CometWatch – 18 October

This four-image NAVCAM montage comprises images taken on 18 October from a distance of 9.8 km from the centre of comet 67P/C-G – about 7.8 km from the surface. The four 1024 x 1024 pixel images making up the montage are provided at the end of this post.

Comet 67P/C-G on 18 October, from a distance of 9.8 km from the centre of the comet.  Credits: ESA/Rosetta/NAVCAM

Comet 67P/C-G on 18 October, from a distance of 9.8 km from the centre of the comet.
Credits: ESA/Rosetta/NAVCAM

At a distance of 7.8 km from the surface, the image scale is about 66.5 cm/pixel, so each 1024 x 1024 pixel frame is about 680 m across (although if we assume the furthest point away is an additional ~1 km further from the centre, the image scale is about 92 cm/pixel).

The combined effect of the comet rotating between the first and last images taken in the sequence and the spacecraft moving in the same time is particularly apparent if you try to match features in the lower left and lower right images, which are the first and last images in the 20-minute sequence, respectively.

In this orientation, the larger lobe of the comet is to the left, the smaller lobe to the right. The image highlights the features of the comet’s neck, including the active region (you might like to compare with the previous, more distant, view of 26 September). A fracture-like feature seen in the 19 September image is also visible in this montage, about 1/3 down from the top of the lower right frame. In the same frame, we also have a much closer look at a group of boulders, some of which appear to be more like protrusions, perhaps exposed by the removal of surrounding material.

Elsewhere, and particularly in the upper frames, you may notice a number of bright streaks. Some of these will likely be dust grains ejected from the comet, captured in the six-second exposure time of the images.

ESA_Rosetta_NAVCAM_141018_A

ESA_Rosetta_NAVCAM_141018_DESA_Rosetta_NAVCAM_141018_BESA_Rosetta_NAVCAM_141018_C

Comments

87 Comments

  • Jacob nielsen says:

    Wow! So much going on in the skies of 67p! A new and less thought of obstacle to both Rosetta an Philae: objects flying around! Distinctly not camera noise. Some are lit, some are black, which can only be interpreted as: in 67p's shade relative to sun, visible on the background of the sunlit / glowing coma. Around pixel-wide meaning meter sized, and moving i many directions, haven't done my homework on movement yet

    • Luke Collie says:

      The streaks look about 30-50 pixels long. so about 30 metres across the field of view in the 6 minute exposure time, or 0.1 m/sec. Velocity towards/away from the camera is impossible to determine, but a few tenths of a m/s total velocity would be a reasonable fist guess. There may be faster stuff too, but the streaks would be too faint to see.

    • Jacob Nielsen says:

      my entry was truncated (due to bad type of smiley, this one should be ok: 😉 ? ), so I will elaborate a bit: @Luke, your calculated velocities: assuming the average distance to objects, same as comet distance? If speeds are as you estimate, that should be be below escape velocity, so even directed away from the nucleus, the are likely to return. Solar wind? will sweep all away? Then wouldn't we expect the dust on nucleus surface to be swept away too? assuming the "dust" is in fact dust. Another thing: the black, flying particles that must be in the nucleus shade, will they not also be in some shade from the solar wind? And is that (@Logan) not what you are hinting at by "tubular flow"? It can, at times, be a little hard for me to follow your line of thoughts 🙂 I do see a possibility for substantial mixing and agglomeration, by combining sublimation, ejection (in various direction) with turbulence caused by: nucleus rotation and solar wind "push" and the heterogeneity of light and dark side. I also see a substantial room for the importance of electrostatic interaction, both between nucleus and "flying objects" and between those. Is there a chance of "smear" so that objects appear larger than the actual source of light? That would be contradicted by the size of the dark particles, that similarly seem to be at least pixel-wide. If things can grow to this size at this stage and density of the coma, then what to expect later? Will it be "Space Invaders" during the Philae descent?

      • Cometstalker says:

        I observe a lot of jpg artefacts. Also some background stars.

    • Jacob nielsen says:

      On closer inspection, it appears all black "dots" appear in pairs, sometimes with a matching number (2!) brigbt pixels adjacent. Som probably pixel noise or undiscernable therefrom

  • Carlo A.G. Tripodi says:

    Waiting for landing........Go,go, go Rosetta!

