Part 64- The Evidence for Long-Axis Stretch Along the Head Lobe Shear Line at Hapi/Babi



The header is the same photo as photo 2 in Part 62 and this post is a follow-on from Parts 62 and 63 which dealt with the delamination of the three Ma’at pits when the head lobe was still clamped to the body lobe. This could therefore be considered the third part in an ongoing mini-series whose underlying theme is always the delamination of the Ma’at pits. More posts will follow, totalling at least five for the mini-series. They build up evidence for the collateral mechanism for the delamination of the holes: long-axis stretch along the head lobe shear line and the consequent sympathetic delamination of layers along the shear line. 


It should be noted that although the term Hapi/Babi is used for the Ma’at 01, 02 and 03 pit delamination line, some of that line was along the short finger-protrusion of Seth. Since it’s confusing to say Hapi/Babi/Seth, this short finger is counted as being part of Babi in this part and in Parts 62 and 63. This expedient is all the more compelling when we consider that the Seth finger is very much a part of the Babi morphological evolution by virtue of finding itself on the Babi side of the mirror-symmetry line described in Part 63. 

The Seth finger was included as part of Seth in the ESA regional map only because of visual similarities on its surface with no known reason for that similarity. The reason is that the head lobe originally sat on the finger, and this caused its characteristic rectangular shape by virtue of the furious outgassing escaping from underneath it (Parts 1, 5, 7, 8, 20). And apart from a tiny extra area next to the finger, described further below, the head lobe sat nowhere else on the official Babi area.

Photo 2-The ESA regional map. The finger is the pink protrusion coming towards us along the Hapi rim (next to the Hapi label). This is counted in this blog as being very much a part of the Babi morphology. 



The originals aren’t part of the numbering scheme. Dots should act as a guide only before verifying the dotted features on the originals. This is because the dots can sometimes partially obscure the detail they’re trying to show. 

Some keys are narrative keys and so some key colours get divided into paragraphs. These longer keys end with ‘/////’.

Photo 3- the header reproduced. 



Green- these two lines are the same shape, a translational match. They show a massif on the right that has slid from its seating on the left. The seating and massif correspond to the second and third bumps respectively. Those are the bumps or mini-volcanos in Part 62, that both delaminated along the shear line. They delaminated along with their respective layers, both delaminating ultimately from the first bump. The left hand green line here is sitting on top of the second bump or mini-volcano. The right hand green line is kissing the bottom rim of the third bump. In this view, it’s the bottom end of the line that’s kissing the upper perimeter of the bump rim. In this sense, the slid massif is only notionally related to the third bump. It will be shown in future parts that it probably was sitting on the third bump originally, but the main point here is to show that it’s a slid massif and that it slid in a direction that’s along the long axis of the comet. Furthermore, it will be shown that it ground along the head lobe rim as it slid i.e. it sheared from the head rim due to the shear gradient set up across the long-axis tensile forces. This shear gradient was described in Part 62.

Red- these aren’t exactly slide tracks but are a proxy for the slide track of the massif. The bottom red line is in line with the section of head lobe that’s 1000 metres directly above it in reality but slightly below it and to the right in this view due to Rosetta’s slight parallax. In other words, Rosetta wasn’t quite vertical over the head rim and shear line when this photo was taken. So the lower red line in question is in line with that straight section of head rim just before it curves round and downwards somewhat towards the right. This match will be depicted in lower photos, as it was in Part 62. 

The reason the bottom red line is a proxy for a slide track is that a) it’s in line with the bottom ends of both the matching green lines and b) it’s actually the ragged line that the matching section of head rim tore away from. So the massif that slid to the right was kissing the future head lobe rim along this line when the head was still seated on the body. It then tore away from the future head rim under the influence of long-axis stretch along the shear line. And of course, the shear line is, by definition, where the head rim originally sat. So the massif slid along, or ground its way along the head rim before the head fully detached ‘upwards’ as viewed in upright duck mode. Upwards is towards us in this overhead view. 

This means the massif didn’t exactly tear ‘away’ as mentioned above but tore ‘along’, i.e. it sheared under the shear force, described in Part 62, which was focussed along the shear line. The massif would have slid only during head herniation and before head detachment because all the tensile forces of stretch would have been transferred almost instantaneously to the incipient neck once the head sheared. That left little or no residual tensile force in the Babi layers to continue fuelling the long-axis stretch and further widen the delaminations. And there was certainly no residual tensile force at all once angular momentum had been conserved at today’s head lobe displacement (T= circa 5.8 hrs, see ‘Spin-up Calcs’ page).

