Last waltz at 28 km – CometWatch 3 February

This four-image mosaic comprises images taken from a distance of 28.7 km from the centre of Comet 67P/Churyumov-Gerasimenko on 3 February. The image resolution is 2.4 m/pixel and the individual 1024 x 1024 frames measure 2.5 km across. The mosaic has been slightly cropped, and it measures 4.2 x 4.6 km.

These are the last images taken by Rosetta's NAVCAM before the spacecraft left its bound orbit around the comet at 28 km from the centre. On 4 February, Rosetta moved into a new operating phase characterised by a series of flybys past 67P/C-G at a range of distances, the first of which will be the very close encounter planned for next weekend, when Rosetta will pass just 6 km from the surface of the comet on 14 February.

ESA_Rosetta_NavCam_20150203_Mosaic

Four image mosaic comprising images taken on 3 February 2015 by Rosetta's Navigation Camera (NAVCAM). Rotation and translation of the comet during the imaging sequence make it difficult to create an accurate mosaic, and there may be some spurious spatial and intensity features as a result of the mosaic-making sequence, so always refer to the individual frames before performing any detailed comparison or drawing conclusions about any strange structures or low intensity extended emission. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

In this orientation, we see the smaller of the two comet lobes in the upper part of the image, with the larger lobe below. Emerging from the shadows of the comet's neck are the cliffs of Hathor, in the central part of the image, crossing over to the Anuket region on the right. Parts of the smooth Hapi region on the neck are also visible in the shadows, just above the bright rim of the large lobe.

Some circular depressions on the Seth and Ash regions are visible on the large lobe; parts of the Anubis and Atum region can also be seen towards the lower right corner of the image.

The view of the small lobe shows mostly the Ma'at region, on the left, while the ridge on the right and the smooth plain above it belong to Serqet.

The four-image montage and the individual 1024 x 1024 frames are provided below:

ESA_Rosetta_NavCam_20150203_FourFrameMontage

ESA_Rosetta_NavCam_20150203A ESA_Rosetta_NavCam_20150203B ESA_Rosetta_NavCam_20150203CESA_Rosetta_NavCam_20150203D

Comments

27 Comments

  • Bucshot says:

    Didn't the probe have a tether on the anchoring system? If so could you set the anchor and play out the tether to maybe a different location? With that being said the same process could be use to move the probe using the roll and pitch of the comet? This all depends on if there is a tether on the anchor and how long the line is.

    • John Geek says:

      the probe's batteries are completely dead, it can't do anything, we cant' talk it, nada.

    • Pointblank says:

      The anchor didn't stick when it landed, hence the bounce and eventual landing in the shadows. Plus, as John Geek points out, the batteries are dead and communication isn't possible at this time.

  • logan says:

    Hi Claudia and H. NAVCAM Team... Beautiful 'rock', doesn't it? πŸ™‚

    Would like to name this very little duck as 'Coraline'.

  • Daniel says:

    Well that's that then, will be hard to spot small changes in the future when Rosetta is mainly far away from 67p. Hopefully we will at least get a NAVCAM close-up during the 6km flyby. As a final hurrah this NAVCAM raster does have a lot of jets though.

    There might be four sources of jets/emissions in the D frame, given a generous interpretation anyway.
    http://i.imgur.com/J3W46s6.png

    I've also added what I believe could be the sources of two of the jets originating from the head visible in the A frame. I've used an image from 9th December 2014 to do this. The pale purple arrow points to a potential jet that wasn't visible this time.
    http://i.imgur.com/wlEJigs.png

    Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
    https://creativecommons.org/licenses/by-sa/3.0/igo/

    • logan says:

      Hi Daniel. Doesn't seems that big jet sources use to be shadowed?

      • Daniel says:

        Seems to me that the "pit" jets/emissions are from areas that are sunlit. It's just that you need dark shadows along the path to provide the needed contrast to see them.

  • Bob says:

    Looks like some of the jets are moving from one lobe to the other? or is it an illusion?

