CometWatch – 24 October

This four-image NAVCAM montage comprises images taken on 24 October from a distance of 9.8 km from the centre of comet 67P/C-G – about 7.8 km from the surface. The corresponding image scale is about 66 cm/pixel, so each 1024 x 1024 pixel frame is about 676 m across.

Four image NAVCAM montage comprising images taken on 24 October 2014. Credits: ESA/Rosetta/NAVCAM

Four image NAVCAM montage comprising images taken on 24 October 2014. Credits: ESA/Rosetta/NAVCAM

In this orientation the larger lobe occupies the upper frames, with the neck filling the lower frames. The smaller lobe of the comet is out of view towards the right.

This image set complements those taken on 18 and 20 October, which together show a number of the same features from different angles, such as the dune-like features seen in the smooth neck region, and the fracture-like feature that runs through part of the rougher neck terrain. In the top- and bottom-left corners in particular, groups of boulders appear to cling to cliff faces, perhaps exposed as surrounding material is eroded away. Meanwhile jagged spires interspersed with flat-topped plateaus make for an attractive view over the horizon.

The four 1024 x 1024 pixel images making up the montage are provided below:

ESA_Rosetta_NAVCAM_141024_A  ESA_Rosetta_NAVCAM_141024_D

ESA_Rosetta_NAVCAM_141024_C

ESA_Rosetta_NAVCAM_141024_B

Comments

81 Comments

  • dave says:

    Such a difficult surface to make sense of, so many flat planes, one of them appears to have a huge overhang over the plain below. So much debris in most of the shot.
    This really does not look like a process of sublimation, If ice is holding rock/ boubers of dust together, how is it that the sublimation has not turned them to dust?
    Can we have a temperature plot for the surfaces we have photos of.
    If its a hot process we should be able to tell.
    For the geologists out there what formed this are there any parrallels anywhere on earth?

    • Sky says:

      Look up some photographs of melting glaciers - there's plenty of similarities.

  • Sovereign Slave says:

    Incredible pictures, especially the obvious sublimation in the lower right picture. It appears that a relatively substantial amount of material is being continuously removed already. “How?” is of course the question. My thought is that if it is due to the standard snowball theory, for a variety of reasons ESA would have declared this by now, or soon will declare it, at least that evidence supports their proposed theories, with more specific papers coming later. However, if it is due to electrical tooling, I’m afraid there is probably no one on any of the teams with the expertise to verify it. There are over 30 engineering fields, and many of those fields are represented in astronomy. And it obviously requires a collaboration of experts in those fields to put together a mission such as Rosetta. It would be ridiculous to think that Rosetta could have gotten off the ground without electrical engineers being utilized in its design and construction. When it comes to electrical properties, electrical principals, electrical applications, and electrical phenomenon, you logically call on the expertise of electrical experts. Just as astrophysicists, mathematicians, geo-engineers, etc etc do not have the background, understanding, or language in electrical principles to know how to build the electrical components of Rosetta, they also do not know how to understand or recognize electrical phenomena in space. They will either not see it or will misinterpret it, and they will tend to provide theories and assert explanations based on their knowledge of their own area of expertise. Now for some reason, the whole fundamental branch of electrical engineering, whose evidence in the natural world and use in the man-made world is all around us, is almost totally absent from mainstream astronomy when it comes to interpreting astrological phenomena. Doesn’t this seem at all strange? For example, how many experts in electrical phenomenon as applied to space do you think are participating on the Rosetta team? I’m pretty sure the answer is none. Which is basically the same answer regarding how many electrical experts are recognized and listened to in all of mainstream astronomy. And that is why mainstream astronomy is almost completely blind to understanding basic electrical principles that are clearly evident in phenomena in space, and has to instead resort to a continuous stream of ad hoc, contradictory, computer modeled, and “supernatural” theories for virtually every new phenomenon discovered. Until electric phenomena and those who are expert in it are brought into the mainstream study of the universe, astronomy will remain a confused and highly speculative house of cards.

