CometWatch 26 November

This four-image montage comprises images taken on 26 November from a distance of 30.1 km from the centre of 67P/Churyumov-Gerasimenko. The image resolution is 2.4 m/pixel so each original 1024 x 1024 pixel frame measures about 2.5 km across.

Four image NAVCAM montage comprising images taken on 26 November. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Four image NAVCAM montage comprising images taken on 26 November. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

A quick look at the lower-left and lower-right images (first and last in the sequence) will rapidly reveal that the rotation of the comet has been substantial in the twenty minutes that passed between the two images being taken, meaning that mosaicking tools are likely to introduce some serious artefacts. For example, look at how the shadows have changed around the distinctive U-shaped feature close to the boundary between the two lower frames.

The comet continues to show outflows of gas and dust, which are even more evident in the higher contrast version of the montage provided below. This higher contrast version also brings out the details of some of the shadowed regions, such as the steep cliffs that rise up to the large depression on the smaller of the comet’s two lobes.

The higher contrast montage also highlights some scattering artefacts (e.g. the rounded feature in the top left frame) and vignetting (centre of the montage).

Higher contrast version of the 26 November montage.  Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

Higher contrast version of the 26 November montage. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0

 

The original four frames are provided below:

 

ESA_Rosetta_NAVCAM_141126_AESA_Rosetta_NAVCAM_141126_BESA_Rosetta_NAVCAM_141126_CESA_Rosetta_NAVCAM_141126_D

Comments

61 Comments

  • Dave says:

    What a fabulous picture.

    I guess it rules out any suggestion that the comet is hollow?
    Maybe, if you believe its a contact binery, then you can hold out with a belief that each lobe is hollow in its own right but thats a big stretch.

    I suppose its still possible to say the porous material was in the neck, and now most of it is gone and thats why we cant see evidence of a porous core, bit again its a stretch.

    It is still possible to say the material is say like an aerogell or 'pumiss like' its just that we dont have pictures with fine enough resolution to see it.

    The underneath of the neck looks like it has been eroded away, almost a knife through butter appearance.
    Admittedly the detail is not perfect, but the faces of the structure ie the exposed faces of the core DO NOT look like there is anything like enough porosity present to permit the quoted density.
    We have no results from the Consert Nucleus to shed light on the inetrnal structure of the comet yet.

    If we continue to get pictures like this, then the Consert data may seem a bit superfluous or at least late to the party, We now have clear evidence the comet is solid

    • Rob says:

      We now have evidence that you will believe precisely what you wish to believe about this comet. Can you drive, Dave?

      • THOMAS says:

        It's called basic scientific method, Rob.

        If the eyes are no longer to be accepted as the primary human organ and brain-interface for perceiving the information which is the starting point and ongoing sustenance of any scientific theory/model/paradigm (photographic/microscope/telescope images, on-screen digital data. etc.), then which sense do you suggest we should replace them by so as to improve the scientific method which you presumably accept?

        To still maintain, as I have often read on this blog, that "It is totally irrational to claim that just because something *looks like* rock, it actually *is*rock" (rather than being a "dirty snowball, for example) has, under the accumulated weight of the ocular evidence, become untenable.

        It is the "40% the density of water" figure (the sole basis of yourposition) which will ultimately need to be accounted for.

        • Robin Sherman says:

          I would be interested to hear what you make of these two images Thomas. I thought a close up view of some cometary material might move things along. We have seen the CIVAS image of the entrance to the alcove Philae is sitting in, but the other four images have been largely ignored. So I decided to have a close look at the CIVA image taken from the back of Philae.

          https://www.flickr.com/photos/124013840@N06/15739269617/in/photostream/

          I have tweaked the contrast and brightness a little to give some detail and perspective. The second image is annotated to highlight points of significance.

          https://www.flickr.com/photos/124013840@N06/15924494402/in/photostream/

          So it appears Philae can travel through solid rock and scrape large scars out of the rock surface, travelling at 3cm/s. When we see the surface of the "rock" close up it is loosely bound and granular, that is very porous and easily compressed as shown by Philae's foot going straight down through it. It reminds me of Vermiculite wall insulation, which incidentally has a density around 20% that of Water. It can't be Vermiculite, that is a clay mineral made from layers of silicate molecules with magnesium and ions trapped in between the layers, and the version used for insulation has been heated to 900 degrees to drive out all the water. The comet analogue might be layers of ice crystals with tiny dust grains trapped between the layers. Fractures planes would naturally form at the surface of the ice layers, just as in the shiny flat silica surfaces of Vermiculite, so certain granules will have this flat sheet of ice exposed. Hence we see the bright specks all over the image, strongly reflecting what little light reaches this deep into the alcove.

