Parts menu (with summaries)

Part 1- Head-to-body matches at Ma’at to Seth/Babi.

Part 2- More head-to-body matches at Ma’at to Seth Babi.

Part 3- A continuation of matches from Parts 1 and 2 round to Anhur and in the opposite direction too, around the ‘cove’. These are larger-scale matches, which are revisited in more detail in future posts (Part 8 ‘Hathor dykes’ and Part 21 ‘Bastet-to-Aker’).

Part 4- Summary of Parts 1-3.

Part 5- A 3D match confirming the matches in Part 1. This is a very close match with tiny replicated details.

Part 6- The matching of strata layers from Ma’at to Seth/Babi.

Part 7- Evidence of extensive outgassing and slurry at the shear line. 

Part 8- The Hathor dykes. Includes an extension of the head-to-body matches from Part 1, on towards Landing Site A. These matches were covered in Part 3 as well but additional close-up ‘mini matches’ are made here and from a different angle. These matches take us round the so-called cove. 

Part 9- Missing slabs A and B (missing from Landing Site A and Babi). 

Part 10- The cracks across the neck straddle perfectly across the rotation plane.

Part 11- The collisional problem. A critique of contact binary and erosion theory.

Part 12- Missing slab C, Hatmehit. This is now thought to have been several layers, possibly tapering to a bulbous pyramid shape (Part 28). Expelled via spin-up to 2.75 hours rotation period. This would be 1m/sec tangential speed at the present-day Hatmehit surface (using a guessed radius from centre of gravity of the formerly single body). This tangential speed just happens to send the head lobe centre of gravity into negative g but not escape velocity. However, this is ignoring the bilobed nature of the gravity field so is approximate in terms of calculating the g accelerations. Centre of gravity of head and body lobe (or otherwise using reduced mass) are rough expedients. 

Part 13- Missing slab D, Imhotep. This probably consisted of three or more onion layers and was probably bulbous. Expelled via spin-up to 2.75 hours. This would be 1m/sec tangential speed at the present-day Imhotep surface (using a guessed radius from centre of gravity of the formerly single body). See Part 12 summary for more information. 

Part 14- Rock A (and B). This 30 million kg rock floated 170 metres across Landing Site A. It had to have been dislodged, lifted and drifted back down the rotation plane. This is because it would have been in a suborbital trajectory while the comet rotated underneath it. The dislodging could be attributable to the head rim shearing away and/or the sympathetic lifting of (now missing) slab A. It’s telling that this cluster of displaced rocks, including rock C, below, were seated right on the junction of the head lobe shear line, slab A and slab B. They all drifted backwards in the same manner. 

Part 15- Rock C. Same scenario as for rock A but a bigger rock. 

Part 16- The same matches as for Parts 1 and 2 but seen from above the head lobe. This part corroborates the 15° anticlockwise head rotation first observed in Part 3.

Part 17- Anuket-to-Anubis. Matches emerging from the terminator. The matches are technically from Serqet/Maftet to Seth/Anubis. However, the best available photo had only recently come out and, from the low viewpoint, the matches are very much looking at the rim rebate under the head. This almost covered the Seth extension when seated on the body. The rebate then matches to Anubis itself further south. So for all intents and purposes we’re matching the underside of the head rim to Anubis.

Part 18- Rocks D and E. Same principle as for rocks A to C. This post also goes into fine detail in matching a section of the ‘cove’ that wasn’t matched in Part 8. This extends the matches to the missing slab A perimeter where they peter out. This is due to missing slab A taking the matches with it along its edge. The matches continue the other side of the slab in Part 24 and from there, southwards in Part 17 and on round to the south pole in Part 19.

Part 19- South pole matches. Large scale due to viewing distance. 

Part 20- The hinge where the head lobe tipped and the finer points regarding the tip. This is elaborated on in Part 28. 

Part 21- The Bastet-to-Aker matches. Much finer-detailed matches than in Part 3. 