  • Dan Owen says:

    I remember reading Jules Verne's Off on a Comet as a child and being fascinated with his thought experiment. Of course, Rosetta is much better. Is there any reference to Verne's story anywhere in the Rosetta expedition?

  • Erwin says:

    I've been able to stitch only the two right frames but the resulting mosaic is spectacular. I've added a Hollywood-like sign for scale: https://twitter.com/pioneer_astro/status/524251244882583552

    Thank you Rosetta!

  • Hi Emily--

    Great new set of Navcam images! The source region of the jets seems to consistently elude the camera's eye. That's the area we'd all like to see.

    Catching up, I finally managed to get decent 3D images of Philae's backup landing site. The stereo separation is so extreme that the frames simply do not match over a large region. However, in small regions the views are impressive. I've posted four 3D images at:
    http://www.wvi.com/~rberry/Rosetta/Images.htm

    --Richard

    • emily says:

      Hi Richard, thanks for trying out the 3D images!
      I'm keen to see the source region of those jets too 🙂

  • Robin Sherman says:

    Welcome back Emily, you've done us proud again. Glorious images. Its scary big close up. Erwin your mosaic is great only I don't know how tall the "Hollywood" sign is. Nice touch though.

    The streamers of dust always seem to be over the horizon. In the September 26 image they are closer and the bottom of the streamers suggests there are 4, maybe 5, pretty much point sources. In this view they are further round the neck and we only see the upper parts as 3 broader bands. It is noticeable that subsurface sublimation is more visible and the coma in general is slightly brighter. Enough light is being scattered to light up the underside of the neck and the insides of craters.

    The most puzzling aspect of this image are the dunes. Unlike other places they do not seem to be just reflecting the underlying terrain, but bonafide dust dunes. They are almost perpendicular to the rotation of the comet. Dunes like this require some sort of fluid motion, gas or liquid. There is no liquid on the surface and no atmosphere to speak of, a deposition phenomena perhaps?

    More evidence of gas plumes creating distortions in the image, but not as clear as I thought might be seen from this close.

    Philae is going to take 7 hours to land and we know she will be taking pictures on the way. Are you allowed to tell us what resolution they will be and the frequency at which they will be taken? In theory she could take over 400 six second exposures, not that she will be pointing at the comet for the whole 7 hours. As the coma brightens and being so close would 6 second exposures still be required? I am sure you will tell me this will all be explained during the landing day briefing, but go on give us a little teaser.

    • emily says:

      Hi Robin,
      For the descent, Philae will use its ROLIS camera to take images of the comet, the majority of which I understand will be taken during the last phase of descent. It has a 1024x1024 pixel CCD and once Philae is on the surface, when the camera will be about 30 cm above the ground, the field of view will be roughly 30 x 30 cm, giving a resolution of 0.3 mm/pixel. More details soon!
      Best wishes,
      Emily
      P.S. The 'dunes' are intriguing aren't they? Looking forward to hearing the outcome of the science team's analysis of those!

      • Cometstalker says:

        Im glad to read your words "science teams analysis" in one sentence. Scientists working in teams and delivering a result of theire analysis is as rare as this comet. So far very little of value concerning scientiffic data is presented. A lot of artistic valuable pictures are presented and that is not very scientific at all. Once we even got a colorized poster of the comet, that was nice but not finished of and gave an impression of some kindergarten work-about, very impressive for a kindergarten but for a scientific workshop rather embarrassing. Most of the information coming from ESA has a note of spectacular but as not much else is presented this also tastes a bit of desperation.

        Im glad that this blog is available because here at least the fantasy and speculation has a free room to play.

      • Robin Sherman says:

        Thanks for the reply Emily. Philae will only travelling at 1m/s so there should be the opportunity to get a few pictures from under 100m. Whatever happens to her when she lands we should get some great closeup pictures of the surface topology.