    • John says:

      Yes SS, the deficiencies you point to have resulted in a tricky situation which could compromise the whole mission. First they would have to admit to themselves and everybody else that they were not able to properly assess the data and it is unlikely they would do that. I think however that whether or not they are versed in electrical theory some of them will recognise the meaning of the results. Then they should open the discussion up and take advice from those with a greater depth of knowledge. And it is knowledge that is important not qualifications, which are just a job ticket. As for status it is worth nothing. The centres of knowledge in plasma physics and electrical cosmology are well known.

    • Ross says:

      I agree with everything you said except the "obvious sublimation" in the lower right image. I'm not sure how you can arrive at that conclusion at all, let alone obviously. Keep in mind that the comet activity is about a 2/10 right now, just imagine when it's nearing perihelion. I'm quite optimistic that the data will be undeniable, and the use of Ockham's razor will remove any necessity of ices hidden from sight beneath the surface.

      Once the electric phenomena of the comet are appreciated, the cratering and scarring amongst planetary bodies will be recognized as products of similar mechanisms, which are being observed currently as "cryovolcanoes" and "geysers" on Io, Enceladus, Europa, etc. Since comet theory relies on an icy nucleus, the failures of planetary accretion theory and gravitational collapse of nebulas must be addressed. Rosetta has more 'potential' than the project scientists could have imagined.

      • Solon says:

        "Rosetta has more 'potential' than the project scientists could have imagined."

        Yes, and possibly for all the solar system planets and moons that, looked at through different eyes, may have been subject to electrical interactions on very large scales and very high energies.

      • Sky says:

        " Keep in mind that the comet activity is about a 2/10 right now, just imagine when it's nearing perihelion." - You forgot one essential thing: that it's not the first time 67P been at it's perihelion.
        And yes - you can see an obvious sublimation out there. But if you prefer to blindly believe in electrical cosmology nonsense than there's no hope for you to see anything that wouldn't match your theory. Open your eyes. It's science, not religion.

        • Sovereign Slave says:

          Right you are, Sky, and so far the Rosetta/Philae science has not supported standard model theory whatsoever, but does continue to bolster the EU model.

  • Bill says:

    Progress. Look at Image D, there is brightening of the shadowed areas above what you'd expect from re-reflected light from the cliffs. And without added brightening in the foreground shadows. I think this brightening is due to a dust jet, and this perspective will allow us to narrow down the vent location.

    And the comet looks, as the kids would say, gnarly... 😉

    --Bill

  • logan says:

    Well, no need to draw 'hieroglyphs' anymore 😉

  • Erwin says:

    Is it the Cheops boulder that we see in upper part of the lower right frame?

    • Johan Zandin says:

      No, Cheops is on the outside of the large lobe, opposite to the neck area.

  • logan says:

    Back to work. More 'fallen' structures over the top of the neck. Super-structure containing this structures clearly visible as a a rhombus around the central point of the mosaic, all over the neck.

    'Twin swirls' again at bottom left corner.

  • Ross says:

    Previous images have shown a lot of activity occurring in the neck area. Are any jets sourced in the region imaged above? I figured that visible evidence of any subsurface sublimation would be very obvious by now.

  • logan says:

    A really 'hipper-active' 'ridge' that occupying most of the left side!

  • Angelo says:

    Looking at the photo "ESA_Rosetta_NAVCAM_141024_A.jpg" I noticed the "dunes" as it is possible to have the dunes on a comet and then I did not feel the wind.

  • logan says:

    Bottom right of the mosaic shows the neck covered in an eroding 'plaque' of dirt and debris. (That's the feeling, at least).

    • logan says:

      (This promise to be savage!)

    • Robin Sherman says:

      Some more thoughts on Laktritz, the very black, surface "dust" layer.

