67P/Churyumov-Gerasimenko. A Single Body That’s Been Stretched- Part 47

THE SETH/BABI PERIMETER MATCHES THE LINE OF BOULDERS IN HAPI






The two terracotta lines are a translational match. 

INTRODUCTION

This post interrupts the series on Imhotep crust slides. Pages were being posted to avoid the problem of interruption. They will be upgraded to posts when the Imhotep series is finished. But now the menu bar is too full with pages awaiting upgrade so there will now be some posts interspersed between the Imhotep slides.

The line of boulders in Hapi matches the Seth/Babi perimeter. It’s a translational symmetry: two lines that when slid together, overlap nicely, following the same twists and turns. This discovery was going to be posted after Part 40 because it follows on naturally from the Babi slide and would have led us into the site A area for a few posts. However, Imhotep took over and this plan was dropped. Nevertheless a new Cometwatch post on the Rosetta blog has a particularly good photo for illustrating the boulder line-perimeter match so it’s getting a post. The Cometwatch post is here:

http://blogs.esa.int/rosetta/2016/06/24/cometwatch-17-june/

In this Cometwatch post, Site A has been officially named Aswan. This blog will try to use it but will have to reiterate that it’s the old Site A on a regular basis because ‘Site A’ has been used hundreds of times in the previous 46 posts and won’t ever get updated. 

Photo 1- this is the same as the header. The line of boulders in Hapi matches to the Seth/Babi perimeter. Therefore the perimeter slid from the boulder line. 


Right hand terracotta- the line of boulders. 

Left hand terracotta- the Seth/Babi perimeter. 

Photo 2- as photo 1 and includes visible slide tracks in yellow.

Yellow- slide tracks.

Fuchsia- a rift along Hapi almost at right angles to the slide tracks. This was mentioned in Parts 38 and 39 along with a promise of a dedicated post, which hasn’t happened yet as of this post. The eventual post will show multiple photos, including the section in shadow. This representation of the match is rather naive because of the actual match being in the shadow but it is there. This rift explains the lateral translation anomaly along the line of the Seth perimeter with respect to the boulder line. The boulder line is continuous with no such rift and the curved slide tracks show the path of the newly freed section as it slid both back with the perimeter and along Hapi with the rift. 

Photo 3- includes a green section

Green- a section that was missing in photos 1 and 2 because it slid further back from the notional perimeter that kisses the dust of Hapi. This is the first indication in this series of photos that multiple delaminations occurred throughout the perimeter slide. In other words, sections of crust delaminated and slid further on while the section they delaminated from stayed put at the location of the delamination. This leads to multiple perimeter lines that are translationally matched. In this case, only two delaminated layers will be shown, giving two translationally matched perimeters. However, along with the line of boulders, it’s three translationally matched lines (see photo 4).

Photo 4- this includes the cove on the head that matches to the body (Parts 3, 18, 35-37). 

Larger yellow- the cove on the head and its seating point on the body. The last two dots at the top in both cases, sit either side of the ‘napkin’ described in Part 5. The napkin is at one tip of the so-called gull wings. The cove line on the head is tricky to depict here but is fairly accurate. It’s tricky for three reasons: 

(1) Head tipping causing foreshortening.

(2) shadow.

(3) the line runs under the visible rim here at both ends. That’s why the dots don’t follow the rim exactly- we are supposedly looking through the head lobe to its underside where the seating is. Photos 6 and 7 show the underside view. 

Dark green-the rest of the visible head rim and its seating on the body (Parts 1, 5, 7, 16).

You can now start to see that the bottom section of the cove in this view is a translational match to the terracotta perimeter and to the boulder line. Photo 5 elaborates on this. 

Photo 5- isolating the translational matches

The cove, the perimeter and the boulder line on the body (all three. to the left of the shadow) and their translational match on the head rim 1000 metres above (on the right). The head match is just showing the section of cove that matches to the most straightforward ‘s’ shape on the boulder line directly below it. Again, it’s difficult to depict and just representative here for the same reason as given for photo 4. However, photos 6 and 7 show that the same ‘s’ shape is indeed very apparent on the underside of the head rim. 

Photo 6- the ‘s’ shape on the head underside that matches to the ‘s’ shape on the boulder line

Photo 7- the rest of the head cove rim line extended from end to end. Again, the two dots at the left hand end are either side of the napkin that’s virtually edge-on in this view. The green section matches to its respective green locations on the boulder line and the cove seating on the body in the above photos. 

CONCLUSION

The match of the perimeter to the boulder line is strong evidence that it slid from the boulder line.

The boulder line moves into shadow at the bottom of the main photo for this post. The matching to the Seth perimeter remains faithful for another few hundred metres which would be about a quarter of the matched length here. It will either be added here in due course or get its own post. The boulder line in this section is blends with very low, solid outcrops and with the crack at the base of the neck. This of course has profound implications for the provenance of the crack. That’s because Aswan (the newly named Site A) used to run along the perimeter of the crack. We know this to be the case because the Seth perimeter (which includes Aswan) matches translationally to the boulder line which follows the crack. 

Either the crack was deep and dominant and caused the rift of Aswan from the crack line; or the rift was just the Aswan onion layer and caused the crack to go a little deeper at its bottom. This perhaps calls into question the theory that the crack is solely due to tensile stresses in the neck. It would be very susceptible to those stresses but its location is related to an onion layer tear, whether the tear was brought about by the cracking neck or vice versa. 

PHOTO CREDITS

Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
To view a copy of this licence please visit:

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

All dotted annotations by A. Cooper. 

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One thought on “67P/Churyumov-Gerasimenko. A Single Body That’s Been Stretched- Part 47

  1. Pingback: Part 73- The 4.5-Kilometre-Long Rift From The Northern Long-Axis Tensile Force Line | 67P/Churyumov-Gerasimenko- A Single Body That's Been Stretched

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