deeper layer than the coloured anchors’ layer (#3) and it was assumed the layer above it had cleaved away cleanly from it and in doing so, sheared along the line of the coloured anchors. Instead, the layer above slid away across it. That was the #3 layer. #3 is the one with three of the four coloured anchors: mauve, yellow and orange. This means the layer with the anchors delaminated from the fracture plane around the time of head shear. They delaminated while being integral to the front lip of layer #3 and did so from where they had sat along and on top of the the front lip of layer #2, the fracture plane. So the two lips were set one above the other as you’d expect them to be before the delamination occurred.
So the mauve, yellow and orange anchors used to sit along the front lip of the fracture plane. They delaminated from it on their own layer, layer #3 and are now 300 metres set back from that front lip of layer #2, the fracture plane. There are additional translational matches across this 300-metre width for the yellow and orange anchors as well as mauve, which prove this.
Moreover, the very flared-out rim of the lowest Serqet layer (i.e. the head lobe rim above the anchors) fits to the fracture plane directly below it. It’s part of the same layer that the mauve, yellow and orange anchors are a part of (layer #3). It was married up to the four anchors when the head was clamped to the body and still stretching. That’s why it’s so flared out- it’s one of the most stretched parts of the comet. It’s also why the head-body matches in Part 24 are so faithful. They match the flared rim to the anchors as well as the apparently softer material between them. It’s a 1km-long continuous match.
The green anchor remained on layer #2 while layer #3 delaminated from layer #2 along with the other three anchors. However, the same scenario applies to the green anchor and head rim above it albeit with the Serqet rim being stretched down more than flaring out (Part 27). This was due to the lack of horizontal movement of the dark green anchor in contrast to the mauve, yellow and orange anchors sliding on layer #3 and giving rise to the flared head rim just before the head sheared.
The four mauve features are denoted mauve because they were all originally nested under or over the mauve anchor, which is the mauve feature #3 on layer #3. Features #1 and #2 were nested under it and #4, the blocky rectangle, was notionally nested over it but in practice it was attached to the back of it (see subsequent photos and the Part 50 header). The slide of the mauve, yellow and orange anchors within their layer and across the 300-metre-wide fracture plane is in keeping with the well-documented red triangle recoil (signature 5 in Part 26) which was the next delamination back towards Apis. The red triangle recoil was the last delamination i.e. layer #4 from layer #3.
It has to be remembered that these ~800m-long, 300m-wide strips are simply the visible parts of the now-exposed, delaminated layers. Each layer carries on under the higher-numbered layer that slid back across it. Presumably, they extend under for quite a long way.
The layer delaminations along the southern perimeter of the red triangle are slightly less obvious but clear once you’ve checked the dots and then gone to the original to trace the line for yourself. Perhaps the most obvious southern extension delamination is the second one, which is the one in the tweet linked above. It shows the green-to-orange delamination which is layer #3 delaminating from layer #2. The third delamination is pretty evident as well. That’s in photo 9, below. It’s the ‘red triangle recoil’ from Part 26. It shows layer #4 delaminating from layer #3. So we have four layers enclosing three delaminations: #2 from #1; #3 from #2; #4 from #3. This means there are three strips or cantilever tool box trays, each one representing a delamination.
Since the three delaminations of the four layers are bounded by very straight extensions of the straight red triangle sides, it means the triangle has grown beyond its former base along which the four anchors are spread (Part 24). The sides are now longer and the base is wider. Since it’s an extension of the original triangle and bigger, it’s ‘similar’ per the strict geometrical definition of similar which means the same shape of triangle with the same proportions and angles but of a different size. The classic red triangle is isosceles in nature and nested inside its larger, new-found companion which is of course, also isosceles. So the sharp end towards Apis is common to both triangles. And since the triangle owes its existence to spin-up and stretch, it’s aligned exactly along the long axis. Its line of symmetry is running down the middle and that line is contiguous with the paleo equator which is the paleo rotation plane. The sharp vertex is therefore on the paleo equator and the base of the triangle is bisected by it.
