CometWatch 28 January

Today's CometWatch is an image taken with Rosetta's NAVCAM on 28 January 2016, when the spacecraft was 67.6 km from the comet nucleus.


Lightly enhanced NAVCAM image of Comet 67P/C-G taken on 28 January 2016, 67.6 km from the nucleus. The scale is 5.8 m/pixel and the image measures 5.9 km across. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

With the declining comet activity, Rosetta is now approaching the nucleus of 67P/C-G at distances that were not possible to attain since March 2015. This is granting us a detailed view of the comet's surface, including of some regions on the southern hemisphere that were still experiencing polar winter at the beginning of last year.

In particular, the southern portion of the 'neck' region stands out in today's CometWatch, with a dramatic perspective on the rugged terrains of Sobek. The small lobe, on the left in this orientation, reveals the seemingly flat southern region of Wosret, with hints of Bastet towards the upper edge.

The large lobe, on the right, shows a variety of different terrains: from the smooth portions of Aker and Khepry, visible as a bright swath at the top, through the rougher and boulder-rich portions of Khepry and Anhur at the centre, to a side-on view of Imhotep on the right.

The great diversity of Imhotep is clearly visible in this image, with smooth areas covered in dust, large circular features, terraces and many boulders. Hints of the Ash region can also be seen towards the right edge.

The original 1024 x 1024 image is provided below.




  • dave says:

    A cooper,

    There is a lot to get your teeth into.

    It looks like a crack, almost vertical almost all the way up the neck into the head, does this fit stretch, or is it more indicative of separate pieces?

    Also strange, there are very few pits, so if sublimation has been making the pits, then not enough temperature on this side? Although there is a long trough of joined up pits visible on the base.

    There is of course plenty of signs of erosion, but not very similar to other parts of the comet especially neck area.


    • Marco Parigi says:

      Hi Dave, Thanks for your interest in stretch! Although, I am not sure of which crack you are mentioning, there is a lot in this image pointing to stretch. You may perceive a large number of parallel lines across the neck region. Cracks on Anuket are also parallel to these lines. My theory is that cracks are opening up on the neck from the rocking of the lobes from asymmetric outgassing. My hypothesis is that this rocking motion is ratcheting the lobes apart, continuing the process of stretch. Measurement comparisons of the neck from the close mapping orbits from early in the mission to late in the mission will find whether there has been any measurable continuing stretch.
      I don't perceive "signs of erosion" . The best bet is to use before and after images to determine individual points of erosion, and only then decide which features are related to erosion, by extrapolation. It is too presumptious to decide any one feature is caused by erosion, when stretch is a valid proposition giving completely different signatures. dozens of stretch signatures are evident, while erosion signatures are all ambiguous.

      • MATION says:


        I must admit it looks very much like stretch, and my first impulse was that the neck is rocking.

        Also there seems to be very little evidence of erosion in the area where what looks like rocking is occurring, strange you might expect some ice to be exposed on what looks like fresh (comparatively) surfaces.


    • A. Cooper says:


      I just did a long reply and my computer ate it. So this is the short version. I've done a couple of annotated photos to show that your line and other parallel lines are torn ends of onion layers. There's a fair bit of 3D in this Rosetta blog post pic so those long lines are stepped out towards us at each successive layer and the layers go fairly vertical (in upright duck mode rotated 90° clockwise). Scroll to "COMMENT 2":

      Also, I think the most obvious match here is the curve on the head which is the same as the curve on the body. That's clearer in the first OSIRIS archive pic from early December. I annotated that showing these two matching arcs in fine detail. That's in Part 30. You can click my name above and then scroll to that part.

      • Dave says:

        A Cooper

        Computer ate it.

        The short version is fine, your middle picture is the most persuasive for me.

        However my question would be, Is it a contact binary that did not join very well, and thus lack of cohesion has allowed the neck to rock, of even hinge in the middle view.

        Or is the origin a single object where erosion and movement in what is now the head, through the neck in relation to the body that has given it its form?

        The so called onion rings are sometimes difficult to define to be sure its a contact binary.