          OK so the argument will be that the granular appearance is the grain of the image, because it is so dark., but Stephan and his lander team used Vermiculite wall insulation to test the harpoons after Rosetta arrived at the comet and analysis had been carried out on the surface of 67P. This was the closest material they could find on Earth to match the surface of the comet. I posted this on this blog some time ago. This is the visual evidence that that analysis was pretty accurate. We don't KNOW what is the chemical makeup of these granules is and they could be actually a silicate mineral like Vermiculite.

          The MUPUS instrument is attached and deployed from this face of Philae and so the subsurface we see hints of in the image is what.the team suggested was hard ice, below the porous low density layer they referred to. Just like the cryorock in the other image, it is impossible to tell what it is made of visually. So I guess the jury is still out until we get a definitive chemical analysis, which sadly the SD2 drill appears not to have got any suitable sample to facilitate. We might have to wait until Philae wakes up again, or if she doesn't, the next comet sample mission.

          • Marco says:

            Hi Robin, I do not really understand where the conclusions to the annotations come from. Was there a before and after? We are trying to find evidence of what the material is. It is not immediately obvious to me that the "scars" are meaningful or have anything to do with Philae. I had imagined that some mechanical activity would be imaged before and after to confirm, but apparently it wasn't possible in this position. I am voting for "vermicast" rather than vermiculite, from the giant tunnelling space worms.

          • THOMAS says:

            Thanks Robin for the chance of commenting on this image which, it is true, everyone has largely ignored. I had assumed that this was because it was too indistinct and enigmatic to be interpretable but once you look at it, it actually turns out to hold extraordinary evidence.

            I guess everyone can read whatever they like into an image such as this one. To be honest, I think that if you see evidence of scrape-marks and of Philae's feet here, it’s because you want to see them as possibly providing some support for the "soft surface", low density model.

            What I find most striking personally is a perfectly obvious feature which leaps out at us off the photo once you look at it but which you curiously make no mention of: namely the very fine stratification of the rock from top to bottom and from left to right of the image, running broadly from top right to bottom left, except in the central part of your annotated flickr picture https://www.flickr.com/photos/124013840@N06/15924494402/in/photostream/ , where the stratification bottoms out and turns slightly upwards: we are clearly looking slightly from above downwards onto a rock feature which is bulging out towards us in the central part of the image, so that the stratifications literally act as contour lines on a map, indicating the contours of the rock formation.

            The fineness of the layering would seem to confirm what I have already surmised elsewhere on this forum, namely that we are no doubt in the presence of a metamorphic rock such as slate: here we are clearly seeing the stack of fine layers of the rock edge-on.

            Thanks again, Robin for drawing my attention to this heretofore neglected but indeed extremely important CIVA image which actually, at a single glance, provides further incontrovertible evidence for the stratified rock composition of the comet, already unambiguously shown in the big picture (http://www.esa.int/spaceinimages/Images/2014/08/Comet_on_7_August_a and http://blogs.esa.int/rosetta/2014/11/20/cometwatch-17-november/ ), at a medium scale (http://www.esa.int/spaceinimages/Images/2014/09/Comet_on_5_September_2014 ) and here at extremely close quarters.

            I find it extremely strange that this utterly salient feature of an extremely rare image (one of only five or six which Philae ever took of its final resting place) has so far elicited no comment whatever from mission scientists. It will need to be accounted for.

          • Marco says:

            To me it looks like "coal", but really, at the low temperatures, frozen crude oil would look like coal, but would melt at higher temperatures

          • THOMAS says:

            Hi Marco,

            You say "To me it looks like "coal", but really, at the low temperatures, frozen crude oil would look like coal, but would melt at higher temperatures"

            In that case, how do you account for the pervasive fine layering/stratification we see in this image (complete with contour lines showing a distinct 3D perspective) if what we are looking at is "coal" or frozen hydrocarbons? Can they be layered in this way, and if so, by what physical process?

            It would be great if Mattias Malmer could reprocess this image with the same extraordinary expertise he used to reprocess the better-known CIVA image of Philae's medium distance view of the rocks and boulders Philae ultimately tumbled down into (http://mattias.malmer.nu/2014/11/civa-depth-cues/comet_depth_cues/)

            I'm sure the result would be equally astounding.