The extended red triangle’s base extends under the Anuket neck. In fact, the base encloses about half of the Anuket neck’s footprint on the notional Hapi plane that extends under Anuket. This is hugely significant for anyone who’s read Part 57 (also Part 25). Anuket was extruded out of the body through this area by Serqet as Serqet lifted from the body, specifically, by the sliced vertical wall layer that’s now a part of Serqet along with the flared rim layer. The vertical wall was probably only able to do this because the mauve delaminations described in this part slid back to reveal much deeper material. This would be non-layered core material or less obviously layered core material that was either three or four layer thicknesses deep. Layer #1’s surface is three layer thicknesses down. Layer “0’s” surface, beyond layer #1 and beyond our triangle (for now), is four layers down and appears to be possible core material. That’s why the Anuket neck looks so different from Hathor and Sobek next door on either side. They were cleaved, Anuket was extruded because it’s at the back of the neck with respect to the long axis and the rotation plane. Thus, it couldn’t avail itself of the cleaving process and was unceremoniously wrenched out of the body. This is why large chunks of icy material are falling from the join between Anuket and Hathor. They’re coming from the Anuket side of the join because they were yanked out from the core.
Photo 6- Simple close up of the four mauve features.
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0/A.COOPER
Photo 7- A more detailed close up. ‘Original’ from part 25.
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0/A.COOPER
Mauve- the delaminated features.
Light blue- the so-called ‘fracture plane’ which is delaminated layer #2 containing mauve feature #2.
Larger mauve dot plus yellow, orange and dark green- the four coloured anchors from Part 24.
Red- this is not the whole rift. Roughly half of it is off-screen to the right, towards Apis. The upper line, kissing the four mauve features is both the southern rift perimeter and the northern perimeter of the red triangle. The red triangle’s northern long side used to extend as far as the larger mauve dot (the mauve anchor and feature #3) and its base was then formed by drawing a line from the mauve dot to the dark green dot.
Strictly speaking, the old triangle base goes all the way along the front lip of layer #3 without jumping across layer 2 to the green anchor. However, when the red triangle was first presented, it wasn’t known that orange and green sat on different delaminated layers so the shear line was assumed to be one delaminated layer lip, not jumping across layers to green at the last moment, near the southern long side of the triangle. It was known to look slightly awkward but put down to the vicissitudes of uneven surfaces. However, 67P is continually showing up even these tiny apparent excursions as having an explanation via the tensile forces of stretch, in this case, the #3 from #2 delamination. Another one is the messy-looking ‘tell-tale line’ (Part 25) at the green anchor that spreads out like a river delta. It’s now been matched to the shape of the green anchor (which has existing matches either side of the delta) and it was matched only a few days ago, bringing eighteen months of head-scratching to an end (see part 70, photos 5/6).
The new delaminations presented here are #2 from #1 and #3 from #2. #4 from #3 was already known as the red triangle recoil in Part 26 (see photo 9, below). Because of the two extra delaminations, the northern long side of the triangle now extends a long way past the mauve dot and into Hapi. It extends to the edge of the frame as shown and then about five red dots off-frame before turning right to go along the new, larger triangle’s base. In doing so the base traces the far end of the #1 mauve feature before diving under the Anuket neck. And the far end of the #1 mauve feature is front lip of the #1 layer. In photo 8, the neck is that isolated feature at the top of the frame that looks like a gnarled tree trunk. It’s the northern end of the neck that looks very squared-off. It protrudes a bit into Hapi thus creating an alcove with the Hathor cliff whose base is at the very top of the frame, in shadow.
This is a long, narrative key with some colour sections broken into paragraphs.
In photo 9, the front lip of the #3 layer is the head lobe shear line and therefore the #4 layer recoiled (delaminated) when the head sheared from the front lip of #3. The head lobe shear line curves across from layer #3 to layer #2, reaching the green anchor which is just off-screen to the right. It then continues on round the body from there (see Parts 17, 19, 30, 21, 2, 1, 3 which match the shear line in sequence all round the head/body and almost back to the mauve anchor). The crossover point from #2 to #3 is exactly at the orange dot where there’s a step-up that’s mirrored on the head rim. You can see this step-up in the tweet photos linked above.