The upper red line is certainly in line with the slid massif and its seating and may be a simple slide track. However, it may have delaminated from the other red line on head shear i.e. at 90° to the long-axis stretch (see Part 62 for this orthogonal delamination scenario). So it would have delaminated from the lower red line towards the top of the frame, which is along the same vector as the Babi slide (Part 40). 


Photo 4- same as photo 3 with additions.


Yellow- on the right, it depicts the back of the slid massif. On the left it depicts the bottom of the second bump. Together with their respective green lines, the yellow lines enclose similar shapes. 

Mauve- a mini match within the slid massif and within its seating. 

Photo 5- the delaminated layers. All annotations except green have been temporarily removed, just for this photo. 


Green- these are just three of the five delaminated layers that are depicted in the header of Part 38. The green line along the front of of the slid massif is the same as in photo 3. So it turns out that the front edge of the massif constitutes the front edge of the third delaminated layer. Its green line is extended round in a dog-leg although the real layer may be under that other terraced or bunched-up detritus beyond it (above it in the frame). That’s the material from the Babi slide (Part 40). 

The seating of the slid massif isn’t shown here because we know where it is. It’s right next to the very obvious line running along the front of the second bump which is at the front edge of the second delaminated layer. The seating is so close to the second layer front edge that we can say that the massif, i.e. the third layer, delaminated from the second layer along the direction of the long axis. This is in keeping with what was stated in Part 62. The second layer’s front edge does a fairly sharp turn and continues down Babi (upwards in the frame) to join another green line on the left. 

That left hand line leads back up to the Hapi rim at which point it describes two waves. Those are actually up/down waves and from the front (viewing from the left and very low down), they look like gull wings. So these are the gull wings which Part 62 describes as the first bump or mini-volcano from which the second and third bumps delaminated. But the bumps are just the ends of their respective layers, perched on the Hapi rim. So if the bumps delaminated, it means the entire layers delaminated too: second from first and third from second. 

The fourth layer is off-frame to the right and technically beyond the scope of this post. However, in Part 63, it’s implied as the southern perimeter of the rift at this end of the long-axis delaminations along Hapi. So it tore rather than delaminating, just as happened at the Aswan/Seth end of the long axis delaminations.


We can see from photo 5 that the bumps delaminated along the long axis in a straight line and yet their respective layers seem to fan out from one point. The first line even has a three-pronged trident shape pointing at the gull wing waves that is replicated at the second bump. The trident staffs are the delaminated layers marked green but the two sets of three prongs are a definitive match (see them annotated much more clearly in Part 38, photo 6). The replication on the second layer is at the place you’d expect, which is the with the prongs pointing at the base of the second bump. And they’re even slightly flipped round by the differential forces within the fan because the prongs are that much closer to the true shear line with the much steeper shear gradient. 

The trident match is less obvious here but is annotated and described in detail in Part 38, photo 6. Here’s a link to Part 38:

The trident movement, arcing over on its staff from the axis at bottom of the fan is strong evidence for the fanned delaminations. It seems highly unlikely that a trident shape would be reproduced at both bumps. 

Photo 6 below is the Part 38 header (not Part 38’s photo 6 with the trident annotated but you can see it here in its header, unannotated). It shows the full fan effect. The delaminated fronts making up the fan in this photo are in light blue because ridges were being denoted in light blue back then):
Photo 6- Part 38 header, reproduced. 

Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Light blue- these are the ridges that betray the the fanned-out delaminations. 

Dark green dot pairs- the three delaminated bumps (lower-left) and two more that were presented in Part 38 (upper-right). 

Photo 7, below, is reproduced from Part 62. It shows the Ma’at pits and their sources on the body as well as many matches from head to body. However, the main point in reproducing it here is to show that the shear line on the body (terracotta) runs contiguously with the lower of the two red slide lines. We’ve already established that the slid massif was originally attached to this line. Therefore, it must have also been attached to the portion of head rim that was seated there. That portion of head rim is that straight section of rim just before it curves round and downwards somewhat towards the right. It’s offset just to the right and downwards from the bottom red line in this view due to parallax (as mentioned above in the ‘red’ description in photo 3). If in any doubt, you can use the additional version with two lines of arrows showing the match or the beige dots that align in one line when the head is reseated. 