      Comet 67P has only closely approached the Sun 8 times since its orbit was changed by Jupiter in 1959. Before that time, I gather its closest approach to the sun was even further away than it is now. We are only now starting to see evidence of small scale sublimation. It follows that prior to its change in orbit sublimation and its effects on the nature of the comet's surface were minimal. The streamers are conjectured to be the result of tidal stress, so they could have occurred in the past at all points of the orbit.

      We have seen sublimation gases scouring the Laktritz layer away from the surface. The bottom of Image D is a clear example of this. We see the underlying surface of the comet with nearly all the surface "dust" layer removed. It is interesting to note this is the warmest area on the comet. This removal of the surface layer can be considered to be a recent and new phenomena on 67P and as such would seem to be saying rapid sublimation due to solar energy is not the creator of the Laktritz layer. It is the result of another process.

      In the past, without rapid Sun induced sublimation, the comet would not have had an extensive coma and what there was would have been easily stripped by the Solar Wind. Thus coma fallout seems unlikely to account for the huge areas of Laktritz which seems to be a minimum of 10s of cm thick wherever it collects and could be metres thick in places. Coma fallout would also tend to be evenly distributed, but we see Laktritz highly localised and only present in large amounts on specific types of terrain.

      The finger of blame is pointing more and more to deposition from cryovolcanic activity, either the regular streamer activity in the neck or the more intermittent result of impacts. We have managed to surmise that the Laktrtz layer is a light, fluffy, powdery material made of very small grains of silicate, other minerals and salts, mixed with a variety of carbon based molecules. It seems to contain very little in the way of volatile ices. Some process other than sublimation must have separated the "dust" from the ices. This process is overwhelmingly likely to have involved heat energy to "dry" the material so thoroughly. Material ejected during cryovolcanism would be separated in this way, lighter gases separating from solid, less volatile organics coated, "dust".

      Freshly ejected material in the streamers is bright compared to the surface of the comet, still pretty dark mind, implying it comes from inside the comet where the organic contamination is less due to less exposure to ionising radiation. If the accretion of small planetesimals to make comets is correct, the surfaces of those planetesimals would be "carbonised" and so there would be organic matter within the comet as well as on the surface. Ejecta is hence still dark, but not as dark as the longer and more highly exposed surface.

      This explains why some areas of Laktrtz are much darker than others. Fresh, brighter ejecta, only covers some areas of the comet as production and deposition is localised. A good example of this is seen in this image.

      http://blogs.esa.int/rosetta/files/2014/10/ESA_Rosetta_NAVCAM_141020_A.jpg

      At bottom left are two areas of darker Laktritz adjacent to a far lighter area. The boundary is marked by a change in orientation of the landscape, the darker area sloping down and facing towards us, the lighter more horizontal plain, perpendicular to the body of the comet. We have seen streamers emanating from the far end of this valley and showering the immediate area with debris. The areas facing us are shielded from this shower by the plain above them and their distance "round" the comet. The contrast is clearer still on the surface of the lump of fallen cliff on the valley floor below. Ejecta debris is funnelled down the valley by the cliffs on either side, many of which have overhangs. On top of the lobes, well away from the neck, the surface layers are very dark compared to the neck region, the region around Cheops or Landing site B for instance.

      The recent arrival of rapid sublimation closer to the Sun and the consequent huge increase in the density of material in the coma, is bound to change the surface appearance of the comet over time. The comet will be stripped of most of the lighter "dust". The insulating layer, which until now has kept the subsurface of the comet in deep freeze, will disappear and the comet surface will undergo a rapid increase in erosion by sublimation. Exposed "boulder" and surface formations seem the first affected. The comet over time will become less gnarly and more subtle of terrain, with far less dust. Comet 67P is far dustier than the scientists and experts expected, this is my explanation as to why.