        • logan says:

          Considering the electronics 'age', don't think there is a huge cache for 'lots' of photos. :/

    • Erwin says:

      According to Wikipedia, the letters of the Hollywood sign are 14 m high. 😉

      • Robin Sherman says:

        Do we now get into the S.I units of size comparison discussion. The London Bus, Elephant, Blue Wale, Eiffel Tower, Jumbo Jet, Olympic Swimming Pool, Hollywood Sign, Area the size of Wales or Texas. These things need to be standardised and controlled. Even ESA are doing it the unit of size, the "Mont Blanc". How many London Buses make a Mont Blanc? 🙂

  • Birgit Hofmann says:

    Yes, GO rosetta, GO philae..
    Every day i look at rosetta-blog, fantastic pictures !

  • Bill says:

    Hi, Emily--

    The ESA Blog seems to have disappeared for a few days. When I go to my Bookmarked URL for it-- http://blogs.esa.int/rosetta/ -- I get a "Top" a page that shows the latest Blog entry as "Green Light for Landing Site J" http://blogs.esa.int/rosetta/2014/10/15/green-light-for-landing-site-j/ . Yet I find that there have been Blog posts that don't show up on the current ESA blog, like posts on the 15th, 16th, 17th and 20th October that I have missed. This post that I am replying at is the blog entry posted 20 Oct: http://blogs.esa.int/rosetta/2014/10/20/cometwatch-18-october/ .

    Clicking on the "Rosetta Blog" link the top of this Comet Watch page takes me to http://blogs.esa.int/rosetta/ and all I see the the old entries up to the 15th Oct..

    Puzzling-- has there been a change in the ESA Blog page coding the past few days? Have I gotten something odd stuck in my Cookies or Browser Cache? I could go and delete Cookies, etc, but I hesitate to do that because I will need to re-Login to several Froums I visit.

    I _can_ get here by going to the "Search Space in Images" bookmark I have -- http://www.esa.int/spaceinimages/content/search?SearchText=rosetta&img=1&SearchButton=Go which shows the latest images for Rosetta, but it's a roundabout method.

    Hate to bug you about this, but I'm stumped.

    BTW, spectacular images over the past few days!

    --Billl

    • emily says:

      Hi Bill, Sorry for the troubles! Last week there were a few technical issues which I understand are now resolved, but indeed you may have to try clearing your cache. Let me know if that doesn't solve the problem and I'll ask the technical team to investigate.

  • JP says:

    I can't help it, but I see dunes in the brightest area of the bottom right image.
    We had on many previous images some features really looking like dust banks forming long streaks, behind many boulders.
    Where is the wind coming from? I read earlier nanobars of pressure nowish, what about perihelion values? Could we reach the microbar? Would that be enough to cause these artifacts?

    • Cometstalker says:

      Quite a few micro bars are possible. The pressure gauge onboard has a top limit of 10 millibars and that is a bit hysterical as to reach this level one third of the comet must evaporate in a hurry to create a spherical shape atmosphere.

      • logan says:

        We all, including you Cometstalker, have elucidated that 67P present phenomena protective of herself.

  • Robin Sherman says:

    I think Curiosity must have got to 67P first. That laser it uses for testing rock leaves rows of tiny little holes everywhere.

    http://blogs.esa.int/rosetta/files/2014/10/ESA_Rosetta_NAVCAM_141018_D.jpg

    Move left from the top of the outcrop by the dunes, towards the shadows on the lefthand side. At about 5 O'Clock, just down from the shadow, there is a narrow dark line. Zoom in on this and there is a very neat line of little black holes, just like Curiosity makes.

    These lines of little holes are seen all over the comet, usually in straight lines. I do hope one of the ESA guys can tell us what they are. Yes I can guess they are probably something to do with subsurface sublimation, but why in straight lines most of the time?

  • Peter says:

    Apparent stratification, long fractures and "sand" dunes - how do you get dunes on a comet? No atmosphere, no wind except the solar wind?? Some interesting explaining to do

    • Cometstalker says:

      Right,
      to explain this place with processes from earth is meaningless. A few essentials given; vacuum, free fall feeling gravity, low average density, old and rare.

      The first thought in mind should be: if dust is sprinkled from whatever origin down onto this place it should be uniformly spread all over the comet and not on fenced in places only. Even at Cheops there are a few dust pockets.