Part 22- The slab A extension. This is the first of 6 sub sections building evidence for the head lobe stretching even before it sheared from the body. It was this forced stretching that caused the onion layers on the head and body (Parts 26, 27 and 28). These layers were sliced through on shearing hence the cross lines on Hathor- the head lobe is actually half an onion. The slab A extension is a curious area of scalped material whose border continues from the missing slab A crater. It’s now believed to have been cracked via the body lobe core stretching beneath it (not stated in this Part- I was still expressing puzzlement as to a mechanism at this point). 

Part 23- Missing slab E, Anubis. This slab’s ‘upper’ edge (in upright duck orientation) fitted to the head rim rebate that’s so clearly defined in the Part 17 header photo. It probably consisted of 3 or more onion layers and was slightly bulbous. Escaped via spin up (see Parts 12 and 13). This is sub section no. 2.

Part 24- The Serqet-to-Seth matches. This introduces the four so-called anchors that held the head lobe down at the opposite end to the hinge at Bastet/Anhur (Part 20). Sub section no. 3.

Part 25- Tell-tale lines across Anuket. Two of these four lines link 2 of the four anchor matches from the previous part. They are each linked from head to body via a continuous line. Another two lines link the other two matches the length of Anuket as far as the base at Hapi and then by indirect means to their matches on the body. Sub series section no. 4.

Part 26- The evidence for head lobe stretch before shearing. This is where the evidence amassed in the first four parts of the sub series is adduced to prove the sub series theme of head stretch before shearing. It’s so long that it continues into Part 27. It introduces the ‘vertical wall’ which is a key feature in attenuating the stretch for a period and causing the tell-tale stretch signatures that are aligned along the rotation plane. This is sub section no. 5.

Part 27- The evidence for head lobe stretch before shearing. This is really a continuation of Part 26. Sub section no. 6.

(Parts 28-43 added on 16th March 2016)

Part 28- “The onion layers and head herniation”. This includes a description of the stepped feature along the rim of Hatmehit bordering Wosret along with the spidery Hatmehit V’s that can be traced as running from the same fractures that cause the steps. When these two features are added to the curving strata further down on the head (the very fat classic head lobe V’s) it betrays the 3D arrangement of the onion layers inside the head lobe. This part goes on to describe the riding up of those onion layers during head lobe stretch before shear and provides the first mention of head lobe herniation and its tell-tale bell shaped rim at Serqet. At the time of Part 28, the emphasis was on the head stretching before shearing. It was because the herniation signature was strong. The body stretch was barely understood at that time and not even mentioned/implied till Part 31 (though one section of Part 26 stabs inadvertently in that direction).

Part 29- “The onion layers that rode up on the head and the raison d’être for Serqet”. This part is dedicated to proving that the head lobe onion layers, presented in Part 28, actually rode up over each other. This is done with several photos where either three or four layers show the same features along their length. It would be similar to taking four playing cards in a stack, cutting a characteristic line along their common perimeter and drilling a few holes through them before delaminating them. You’d see the matching features. This part also discovers that the vertical wall must have forced its way between the two layers above it when on the body and just before head shear. 

Part 30- “The south pole head-to-body matches”. This is a short part which shows the south pole matches in the newly released OSIRIS close up photo of that region. Little explanation was needed as the photos speak for themselves. 


Part 31 and those subsequent to it include some of the gradually evolving reasoning that led to each new discovery. Perhaps it will illustrate that stretch theory isn’t a breathless pointing-out of disparate, far-flung matches and unrelated mechanisms. It’s all been slowly, thoughtfully and incrementally worked out over 19 months from August 6th 2014 to date. It’s the incremental part that is the reason for it being an internally consistent theory that now explains the morphology of every ESA region. Although there will inevitably be a few corrections and much refinement, especially for the south pole, the mechanisms all complement and influence each other in an intuitive and consistent manner. This thread of reasoning wasn’t included for the previous part summaries. Certainly, for the sub series (Parts 22-29) it was all worked out in a very short time in May 2015 but then took six months to write. However, the chronology of reasoning and discoveries is documented very well in Part 28. Indeed, the incremental aspect to the evolving ideas can be traced all the way from the specific discovery that the ‘yellow’ triangle at Serqet had been tugged, to the massive 700-m rift at Imhotep. So the DNA for stretch before shearing, the paleo rotation plane and crust sliding runs from Part 22 to Part 43 and beyond, each part building on the one before. Prior to Part 22 it was entirely related to stretch after shear (i.e. the head stretching on the neck and leaving matches behind, along with other aspects related to it like missing slabs)