Red arrows- direction of the recoil (layer #4’s slide) directly away from the head lobe shear line (layer #3’s front lip) and towards the long-axis tip at Apis. The recoil distance is about 200 metres and in line with the 67P long axis as are the other delaminated layers’ slide vectors. This is a strong signature of stretch via spin-up being the cause of the delaminations.
Mauve- this shows the face of the entire mauve anchor i.e. the section that clamped directly onto its head lobe match 1000 metres directly above. It’s a mirrored match. The mauve anchor is the #3 mauve feature in the header photos for this part. This shape and its head lobe match are shown together in close up in Part 24 (photos 17, 18 and 19). They of course look remarkably similar. Notice how in photo 9 the mauve dots go round three sides of a square, which is in profile to us. These three sides define the two sides of the match and the top between them. That would be in ‘upright duck mode’ with the dust of Hapi sitting below the match i.e. the open end of the square facing down to the dust.
The three-sided square comprises the entire blocky massif that comprises the anchor itself. The classic mauve anchor location denoted by a single mauve dot is always at the centre of the top perimeter. There’s a reason the bottom side of the notional square isn’t marked. It’s because this photo is from Part 26 and at the time of writing that part, it was suspected but not known for sure that the mirrored match to the head rim ends across this line. The direct match does indeed end across this line. It can’t match any lower because the curved shadow below it is the seating for the blocky massif that’s off-frame to the right here. That massif is the #2 mauve feature and it’s shown in photos 10 and 11. In those two photos it will be shown to nest into this curved, shadowed area.
There also appears to be a match on the head rim to the #2 mauve feature and not to its curved seating under the mauve match. That match is a continuation of the head rim’s direct match to the main body mauve anchor in this photo, photo 9. This proves the head rim sheared from the mauve anchor on the body when the #2 feature was still nested at the mauve anchor (#3). Otherwise the #2 feature couldn’t match to the head rim where it does.
In part 24 photos 17, 18 and 19, the shadowed curve was the one actually matched to the head rim instead of the #2 mauve feature. This is because it looked remarkably similar from that angle because the seating matches the mauve feature anyway. It was also due to not knowing that the #2 mauve feature nested here or even that layer #3 had delaminated from layer #2. However this extra match below the direct mauve match was dotted light yellow because it looked as if it was essentially a match but there was more to the story. The delaminated #2 mauve feature nesting in the shadowed curve is the rest of that story- another slight anomaly resolved by invoking the tensile force vectors of stretch.
The shadowed curve is the line that’s dotted mauve in the close up photos above because that’s the exact nesting line on #3, the anchor, for #2 to nest to.
Bright green- this annotation is bright green instead of mauve and red. It’s owing to the fact that this photo is from Part 26 when features spread along this line behind and in front of the mauve anchor were in bright green. This was in deference to the slab A extension perimeter line. That very straight line is exactly the same one as the southern rift perimeter which itself is the demarcation line for the slab A extension. They are one and the same. Thus these bright green annotations can be translated to the mauve/red language of this part as follows. The left hand bright green line is the front end of the blocky rectangle and so would be the #4 mauve feature in the header. As mentioned above, it notionally nested to to the mauve anchor but in practice it was clamped to the back of it. This seating for the blocky rectangle on the back of the mauve anchor is the middle bright green line. The seating hasn’t been pointed out or annotated in any colour in above photos. The right hand bright green line is just a small portion of the southern rift perimeter extending into Hapi and so is part of the red-dotted rift line in photos above. It should be said that the blocky rectangle line and its seating line are both a bit too long. The match has been refined since Part 26 (see Part 50).
Larger yellow dot- the classic position of the pointed tip of the yellow anchor. This matches to the tip of the pointed head rim section above. That point on the head rim is the very obvious southern pillar of the C. Alexander Gate. The anchor on the body itself spreads either side of this dot as described in Part 24.
Larger orange dots- the right hand one is the classic position of the orange anchor. It corresponds to the apex of a sharp, V-shaped dent in the head lobe rim above. The left hand one is the position of its slid match on the red triangle recoil layer which is the #4 layer for this part. So the right hand orange dot is on the front lip of layer #3 and the left hand one is on the front lip of layer #4.