      The conclusion might be that this dust is not at all spread about from abow and drifting in the "vacuum wind". To me it is a lot easyer to believe that this is a very special but on this comet a common process and not at all dust or sand.
      It is a dust-like surface created from a process going on inside of the comet, extruding this kind of glazing to its outside on quite a few places. I have no word for it and sublimation does not fit the bill at all, nor does lava but it has something in common with both of these processes. So far ESA scientist do not dare to speculate or spoil us with any information of concern about just anything.

      We only get things like, hey there is a new comet close to Mars and it might be interesting. Then it passes and thats it! The same with this mission. look here and there and then and soon. But thats it folks. Its up to you to do the science with whatever data you recieve and trust me if the scientists are able to find a Higgs that by definition impossibly can be a Boson or Neutrinos that definitely can not speed faster then light or fill in some algos with dark matter and very dark energy plus a lot darker urge then whatever you discover it is just as worthy as what our well established scientists are able to deliver. The major difference is that you receive no paychecks or Nobel price.

    • Jacob nielsen says:

      Looking at the "dunes" there seems to be no harmony, as such created by waves over a sea bottom or rolling winds over a sandy desert. The size of waves and the speed and direction of winds create harmonic structures in an interplay with the sediment structure: normally there will be a "wavelenght" in the ripple structure. In this case it looks more as though the sedimentation occurs fron a sharp angle, and this amplifies existing irregulaities in the sublayer. Also it appears to be a steep slope tha might have expirienced a series of small "dust slides". Thats my guessing anyway. Apparently no need to include liquid flow or atmosphere (wind) 🙂

      • Robin Sherman says:

        Not entirely persuaded by that scenario Jacob for these dunes. The other examples we have seen, yes. They do seem a little too regular for that, but ripples in subsurface terrain could possibly account for them. That just moves the problem onto, how did the subsurface terrain get like that to create that dust pattern in the first place?

        The other problem is the "apparent" slope, they are on. The small circumference of the neck would mean that the gravity vector changes so rapidly that, over the area covered by the dunes, it would remain perpendicular to the surface. From the experience of the surface layer it will flat apart from perturbations in the gravity vector from the head and body lobes. This could explain the dunes themselves and may be an important clue to the cohesiveness of the surface layer. If this is their cause, we need to explain why there are not dunes all over the neck plains.

        This problem applies if interactions with the Solar Wind are thought to shape the dunes. The surface layer is likely to be charged due to continual hard radiation bombarding the surface. An argument for the "Solar Wind shadow" created by the the specific nature of the local geography would be needed, so that this is the only place they exist. Elsewhere the interaction is random and the surface layer even.

        Not an easy solution to this one methinks.

        • Jacob nielsen says:

          My only real point is that the ripples do not resemble the harmonic structures seen where wind and waves are the ruling forces. I only suggest other explanations, and suggest a scenario in which recent sedimentation (of some sort) is not causing the pattern, but simply not eradicating it/ possibly amplifying it. I really like the idea of a lot of "weather" going on. To my view the nucleus is in a stage of rather rapid development, and the idea of 67p beeing a sort of timecapsule reaching back 10E9 yrs, must discount at least the top 1-? Metres, and I do find it possible that the nucles has been struck by 100+ smaller, fast object, either traversing the whole thing, or making deep narrow shaft (now filled by some sort of porous, frozen 'stuff') some of which may retain still a function as (drain pipes, venting holes, volcanos, geysers, jets, forget some? Take your pick, or better, name a new) Anyway I think it crucial to cook up ideas by november 12, In order to be able to take proper precautions for the landing.

          • Robin Sherman says:

            Your point was well made about harmonic relationships and I agree the other non "fluid solutions" you suggest are viable. I still like the idea of close to the surface "weather" effects too. This dust is not necessarily free flowing or frictionless though. ESA were surprisingly keen to emphasise the presence of organics in an oil/tar like form in the surface layer, which intuition says would stick dust grains together and reduce the movement of dust, especially by the very, very weak gravity. Sublimation of ices from below the surface would seem to be the key process involved in shaping the surface terrain of the plains here. A localised energy source with sufficient kinetic energy to move dust around. Amplification of underlying features somehow through this process seems the most likely scenario.