          • Robin Sherman says:

            Hi Thomas. Thanks for the reply. I was also extremely surprised after seeing what was shown in this image that we have heard nothing about it. It contains loads of very informative information. I wanted to see what you thought before I made comment about the actual formations in the image. Leaving aside the marks made by Philae for now, indeed what we see is a finely layered formation present in the subsurface material and a definite sense of flow to the whole view as if some volcanic cryolava has flowed from the back of Philae's alcove to the front.. The MUPUS team suggested it was "sintered" ice, in other words some metamorphic process has taken place to harden the material. You used the Earthly rock slate as an analogy, a metamorphic rock produced from finely layered clay minerals. To an amateur, the morphology of the material suggests a type of "rock", that is, "a naturally occurring solid aggregate of one or more minerals or mineraloids", to quote Wiki. Bill is our resident geologist, maybe he could comment.

            This is not "very hard ice", it is a composite material of minerals, minerals which contain a lot of volatile ices within their structure. Such a material would not occur on Earth, it is not cold enough, but by definition it must be referred to as a type of rock. I have been calling it "cryorock" for some time now.

            Its nature seems to be layers of silicate containing minerals, with large, but variable amounts of ices, or different ices, making slightly different mineral structures to differentiate the layers. Minerals here on Earth contain Water in their structure, cometary cryorock contains ices as part of its structure. Difficult to detect when its embedded throughout the silicate structure, mixed with and covered in organic material to boot. At the surface, in the presence of a vacuum and sufficient energy, the ices would sublimate from the mineral structure, in effect the same process of Exfoliation that creates the very low density Vermiculite insulation material. Thus we get a gravelly, very light, porous silicate structure left behind as the surface layer we see all over the comet.

            A long time ago Logan suggested this surface layer was sublimation residue and this image shows that to be the case. At the surface of the cryorocks we see in this image, little gravelly bits have already formed, but remain attached to the surface. With no "wind" or "weather" in this alcove they don't move and the dark organics provide enough cohesion to keep them in place retaining the shape of the original solid material. Eventually gravity would slowly remove the outer layer of gravel, if it is not blown off by sublimation activity. We can see how scoured the cliffs in the neck region are, new surface is continually being exposed, This would explain the dull, crumbly looking cryorocks seen all over the comet as rubble and scree. Naturally occurring veins of ice within the cryorock would allow for the fissuring and cracking of the exposed surface when that ice sublimates.

            When Philae came into land and scraped against the cryorock the top layers of gravel were removed. When the foot pressed down at the very edge of the formation, the granules there were squashed, all the space that had once been occupied by volatiles compressed. So Philae didn't slice through a solid material, but flattened a material akin to a silicate aerogel. Material that still contains the frozen hard ices, below the insulating surface layer, still retain their hardness. This area almost in complete darkness for the cold part of 67p’s orbit, would be particularly cold and so the ice laden material would be hard as MUPUS found. I guess because it is not pure ice, their readings were ambiguous, hence the vague answer.

            So you will be glad to know Thomas that ,what I have always agreed looks like "rock", is I think from this evidence, a TYPE of rock, just not one found on Earth. I would imagine a chemical analysis would be inconclusive, because it would contain silicates, metallic ions and various volatile ices in a mineral type structure. The only way the molecules could all be rearranged to form this mineral would be through some metamorphic/volcanic or weathering process. The mechanism of such a process is another story, but there is any amount of visual evidence that some sort of volcanism or melting has shaped the surface of the comet as you highlighted.

          • Marco says:

            Crude oil, unlike water, can melt and "refreeze" at these sorts of temperatures and pressures. Thus, linear surface flow limited to times closest to perihelion could explain the parallel lines. A little like when I leave my wax crayons out in the sun. I really think there are a lot of possible "natural" explanations that may seem contrived, but at least they do not break "physics". If you count living processes, it becomes an engineering problem rather than relying on exotic non-living processes.

          • THOMAS says:

            @ Robin Sherman, in response to his
            03/12/2014 at 14:38 post

            Hi, Robin, thanks for this detailed interpretation, even if I guess you will be not be surprised to learn that I am not convinced by it…. But, for what it’s worth, we seem to be moving towards agreement at least on the visual appearance of the surface material as resembling some type of rock formation in varying states.