Small yellow- the three concatenated curves running down from the larger yellow dot are sitting exactly on the head lobe shear line. The three-sided feature below the three curves and incorporating the orange dot is largely following the V-shaped match on the shear line but extends past the exact match at either open end. This feature marks the solid massif comprising the main body of the orange anchor. The isolated yellow curve to the right of the larger yellow dot marks the solid massif comprising the main body of the yellow anchor. Only its top edge follows the shear line.
Very small yellow- mini matches that map over to very small red dots (see below).
Red (large and small)- all these features match to their respective yellow matches along the shear line. They are a translational match, not a mirrored match as described for the case for the mauve anchor and its match. They are translational because they slid (recoiled), in the direction of the arrows, from their yellow matching features. The mauve match broke in two hence its mirrored character.
Regarding the red triangle recoil, It’s interesting to recall that layer #3 delaminated from layer #2 while the head was still clamped to the body. We know this from the tweeted orange-from-green (#3 from #2) delamination which the head rim obeyed in lock step with the body. We also know this from the fact that the head rim matches to the coloured anchors on layer #2 (dark green) and layer #3 (mauve, yellow and orange). So the #3 from #2 delamination on the body dragged the yet-to-shear head with it because head and body were essentially a single stretching body at that time. But the #4 from #3 delamination (the red triangle recoil) was a genuine recoil when the head sheared. It didn’t drag head lobe layers across with it like #3 from #2 did.
Of course, since #3 from #2 dragged future head layers with it then #2 from #1 absolutely had to do so as well. This is key to understanding the behaviour of the Serqet ‘vertical wall’ as it was herniating prior to head shear. It’s why it looks the way they do as described above (sheared by the red triangle extensions at either end; tip up along the front lip of layer #2 acting as a long hinge). Parts 57 and 29 provide much extra information and future parts will elaborate on this.
And finally, for photo 9, the layer #2 from layer #1 delamination is why Serqet (and Nut) are constrained to be directly above and exactly within the extended red triangle sides i.e. the width of its new, extended base. That delamination caused slip shear by definition. The slip shear happened along the ends of the triangle long sides at either end of the new base, cutting the future vertical wall into a flat, rectangular tablet, one layer thick, which tipped up on herniation. The thickness of that layer is the width of Nut. The slip-shear event is the reason for saying “sheared by the red triangle extensions” above.
Yellow- these lines show various outlines of the head rim and the Anuket neck. The right hand one at a 45° angle is the actual head rim. The dark feature outlined in the middle is the obvious lump that can be seen in many photos, sticking out at the top of the neck. There’s a small, brighter part of neck beyond it and to the right. To the left of the lump, we see the Anuket neck running steeply down to Hapi. This section is in extreme profile from this viewpoint, looking down on the head lobe.
Red- the 1.6km x 200m rift. The important southern rift perimeter is the one nearest to us. It’s the one kissing all the mauve features that delaminated from each other along it. Much of the rift is out of view at top left. This shows roughly half its length at most. The southern perimeter is shown dropping down into Hapi along the red triangle extension. In doing so, it runs down the centre of the mauve anchor and along a very straight line that continues out of view behind the head lobe. It kisses the shadowed curve mentioned in photo 9 and so this is the definitive #3 mauve feature to which #2 nests. The shadowed curve has been called the mauve anchor above because it is for all intents and purposes, the mauve anchor. It’s just that it doesn’t match directly to the head because the #2 feature matched to the head when it was seated in the shadowed curve. This was mentioned above. The area of the mauve anchor above the shadowed curve does match directly to the head so the very top rim of the cavern that forms the shadowed curve is the bottom perimeter of the mauve anchor. But the cavern itself isn’t a direct match to the head.
You may recognise the track of this drop-down into Hapi of the red, southern perimeter. It looks similar to the bright green curve in Part 69. Strictly speaking, it’s not: it’s a straight line (when viewed from directly above) that runs down the centre of the mauve anchor. That bright green curve in Part 69 was representing the northern edge of the mauve anchor which is indeed curved. We are now in territory where the matches and mini-matches are highly nuanced. The shadowed curve, representing the #3 feature extends almost from the anchor centre line (the red line) to the southern perimeter of the mauve anchor and a little beyond it. Although the red line notionally represents the top of the mauve anchor as it passes it, it’s more to do with the fact that it defines the anchor’s central rib. The rib appears offset to the north of centre somewhat in this photo but it’s an optical illusion in this photo and photo 9. Photo 12 shows it as being central.