Part 31- “The lattice of stretch lines on 67P”. This is another short post which observes that there are stretch lines on the body. It’s stabbing its way towards the realisation that the body had delaminating layers like the head. It was already known that the ‘red recoil’, Part 26, had two more ‘recoils’ mirroring the head layers riding up. This fact plus the lattice suggested body layers delaminating under stretch as opposed to recoiling simply due to head lobe shear. The extra red delaminations still haven’t had their sorely deserved post as of now (Part 43). 

Part 32- “The large sink hole delaminated into the three sink holes we see today”. This was the first conscious identification of body onion layers delaminating and sliding back, just like head layers in Parts 28-29 but in the opposite direction. This was a strong sign of the body stretching before the head sheared. As such, it would mirror the head stretching (and herniating) before shear. The two specific tell-tell signs that were a lead-in for the discovery the three holes had delaminated were (a) that the second hole’s floor is at the same level as the flat Site A and (b) that the step feature dropping down the side of the second hole has been whipped round backwards. When its picked up and draped round the main hole it joins to the broken rim at the front- but only if the main hole is the diameter of the second hole. Ironically these two obs never got into Part 32 and need their own post.

Part 33- “The monolithic slide that opened up the crater and cove”. This could be considered as the same process as described Part 32 except that it opened up a single hole rather than delaminating an existing one into three. It happened at the other end of Site A which is why the mechanism of radial tensile forces causing crust slide is the same. The present-day result of the monolithic slide is a horseshoe crater but when the head lobe was clamped to the body it formed the missing end of the crater, making it whole and circular. This part also updates Rock C’s behaviour and mentions the paleo pole for the first time (as opposed to the paleo rotation plane, first mentioned in Part 26).

Part 34- “The cove delaminated into three scalloped sections”. This process was the mirror image of the monolithic slide. The cove is on the head and the horseshoe caused by the monolithic slide is directly below it on the body. The two fit together to form the crater mentioned in the Part 33 summary. As a result, when still clamped together, the cove delaminated upwards on one side of the shear while the monolith slid downwards, forming the horseshoe. This is very clear in photo 3 of this part. This part also discusses how the cove widened further.

Part 35- “How the cove opened up”. This is a short part concentrating on the matches within the cove itself. They betray how the cove ‘scallops’ opened outwards as well as delaminating upwards. The mirror image process of opening up on the body (when the cove was clamped to the body) was described in the previous part. This was the ‘shallow crater’ that extends beyond the classic horseshoe crater. 

Part 36- “Cove photos and exact original hole location”. Since the cove is quite slippery in the NAVCAM photos in terms of looking completely different from different views, this part attempted to firm up what it actually looks like. By using multiple views, one can build up a solid 3D picture and not be wrongfooted by shadows, whiteout or perspective issues. This isn’t simply an exercise in getting familiar with the cove, it firms up all the cove observations from Part 34 onwards. In doing so, it identifies the exact seating of the original hole (another one, this time one that delaminated into the three on the head).

Part 37- “Summary of radial stretch vectors around the cove/horseshoe”. All the crust slides from Part 32 to Part 36 are related in that their direction is radial and away from the north pole. The header photo shows this quite clearly. As such, a pattern was gradually emerging. This led directly to noticing the gull-wing delamination across Babi, then the related Babi cuboid slide. And from there, the mirror-image Ma’at slide that the cuboids tore from (Parts 38-40).