            Where we still differ by many miles is that personally, I do not use the word “rock” as an *analogy* (as you presumably do when you speak of “cryorock, for example, which remains a theoretical construct), I use it as a rock-solid *fact* corresponding to a widely observed reality on the two planetary bodies we know most about: Earth and Mars.

            Take a look, for example, at this image of a NASA HIRES image showing a close-up of an infinitesimal part of the humungous Valles Marineris canyon on Mars: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA17570.

            With its finely stratified rock formation, partially/completely covered in parts by smooth lava-like downward flows of presumably molten rock (what else could it be on Mars other than *rock*?), doesn’t it remind you of something?

            In my personal reading of the EU model, Comet 67P is just a tiny fragment of the *3-4 million cubic kilometers* of stratified rock which were gouged out of the Martian surface within a few seconds by a catastrophic electric discharge in the indeterminate past, to form the scar of the Valles Marineris canyon as we currently observe it (“4,000 km (2,500 mi) long, 200 km (120 mi) wide and up to 7 km (23,000 ft) deep”: http://en.wikipedia.org/wiki/Valles_Marineris). The other resulting lumps of rock of various sizes are also floating around the Sun on varying orbits inside and outside that of Mars itself, some as short-term comets but most as simple asteroids, depending on their degree of ellipticity. Quite a few of the really tiny bits have even been found down here on Earth as “Martian meteorites” (http://en.wikipedia.org/wiki/List_of_Martian_meteorites) ….

          • J.H. says:

            Marco said.... "It looks like coal". If P/67 has a density of 0.4 g/cm3, it couldn't be "coal" which has a density of 1.4, but staying with the hydrocarbon idea, it could be mostly made up of a Ethane ice nucleus,( 0.54 g/cm3), with a crustal surface of "Charcoal",( 0.2 to 0.3 g/cm3), like material which the suns heat creates at perihelion causing chemical changes, creating compounds and cooking them to a crispy light but brittle crust, etc.

        • Rob says:

          Do not presume to lecture me on the scientific method, "Thomas". The scientific method is based on patient gathering of objective data, rigorous analysis of the data according to accepted standards and deriving a conclusion based on the results of that analysis, referring all the while to the vast body of accepted scientific knowledge. The human senses are at best mere adjuncts to this method.

          To come onto this forum and bleat about your conviction that what you believe you see in a collection of post-processed photos should be taken as proof positive for the ridiculous theories you happen to espouse, is all the proof anyone here would need that your "method" displays a complete lack of scientific rigour.

          • THOMAS says:

            Hi, "Rob".

            To follow your reasoning, and with your declared conception of the "scientific method", if you had lived towards the end of the 18th century, you would presumably have "referred to" the "vast body of accepted scientific knowledge" of the time and have thus supported the church authorities in refusing to look through Galileo's telescope at those "ridiculous" Jovian moons, arguing in the same way that "The human senses are at best mere adjuncts" to the claimed “method”.

            Sorry to appear to “lecture” again, but I have always taught the absolute need to set things in their context so as to see their place in the bigger picture. The present gravity-only, Big Bang-driven standard theory is still *ONLY A THEORY* and depends entirely on all the other unobserved and unobservable mental constructs ('inflation", "black holes" "dark matter", "dark energy", etc. etc.) which are now presented as undisputed fact whereas they were merely invented as successive patches to an essentially Creationist theory. I abandoned it well over a decade ago when I started realizing the implications of actual observations, starting with the paradigm-shifting work of the greatest observational astronomer of the modern era, Halton Arp (after whom hundreds of peculiar galaxies are still named in the catalogues). Arp et al. conclusively proved the *intrinsic*, quantized nature of redshift over 30 years ago, thus falsifying the "recessional velocity" interpretation of redshift which had originally been seized upon by a Belgian Catholic priest to suggest the Creationist story that only more recently came to be known as the Big Bang theory. Arp’s discordant observations, which killed the Big Bang theory stone dead at a stroke, prompted the Establishment to close ranks and punish him by depriving him of his institutional access to the biggest ground-based telescopes he had up until then used routinely to compile his extraordinary observations. The parallels with Galileo are total....

            I have nothing whatever against religious concepts as such but when they are actually driving science in the face of *empirical* scientific observation, I prefer to believe the observations rather than the theory and then reject the theory if the observations falsify it.