      Take away the cryovolcanism and the argument is a bit thin, but hey any hypothesis to explain the unknown, has to be based on some assumptions. If all the starting conditions are known, it becomes a calculation, not a theory. If those assumptions are shown to be inaccurate to some degree, the theory might have to be revised or ditched. That's science. 🙂

      • Sky says:

        "prior to its change in orbit sublimation and its effects on the nature of the comet's surface were minimal." - I stopped reading there. Obviously false statement. Comet been in Solar system for thousands if not millions of years, and sublimation DID occur exactly like it does occur on a Jupiter moons - the old perihelion of 67P was at 2.7 AU, by far closer than Jupiter moons ever been. Changes to the comet surface were far from minimal. In fact: they shaped it by far more than it was shaped since being pushed to the new orbit.

  • Ileana Calvo says:

    If I am not wrong these are the first pictures of a comet, from that distance. It was so close!!!
    Wasn't it?

  • DavidW says:

    Just to incredible for words Emily, I'll have to write a poem this time instead of prose 🙂

    David

  • Antonio Gutierrez says:

    Dune-shape figures? Wouldn't that indicate presence of winds?

    • logan says:

      Hi Antonio. Several arguments which include extra-cold repting dust gas, vibration, gravitational recapture, even 'wrinkles' expressed here. Intriguing issue 🙂

      • logan says:

        Any gas speedy enough to be called 'wind' would reach scape velocity and abandon the comet forever.

      • logan says:

        The 'swinging' g forces of Paul model. This is a polar area.

        • logan says:

          What relation is imaginable between this 'collimated' jets and auroras?

  • Henk Smid says:

    This not the dirty snowball we expected. How did this thing grow ?

    Further, what are all these rocks doing there ? (Well, rocks, Cheops is some 40 m in size).

    It is stranger than we expected. Kindest, Henk

  • Robin Sherman says:

    Another information filled image to pick the bones out of. Thanks Emily.

    We can see Landing Site A in the distance in this image, but the majority of what we saw in the 20th October image is hidden by the body lobe in the foreground. What is evident is the area we saw in the 20th October image is actively producing dust, confirming the areas seen to have been distorting the image are in fact gas plumes carrying small amounts of dust away from the surface. The activity seems to emanate most obviously from the brightest areas not covered by Laktritz. The source of the large streamers is not evident in either picture.

    Large amounts of small scale activity is taking place in the large area of rough ground on the neck, bottom right, though little evidence of activity associated with the long crack.

    The new and interesting areas of this image are on the right and left of the body lobe. On the right, "behind" and "above" Site A, (top right Image D & right of Image C), is a large area free of evidence of molten material, "ice lava" flows. This looks like fairly untouched comet material exposed by whatever created Site A. Apart from the darkened surface this appears to be a glimpse of pristine material from inside the comet.

    Top left side of the mosaic, (left side of Image B & top left Image A) there is a clear demarcation between the "ice lava" material and a flatter area of entirely different appearance to what we have seen before. It is covered in large part by the ubiquitous Laktritz, but elsewhere there are numerous closely packed little circular features that look like cups and bowls.

    Further down towards the bottom of Image D, these features can be seen buried under the surface layer. There is a raised area, with a small scarp running along its edge. On the left side, this scarp is expelling gas across the surface eroding the surface layer. There are other indented areas where the thickness of the surface layer appears much reduced, possibly by a similar process, (top left Image A). Areas of "bedrock" exposed by different amounts can be seen too. This layer of material has a different structure and texture to the "ice lava" adjacent to it. That area appears brittle, crumbly and nobly, numerous pieces of rubble have fallen off the edges onto the flatter more compact area next to it. I would suggest this flatter area is an example of the original, underlying cometary surface.

    P.S. Bob the Builder's tool shed bottom right, Image A

  • Jerry Carlton says:

    What are the advertising rights to that thing?
    Is it rentable?

  • Tom says:

    Yup, I'm googly-eyed alright. I was looking at the lower rez version. The high rez shows the boulder and a little one in both pictures! Oh well. Hope we see some cool 3D shots soon.

    Emily, has there been anything you have noticed that shows surface changes like crumbling pieces falling off since Rosetta has been there?

  • Tom says:

    My first comment didn't post. Here it is again.

