This is the explanation post that goes with Part 48. This part contains all the photos from that part. Part 48 had no explanations at all, just clear photo headings. The idea was to present the rift and let the reader decide if it is a rift without recourse to the usual explanations of mechanisms. If you haven’t seen Part 48 yet, it may be worth clicking the ‘previous’ link at the top of this post and have a quick scroll through. It’s a good primer for this part.
A NOTE ON PHOTOS AND KEYS
All but one of the photos in this post are NAVCAM images. The single OSIRIS photo has its photo credit below it. The NAVCAM credit is at the bottom.
The header photo is reproduced with its key below. Many keys are narrative keys. Some are divided into paragraphs if they’re long. They either end with the next photo or ‘/////’ if they give way to general prose.
It should be remembered while reading these keys and the rest of this post that the 1.6 km rift happened when the head lobe was still attached to the body i.e. it was still a single-body comet and that single body was stretching due to spin-up. There is clear evidence of the rift extending up onto the head lobe that was herniating from the body at this time. This is proof that the head was still attached but showing photographic proof of this extension onto the head is beyond the scope of this post. However, it was mentioned in Part 22 and will be revisited soon as a separate post. Only one side of the rift was discovered at the time of Part 22 so it was described as a very straight ridge, not a rift. Regular readers will remember it as always being marked bright green on both head and body.
Some keys repeat small amounts of information to allow future citation of specific photo numbers in the knowledge that they have all necessary information in their keys.
Most photos in this post are in pairs of the same photo with extra annotations on the second version, overlaid on the first version. This is because the nature of the rift behoves us to concentrate on its line in an uncluttered view before adding other information.
As usual, the originals are appended after the annotated versions. The reader is encouraged to scrutinise the originals after looking at the annotations because the dots sometimes obscure some of the detail they’re drawing attention to. Also, the originals are raw data whilst the dots are a human interpretation of features. You need to believe your own eyes rather than my dots.
A NOTE ON THE PALEO ROTATION PLANE.
The paleo equator, which is also the paleo rotation plane is mentioned a lot in this post. It hasn’t just been discovered and doesn’t just exhibit signatures in the vicinity of the rift. It was discovered a year ago and was fully characterised just a few months later in the Paleo Rotation Plane Adjustment page in the menu bar. That page shunted it 3° owing to the discovery of a slew of signatures across Imhotep. It’s at 12°-15° to the current equator or rotation plane. The current plane precessed about the comet’s long axis from the paleo plane. The paleo plane follows 17 signatures spread all round the comet. The paleo plane is a highly refined aspect of stretch theory, explaining directly or indirectly the morphology of every named region on the comet.
The length and orientation of the 1.6 km rift in this post is a direct result of the paleo plane alignment during spin-up of the comet. This caused a cascade of other delamination and slide events across Aswan (formerly Site A) and Ash. The conclusion to this post emphasises how important the 1.6 km rift is for understanding the morphology of Aswan. Aswan’s morphology analysis will be published soon.
Photos 1/2- this is the header reproduced. These are two successive annotations on the same photo in order to see just the rift before cluttering it with slide vector arrows.
Red dots- the rift. The apparent gap in the middle, where there are no dots, is a red herring. It’s a piece of crust that’s attached to the lower-left perimeter but tore from further beyond the upper right perimeter than the rest of the tear. So it ended up draped across the rift and the rift runs underneath it. See photos 9 and 10 for a close up of this as well as other ‘mini matches’ across the width of the rift.
Red arrows- the tensile force vectors (force directions) of stretch brought about by the comet spinning up to a 2-3 hour spin period due to asymmetrical outgassing. You can see that the arrows are pointing in different directions either side of the rift. The crust sections the arrows are sitting on moved in the direction of the arrows. These crust slides, being angled to each other, resulted in the opening up of the rift. If you and a friend stood on either side of the rift just after it first cracked open, you would perceive them moving directly away from you and at 90° to the two parallel rift perimeters. This would be an artefact of the slide vectors: you’d both be travelling down the body lobe in your respective crust slide directions so the rift would open up at 90° to the average direction between the two slides.
The three inline arrows on the right have their vertices on the paleo equator, also called the paleo rotation plane (see further below). This means the direction of stretch along the crust at this point was straight down the rotation plane line towards the long-axis tip at Apis. This is of course to be expected on a comet that’s stretching due to spin-up. Four matched delaminations along the paleo line prove that this area did indeed stretch in that direction. Only one delamination has been mentioned so far (the ‘red recoil’ in part 26, signature 6). The rest will eventually get their own post.
Regarding the other three arrows next to each other in a row, these crust slide directions were verified with crust slide matches along these vectors. That was done in Part 32. They’re in keeping with that curiously smooth arc just above them. That’s the ‘Ash recoil’ which is described in Part 32 photo 5 as betraying the averaged or evened-out stretch forces arcing out over Seth and Ash.
Photos 3/4- the rift as viewed from just behind and above Apis at the long-axis tip. Again this is two annotations of the same photo. Apis is added in the second version, photo 4. It’s technically off-frame.
Pale green- Apis, in photo 4, is in shadow at the bottom and technically off-frame. It’s a rectangle straddling the brown line so it’s laid longways across the line. The brown line is the paleo equator or paleo rotation plane. Apis is highly foreshortened across its width in this view as it’s angled round towards the base of the comet. The paleo rotation plane runs through that little dip or niche midway along the rectangle as it crosses into Imhotep on the base. The current rotation plane or equator is at 12° to 15° to the paleo plane. It goes almost through the same niche because paleo and current equators cross at two places: the long axis tips. The current equator runs just to the right of the niche and crosses the paleo equator just beyond the far lip of Apis.
The official ESA delineation of the Apis region is a very stubby triangle but I always add a small section that really is part of that little tablet of crust (because it’s already been matched to its seating). The tablet is quasi-rectangular and, very roughly, 700 x 400 x 50-80 metres. The 50-80 metres corresponds to the torn, exposed sides which are presumably the thickness of this top onion layer of crust. This description of Apis may sound off-topic but all such apparent peregrinations are planted carefully to let them sink in gradually for later paragraphs or upcoming posts.
Red- the rift as depicted in the header. However, there are several extra details. Firstly, there are eight red dots forking up to the right from the brown line. This line together with the right hand perimeter of the rift forms the so-called red triangle that was first presented in part 26. Not all of the triangle is in frame, there’s a chunk to the top-right which is off-frame. The red triangle was somewhat protected from the full force of the strongest tensile forces of stretch which ran from one end of the comet’s long axis to the other. After those forces were directed around the soon-to-be neck, they ran in a straight line to the stretching tip, causing a long, thin triangle. That’s the red triangle which experienced a somewhat reduced stretching force on the crust within its perimeter. This led to simple delaminations occurring within the red triangle and complete mayhem outside it. The mayhem comprised the rift in this post, the scalping of the slab A extension, the Ash recoil and the opening up of the main sink hole. And the Anubis slab loss on the other side of the triangle.
Another feature in red dots is the end of the rift that broke away from the two ends of the long perimeter sides. It continued sliding down towards the long-axis tip at Apis. It’s significant that its direction of travel is exactly in line with the brown line which is the paleo rotation plane and therefore the stretch direction at this point near the tip. This isn’t an isolated observation. It was happening in a more spectacular way at Khonsu at bottom right (but off frame and round the corner anyway). The Khonsu stretch happened with multiple delaminations being pulled towards the long-axis tip by the short side of the Apis rectangle (not published as of the date of this post). The most talked about of those Khonsu delaminations is the three bright ‘gills’, as they are often called, but they have not been recognised as delaminations by any scientific papers as of the date of this post.
Brown- the paleo equator or rotation plane. The paleo plane held sway when the head lobe was still attached to the body lobe. Seeing as all the tensile forces of stretch were transferred to the growing neck immediately after head shear, the rift in this post had to have happened when the tensile forces of stretch were still running through this section of crust. That means the rift opened up when the head was still attached to the body. This is additional proof to the ‘bright green’ ridge match going up today’s head lobe.
The rift may have opened up only just before head shear because it certainly caused a major weakening at the head lobe shear line. So it rifted when the head was still attached to the body, but herniating and straining to leave the body. This means the paleo rotation plane still held sway at that point in the stretching process. The strongest tensile force vectors of stretch therefore ran from long-axis tip to long-axis tip (Hatmehit cliff to Apis). This explains why the very end of the right hand rift perimeter kisses the paleo rotation plane as the rotation plane line crosses through the sharp vertex of the red triangle. This could hardly be a more stunning affirmation of stretch theory, a confirmation of all the discussions regarding the red triangle and how the tensile forces of stretch were directed around it like wind around a rock, meeting up at the vertex of the wind tail.
The paleo rotation plane runs straight down the middle of the red triangle, bisecting it longways. It doesn’t appear to bisect it here but that’s an optical illusion unique to this photo. The sharp vertex is where the tensile forces of stretch from the north pole side of the head met up with the tensile forces of stretch from the south pole side of the head. They were forced outwards from the centreline (the paleo plane) by the width of the neck and especially by the ‘vertical wall’ (Part 26). They met up at the red triangle vertex- the winds meeting at the wind tail vertex behind the rock.
So our 1.6 km rift not only constitutes one side of the red triangle, its end is in line with the vertex where the north pole and south pole tensile forces met. The rift, being on the north pole side of the red triangle couldn’t run past the triangle vertex because it would run into the tensile force vector coming from the south pole. That was probably a rift too but it turned into the major sliding and possible slab loss on that side of the triangle. Instead, the end-wall of the rift broke away and travelled on its side of the paleo rotation plane line so as not to encroach on the south pole tensile force vector that was falling into line after passing its side of the red triangle. That tensile force vector was falling into line down the other side of the brown line.
This is why the rift stopped at the triangle vertex and its delaminated end travelled on, kissing the brown line without crossing it. And that’s the reason it’s such a neat confirmation of stretch theory. It’s a physical representation of the tensile forces as well as the shear forces along the triangle sides. It explains the wind tail phenomenon and the two tensile force lines merging along the paleo rotation plane line just before the long-axis tip at Apis.
Regarding the force vectors running from the red triangle vertex to Apis, those forces came from either side of the soon-to-be neck and ran down the triangle sides to the vertex where they met. They then ran together and contiguously with the paleo plane line for a short way from the red triangle vertex to Apis at the long-axis tip. Or at least theoretically so. In reality, it’s just the mathematically derived strongest tensile forces extending from the triangle sides that followed this neat, theoretical path. In reality, the forces as a whole were spread across the length of Apis. Apis was mentioned above as being a rectangular tablet straddling the brown paleo plane line lengthways. The effect was that the Apis rectangle pulled this end of the comet into this half of the straight-edged diamond shape. That’s why the body is diamond-shaped. The head is diamond-shaped at Serqet/Maat as well but smudged at Bastet, probably by its herniation and tipping motions (Part 20). The role of Apis in pulling on the matrix evenly from around its perimeter, instead of a smaller area pulling it into a point, is the reason that the diamond has a flat tip (Apis). It certainly explains why that tip straddles the paleo plane symmetrically. This phenomenon was duplicated at Khepry/Aker at the other end of the body (see the Paleo Rotation Plane Adjustment page). The following paragraph repeats some of this paragraph but with some additions to try and nail down the reason for the morphology of Apis.
In photo 4, Apis is located where the brown paleo plane line is curving round to run across the comet’s base. It bisects Apis in the process. The raison d’être for Apis being a small, rectangular tablet stuck on the long axis tip is that it performed this very function of stretching the cometary matrix at the long-axis tip. It was thick and stubby enough not to be snapped in two by the tensile forces coming from the north and south pole sides, down the red triangle sides and converging at the long-axis tip. Instead, it straddled the tip, causing the tip to flatten. It chose to snap from its neighbouring sections of crust equidistantly either side of the paleo plane. This was where the tensile forces rounding the tip became flexion forces. The distance from the paleo line at which they snapped was the distance at which the increasing moment (leverage) of the flexion force was stronger than the Apis crust’s tensile resistance. Flexion force overcame tensile resistance at this distance and it’s the same distance for both tears (or rather, snappings) either side of the paleo line. The equidistant snaps betray the symmetrical flexion forces acting on a presumably even thickness of crust with consistent tensile resistance (see the Paleo Rotation Plane Adjustment page for a fuller explanation including additional proof of this mechanism playing out on Khepry/Aker at the other end of the diamond).
Photos 5/6- viewing the rift from the opposite direction, above Ma’at. Again, the annotations are added successively over two versions of the same photo so as not to clutter the mind’s eye with red arrows.
Brown- the paleo rotation plane, which is the same as the paleo equator.
Bright green- regarding the left hand of the two curves: this is the 1.6 km rift’s southern perimeter extension that drops down into Hapi. It’s the same as the bright green ridge extension in Part 22 and matches to the head lobe. Regular readers will be surprised this is curved and not straight but it’s depicting the fluted edge of what is a long, pointed ridge. The straight spine of the ridge is what’s customarily dotted green and that’s just to the left, highly foreshortened, and extending on towards us beyond the bottom green dot. Regarding the right hand curve: this massif matches to the ridge extension. This bright green slide is almost the same distance as the red rift width, as judged here. And the two curves would nest back together only if they slid back in exactly the reverse direction as the rift-opening vector. These two facts show that the rift extends into Hapi. Photo 4 will give a much better view of the bright green match but this photo shows the entire rift length from this angle as opposed to a closer shot from a similar angle in photo 4.
Red Arrows- the big ones are the crust slide vectors for the two sections of crust either side of the rift, as in the header photo for this post. The red triangle is on the left of the rift and Ash/Seth is on the right. Note that the single arrow on the left is pointing straight down the paleo rotation plane line. The small arrows in the rift show the vector for the two sides pulling apart from each other as the two pieces of crust either side of the rift move along their respective slide vectors.
Photos 7/8- a closer view from above Ma’at. Annotations are added successively again. In this case, it’s the slate blue dots that are added in photo 8.
Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER
Red- the rift.
Bright green- the left hand curve is the edge of the ridge extension into Hapi that’s usually coloured bright green. The right hand curve is the matching massif that used to nest to the left hand curve before the rift happened. So these two torn-apart curves are in effect an extension of the rift into Hapi. They happen to be staggered from the very straight perimeter lines. There’s a reason for this which is beyond the scope of this post. It will get its own post.
Mauve- two dots showing the top two corners of the mauve body anchor that matches to the mauve head anchor component (Part 24). The two dots aren’t obvious. They’re at the end of the red line and green line.
Slate blue- two large dots which show that the horseshoe shape clearly slid, as it had to if the curved massive slid. Of course, the slide length and direction of the horseshoe slide is the same as for the massif but the interesting thing is that it left its horseshoe seating imprint behind in the middle between the two bright green rift lines. That’s a nice piece of extra evidence.
THE MINI MATCHES THAT PROVE THE TWO SIDES OF THE RIFT USED TO BE JOINED
Although the rift is depicted as two straight lines and really does look to be straight lines in most photos, there are subtle curves and dips along the two perimeters that clearly match across the divide. This is normal procedure in this blog, however in this case the matches seem to be thin, ragged bits of dusty surface crust that have torn from beyond the notionally straight lines and draped themselves within the rift or even right across the rift. The straight lines that define the two perimeters are clearly there, representing the dominant average width of the rift but the mini matches meander along just inside or just outside the lines. The long tip of the largest mini match slide delamination merges with its seating. So in certain photos, such as the header, it looks as if there’s crust draped right across the rift at this point.
Photo 9- mini matches between the two rift perimeters.
Red- the left hand line matches to the right hand line. The dots really don’t do these matches justice. You need to study the unannotated version to see that they are quite faithful. The reason for the dots not showing it well is that the matching lines have some width and matches within that width. Judging where on the line to put the dots is tricky whereas the eye can pick out the matches within the width of the line. The dots often obscure the detail too. Photo 10 is an attempt at depicting some of the more obvious matches across the width of the lines.
Photo 10- extra mini matches (in pink).
This is an important post. The 1.6 km rift loosened the Seth crust layer enough to set off a domino effect of major crust slides and delaminations across Aswan (formerly Site A). It explains the existence of the main sink hole which is simply a deeper rift of the same nature that tore from the red triangle perimeter before the 1.6 km rift did so. It’s uniquely deep because it sat at the end of the rift on the three-way point between the two rift perimeters and the herniating head lobe rim. The main sink hole then slid, along with the whole of Aswan, in sympathy with the Seth/Ash side of the 1.6 km rift. So it isn’t a sink hole but a rift whose tearing vectors induced a notional square or triangle that has now been worked to a circular shape by erosion. But we’ll still call it a sink hole with occasional reminders of its true provenance because that’s what it’s commonly referred to as being.
The 1.6 km rift also explains indirectly why the main sink hole has two more holes behind it as well as shedding light on the reason for the flatness of Aswan, the bunched-up terracing around its back rim and why that rim overhangs Ash.
The rift also confirms why the red triangle exists at all, perched as it is on the edge of Seth and bordering Anubis. The explanation regarding the tensile forces involved in opening up the rift fully complements and corroborates everything said in Part 26 regarding the red triangle as well as all other mentions of it thereafter.
The rift even explains the morphology of Anuket, Hathor, Serqet and Ma’at because it’s the demarcation line between two tensile stress vectors (stretching force directions). Those different vectors resulted in the rift opening up in the first place. They’re the red arrows in the header. It’s no coincidence that the southern perimeter of the rift is directed straight at the place where today’s Serqet-Ma’at border used to sit, clamped at the end of the rift. And although Anuket is deemed to run under and past the Serqet-Ma’at border, the part that does so is really the scalped piece of the slab A extension that was taken up with the head lobe and splodged against the neck. It’s an imposter, confounding our understanding of the neck morphology. Underneath the splodge, Anuket almost certainly yields to a buried Hathor cliff at exactly the same demarcation line as the Serqet-Ma’at line.
The Serqet-Ma’at demarcation line is now on today’s head. When this demarcation line was clamped to the end of the rift, specifically, the rift’s southern perimeter line, everything to the north in these photos (left and along Hapi in the header) was stretched along the long axis. Everything to the right of the demarcation line stayed put and didn’t stretch, or at least, not at first. It therefore acted as an anchor or in fact, as the spinning counterweight doing the pulling to stretch the section to the left. A similar counterweighting process happened at Babi/Aker but with a much more stunted rift. Together, the two counterweights stretched the middle section of the comet. That middle area corresponds to Hapi on the top of the body and the width of the Imhotep rectangular plain on the base of the body. Imhotep has already been described as being the result of the middle section of the comet being stretched disproportionately (Part 43, the ‘red crust slide’) so the domino effect ramifications from the 1.6 km rift already have a good corroborating mechanism for the opposite side of the body lobe. It would indeed be strange if we couldn’t find such evidence of large scale central stretching on the base at Imhotep as well. In the case of the red crust slide, it was just the crust sliding like many other crust slides but the fact that in this particular case the smooth area it left in its wake was so long and wide, betrayed the stretching of the core beneath it. The red crust slide was simply sliding in sympathy with the core, just like all the tearing and delaminating crust along Hapi, diametrically opposite on the body. Looking at that neat rectangle of smooth terrain on Imhotep from a distance, the central stretch becomes very apparent.
There was also at least some stretch within the depression on Imhotep too (not posted as of the date of this post). Since the depression is the fourth onion layer down, this would be suggestive of core stretch too, rather than idle sliding about due to coriolis forces and general reconfiguration as with most of the slides.
The result of the stretch along Hapi is the remarkably straight line of the Hapi rim, which aligns with the long axis of the comet running through the body beneath it. This is what caused the head to shear eventually: the Hapi rim is by-and-large the head lobe shear line. The head was clamped at that time and stretched with all the delaminations and tears on the body. We know this because today’s head rim underside has mirrored matches to the body (Parts 1, 2, 3, 5, 17, 21, 24, 29, 30, 40, which together match the entire head rim to the body).
The stretch along the long-axis (along Hapi) involved delaminations, slides, more rifts and tears and actual stretch, in fact anything that would allow the crust as a whole to stretch with the core of the comet below it. These processes have already been catalogued and described at length from Parts 31-41, especially Parts 38-41 so we’re not invoking anything new here.
The domino effect that the 1.6 km rift set in train will be discussed in future parts. The next part will deal specifically with the effects on Aswan, including the sink hole, the terracing at the back and extra photographic proof that the entire onion layer of Aswan (the flat part) slid on the onion layer below it.
PHOTO CREDITS FOR NAVCAM PHOTOS:
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
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All dotted annotations by A. Cooper