            Thanks for the "bleat" and the "ridiculous". If you are a scientist (as I presume you are), perhaps your language should be a little more "objective” and less insulting.

            I, for one, am NOT one of the "bleating" flock of sheep. And I have as much right to “come onto this forum” to argue a discordant point of view as anyone else, since it is not yet being controlled by mainstream thinking as perhaps you would prefer it to be.

          • THOMAS says:

            Sorry, instead of "towards the end of the 18th century", that should, of course, have read "in the first half of the 17th century". (Crossed wires with a parallel forum on a completely different subject). The point I'm making about Establishment censorship of discordant observations, whatever the era, remains unchanged.

    • logan says:

      Hi Dave. A pack of 'packing' cardboard looks 'solid'. Nowadays, it's not.

    • Bruce says:

      It's probably better understood as a rubble pile held together by gravity and glued together by frozen gases - wtaer, CO2, CO, ammonia etc. There will be a lot of cavities througout the structure - like a spongue - but probably not any single large voids.

      I'm curious to see how many bits fall off as we approach perihelion. I strongly suspect many of the white specks in tha image are real lunms and not just imaging noise.

    • AndreH says:

      Yeah.....it still can be solid as lumps in a powdered sugar package. Those can be pretty "solid" and still ar poruos.
      I find it still funny you use a theory to explain the structure of a comet which cannot even explain how rosetta itself could reach that comet. All trajectory planning was based on gravity only....

      • THOMAS says:

        The gravitational attraction of the comet itself has only been in play since Rosetta arrived on zone back in August. Up until then, its 10-year trajectory was determined by planet flybys, using the gravitational forces of the planets concerned, which are very well known (though even there some small, yet unexplained anomalies were observed).

        If the nucleus of 67P were only as dense as powdered sugar (with or without the lumps), the overall density would already be over twice the 0.4 g/cm3 figure, even without counting the rock which is visible everywhere on the surface.

  • Charles Bell says:

    Gas and dust activity rising on comet 67P/Churyumov-Gerasimenko
    2014 November 28 00:00:00.0 UT = JD 2456989.500000
    Earth distance delta = 3.481 AU
    Solar distance r = 2.886 AU
    days to perihelion t - T = 258

  • Max says:

    If that's a hollow comet, then that "distinctive U-shaped feature" must be Batman's shadow on it as he's surreptitiously approaching to smoke out the evildoers lurking within.

    No, seriously: It's all good, solid comet material and the more of it outgasses, the more we'll see what it consists of. If it was any less than solid, it wouldn't be so heavy, and anyway we'd long have seen from the Consert data (plus we'd have a big mystery because it simply doesn't make sense for an object that formed through accretion in the early days of the solar system to have anything other than a solid core).

    One thing that strikes me: It was recently said that the surprising hardness of the surface might be due to sintering of loose particles near the surface, whenever the comet approaches the Sun. But didn't it spend most of its life far out in the Kuiper belt, and has only been coming closer than 4AU since 1959? Then we should expect that any sintered material will mostly sublimate sometime, and the core would be softer than the surface. Did the seismic measurements with Philae give any indication about the hardness of deeper material?

    • Marco says:

      There appears to be a corresponding u shaped feature on the head at the same longitude. Infact, someone was telling me that many features on the head would interlock with body pieces like a jigsaw. Almost as if the comet started out as a spheroid and had a "bit of a stretch"

  • Ross says:

    Why do I feel like the mysterious source of these jets are always slightly out of view? Can we get one image targeting the speculated nozzle- like vents which "must" exist to form these collimated jets?

  • Rich_T says:

    My observation is that, with continuous flux of material from between the two lobes, the comet will eventually break into two. Is this a reasonable deduction?

  • simon frederik says:

    Maybe I am wrong , but on these latest fotos it looks to me that a piece of the neck is gone

  • cheapopete says:

    Fascinating images. To see stuff like this was always a dream for me right from when I was teen reading science fiction.
    From some of what I've read, the narrow 'neck' is possibly softer material and one day will possibly break. If that happens, I wonder which of the two pieces will land in my garden. :¬)

  • logan says:

    Very grateful for this one, H. NAVCAM Team. Additional comments on geometries now seems redundant to me 🙂 [Of course, maybe I'm wrong].

    • logan says:

      67P was formerly a polyhedron, I presume, as the most possible basic shape.

    • logan says:

      Just look and the underside of the head, and their two back border lines. In the high contrast nov26 montage.