Photo 7- the head rim was seated along the lower red seating line for the slid massif. Therefore the slid massif was originally attached to the head rim before shearing along it and sliding to its current position. 


Dark green- as for photo 3 but there’s an extra fan rib or delaminated layer on the left. It’s one of the two extra ones shown in the Part 38 header above. The other one is off-frame to the left. This extra one that’s shown also extends to the common ‘stalk’ of the four fanned lines while, if you recall, the fifth one is detached from the fan in the form of our slid massif. The first line, the off-frame one, branches to the left from a point that’s a fraction off-frame in the top corner. 

Notice that the faint dark green dots on the head rim match to the wavy line on the first green line on the body. This is the gull-wing match, matched in 3D (from the side) in minute detail in Part 5. Except, this is a slight cheat because what we’re seeing on the head rim is a second, curved-up gull wing delamination that sits directly above the true set it delaminated from. It bent upwards during head lobe herniation and now exhibits a gentle curve. It constitutes the upper component of the first zig zag in Part 62. So there are actually two sets of gull wings on the head that sandwiched down onto one set on the body. This was described in detail in Parts 5 and 7. 

Although the sideways, 3D match of the gull wings isn’t strictly related to this post, they were sitting right on top of the Ma’at 01/01A source (Part 62) and that’s why they were raised into two gull wings. You can even see the two slurry piles that oozed neatly out in front of each wing on the body’s set of wings. They’re semicircular piles, each one the same width as its wing. They exhibit more concentric semicircles within their semicircular perimeter. Any engineer would identify that as classic signature of slump. 

So, since the 3D gull wing match is somewhat related to this post and intimately related to Ma’at 01, various links to the gull wing 3D match have been put at the end of this post along with a photo of the match with exquisitely detailed fiduciary-point matches. Please see the appendix. 

Red- still with photo 7, this is the massif’s seating against the head lobe which doubles as its implied slide track. The slide track betrays the long-axis shear force vector causing the layers to delaminate along the long axis. This led to the pits delaminating along with their gas sources being emitted from each of the layer fronts. The gas sources uplifted the layer fronts into bumps or mini-volcanos before exiting through the actual pits. One of those uplifting zones was the two gull wings constituting the first mini-volcano. On head shear, the pits recoiled up the head and down the body (Part 62; also Parts 40 and 41). Their gas sources were left marooned at the shear line and are clearly visible today directly below Ma’at 01, 02 and 03 (Part 62). 

Orange- this is the now-bunched-up layer that slid away from the shear line after head lobe shear. This layer used to sit over the bumps and the fan shape. It fully delaminated as opposed to undergoing a fan delamination. That’s how it was loosened enough to slide. The very fact it sat over the fanned layer meant that it was overburden that increased the tensile strain resistance of the fanned layer. That’s why the fanned layer resisted full delamination and didn’t end up joining its overburden layer behind the orange line. 

Other colours- these are as for this same photo in Part 62 (photo 17).


Photos 8 and 9- these are a comparison of the header and a close-up of the Part 38 header. They exhibit exactly the same annotations and so are presented together with the same key. The focus is on the intricacies of the attachment of the massif to the red line. 


Photo 9: Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Red- the attachment and implied slide line.

Dark blue- the outside curve of the massif (not annotated in other photos further above) and its seating on the ‘outside’ of the red line. In reality, it’s simply at the bottom of a long, thin sloping area that constitutes a widened version of the red line. The green line runs along the top of that widened line. 

Green- the front of the slid massif and its seating on the second bump (as for photo 1).

Light blue- fiduciary positions of certain larger boulders.


Photo 10- the 3D gull wing match. Fullest zoom required for all detail.
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

The photo above is the finer-detailed match from Marco Parigi’s summary post of my Part 5. 

My Part 5 is the first link below, which shows how I traced the sideways view of the gull wings on head and body and checked meticulously that they were indeed the same features as those we see for the green gull wing match in photo 7 above in this post.

Marco’s summary post is the second link for which I did the more detailed version of the match shown above. A quote from his post sums up why this match alone, made in December 2014, proves almost beyond doubt that the head lobe sheared from the body. This, despite it being around 1% of the evidence to date for head lobe shear.

“These mini matches make the original match conclusive, because if the large scale match was a coincidence based on large features, there is extremely low expectation of the constrained smaller section also matching in the small scale and/or in the third dimension.”

Quote from above link by Marco Parigi, October 24th 2015.



Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

To view a copy of this licence please visit:

All dotted annotations by A. Cooper. 



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