    Fantastic photos!

    I have been going googly-eyed crossing my eyes on all the sections of the top 4 panels that overlap. Pretty cool 3D effect! Somebody make some 3D anaglyphs!

    What caught my eye(s) is the big prominent boulder in the lower 2 photos about mid-way down resting on the "Laktritz". It appears different in each picture. It looks to me like a chunk of it has fallen off (white piece with shadow) at the top of the boulder. Was the lower right photo taken after the lower left photo? And if so, how much time has elapsed between the 2 lower panels?

    • Sky says:

      It's usually few minutes between shots. If I remember well - OSIRIS sensor takes over 3 minutes to even read the data down and save it in a memory (these are 16 bit files in original, raw data)

  • dave says:

    Bill,

    Do you mean jets? as in from a hole, you mention vent?, look at all those flat bottomed craters to the right of the picture, this is clearly not from collision, so it has to be erosion of some kind ( there has been theories of Cryovulcanism, which if a there is a method may make this shape).
    If the erosion was from jets from a hole or vent, then we would now see them clearly (ie a hole in the middle of all those craters) but they are not there.
    There is something being ejected at bottom right, but this is not from a hole, it looks like its coming right off the surface.
    If there was ice on the surface , we could say here is evidence of sublimation, but there is no ice on the surface, some think the ice may be hidden in the dust, but the area here looks like rock and rubble, so sublimation looks less likely.
    What we see when we stand back from the comet we call jets, because the ejecta looks very columated, but every picture we see where 'jets' may have been eminating looks like flat ground.
    Even with our previous picture where we had head lights or cups. This could of been good news for sublimation from underneath the surface, but if that method of sublimation was the cause of the cups, I think we may of expected the inside of the cup to be conical reducing to a hole.
    We know fom NASAs lab experiments that the solar wind rips the surface molecules apart, this is an electrical process, and will attack the exposed surface.

    Surely when you can see a wispy ejection like that in the bottom right of the picture that appears to be rising from the ground, then you might wonder why do we need vents?

    • Bill says:

      By "jets" I mean sublimated gas outflows and "dust jets" the visible nano- and micro-sized material. composed of silicate minerals and refractory organics entrained in the gas flow, plus any desublimated dihydrogen monoxide also entrained.

      And unknown are the properties of thi s mixture under the conditions near this comet, especially at the always-in-darkness cold trap in the South polar region. An idea of what could be found can be gained by reading "The Endochronic Properties of Resublimated Thiotimoline", I.Y. Ozimov, 1948, Campbell Press.

      The concept of a singular vent is related to the idea of a volcanic vent or a hydrothermal vent and is used in the context of a vent area or a vent system. From what we have seen on 67P the actual vent areas are linear fissures or the rubble piles seen near scarps or the friable and vuggy-looking bare rocky surfaces.

      We'll know more with high-resolution views, with "boots on the ground" and a warmer comet in a few months.

      --Bill

      • Robin Sherman says:

        The powdery/dusty material covering the solid material is black, but the material making up the solid surface and "boulders" is also black all the way through. We are seeing ice, just very black ice, or more colloquially "very dirty ice". Some places and bits of material are just slightly less dirty than others.

        Material being sublimated will be mainly invisible gas, Water Vapour, Carbon Dioxide, Ammonia, etc. They are colourless. Small amounts of solid material may be suspended in the gas plumes, this is black too. I have likened the gas arising from sublimation to a heat haze. A heat haze is formed by the different temperatures of air layers having a slightly different Refractive Index, they "bend" light by a slightly different amount. A vacuum has a Refractive Index of 1. The sublimating gases something of the order of 1.002. Thus the light travelling direct from the surface takes a different route to that passing through a sublimation plume and a distortion in the image is seen. This shows up as a blurry shape visible from the larger size of pixels that make it up.

        On the bottom left of Image B, there is a low ridge of material that looks just like any other area of dust. To the left of it there is a continuous line of larger pixels where the transition of different shades is totally un-uniform. This is the distortion caused by small sublimation gas plumes.