  • logan says:

    The body back jets of nov20 mosaic...

  • logan says:

    Hi Robin. Seems like somewhere near the 'lakritz' hanging drapers are the source of the jets. At past I suggested that those act as a 'sanding' paste, leaving a 'mirror' of 'core' material. It could be that 'core' material itself is the jet's source in the back of the body, additional 'tide' grounded material at the neck.

    • Robin Sherman says:

      Hi Logan. Exactly where the streamers are coming from is still a mystery, the sides of the trench or its floor. They do seem to have some sort of erosive effect though. I am struck mainly in this image by how many flat planar surfaces there are. There seems to be another trench developing further up the head lobe, with the side visible fairly flat and the near side rugged and lumpy, just as in the neck region. These flatter, more refractory surfaces remind me of cell walls. The internal structure of the comet may be made up of "cells" creating a lattice of more refractory material surrounding less dense, more porous/granular, more volatile material.

      A marine sponge might be a good analogy. The images of Hyperion also show what the comet structure might look like without the surface crust and the volatiles largely missing. Again it goes back to how did the surface crust form to seal in the insides of the comet?
      What process formed all the flat plates, like coral "leaves", large and small, at all angles over the surface? Are there large scale cells making up the body of the comet with smaller ones making up the crust.? I think Mark H. and his fungi pictures has got me thinking all "biological analogues". Evolution has been carrying out a 3 billion year old experiment to find the best ways to utilise the physics and chemistry of the universe, never a bad place to look for solutions.

      Then of course it needs a mechanism for such a construction, starting basically with a pile of icy pebbles and dust grains. That one is beyond me at the moment, I shall have to ponder a while. Wait for some other data and ideas to emerge.

      All I know so far is, the more we see of 67P, the more complicated and confusing this amazing place gets.

  • Dennis Cowdrick says:

    This is where it really gets interesting. Anomalies are what we hope for in Science.When we have them there is a chance to learn something.Think about the following:

    Look at the Plumes - they appear to be twisting about each other. What kind of gas jets do that?

    The density appears to be all wrong. What can cause that?

    I think we must face the facts that OTHER FORCES are at play here. The simple guess is ELECTRICAL forces. Electric interaction is 10^39 times gravitational interaction. The twisting action may be explained as Birkeland currents which often show filamentary, or twisted "rope-like" magnetic structure. They are also known as field-aligned currents, (magnetic ropes and magnetic cables).

    I understand that the density is inferred from path deflections of the spacecraft. If the spacecraft and the body are not at the same potential, then the deflections will not fit gravitational theory. I hope this will be considered in the studies of density anomaly. At least in this environment we get a chance to test our gravitational preconceived misconceptions.

    What a wonderful time ESA and its partners have provided us.

    • AndreH says:

      Why does the density appear wrong? Have you ever seen lumps in powdered sugar. They can be pretty hard.
      There is no density "anomaly" in this comet.
      As hard as I look at the picture, I do not see any twisting of jets.
      IT RIDICOlOUS to use a theory for explanation that cannot even explain how rosetta could reach the comet.
      This is like saying 2 + 2 is for and 1 + 1 is 2 and then insisting that 1 + 1+ 1 + 1 is NOT 4.
      Have a look at the trajectory rosetta took to get there. All calculations are based on GRAVITY ONLY. And it worked. Proof!

      • THOMAS says:

        See my post above on Rosetta's trajectory to arrive on zone. Nothing whatever to do with the hypothesized density of 67P.

      • Dennis Cowdrick says:

        thanks for your interest. the calculated density was far less than water. Now it is estimated to be much higher. The previous estimate was so low that it was thought that the lander might sink into the surface. Getting to the comet did involve normal Newton type Gravity calculation. However, final approach involves active tracking and not theoretical orbital parameters. Now we are in a microgravity situation where even if the lander is on the surface its weight would only be about 1 gram! In these conditions Electrical forces become important at much lower potentials.

        Perhaps I see plume twisting where their really is none. It is hard to tell from the plume images they have shown us. The question remains - how can the plumes remain 'collimated' over large distances in the vacuum of space? What force keeps the supposed gas from expanding at right angles to the plume direction? Where are the holes the gas is supposed to be escaping from? Why are some plumes at different angles? Perhaps electrical forces are removing material from the surface - what do you think?