            At the moment the rate of sublimation is minimal, but if and when it increases we might be able to see the formation of dunes in action. ESA has been clever in enabling a baseline "map" to be acquired, before all the fireworks start. What precautions Philae can take is a moot point, it looks pretty much like pot luck.

          • logan says:

            Hi Robin. On your comment:

            ..."intuition says would stick dust grains together and reduce the movement of dust,...".

            I can't imagine this going on sunlit surface. Even if it is 220K. Maybe some weeks from now.

          • Robin Sherman says:

            Since when did intuition match reality, especially at 220K? Thanks for the reminder.

      • logan says:

        Hi Jacob. Remember the CO2 mist of magician shows? If these are dunes accreted by very cold gas then they follow gravity for a few -dozen?- meters before it disperses.

        • logan says:

          A continuous flow could progressively down surface temp and extend long enough to form a 'river'.

          • Jacob nielsen says:

            Ok, some sort 'mud slide' the mud beeing liquid gas mixed with 'black stuff'? Now intirely crazy idea. Only thing: it should be super short lived due to the super low pressure? Of course imagining water CO2 NH3 or the like, liquefied in the interior and expelled by the expansion of som lower-boiling point gas: it would mix with the lowest layers of dust, where temperatures may be lower than at the top. The liquid gas/ dust mixture could act like a 'lava' and possess some resistance to evaporation, by forming an upper crust, covered by an upper dusty coat. Still it should be limited to 'an event'... Maybe we get to see one, if Rosettas vision penetrates the coma in the months to come, or else as a changes to the surface as the coma clears many months from now. It should depend on what initiates the liquefication: impact or tidal force heating, while solar radiation would limit, rather than evoke this.

          • Jacob nielsen says:

            Typo: ment to write: no entirely crazy idea 🙂

          • logan says:

            ..."some sort 'mud slide' the mud beeing liquid gas mixed with 'black stuff'?".

            Think that's the atmosphere under a heavy dust layer in 'sublimating' zones.

            🙂

      • logan says:

        As you, think that electrostatic charges play an important role in dust dynamics.

    • THOMAS says:

      There's no sand and they're not dunes, just ripples in what will soon be established as being charcoal-black vitrified surfaces created by the extreme heat of electric discharge phenomena acting on the stratified rock the comet is visibly made of.

  • Chris van Dam says:

    Great work ESA! Fingers crossed for a successful landing & great science.

  • logan says:

    Hi Emily. How carefully chosen dynamic range. Beautiful beyond the name. Incredibly revealing too. Neck is a ship wreck.

  • logan says:

    The fracture-like feature goes directly into 'impact wave' signaled by Robin. Lot of calcareous cave style crystallizations all over the place. Kids, here you have your real 'another world' picture.

  • Rocket Nut says:

    When will we start to see the jets of gases and debris being sheded from the comet?

  • Tog says:

    I wonder whether that fracture, which is visible around a lot of the neck, is where the jets are coming from.

    • Robin Sherman says:

      This image taken on August 16th provides broader view of this area and the extent of the crack.

      http://www.esa.int/spaceinimages/Images/2014/08/Comet_on_16_August_a

      It can be seen extending to the top of the cliff we see in the above image, but no sign of it continuing into the plain on the other side. A closer view of the other side of the cliff can be seen in this image taken on October 2nd.

      http://www.esa.int/spaceinimages/Images/2014/10/Comet_on_2_October_NavCam

      In the bottom right corner the cliff can be seen along with the fault line, which stops at the top of the cliff. No evidence of the crack continuing around the neck can be seen.

      The image mentioned by Emily from September 19th, shows the crack/fault does not extend the other way round the comet. This fault appears to be a surface feature confined to one large "ice lava" flow of comet material.

      http://www.esa.int/spaceinimages/Images/2014/09/Comet_on_19_September_2014_NavCam

      Todays image is great, because we can see a more detailed view of the nature of that flow. It is not made of crystalline blocks and smoother compacted material like the flows on the lobes. It is rough and nobly with lots of debris buried within it, which makes me think it is where a whole section of comet has melted and flowed carrying the aggregate within it, along in the flow.

      The visual nature of lava flows on Earth varies due to the chemical and gas composition of the magma, the rate of flow and how that lava cools. The same should apply to "ice lava" on 67P. Right at the edge of the flow near the neck it seems to have flowed over a more compacted, stratified formation, a little bit of which can still be seen. This more sold material might have been colder and cooled the bottom of the flow more quickly resulting in the crack running across the flow.