        There are many of them in the bare neck region. Individual plumes rising from the exposed "clean" surface, "boulders" and promontories can be seen. These plumes are barely moving and are small in scale and are totally different to the streamers we have seen which extend for Kilometres not metres. The mechanism for their production is different. A clear knowledge of what that mechanism is, has not so far been uncovered so the nature of the source, what it looks like on the ground, is not easily defined.

        The streamers appear collimated so a circular or oval source is suspected and the similarity with geysers here on Earth would lead one to think the source would look similar. The vent hole of a geyser is not visible on the surface, the fluid around it tends to submerge it. The speculated fluid like properties of the very light, fine dust of the surface layer, could do the same. At best we might see circular indentations in the dust, as seen on the neck plains, in a group or line over an area of subsurface activity. Like Bill, I suspect we will have to wait for a lot more vigorous activity before we can see it.

        Of course there may be dozens of OSIRIS images already, clearly showing the sources and associated active streamers, but us mere mortals are not fit for such holy revelations ahead of the great ceremony on November 12th.

  • Atom Universe says:

    I have a question( may be a stupid one, still). Is it possible to hijack the comet from its orbit and land it safely on earth?
    I know its huge object with 1 * 10 ^13 kg. Is it feasible? if not why?

    • Jacob nielsen says:

      Your question isn't stupid, doing what you suggest would surely be.

    • logan says:

      Biggest things we have been able to bring back NOT by accident are a few kg of lunar rocks.

  • Bill says:

    We still don't have a good hi-rez view of one of the dust jet source areas, but the one that we _do_ have, near the "Ampitheater", SIte A, is still likely:

    http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets/i-DHNvtXr/1/L/24sept_2oct_20oct-14_vent_activity-L.png

    This is the area with the line of pits along a supposed fracture.

    The other dust jet vent area, east or west of this north polar area, is the one not seen clearly, but it is probably the most likely area. We just don have, ahem, a smoking gun yet...

    http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets/i-VtWPtzS/0/L/24sept_navcam--jet-L.png

    http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets/i-cJ6HN5G/0/L/ESA_ROSETTA_NAVCAM_20140811%5B-%5D--res2x-enh-L.png

    --Bill

    • logan says:

      Hi Bill. Have you considered as a possibility that we are actually seeing them?
      The brightness of surface being 100%. The brightness of jets being 0.1%.

  • Atom Universe says:

    My own theory of Comet formation :
    .
    The comet has been formed from two molten rock from the same object (? ).

    1) The object (?) exploded
    2) Two molten rock being two debris among many, flying at high speed with almost same speed with small inclination, got collided, stick to each other but due to impact the smaller object try to move away from the bigger rock.
    3) As both object sticks together and the both rock was cooling the smaller rock got locked with the bigger one, before it can escape from the bigger one.

    • logan says:

      Hi Atom. As you, have not discarded 'explosions' 🙂

    • Marco says:

      Hi Atom Universe. My main objection to any "rock" theory is the density. Despite protestations on comments on this blog to the contrary, the density of .4 that of water is ..ahem... Rock solid.

      • Atom Universe says:

        Good point Marco. The word "Rock" may be an exaggeration, it could be any thing in molten state.

        Since 400kg/m^3 is Mean density,What if it has good metal outer surface with many gas trapped pockets( as result of solidification where the gases failed to escape).

      • Atom Universe says:

        This image (http://blogs.esa.int/rosetta/2014/08/20/cometwatch-19-august/) from rosetta was the reason for me to think its formation this way.

      • John says:

        Marco, there is a plausible theory that mass can vary according to charge state. So mass would not equal quantity of atoms. An Earth type rock with a density of 2.5 g/cc could therefore be perceived in an interplanetary comet material as 0.4. and still be solid rock.

        • Marco says:

          @john. It is not plausible. There are other explanations that don't cotnradict EU, without a denial of our known underlying physics models. Continuing to deny the low density will just severely embarrass those that keep persisting.