        Thanks for the link


        • A. Cooper says:


          Your questions regarding whether it could still be a contact binary or eroded body while exhibiting these lines or layers are valid. But only when considering the lines and layers in isolation. For anyone who considers the matches between Babi/Seth and Ma'at/Serqet to be genuine, it simply follows that these lines and onion layers would look this way. I also think it's telling that the four lines I annotated are quite far apart when compared to their parallel sibling and its neighbours on Wosret further up the head. The lines on Wosret are much closer together. If the neck stretched, you would expect these lines across the neck to move apart to about the degree that they have.

          The head-body match for the s pole referred to in the above comment is fairly compelling too I think but it's not matched in anything like the detail along Seth and Babi (yet). That's due to a dearth of close up photos.

          Incidentally one of the purported Babi matches will get the 3D treatment soon, showing that it's like two bell-shapes nesting over each other.

        • Marco Parigi says:

          Hi Dave,
          re:"However my question would be, Is it a contact binary that did not join very well"

          Absolutely not! All the evidence is pointing to a stretch binary. The stretch signatures on the "onion layers" absolutely cannot be reconciled with the nucleus being from two separate lobes. Sliced onion layers on the head lobe match and continue on on the body lobe. Calculating backwards from how the layers have fractured, delaminated and slid has them being concentric spheroids around a single body. By Steno's law could not have been from two separate spheroids.

          In the future, through more stretching and accelerated corotation, they might end up being a non-contact binary.

  • logan says:

    The best shot I have seen on the family of horizontal layering belonging to neck and shoulders, Claudia 🙂

    More of a Sphinx, doesn't it?

  • masanori says:

    The difference in how the terrains look like between northern & southern part of neck regions is unbelievable!! Looking forward to hearing the scientists explain about this!

    • Marco Parigi says:

      Hi Masanori,

      But how symmetrically similar are the angles! A. Cooper explains more below, but the symmetry of the overall shape of the South Pole with that of the North Pole is uncanny. Possibly even more so with the texture of the terrain being, as you say, contrasting. The neck, for instance is concave all around, yet the solar influence should have eroded asymmetrically due to the contrasting Polar/equatorial seasons.

      The contrasting morphologies point to sliding,delaminating layers, and the symmetry points to stretch due to centrifugal forces from a previously fast rotation.

  • Kamal says:

    61 kilometres! hope you have spotted Philae.

  • logan says:

    On a global scale quick view:

    Small lobe left horizon line and erosion line to its right form a "<<" shape. This [120º?] seems to be an angular constant around Ducky. Jetting conforms to this geometry.

    That erosion line "_<" ending in a 'quadratic' feature. With 3 apparent jetting pits in the middle.

  • C. Bures says:

    When the Rosetta lands on the comet in later 2016, will it still be able to make measurements and send them back to earth ? Thank you.

    • Gerald says:

      Would be great, nobody knows, but probably not.
      The landing may destroy some of the hardware, pointing the antenna to Earth is difficult, Getting enough power from the solar panels will be hard, NASA's Deep Space Network antennas might be needed for other missions.

      If hopping would succeed, this might be a very remote hope.

      Another very remote hope would be survival in hybernation until next perihelion.

      Both unikely, but who knows?

    • Harvey says:

      Basically it's extremely unlikely.
      The high gain antenna could not point to earth, and is extremely vulnerable to damage.
      There is however a low gain antenna which does not have to 'point', and is probably more robust, but data rates would be very low.
      The huge, vulnerable solar panels will almost certainly be destroyed, and cannot be pointed at the sun; but there are fairly substantial storage batteries which could power things for a short time.
      None of the optical instruments could work, because they cannot be pointed and would be out of focus.
      It's just possible a few of the other instruments could operate, but those with instruments on extended booms (some plasma measurements, possibly the magnetometer unfortunately) will probably get wrecked.
      But it's not clear if the craft can send data from them via the low gain antenna.
      In summary, perhaps there is a very, very small chance of some limited operation for a short time, but I w opulent bet on it.

  • logan says:

    On visually scaning Big Lobe from top down appears a clear rectilinear frontier separating blanketed surface from "the rugged terrains [being the 'shoulders' continuation] of Sobek." That frontier ends in a vertex at Imhotep periphery..