      I'm not a volcanologist, so this speculation is based on knowledge picked up from TV documentaries and such. It just seems so obvious now from these closer pictures that comet material has flowed across the surface on numerous occasions in the past from both impact events and cryovolcanoes. This comet is a burnt and melted object. The big question is, where did all that energy come from? Some from impacts undoubtably, some from tidal interactions with Jupiter and the Sun and some from solar radiation. How do we explain the different composition of "ice lava" in different regions of the comet? Has material in the comet been fractionated inside the comet in some way? Did it once have a semi-liquid core that centripetal forces acted on to move heavier volatiles like water to the tops of the lobes, leaving lighter ones in the neck area, hence more rapid erosion?

      Lots and lots of questions and possible ad hoc theories., but I am still none the wiser. Landing day and the science updates can't come soon enough. Even then I doubt we will get very many answers, just a long list of things the team expect to be investigating over the coming months. At least that will give us some pointers as to what the science teams think is going on.

      • Cometstalker says:

        I have seen ice flow downhill with speeded up films and i know that cold glass is liquid even if it breakes.

        On the comet there is a process that reminds of lawa flow but is not, also it must be a lot of sublimation going on in some odd way.

        There must be a common process not named yet that extrudes the comet-glaze from its inside to its surface and some time it is ruptured by impacts. This glaze is not dust or sand or snow.

        The temperature is cryogenic and the gravity is low plus the timescale is huge.

        Give this a name rather then naming the landing spot. Lacritz?

        • Jacob nielsen says:

          Exactly: naming the landing site is just a celebration of heroes. Totally irrelevant to science. 'Site J' does the trick as it has already been used consistently to refer to that spot. Childsplay. It is not a feature or landmark, it is an area of likely contact, say maby the 99 percentile, but what if Philae misses? Or lands near the edge? After november 12, the red border is obsolete, and there is only the tiny spot left,, where Phile was engulfed by the soft surface :-))

          • Jacob nielsen says:

            ....Therefore I suggested the name 'Jacobs ladder': it has my name in it, yes it is my real name 🙂

          • Jacob nielsen says:

            By the way: would be a very 'ancient egyptian' way to handle dead heroes: bury them in a giant 'rock' 🙂

          • Jacob nielsen says:

            The rosetta stone was not important as a document, but as a key to interpretation, this mission is trying to track the formation of our biosphere. That is a case of 'trying to read the book' as opposed to: 'deciphering the alphabet'. Now jacob, the biblical one, claimed he found the staircase to heaven, the link between earthly, human life and the celestial 'being'. The rosetta mission is trying to set foot on the very same, just remove 'being' from celestial, and then doing it in physics, instead of conjuring it up in dreams.

          • logan says:

            'Site J' Already named.
            'J Ladder Point' the actual attaching cross line 😉

        • Robin Sherman says:

          Good point that about glass, Cometstalker. Some "hot" process would be needed first to produce such a material, but the analogy fits the visual evidence nicely in a number of formations. Maybe some of the very slowly eroding "Tors" and "boulders" are the ice equivalent of Obsidian, a "glass" made naturally in volcanic regions on Earth.

          • THOMAS says:

            I mentioned the idea of "lava flows" with a black vitrified appearance several days ago in another thread. Sorry to labour the point, but this result is actually EXPECTED and PREDICTED in the EU model. Glad to see growing recognition of the hands-on photographic evidence and its inevitable implications.

  • Steve Mencinsky says:

    These images are fantastic, but you need to take a leaf from Richard Berry's website and provide some "size context". At the minimum, a scale bar. Saying that the image is xx cm per pixel is not quite enough. It's too much work for us lazy public to extrapolate that for ourselves. Of course you could go the whole hog as Richard id and superpose a to-scale "familiar ordinary object" - in his case, a mischievous Boeing 777.

  • Birgit Hofmann says:

    Hello Richard !
    Ooops.., i think, that philae the first lander on the surface from 67P, and now i see a aeroplane, which Airline it is ?
    For the Nest holiday.....
    Birgit

  • logan says:

    If comets start their life at 'tubular' turbulences, then they could start with a 'tubular' form. Forget the 'sphere' as the base of everything.

    • Cometstalker says:

      A sphere works well for low gravity objects if the surface tension is high like balloons or droplets and also if gravity is high, this is by evidence. All the rest is the rest.

      • logan says:

        Interesting point, Cometstalker. But can't present myself with scenarios of comet initial accretion being subject to surface or big gravity forces. Really open to any schema.

  • Paul says:

    Perhaps the jets are made out of whatever loose material the dunes are made of?

  • Paul says:

    Could that material have formed dunes through irregular gforces in this area? (combination of rotation and difference in mass between both lobes)

    • logan says:

      Another model of deposition, Paul.
      This one can 'interact' with the others.
      🙂

  • Cometstalker says:

    All streamers so far that are on the pictures seem to emerge from the neck region. Not one single picture can show an exhaust area or spot. The exhaust is not continous. The conclusion i make is that the neck-region is breathing out its streamers uniformly and very faintly only to be visualized due to post-processing against a black background. This is like trickery to enhance specularity. Sometimes science is called for but so far this mission has very little to do with science. I se a lot of congratulations for great science and must admit that i am equipped with some kind of odd blindspot not being able to notice this science.

  • Clive Hartland says:

    Perhaps the dunes are formed by vibration? The Comet obviously is active in an unknown way and this could cause harmonic vibrations throughout the Comet but certain areas with dust accretion will then show as ripples.

    Clive

  • dave says:

    There is a possible reason for the dust looking like blown as if it is moving.
    Apparenty on the dark side of the moon the dust lifts just off the ground due to electrical effects (hair raising stuff) Apparently a different potential from sunny sie to dark side. Maybe the same electrical effects on the comet, lifting it up and dropping it again?
    The 'solar wind is a bunch of charged particals flowing the same way so there should be some magnetic fields due to the current flow and some electrical effects more so if there is a potential diffeferance between the solar wind and the comet.
    Brighter areas around the bottom of crater walls looks like an electrical effect, or at least how you might expect it to look, this then could be powering the jets, I am not convinced that we really have holes acting to concentrate ejections yet.
    The view we have of of what previously looked like a railway siding or Bob the builders rubbble pile does not look quite so pretty from this angle. It does look if it got there by some heat process, above there are suggestions of extrusion or volcanic activity, but it is hard to envision what drove the melting on the coment although there are theories put fwd. For the electric people then they may say yes, some material melted up on the head while being electro machined and just fell/rolled back down to the neck, but there seems to be no landing splash (what that would look like in this gravity I am not too sure).
    I not sure how we burn water ice, it should already have enough oxygen, but if the volotiles in the tail really are present near or on the surface then maybe there could be an extrusion of some tar type substance.
    At the the moment the big dark lump now looks like something that has been exposed through an erosion process and maybe is not sitting on the dust, but is surrounded by dust.
    In reality I am still sumped, any one any other theories?

    • logan says:

      Thanks for that theory, Dave. That is news for me.

    • Jacob nielsen says:

      certainly, electrostatics should play a role when moving about a powder such as carbon black, after all, that is how a laser printer works it little magic. Arc welding is just a little too much action to me. Something in the neighbourhood of rubbing a ballon agains your hair should be able to do a lot of remodeling, considering the local gravity, while some other forces like cohesion should be a little harder to overcome... I think. We are all faced with shortage of data. We are in the little sandbox with our noisy little images. No framework of environment data to support: infrared map? No, particles? No, gas, chemistry and flow? No. That's just how it is. Just makes the speculation bit so much more... exciting?

    • Robin Sherman says:

      Hi Dave, This making dunes and drawings seems to have us all stumped. Any number of possible theories seem plausible. I too read somewhere about dust on the moon and I would be very surprised if micro scale static electricity and charged particles don't have some influence on the surface layer. This might be lots of tiny effects adding up to one big one we see on the surface.

  • Pat says:

    "some material melted up on the head while being electro machined and just fell/rolled back down to the neck"

    Knowing where is "down" is far from obvious given the shape of the comet...