Mauve- the four mauve features. They run from #4 at the top of the frame to #1 at the bottom. Only three are actually visible in this view: #2, #3 and #4. #1 at the bottom is denoted as a single dot where it would be if we could see through the head lobe to where it sits in Hapi. We can now see how feature #2 nests into the shadowed curve of #3 below the classic mauve anchor. The best ‘mini-match’ for them in this photo is the curved top of #2 that fits to the curved roof of the #3 cavern that causes the shadow of the eponymous shadowed curve. However, #2 has a triangular shape (very small mauve dots) and that is what fits to the actual recess of the cavern (dotted the same way in the recess shadow- for guidance, not very accurately).
From this angle both features look less curved, more angular. You can see how the seating at #3 uses the southern edge of the central rib (just to the left of the red line) as the northern perimeter of the seating line (mauve). The red line goes down the centre of the rib so the mauve seating line is the southern rib edge and the bright green curve of part 69 is the northern rib edge. The rib will become highly significant in the next few parts because it’s a very strong demarcation line between these mauve delaminations along it and the Hapi/Aswan slides away from it at 90°. It’s much straighter and more symmetrical when viewed from directly above than when viewed slightly from the side as in the last two photos.
Photos 12/13/14- context for photos 10 and 11. These are culled from Part 69 but have added annotations. Photo 14 is the main header for this part. Photo 13 is the same as 12 but with the mauve feature delamination vectors shown along with the rift/Aswan layer slide vectors. The vectors are the red arrows. 14 numbers the four mauve features that delaminated on the four layers.
Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER
Photos 12/13/14 show another view of the mauve delaminations. They’re a zoomed-out version of photo 11 in which you can see all four mauve features. Their mauve outlines are dotted with small mauve dots while the main mauve anchor (direct match to the head rim) has three larger dots denoting its top and southern side. These three dots betray the width of the rib that is itself dotted bright green. The smoothly curving bright green lines show how symmetrical the rib is. Again, you can see how it’s almost acting like a wedge between the mauve delaminations along it and the Aswan/Hapi slide away from it. Of course it never acted as an actual wedge- it’s the physical manifestation of the tensile and shear forces that gave rise to slip-shear and ultimately to those two different layer movement vectors. It’s the force vectors stamped on the comet for us to see and the two bright green ends are flared out because they were yanked in opposite directions along the shear line while the pointed part remained intact under the head lobe. More on that in ensuing parts.
THE DUAL IDENTITY OF THE RIB AND ITS CONSEQUENT DUAL COLOURING.
The rib is dotted bright green in photo 12 and not red because there’s a history of denoting this feature as a whole in bright green, dating right back to part 22, as well as noting its close relationship to a particular ridge on the head that’s also always marked bright green (since Part 24).
Although the rib centreline defines the red triangle extension and so was dotted red in photos 10 and 11, that centreline also denotes the slab A extension perimeter from part 22. The two areas share this border precisely because it was such a strong tensile force line with such a steep shear gradient. The steep shear gradient was what made the line narrow. And the shear caused the 1.6km x 200m rift which means the southern perimeter of the rift is also contiguous with the red triangle and the slab A extension perimeters. That’s because the rift caused the divide between the two areas and their two distinct morphologies. The 200-metre rift floor is wholly within the slab A extension area and the mauve delaminations are wholly within the red triangle. The two morphologies are divided by this startlingly straight slip-shear line that’s no more than 20 metres in width. That’s the southern rift perimeter, including the bright green rib in photo 12. This is how we know the shear gradient was so steep across the line. The tensile force vector diminished suddenly across the 20-metre width and this diminishing set up the shear gradient which led to slip-shearing of the crust. The reason for the sudden diminishing of tensile force across the line was presented in Part 26 (red triangle likened to a wind-tail in the lee of a rock) but will be elaborated on in the next few parts.