    Why blanket extension stops so sudden and linearly? First idea is a strongly differentiated sublimation index, related to the lattice. Another idea -already mentioned around here- is geometry creating an 'umbrella' to the ComaReturn aphelion precipitation.

    A lot more scenarios should also fit well.

  • logan says:

    At the begging of my exploration, expecting here a continuation of Hapi. So terribly wrong ;/

  • logan says:

    Global layering at Small lobe matches that of Sobeck area:

    Consider clues like these detrimental of contact binary scenarios.

  • logan says:

    The 'crow' perspective is one I have lot of difficulty to integrate to a global geometry. Really looks 'binary'..

    Hi RamComet. Is this zone already defined in your previous 3D models?

    • Ramcomet says:

      Hi Logan,

      Sorry for delay.

      My physical 3D models, which used Mattias Malmer's shape model at the time, (May 10, 2015 based on Navcam images, not Osiris and south not as well illuminated as here) are only three inches long.

      But even so, I do see hints of the crackly "baklava pastry" in the Osiris image, on the right side of ducky's throat, and of course back of the neck, Anuket.

      Mattias says on his site that he would add further enhancements as time goes on, and would be working on an ultra high definition normalmap to bring out the smallest details. Maybe his shape model has been updated, I cant actually open it myself.

      OR, Maybe he was waiting on these Osiris images???

      One day I hope to have UPS make a six inch model for hopefully under $200 USD. Using Osiris based 3D from either Mattias or ESA.

      His site is amazing!!! Check it out.

  • logan says:

    "...packing within a confined space depends less on particle shape and more on the ability of the particle clusters to take on the container's shape."

    Erin G. Teich et al. Clusters of polyhedra in spherical confinement, Proceedings of the National Academy of Sciences (2016)


  • logan says:

    Once grain clusters are formed, sublimation|deposition goes on, and on, until all of these clusters becomes single grains, in itself, with the primigenial dust 'seeds' embeded... Reversible processes like this goes all up the scales.

    • logan says:

      The more constant the forming environment, eventually homogenization triumphs. The less constant, develops breath-paths. Drastic environmental 'weaving', erosion, fracture..

  • A. Cooper says:

    The side of the head lobe in this post's photo exhibits an area that's remarkably similar to Hathor at the north pole in its shape and dimensions. It's the area under the curve, bounded by that curve, the head/neck boundary and two fanned-out ends that yield to different morphology (Bastet and Anuket). Standing back, it looks like an elongated fan shape, fanning by about 120°. (Logan has already pointed out that it's 120° and I suspect this shape may be the area of Wosret that the scientists are considering renaming due to its different morphology). If you compare it with the following photo, you can see that it is indeed remarkably similar to the shape and size of Hathor. It's the top left photo in the four-photo composite. The area of concern is labelled 'Hathor' and has a preponderance of red lines on it. I would include the obvious coved part of Anuket (whiter, no red lines, fanning up and out to the right) in my description of this corresponding fan shape that resembles the south pole fan.

    Moreover, the latest OSIRIS picture of the s pole head lobe is at 47km distant and for the first time it shows vertical striations going 'vertically' up the s pole fan shape resembling the straight lines going straight up the Hathor fan. These are especially apparent on the left-bottom side of the fan:

    So we have two fans of the same shape and of equal dimensions with the same ~120° angle of fanning. Both are bounded by the different morphology of Bastet at one end and Anuket at the other One is centred across the north pole and the other on the exact opposite side of the comet because it's centred over the south pole. In other words, both fans are aligned along the long axis of the comet and both straddle the rotation axis, with half their areas on either side of the axis, evenly spread. The longitudinal or 'vertical' striations are at right angles to the long axis (even though Hathor is slightly more tipped down towards Seth/Babi than the s pole, the tip doesn't affect this 90° configuration of the striations).

    Can anyone think of an elegant explanation for this stunning symmetry between the north pole and south pole sides of the head that's so intimately related to the long axis, rotation plane and rotation axis?

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