  • Robin Sherman says:

    It is to be hoped that most if not all these plausible and implausible theories were looked at in the planning stage and Rosetta and Philae's instruments specifically designed to sort the "wheat from the chaff". I think Philae landing safely and doing her science has got a lot more important now we see what 67P looks like close up. The exact nature of this Liktritz layer seems key to understanding the dynamics of 67P.

    • THOMAS says:

      @Robin Sherman. "It is to be hoped that most if not all these plausible and implausible theories were looked at in the planning stage and Rosetta and Philae's instruments specifically designed to sort the "wheat from the chaff".”

      You should know that the 2004 launch of Rosetta took place PRIOR to:
      - the double flash produced by the Deep Impact impactor on Comet Tempel1 in July 2005 which the EU people had PREDICTED but which left standard dirty snowball theorists floundering to explain.
      - the analysis of the Stardust samples from Comet Wild2 starting from 2006 showing the role played by extreme heat in the formation of most of them, which was also PREDICTED by the EU people.

      Since the planning stages of the mission spanned the decade EVEN BEFORE the 2004 launch, there is no logical reason why Rosetta should have been equipped with anything specifically designed to test the EU paradigm.

      Despite this understandable lack of EU-dedicated experimental equipment, however, the accumulating evidence will show itself to be so overwhelming that the validity of the EU model of comets will necessarily be recognized. It is the only one which fully agrees with the images Rosetta is providing us with, without any need whatever for the contortions and speculations which proponents of the standard theory or of other pet theories have to resort to to explain each new “surprising” or “astounding” picture.

      Each new release fully supports the EU model, with no need for any particular speculation. There are no surprises whatever for EU proponents. The more detailed the images become, the harder it will be to deny that this comet is a totally rocky object, largely covered by lava flows which have been produced by the extreme heat of intense electric discharge activity melting the comet’s crystalline rock formations over an indeterminate period of time.

      • boris says:

        Tom van Flandern's EPH model also practically predicts these observations, as well as more recent results from New Horizons at Pluto. The mainstream continues to be nonplussed by unexpected results, when these results have been practically predicted for nearly twenty years now. Everything from asteroids with satellites, comets with satellites, apparently stratified cometary nuclei, binary or dual lobe asteroids and nuclei... etc. Twenty years ago, no one would have guessed that comets and asteroids had the same recent (65M years) origin, and yet today's data shows again and again, it's getting hard to distinguish asteroids from comets (up close), and the surface features and chemistry are getting harder and harder to explain with the mainstream theory.

  • dave says:

    Pat,
    I agree, up and down due to gravity on 67p is a bit hard to imagine, especially when we can see rock sitting on planes seemingly perpendicular to each other.
    Just trying to make any sense of how the big lump got there.
    I havent seen Airs rock yet, but I imagine I will have the same problem when i get down there.

  • JP says:

    dunes and streams, another possible cause:
    we could also consider radiation pressure: among the dust set in movement on the comet's surface, some particles are emitted at low speed, and will fall back. Actually, we could consider dust as a kind of "dust gas" composed of dust grains around the comet. Big grains will behave nearly only influenced by gravitation, smaller particles will be more influenced by the radiation pressure (acting as a wind), and would eventually create dunes which crest should be perpendicular to the Sun's direction. Dust could settle on the cold side, when radiation pressure and gas flow decreases, leaving gravitation as the dominant force.
    More dunes on the neck, because the Sun illuminates these areas close to perihelion predominantly from dominant directions? => dunes crest lines indicate the dominant Sun direction when these dunes are formed.

    • logan says:

      Adding to Logan's hat 😉

    • Robin Sherman says:

      Certainly with gravity being as tiny as it is, a very fine grained "dry" dust might be influenced by radiation pressure. For most of it's orbit the radiation pressure at the 67P's surface would be micro tiny. I tend to think static charges, charged particles, sublimation gas pressure and solar wind interactions, would be of greater influence. They all probably contribute to a greater or lesser extent depending on the exact physical and chemical nature of this surface layer. We don't even know if it is actually "dust" yet.

      Another plausible theory for the pot.

  • Damian says:

    Following up on the question about "up" and "down", specially on the neck and the "bottom" of the cliffs, is there a "gravity" model/map for the comet's surface?

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