Part 38- “The gull wing delamination on the body”. This was where the classic set of gull wings from Part 5 (matched perfectly in 3D to the 20-metre scale) were found to have delaminated along the shear line at Babi. They delaminated into five sets (four delaminations). Although the tensile force vector was along the shear line, it was essentially radial from the pole, like all the other slides. However, Babi itself remained curiously scalped but for a stack of material at the opposite perimeter. Since it looked finely terraced like the site A slide around the sink hole delaminations it was realised that this too was a slide, away from the gull wings sets. The bare-looking gull wing sets were therefore originally buried even when delaminating. 

Part 39- “The reason for the shear line direction at Hapi and its implications for stretch vectors”. This part explains the difference between the core-directed stretch vector and the radial tensile force vector acting on the surface crust once it was loosened. The crust appears to have resisted the radial forces while delaminating in sympathy with the overriding exigencies of long-axis core stretch. But once loosened on their underside due to that delamination, they were liable to succumb to the weaker radial forces that they had hitherto resisted. This explains the partially radial tugging of the gull wing sets that were otherwise notionally following the core-directed stretch vector. Indeed it was this tugging and also the not-quite-radial path of the third/fourth Babi cuboids that led to distinguishing the core stretch vector from the radial vector. 

Part 40- “The 800-metre radial landslide at Babi”. This is the description of the Babi cuboid slide. They weren’t always cuboids. Their present bunched-up shape, ‘overhanging’ Aten is because they were once strips of delaminated crust, running from the shear line to their current line at Aten. The strips or bands had originally delaminated across Babi like pulling out the slats of a Venetian blind, horizontally along the line of the long-axis stretch vector. That would be as per the core-directed tensile force vector in Part 39. The four strips then slid radially. Since they were close, parallel and very loosely attached, their aggregate slide vector averaged the small radial differences. Hence they slid in parallel, scooping themselves up as went like a croupier scooping a spread stack of cards back into a stack. The four stacks are the four Babi cuboids overhanging Aten today (the cliffs of Aten). Each cuboid top looks like surface material because they used to sit in the four interstices between the gull wings and stayed on top throughout the Babi ‘scooping up’ slide. Recent close up photos (March 2016) of the sloping backs of the cuboids betray the flaccid, crumpled lines of the original delaminations as well as the cross-cutting tears of the shear line (part 41). 

Part 41- “The recoiled head lobe layers that match the cliffs of Aten cuboids”. That is, the Babi cuboids. This part shows two head lobe ‘layers’ that tore away from the Babi cuboids when they were still strips arranged between the gull wing interstices. These are *not* real layers. They appear to be so due to riding up the head lobe. But they consist of the original ‘Venetian slats’ or bands that simply continued on up the herniating head lobe when it was still on the body. The lines between these bands are barely recognisable today. The shear line tear was at roughly 90° across the delamination and so when each head lobe tear recoiled it gives the illusion of being the naturally exposed end of one layer. It’s actually the torn end of four delaminated layers. So these two pseudo layers were once nested at the shear line and attached to the identical Babi cuboid precursor material. So the current head ‘layers’ and the Babi cuboids that look so different today were morphologically indistinguishable when originally attached either side of the shear line. 

Part 42- “The Imhotep crust slide- initial overview”. The Imhotep crust slides are numerous and can be loosely divided into four categories. This is why an overview was needed before addressing each one with detailed matching. The four categories are red, orange, blue and green. Really, they are just reflecting the radial nature of the sliding. But since there were two onion layers involved, there was a preference for the top layer to slide at 90° to the lower one. Although this is still radial in topological terms, it adds a rectangular element to the rift that opened up. That’s why the flat Imhotep plain is a long rectangle. Whilst this radial-but-rectangular behaviour operated west of the comet’s short axis (the main rift line), it didn’t so much to the east of the short axis. To the east it’s mainly radial in the usual sense. The upshot of this is three notionally different sliding behaviours: (1) east of the short axis, radial (2) west of the short axis, rectangular (3) north as well as south (i.e. the top layer’s behaviour). There’s a fourth which is sub-delaminations that decoupled and rode on from the main ones. The four types correspond to the four colours above. 

Part 43- “The red slide”. The detailed matches for the red slide. 

This page was updated on 16th March 2016. It added the summaries for Parts 28 to 43 (Part 43 was not written yet at that time).