  • Ram says:

    Do comments naturally have that grayish color or rosetta is not using the color camera's yet?

    • Marco says:

      Hi ram, comments are always in shades of gray :-). Comets are various shades of black. Any colour we apply, including lighter greys, is false colour to highlight the features.

  • jimmy says:

    什麼時候,中國才可以跟上?

  • Guili says:

    Isn't there a huge crack or fault in the neck region (bottom right picture) ? I don't remember having seen that in any of the pictures before.
    I hope the whole thing doesn't break apart in two pieces before Philea tries to land.....

    • Guili says:

      My bad,

      The crack could be seen already in CometWatch on 18th of October (bottom right picture again).

      • Guili says:

        Crack also seen on cometwatch 19th of september.

        • Guili says:

          And I feel ashamed because Emily wrote about it in the blog entry. Sorry 🙁

      • logan says:

        Wonder if only 'superficial' 🙂

        • Robin Sherman says:

          Having looked closely at it in this image, it may not be a crack at all, but just a very low cliff like we saw near Cheops. I remember when we all commented about it the first time it appeared, someone said we were all panicking over nothing it was clearly just a cliff. If it was a real crack I would have expected to see gas coming from it.

          I thought that about the jets and it has been mentioned before by Bill, myself and others, that unless we see them from the right angle and with the right angle to the Sun, they are practically invisible because they are so diffuse. Experience with the small plumes of gas from sublimation tells me we would certainly notice the change in refractivity and the distorted parts of the image, not to mention the like huge streak of pixelation.

          Cometstalker thinks that the jets might be intermittent, short lived phenomena, so the chances of catching the source of one are reduced. An illusion caused by the random and intermittent appearance of appropriate images I think.

          Having said all that, there is possibility in Image A. We know that the NAVCAM CCD has a set range of brightness it can record based on the average light levels at the comet. If the maximum brightness is exceeded then a black pixel is seen. Near the dunes, at about 10 O'Clock is a black area, apparently shadow, but it is difficult to figure out the source of the shadow. It also has edges defined by pixel edges, other shadows appear to have less "digital" edges. I still find interpreting shadows of 3D objects on a flat 2D image impossible some times, so I attach a very high level of doubt to this idea, but it may be very bright activity/streamers appear black in the images.

          I know, I know, I'm clutching at straws here.

          • Jacob nielsen says:

            @Robin Sherman, "If the maximum brightness is exceeded then a black pixel is seen. " Where did you read this? Would we then interpret 2 by 2 checkerboard pixelation as: very bright object 0-2 meter size-range? Up till now I have discounted such as random noise, also partly because it appears to occur, well, randomly... And how to distinguish 'too bright' from random noise in general, when these specks occur in such small numbers of pixels? (1-4). Navcam is better for navigating at this stage of close scrutiny.

          • Robin Sherman says:

            Hi Jacob. All this is explained in Claudia's excellent blog post about how NAVCAM obtains it's images.

            http://blogs.esa.int/rosetta/2014/10/17/navcams-shades-of-grey/

          • Bill says:

            @Jacob Nielson ""Would we then interpret 2 by 2 checkerboard pixelation as: very bright object 0-2 meter size-range? Up till now I have discounted such as random noise, also partly because it appears to occur, well, randomly... ""

            Hmm, 2x2 checkerboards, randomly. In Sept, that may have been the cause of embarrassment for me-- I saw on an 23Aug image many "new" features, small craters or mounds, which were a false alarm and caused by random noise. 2x2 patterns, which mimicked a crater at the limit of resolution. Uploaded an image series, and left it up for posterity:

            http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta/i-q6tNgVx/0/L/_compar_20140806_to_21040823-annot-L.png

            The Gallery page is:

            http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta/

            third or fourth image down, if you need to read the caption.

            "Solves" that mystery, and may be an indication of a "snowstorm"...