  • logan says:

    At the top quadrants of high contrast nov26 mosaic you can see tee the characteristic 'glow' of NAVCAM lenses, too.

  • L De Witt says:

    Did the Philae probe manage to sample the material the comet is made of?

    Is it in fact a 'dirty snowball'?

    On November 19th, this site reported, "As for whether COSAC received a sample from the drill, the analysis is on-going."

    Ha the team found out whether or not a sample was retrieved? If yes, does the team have an analysis of the sample yet?

  • logan says:

    A lot on morphology in this nov26 mosaic 🙂

  • THOMAS says:

    Unless I’m much mistaken, this is the first image in which we see not only the frequently observed deeply cut-out *front* side of the neck but also, quite distinctly, the considerably eroded *back* side which was thus far always plunged in the deep shadow on the nightside. The in-curving profile of the eaten-away part at the back of the neck would seem to be at least as distinct as that on the two lateral parts of the neck, which we have already seen in images such as http://blogs.esa.int/rosetta/2014/09/19/cometwatch-19-september/ or http://blogs.esa.int/rosetta/2014/08/14/comet-67pc-g-in-3d/.

    Piecing the images together, it now seems evident that the “neck-region” is an even more strikingly slender feature than was previously supposed. Someone on one of the threads (sorry, I can’t remember who) very recently suggested a comparison with an apple eaten all around the middle, leaving just the core connecting the top and bottom parts. I agree, except that it’s perhaps rather more like a pear than an apple, with the bottom part more bulbous than the top part.

    Whatever, from the accumulation of observations, it would seem increasingly difficult to believe that the “core” of the pear (the slender neck) can be in any way hollow or filled with some sort of fluffy material, as the density data requires, particularly since it seems to be doing a pretty robust job holding the two much more massive lobes together. For the density data to be correct, the two lobes must therefore, by some utterly unknown mechanism, each be completely hollow beneath a few metres of rocky crust (not even partially filled with ice or water).

    There is an increasingly clear and total discrepancy between the observed appearance of the comet and its measured density which will soon need to be accounted for.

    • AndreH says:

      No, they must not be hollow. Only porous. like lumps in powdered sugar.
      Again funny how you insist to use a theory that cannot explain how rosetta got there.
      the trajectory was calculated all gravitational based.
      You cannot say: 1+1 is 2 and 2 + 2 is for but insist that 1 + 1 +1 +1 is NOT 4.
      EU doesn't work.

  • Thomas says:

    My take at this mosaic:
    https://www.flickr.com/photos/105035663@N07/15900422392/in/photostream/
    Indeed there are artifacts in the mosaic because of the rotation of the comet between images.

  • mark homer says:

    What looks like a rock, not very dense and gives off plumes that go miles?
    Let nature have its say...

    http://2.bp.blogspot.com/_PoCiw1AfuYU/TPQzFxYwJ_I/AAAAAAAAAdw/37OaLSzwA5M/s1600/Monster+puff-ball+fungus.jpg

    Here's the tail...
    http://upload.wikimedia.org/wikipedia/commons/1/12/Puffball_fungai.jpg

  • Rangertech1 says:

    Great composite image.

  • Artiom says:

    For me it looks like a dirty pile of snow and ice in the spring, covered with dust. http://g1.nh.ee/images/pix/image-46443jpg-65943374.jpg
    Such piles are very common throughout Eastern Europe in early spring, and they do not melt as fast as the surrounding snow, despite their black colour.
    Probably, the dust acts like an insulator from solar heat, so the surface melts slower in places, where there is more dust.

  • mark homer says:

    Has anyone tried the golden ratio with the comet?
    Dimensions of 4.1km for longest end on large lobe. The golden ration gives us 2.53 km and 1.57 ; which is close to the 2.5km of the smaller lobe the other end and the 1.57 is 'gone'.
    The comet length of 4.3km gives 2.66 which i'm guessing it might be about central to the cut of lobes? I dont have the full dimension detail sorry and then 1.64 km. Could be straight out wrong with the maths (wont be the first time) but could it be the comet is fashioned according to the golden ratio? Maybe coincidence?

    BTW consistently awesome images. Can't you rob NASA of a rover?

  • Dave says:

    Rob
    I used to race formula ford as a young man, I still drive but a bit slower. I can still see too.