    • logan says:

      Illusion, delusion or not, something is going between lobes. Bob πŸ™‚

      • logan says:

        Speculation:

        Sand cascades, global, falling from head to body πŸ˜‰

      • logan says:

        As pointed before by several resident and drop-by scientists. Loose material is generated by thermal fracture, too.

        • logan says:

          [That could be the mechanism giving the neck, -should be toroidal- a trench aspect]

        • logan says:

          Thermal stress = my old visual allusion to 'wood eaten by worms'

        • logan says:

          Thermal fracturing 'exposing' inner geometries, too πŸ™‚

  • Birgit Hofmann says:

    Wow. !!
    Big picture....and this weekend rosetta's swooping down for an extreme close pass over the surface....
    I am very excited !!!
    Birgit

  • Robin Sherman says:

    Sadly our last bound orbit image for a while, but a beauty to finish with Claudia, thank you.

    So I can't ignore the so called "jets" in this image, they are everywhere. Thanks to Judy H. for the links to various articles. Firstly the distinction has to be made between what is seen in the image above and the "activity" discussed in those papers. They are analysing active features that can be seen near perihelion and then only by extravagant image processing techniques. These are minuscule compared to those "jets". I shall call them dust columns and dust curtains. Their speed is clearly not supersonic, they disperse into diffuse clouds only tens of metres above the surface.

    As to the merging or not merging, aided or unaided, magnetic fields, electric fields etc., I feel everyone is trying to make it too complicated. Dust is being propelled from the surface of the comet wherever it is found, once the area is exposed to sufficient energy from the Sun. We only see a tiny fraction of the activity, where the phase angle between Rosetta, the surface and the SUN is just right and a dark background highlights the scattered light from the dust.

    This image picks out a selection of the different types of dust movement. There are some quite clearly defined longer, narrow columns and some broader curtains of dust emission. There are also gaps.

    https://www.flickr.com/photos/124013840@N06/16300030867/in/photostream/

    The angles of the narrow columns are quite clearly defined by the angle of the surface. In general this is perpendicular to the surface, but we see other columns' angles being determined by a surface feature at angle to the general plane of the surface, The small columns in front of the cave in the centre of the body lobe for instance, (although the warning about mosaic making distortions may apply here, so I didn't prepare an image of this).

    The three well defined columns to the left of the image do merge, no braiding, spiralling, bending, they just become more diffuse and since they are all basically heading in the same direction, merge into a cloud of dust heading in that direction. Those dust grains starting with highest velocity, from the middle beam in this case, will travel the furthest and so give the appearance of the 3 columns having merged to be one combined beam.

    This second image is related to dust columns, but this time what is carried in them. We have seen many blobs, streaks and dots in the images over the last two months and have guessed at sizes and sources, mechanisms and practicalities, with little firm visual evidence.

    https://www.flickr.com/photos/124013840@N06/16299953379/

    Finally to Hathor cliff, layers, and resurfacing.

    https://www.flickr.com/photos/124013840@N06/15866204623/in/photostream/

    Further comments, theories, guesses, crackpot ideas etc. are in the descriptions of the images.

    • Robin Sherman says:

      One further thought on gas/dust columns. The velocity of the gas and hence the dust, is determined by the vapour pressure created by the sublimating gas. It will naturally propel the gas and dust into the vacuum around 67P. The pressure that builds up under the surface dust layer would, I should think, be in large part dependent upon the porosity of the layer above. In the Hapi region the dust grains we are told, are a lot smaller and would therefore pack together a lot tighter, decreasing the permeability, thus enabling larger gas pressures to build up under the surface layer. Result, higher velocity gas columns.

      Why is the dust in the Hapi Valley finer? Todays image gives a clue. There are several dust columns rising and striking the face of the Hathor cliff. We know how easily the ejected grains crumble into micron sized dust particles on contact with solid surfaces and one has to imagine the energy they carry is only sufficient to scour tiny crumbs off the cliff. These micron sized particle in their millions will fall back to the surface of the valley creating the much finer grained surface layer.