When we’re dwelling on the red triangle, as in this part, the rib centreline is marked red because it’s related to the vast area of the triangle behind it. If we’re dwelling on the slab A extension it has to be marked bright green in order to see its relationship to that area and to the ridge on the head directly above it. Since the Aswan/Hapi slides were entirely on the slab A extension side of the rib, it gets marked bright green for anything to do with the Aswan/Hapi slides. This is why the northern curved edge of the rib was marked bright green in Part 69. And it’s thus coloured in photos 12/13 because they are preview photos from a future part concerning the Aswan/Hapi slides.
Since photos 12/13 are from a future part, you can see the bright green line extending further into Hapi beyond the #1 mauve feature and right up to the boulders. This is the line along which the Aswan layers were once attached as we’ll see in due course.
APPENDIX 2- various photos showing the four mauve delaminations on their respective delaminated layers.
Small red- the layers, #1 to #4.
Large red- (in the second photo) the red triangle. Notice how it drops down into Hapi at the mauve anchor which is a dot that’s almost obscured by the red triangle dots. The red triangle line does a similar thing at the green anchor but with a small dog-leg round the solid, front corner of the anchor before the drop-down.
Small red and large red- as for A1
Brown- a small portion of the paleo rotation plane (paleo equator). Notice how it runs straight through the sharp vertex of the red triangle and then across the centre of Apis at the long axis tip (bright green). It also bisects the red triangle longways as well as Anuket longways and Serqet widthways. This is because all these features were caused by the tensile forces and slip-shear forces of stretch via spin-up. That’s why they’re all symmetrical across the line that runs around the comet from long-axis tip to long-axis tip. That line is the paleo equator and the rotation plane that caused the stretching along the long-axis line.
Dark blue- a nearby portion of today’s equator/rotation plane for comparison.
Bright green- Apis on the horizon. This is one flattened end of the highly symmetrical, diamond-shaped body. It’s centre is the exact long-axis tip of the comet.
In some photos in Part 70, the red-dotted layer lines traced their way round the shape of mauve features #1 and #2. However, this was for convenience to show where the mauve features were as they were somewhat whited out. The actual layer lips run across the front edges of these two mauve features i.e. the #1 layer lip and #1 mauve feature front edge are contiguous. And the same goes for #2. So the mauve features sit on their respective layers, not in front of them. This correct, straighter line for the layers is shown in the above photos and because of this, the mauve dots showing the delaminations sit directly behind the red lines.
Photos A3 and A4 below are from Part 70 with the red layer lines going round the back of the mauve features #1 and #2. They’re reproduced here because the mauve features weren’t presented yet in Part 70 and so weren’t marked. So they’ve been added here to show again that there’s one delaminated mauve feature for each delaminated layer. The four mauve feature delaminations therefore serve to corroborate the four layer delaminations. This is because they’re more obvious in themselves than the layer delaminations as a whole and each one sits on a layer lip. This is the lead-in for looking for other translational matches between the layers. These matches are indeed there for all four layers and have been presented for #4 from #3 (red triangle recoil) and part of #3 from #2 (the tweet photos). Several more such translational matches exist, completing the matches between all four layers but these will be presented in a future post.
But you don’t have to wait for those posts. All you have to do is look at enough close-up photos that include the layer front lips shown in this part and see the matches for yourself. Some of those matches are evident in the close ups in this part but weren’t noted because there’s enough evidence to prove the delaminations and its just too much discussion for one Part.
Continuous mauve line- the classic mauve anchor (Part 24). This is the outline of the direct match to the head rim above. You can see that head match in this photo. Look for the mauve dot on the head rim and then trace the much smaller mauve dots either side of it to trace the same shape as on the body. The close up matches are in Part 24.
Four separated-out mauve dots- these are the mauve feature delaminations, one for each layer delamination. each one is sitting on the front lip of its respective layer but #1 and #2 have the red layer line going round the back of them. It should really go across their fronts so that #1 and #2 are included on and within their respective #1 and #2 layers instead of sitting just in front of them.
Yellow and green- annotations from Part 25. See that part for a full description but these two colours essentially trace the shear line where the head rim once sat. The continuous mauve line is also part of the shear line because of being a direct match to the head.
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
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All dotted annotations by A. Cooper.
Copyright: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER