67P/Churyumov-Gerasimenko. A single body that’s been stretched. Part 6

Incorporating matching structural ridges into existing matches (orange dots)

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Annotated photo of the shear line where the head broke away from the body, as described in parts 1-5. Click for hi-res. Zooming is advised.

Key:

[There are a couple of anomalous black blobs that appear to be artefacts of dots mistakenly placed and then erased. These are on site A (the flat crater) and on the neck. Please ignore these]

Green dots: shear line as described in parts 1-4

Blue dots: show matching ridges across head and body lobes. The long blue ridge across head and body overlapped at the scalloped triangle (blue dot in 2nd photo below) and incorporated the pushed-up ‘gull wings’ along that short distance. These gull wings are described in part 5 and match the gull wings directly above, under the head (not visible here).

Yellow dots: show how head cove fits to base

Red dots: point-to-point matches

Light orange dots: ‘geological’ or structural shear ridges (head lobe shows these with one large dot either end). These are not the actual shear line but ridges that were exposed by the head uplift and the uplift of two hypothesised adjoining slabs that drifted away. However, because the head uplift caused them to be exposed, the main shear line does follow both ridges for a short distance- the rest of their extent was covered by the slabs. The two ridge lines on the head match the two on the base. However this is tricky to visualise: since the head has to be tipped back 30 or more degrees to seat down on the body, it is the bottom ridge line on the head (as viewed from this shot) that fits to the top ridge line on the body. Similarly, the top ridge line on the head fits to the bottom ridge line on the body. There is also a small anticlockwise rotation needed for them to fit.

Brown dots: supposed shear line running in ‘mid air’ across missing slab area. This would be the third and largest missing slab.

Fuchsia dot: next plausible match point (mirror point on head not in shot).

Below is a similar annotated photo from a different view. This excludes the orange dots for the structural ridges since these aren’t thrown into relief as much. It also excludes the fuchsia dot (off frame to right) but includes a large blue dot to denote the centre of the scalloped triangle. You can see the two circular slurry piles which were ejected from under the scallop and which pushed up each gull wing 20 metres or more (wings only just visible from this angle). The gull wings correspond to the wings under the head which again are not visible. However, a third tier of wings is visible here. They are next to the first green dot on the head and appear to match roughly to the scalloped triangle. That is because the three tiers of wings were stacked loosely like puff pastry, one on top of the other. The true match to the scallop is pictured side-on in part 5.

The three green dots on the head correspond to the first three green dots running along the back of the ‘rectangle’ that incorporates the scalloped triangle. This short section is the subject of part one with the rest of the green dots dealt with in parts two and three.

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

http://creativecommons.org/licenses/by-sa/3.0/igo/

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67P/Churyumov-Gerasimenko. A single body that has been stretched- Part 3

(Please scroll down for parts 1 and 2)

This post carries on from Part 2, that is, from the fuchsia dot in the recess on the head and its counterpart on a distinctive peak on the body. I’ve marked them yellow this time because they also act as end points. The matching head and body shear line will now be extended round as far as the shadowed side in one direction and to the crater rim of site A in the other direction.

If you have followed parts one and two you will be familiar with the coloured dotting technique but in these photos there are no sequential colours marking long wavy lines. It’s somewhat simpler. Generally speaking, it’s yellow dots for specific points or end points of lines (except for the last photo where they delineate a crater edge). Light blue for ridges that match. There are some dark green dots in two photos, roughly showing matching points or lines that were dealt with in Part 1, but this time from a different viewpoint. That’s more for orientation. And some terracotta thrown in specifically for two points, side by side, which don’t have their respective twins in the same photo- they match across photos.

In photo 1, the end point of the line in part 2 is marked with yellow dots in the head recess and the peak below. The peak doesn’t look very pointy because we are looking up from below the body. Notice two small dimples on it which are almost obscured by a blue dot. Those crop up in a clearer view of that peak in photo 2 and show that it is indeed the correct peak.

The left hand yellow dots are the end points situated at the near-90 -degree turn towards the terminator shadow. The top section fits to the bottom section at this corner. If you measure the distance between the dots (or the points they are marking) you’ll find top and bottom are identical in length. Also, the wavy line along the bottom matches fairly well the ups and downs of the top line despite being seen from a low vantage point.

The blue dots show a ridge that was contiguous from head to body. The terracotta dots match their counterparts in photo 4

Photo 1

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Photo 2

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In photo 2, the yellow dots serve the same purpose as in photo 1.
However it’s a bit whited out on the head so I left out the top left corner dot because I couldn’t really place it. The same goes for the curve up to the yellow dot in the recess. It’s whited out so I marked the curve you can discern in green (the Part 2 head perimeter) and the eye can then extend the curve to the recess. The centre green dot is on the ‘frill’ mentioned in part 1, which is now well lit. It’s counterpart is roughly placed at the seating point against the low, bulbous ridge below on the body. The blue dots denote the ridge again. This is less obvious in the high illumination but you can see small holes running down both sections. The wayward blue dot is a rogue addition but it happens to mark the terracotta point from a good perspective.

Photo 3

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Photo 3 shows the shear line emerging from under the head, along to the corner. Everything to the outside of it slopes steeply. After the turn, there is a small dogleg after which it extends to the shadow where it appears to turn further clockwise. The head line isn’t marked because most of it is probably just out of sight. It doesn’t look as straight as in photo 1 which clearly looks to be a crisper line that would fit the straight edge below it. I didn’t mark it after the corner in photo 1 either because it was truncated and I couldn’t tell if it was due to shadow or the dog leg. Anyway, toggling from photos 1 to 3 show obvious fit lines up to that point. The blue dots again show a ridge, a fat one this time. The two parts are in line as you look down on them, and have similar pock marks top and bottom.

Photo 4

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Photo 4 is fairly self explanatory. It continues in the other direction from where we started in part 1 (green dots). The yellow curve is much less pronounced on the head due to foreshortening. This is in turn due to the head being tilted forward by some 30 degrees. The terracotta dots from photo 1 finally find their twins. The blue dots show a ridge that is much more prominent in the top down photo in part 1. It may appear that the upper part should be the fluted end section seen in part one and should sit down on the base but it is the section that was above it like a flap. Only the long, front edge of the cliff matches the green dots. The rest is hidden below the flap/ridge. The half-moon green dot is a rogue artefact.

Photo credit: ESA Space in Images/ Rosetta Blog.

I’ll reproduce all photos in this post below, but without annotation dots. Sometimes it’s easier to see the lines and ridges without them.

There will be a part 4 but due to my hunch that huge slabs were lifted as the head sheared away from the base and one of them was sitting on site A, the matches are fewer and less clean. They might match something but it could be a slab orbiting millions of miles behind 67P/C-G. Still, I believe there are some matches beyond site A.

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67P/Churyumov-Gerasimenko. A single body that has been stretched- Part 2

This is the second post which matches features on the two lobes of 67P/C-G in order to prove they were once joined. Some of the text below is a repeat of yesterday’s post since it applies to this post too. However, I would recommend reading yesterday’s too as it will serve to orientate you before moving on to this next section of the shear line. This section’s start point should in fact be yesterday’s end point as it is the continuation of that line. All told, it continues unbroken for the best part of a kilometre.

Below are two photos of comet 67P/Churyumov-Gerasimenko. The first is a close-up of the so called body, the second is a portion of the head. These two areas exhibit an identical wavy line showing that they were once joined together. It therefore follows that 67P/C-G was once a single body that has since been stretched, resulting in the two lobes we see today. This stretching would most likely have happened due to a very close approach to Jupiter, under the Roche limit, or a spin-up due do asymmetrical outgassing.

The colour-coding of the dots in the photos is listed further down. And there are two undotted versions at the bottom of this post which may be easier to work with once you know where to look for the matching lines. You will need to zoom in to see the detail (and please ignore the spurious grey line in the ‘head’ image!)

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As with yesterday’s post, the 11 coloured dots trace the same line in both photos. Each colour marks the same twist or turn along both lines. The sequence is:
Pink
Orange
Light blue
Dark green
Yellow
Bright green
Brown
Dark blue
Terracotta
Mauve
Fuchsia

As the head fits to the body, it follows that 67P/C-G is not a contact binary as has been suggested. Nor is it an unstretched single body that has been eroded to form the separate head and body.

Since the two photos show opposite sections that once fitted together, they are mirror images of each other. They exhibit a geological line formation tracing a convoluted path which is faithfully reproduced in both photos. The shapes of the line in both are topologically identical but due to foreshortening, one is somewhat more squashed than the other. The matches are nevertheless very clear.

These two portions of the head and body of the comet already showed multiple matching features both in the areas shown annotated in close-up and in their immediate vicinity. The dots also match in the third dimension, not just in plan view. For example, the fuchsia dot on the body is at the tip of a pronounced peak. This peak nestles up into the deep recess in the head where its corresponding dot is to be found.

There are many other matches between head and body along the ridge that forms the base of the ‘neck’. The above matches are simply the most compelling ones.

The photos from which the annotated close-ups were taken:

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Photo credits:

1) ESA Rosetta mission blog

2) Bill Harris who posted the photo of the body portion on the Rosetta blog in the comments on this post:

http://blogs.esa.int/rosetta/2014/12/11/cometwatch-9-december/

The original close-up versions of the shots that were used for the purpose of annotating with dots are below. It may be easier to see the matches without the dots once you know where they are.

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67P/Churyumov-Gerasimenko. A single body that has been stretched- Part 1

Below are two photos of comet 67P/Churyumov- Gerasimenko. The first is a close-up of the so called body, the second is a portion of the head. These two areas have numerous matching points showing that they were once joined together. It therefore follows that 67P/C-G was once a single body that has since been stretched, resulting in the two lobes we see today.

67P/C-G is therefore not a contact binary as has been suggested. Nor is it an unstretched single body that has been eroded to form the separate head and body.

As it’s clear the comet was stretched, it must have been subjected to one of two scenarios. It either underwent a close approach to Jupiter under the Roche limit in the distant past or it underwent spin-up to around a 90-120 minute rotation period which would overcome its gravitational pull. The former scenario would need to allow stretching without breaking up as Shoemaker-Levy 9 did on passing Jupiter, so possibly between 115,000 and 135,000 km above Jovicentre. The latter scenario might occur due to asymmetrical outgassing and would suggest a spin back down from the ~2 hour rotation to its current 12.4 hour rotation period. A close approach to another planet on its way in from the Kuiper belt is possible but much less likely than a close encounter with Jupiter.

Since the two photos show portions of the head and body that once fitted together, it follows that they are mirror images of each other. They exhibit a geological line formation tracing a convoluted path which is faithfully reproduced in both photos.

The 11 coloured dots trace the same line in both photos. Each colour marks the same twist or turn in both lines. The sequence is:
Pink
Orange
Light blue
Dark green
Yellow
Bright green
Brown
Dark blue
Terracotta
Mauve
Fuchsia

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These two portions of the head and body of the comet already showed multiple matching features both in the areas shown annotated in close-up and in their immediate vicinity. The matches even occur in three dimensions, for example, the finger-like protrusion in the cliff face under the head (almost reaching the yellow dot) fits neatly into a U-shaped cove below its counterpart yellow dot on the body. Also, just to the left of the finger-like protrusion there is a set of nested curves. These fit to nested curves in the body. These are just above/below the fuchsia dot in both cases. Although these matching protrusions are easily discernible in the head photo above, it is easier to see in the two annotated photos at the bottom of this post. In this case yellow dots denote the finger protrusion and its U-shaped counterpart. Terracotta dots denote the nested steps on the body photo (the steps are only visible on the neck portion in the neck photo above. They are to the left of the finger, above the fuchsia dot and not annotated so as to avoid confusion with the other dots in that photo).

Another example of the head/body fits matching in three dimensions is found with the annotated wavy line itself. It doesn’t just match in plan view: the edge of the cliff along which it meanders is pushed up in a frill. That frill seats against a very low, bulbous ridge on the body where its corresponding wavy line sits. Also, the sections running at 90 degrees to the pink dot nest together in the third dimension.

There are many other matches between head and body along the ridge that forms the base of the ‘neck’. The above matches are simply the most compelling ones.

The photos from which the annotated close-ups were taken are below. For orientation on the body photo, the first dot (pink in the close-up) would be sited at the end of the deeply shadowed ridge that’s shaped like an elongated question mark. From there, two triangles that are point-to-point are what constitute the main part of the close-up.

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Photo credits:

1) ESA Rosetta mission blog

2) Bill Harris who posted the photo of the body portion on the Rosetta blog in the comments on this post:

http://blogs.esa.int/rosetta/2014/12/11/cometwatch-9-december/

Additional annotated photos as described above:

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