      Makes sense, but when has 67P ever made sense? πŸ™‚

      • logan says:

        "...Why is the dust in the Hapi Valley finer?"
        Is my speculation that there shouldn't be dryer place on 'Corine' than That surface.

    • THOMAS says:

      @ Robin Sherman

      "The three well-defined columns to the left of the image do merge, no braiding, spiralling, bending [...]"

      Maybe, though we'd need some OSIRIS closeups to see any braiding or spiraling: we obviously can't see such features in this image.

      Interestingly, you also seem to see "bending" as an indicator of electromagnetic activity/colimation and there you have it, in the horizontal, upward-curving jet shooting out to the left. (The other jets may, of course, also be bending more or less towards or away from us...). We already know it happens big time anyway, from the spectacular image on the FINE STRUCTURE IN THE COMET’S JETS thread: http://blogs.esa.int/rosetta/2015/01/16/fine-structure-in-the-comets-jets/

      These are certainly not just "columns" or "curtains" of dust and they still haven't dispersed a couple of kilometres above the surface. It is easy to believe the dust is travelling at around 700 metres/second as mission researchers have announced. With similar over-exposure and a wider view of the surrounding space, I think it can be safely assumed that the image shown at the top of this thread would show comparable behaviour from the comet.

      Further confirmation of these jet-features will certainly be provided in the coming weeks and months if cometary activity increases exponentially as expected. We may even get some OSIRIS images showing spiraling, braiding and/or filaments in the jets.

    • THOMAS says:

      @ Robin Sherman

      "The three well-defined columns to the left of the image do merge, no braiding, spiralling, bending [...]"

      Maybe, though we'd need some OSIRIS closeups to see any braiding or spiraling: we obviously can't see such features in this image.

      Interestingly, you also seem to see "bending" as an indicator of electromagnetic activity/colimation and there you have it, in the horizontal, upward-curving jet shooting out to the left. (The other jets may, of course, also be bending more or less towards or away from us...). We already know it happens big time anyway, from the spectacular image on the FINE STRUCTURE IN THE COMET’S JETS thread: http://blogs.esa.int/rosetta/2015/01/16/fine-structure-in-the-comets-jets/

      These are certainly not just "columns" or "curtains" of dust and they still haven't dispersed a couple of kilometres above the surface. It is easy to believe the dust is travelling at around 700 metres/second as mission researchers have announced. With similar over-exposure and a wider view of the surrounding space, I think it can be safely assumed that the image shown at the top of this thread would show comparable behaviour from the comet.

      Further confirmation of these jet-features will certainly be provided in the coming weeks and months if cometary activity increases exponentially as expected. We may even get some OSIRIS images showing spiraling, braiding and/or filaments in the jets.

    • logan says:

      "...I feel everyone is trying to make it too complicated."
      I agree with you in the feeling, Robin. But not in the case. Many of us grew up in front of devices focusing charged particles with magnetic lenses.

    • logan says:

      "... We only see a tiny fraction of the activity, where the phase angle between Rosetta, the surface and the SUN is just right and a dark background highlights the scattered light from the dust".

      It's a beautiful description of our pauper view of the jet activity πŸ™‚

    • dennispoe45 says:

      Just wondering if the comet will break apart when it encounters the sun in August, what do Um think?

  • Marco says:

    This is a very good side on view of the same monoliths on the amphitheatre. I'd love to see a 3d model of just the amphitheatre and its boulders. See how they could have got there from their seating positions:
    https://scute1133site.wordpress.com/

  • logan says:

    Got screen distance adjusted lenses. Courtesy of my lovely big brother. Now I can see those OSIRIS details πŸ™‚

  • logan says:

    At this bow shock we have the inverse mechanism: deflecting charged ions are creating a focusing magnetic lens.

Comments are closed.