  • Cometstalker says:

    So far the outcome of this great mission is 95% spectacular images then 3% reasonably accurate information and the rest is 2% good for nothing data. All in all not bad but still not what i expected of a space research system where the majority of the experimental payload is NOT the cameras. And by the way when the lander made its additional of route exploration all the sudden the cameras are not used a lot and the other systems are for not much of a value when it comes to track and trace. In the future we will see a lot of navcam pictures but what this can add is not much to what we already have. The next highlight will be when Philae wakes up and delivers some more pictures.

    I hope it will be possible to get a bit more data of essense in the future but the wait will be a long one as the researchers are not the speedy Gonzales type.

    Lets hope that something spectacular happens like a real big shift in the neck region resulting in a huge outburst.

  • Dave says:

    Ross
    Re mysterious source of jets.
    The source of some of the jets is in plain view, if you look carefully you will will see shiny areas under the jets on flat ground. In the last few pictures this is very obvious. In the picture where Rob pointed out a white object splitting one of the jets not far off the surface of the comet. If you follow this jet back to the surface you will find a bright area on the surface under the neck
    You are right to say there is no evidence yet of vents with some sort of rifling to cause collimating of the jets. The columated jets can be caused by magnetic fields if something like a Birkeland current is operating. If this is happening there are instruments that can measure both the magnetic fields and the plasma from the birkeland current. There is not much data from these instruments yet, so there is no way to confirm this method of columation yet.

  • Marco says:

    I've just had a thought. Someone had calculated the L1 and L2 Lagrangian points as being within the comet itself. This would mean that Solar tidal forces combined with centrifugal forces should be greater than gravity when the rotational plane aligns with the ecliptic- at least for some time twice each rotation. Thus any loose dust on the ends of the lobes (and actual boulders) should be thrown off at that point in the orbital cycle, as well as a significant spring-like stretching impulse for the neck.

  • Ken says:

    Having some fun - here are 2 candidate Philea locations in this NavCam - I think the red circled one looks more promising - rocky cliff, lots of shadows, partial late sun. - nice solar panel glint

    http://s30.postimg.org/pv1p9camp/Philea_spotted_11_28_2014.jpg

    Here is the same location in the NavCam from a few days ago Nov 20- there is a possible spot matching the reflection

    http://s22.postimg.org/8p3ka8lsh/Philea_spotted_11_20_2014.jpg

  • Bill says:

    Occasionally comets do display extreme bursts of activity and that burst is due to a collapse, fracture or catastrophic event exposing fresh comet

    material to solar heating. A supposed "contact binary" like this system might be a candidate for a burst like that if it toppled, so it could happen _some day_.

    It would be neat if it did whilst we were a-watching up close... 🙂

    --Bill

    • Bruce says:

      Hi Bill, I'm curious to see how many bits break-off as we approach perihelion. If this is a rubble pile glued together by frozen volatiles, presumably the glued will weaken and volatile pressure will eject some of the overburden. Perhaps bits that don't achievbe escape velocity will reassemble as it returns to the outer solar system.

    • originalJohn says:

      Bill, the stored energy and extreme sublimation theories for the recorded bursts are not plausible. Comet Holmes in 2007 brightened by a factor of half a million and the visible diameter of the coma at its maximum exceeded that of the Sun, from a nucleus about 3 km across.

      Much more likely that the bursts represent a sudden change in the electrical environment of the nucleus and a rapid expansion of the self illuminated plasma coma.

  • logan says:

    Maybe not every souls knows, but there is an AMA at Reddit with:

    Michael F. A'Hearn - Astronomy Professor (emeritus) and Principal Investigator of the Deep Impact mission (ma)
    Claudia Faber - Rosetta SESAME Team, DLR-PF/Berlin (cf)
    Stubbe Hviid - Co-Investigator of the OSIRIS camera on Rosetta at DLR-PF/Berlin (sh)
    Horst Uwe Keller - Comet Scientist (emeritus), DLR-PF/Berlin and IGEP TU Braunschweig (uk)
    Martin Knapmeyer - Co-Investigator of the SESAME Experiment at DLR-PF Berlin (mk)
    Ekkehard Kührt - Science Manager for Rosetta at DLR-PF/Berlin (ek)
    Michael Maibaum - Philae System Engineer and Deputy Operations Manager at DLR/Cologne (mm)
    Ivanka Pelivan - MUPUS Co-Investigator and ROLIS team member (operations) at DLR-PF/Berlin (ip)
    Stephan Ulamec - Manager of the Philae Lander project at DLR/Cologne (su)

    🙂

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