            --Bill

          • Jacob Nielsen says:

            @Robin, did reat that, but found no reference to: "If the maximum brightness is exceeded then a black pixel is seen."

          • Jacob Nielsen says:

            @Bill, @Robin, how do we deal with noise then? As random artifacts alone, which should be ignored, or as possible over-saturation, which needs some interpretation?

          • Robin Sherman says:

            As a rule of thumb Jacob I treat the 2x2 checkerboards as noise and the odd singular dots. As I explained before, I view these images of a large HDTV screen and I can only relate what I see. There are large areas of the plains and mountains were there is no evidence of pixels in the image even at 5 or 6x zoom. Other regions particularly "above" collections of ice rocks and ice boulders where this clean image is replaced by areas of extra large pixels containing a few to tens of these "super" pixels. Often they are rectangular rather than square. This is seen at less zoom as a hazy distortion of the image. Something is moving during the 6 second exposure. In the absence of any physical force to move things, it must be moving gas and dust resulting from the surface sublimating. I have spoken about refractivity and the distortion that causes, which adds to the haze and blurry nature of these areas. In a few cases I can make out the shapes of the plumes by looking for the edges where the pixelation stops and the normal resolution returns.

            This is my interpretation given what I am seeing, other's perspectives are different and I fully understand some are sceptical, their image may not be being reproduced in the same manner as mine. I certainly did not see the big block pixel areas on earlier NAVCAM images, the 2x2 checkerboards yes or the diagonal pair of bright or dark dots. That I deem to be noise.

            Sorry, about the black pixels, that I believe was mentioned a lot earlier, by Emily I think, in one of her posts when we started getting images from closer in. I seemed to have merged the two into one article. It may not apply to NAVCAM, but as I remember, an oversaturated pixel cannot display more brightness, so it would turn itself off to avoid "burnout" and and give a zero or black reading. I am sure one of the Rosetta team could clarify this.

            As to determining if black areas are over saturation, its a case of looking for the feature creating the shadow. Not much of an answer given the orientation problems we all have, especially with shadows. Hence my honesty in not claiming any great belief in this idea as an interpretation tool as Emily warned us not to.

  • Atom Universe says:

    Today I read about comet Lovejoy and I came to know that it plunges into the sun and survives (http://science.nasa.gov/science-news/science-at-nasa/2011/16dec_cometlovejoy/)

    How does it survives the high temperature which prevails in sun? Does this mean these comets have very high refractory surface which can with stand even sun's temperature at core (10-15 million K)?

    Does comets have any new elements which are not yet discovered?

    or Does these surface have been formed due to new process of solidification?

    I have a doubt on comet LoveJoy (not a forum to discuss about his). How does it escape's from sun's gravitational field which has escape velocity of 617km/s? Its mentioned as comet lovejoy traveled at a speed of 536 km/s when it dives into the sun's core.

    who told science is dead? billion's of things to unfold, does humans survive till that time?

  • Kamal Lodaya says:

    Atom universe: On comet Lovejoy C2011/W3 (Terry Lovejoy has discovered many comets so it is better to be specific) you might want to read an article which addresses your question:
    http://www.universetoday.com/94115/how-did-comet-lovejoy-survive-its-trip-around-the-sun/
    and the comments on it. It is not clear that a significant part of the comet's nucleus survived.

    • Atom Universe says:

      Thanks for the link (I have indeed gone through the same post previously), not convinced with the explanation on how it survived.

  • Lewis says:

    Spectacular images as always!

    Not sure why but I thought I would create this particularly pleasing (at least, to my eye) framing, which shows comet activity, boulders and fractures:

    https://www.flickr.com/photos/shibbyuk/15635322176/in/photostream/lightbox/

  • frankebe says:

    GREAT rendition, Lewis! Can you make some more of these?

  • William E. Nelson says:

    One has learned that the comet is releasing dust particles from its surface, so doesn't that mean that the comet is getting smaller through its existence from the beginning? William

Comments are closed.