Today’s CometWatch entry is a single frame NAVCAM image obtained on 28 April, from a distance of 151 km from the centre of Comet 67P/Churyumov-Gerasimenko. At this distance, the resolution is 13 m/pixel; the image has been cropped to 11 km (the original frame, provided at the end of the post, measures 13 km across).
Cropped and processed single frame NAVCAM image of Comet 67P/C-G taken on 28 April 2015 from a distance of 151 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
With the large lobe of the comet in the foreground and the small lobe in the background, this image provides another interesting view on the smooth area on the large lobe that was featured prominently in CometWatch 26 April. In today’s image, this portion of the comet, consisting of parts of the Aker and Khepry regions, appears as a bright, slab-like feature pointing upwards. Behind it, on the small lobe, are parts of the rougher Bastet region.
The image has been processed to enhance the activity of 67P/C-G, with jets of material outflowing gloriously from the sunlit parts of both lobes. A bright, diffuse spot in front of the dark underside of the comet’s large lobe, home to the Imhotep region, seems to be strongly suggestive of activity there, too. From this distance, however, it is not immediately possible to know whether this is linked to the dust jet caught emanating from this side of the comet by Rosetta’s OSIRIS camera a few weeks ago.
The original 1024 x 1024 image is provided below:
Discussion: 38 comments
Hmm Jet on the dark side… What consensus theory has to say about it? Should’t it be impossible?
One straightforward approach would be assuming sublimation of ices (probably rich in supervolatiles like CO) or decomposition of clathrates within a somewhat deeper subsurface layer as the source, which is less sensitive to diurnal temperature oscillations, provided the jets actually.originate in region which is on the night side, local time. This approach wouldn’t apply to the polar night.
A nice picture Claudia and as you say with further evidence of an intrinsically illuminated jet emanating from the shaded area of the nucleus, suggesting that all of the jets are intrinsically illuminated.
originaljohn!
… “intrinsically illuminated” …? Nonsense!
You’ve made claims like this before. On the 2015/04/14 [1] thread, you write, “A discharge current occurs Harvey at the points of discharge, which are the regions of jet emission. Elsewhere where there is no visible discharge the current would be expected to be as low as you are surmising or lower, ie zero.”
Let us focus on this idea of “visible discharge,” and see what we see …
To begin with, I state emphatically that there is NO visible (or physical) evidence of electrical discharge activity being responsible for the observed jets! NONE!
Here are three randomly selected NAVCAM images. Please show me your visible evidence of electrical discharge!
1) Single frame NAVCAM image : 2015/02/20 : Distance = 118.5 km / Resolution = 10.1 m/pix
https://blogs.esa.int/rosetta/files/2015/02/ESA_Rosetta_NAVCAM_20150220.jpg
2) Single frame NAVCAM image : 2015/02/28 : Distance = 102.6 km / Resolution = 08.7 m/pix
https://blogs.esa.int/rosetta/files/2015/03/ESA_Rosetta_NavCam_20150228.jpg
3) Single frame NAVCAM image : 2015/03/14 : Distance = 081.4 km / Resolution = 06.9 m/pix
https://blogs.esa.int/rosetta/files/2015/03/ESA_Rosetta_NavCam_201503141.jpg
Perhaps a refresher is in order. It is common knowledge that the majority of CometWatch images have been captured by Rosetta’s Navigation Camera. In it’s simplist form, a camera is a device that gathers reflected/emitted light at various frequencies, and either transmits directly to an observer, or records it to media of some description for later processing and/or review. Specifically, the Rosetta NAVCAM employs, as media, an Active Pixel Sensor (APS) Charge-Coupled Device (CCD) with a viewing angle of 17 arcseconds per pixel. At 1024 x 1024 pixel resolution, this yields a maximum five degree field of view. To provide the required navigation and science context imagery, the front-illuminated frame transfer CCD detector is designed with broad spectral sensitivity in the “visible” range. Please note, this system was not specified, nor designed to detect IR, UV or X-rays.
Now, the three NAVCAM images provided have been processed to highlight nucleus detail. The darkest pixels were set to black, while the brightest pixels were set to white. Given a reported albedo of 0.06, we recognise that the brightest and whitest pixels are only reflecting 6% of the incident “visible” light! If these images had not been processed for release, the frames would have been essentially black with almost no discernible features.
So, in the three images, where are these “visible” discharges? According to your statement, no visible discharge implies no current. That’s what you said. Yes? Next question – what are these visible discharges supposed to look like? Aside from some undefined “visible” footprint, are there other forms of evidence you can use to corroborate your claims? And what are these jets EU proponents draw so much attention to? In the initial images, these jets are so optically thin (i.e., reflect so little light) that they require additional processing to make them visible. So what are these jets? The emitted light of electrical discharge? Or dust ejected from the comet’s surface by sublimation and subsequently illuminated by sunlight? Recall that at 3.4 AU, 67P was ejecting dust at 7 kg/s. As 67P approaches perihelion, dust output is expected to increase dramatically. For example, Osip et al. (1992) calculated Qd = 54 kg/s at 1.5 AU for the 1982-83 apparition. If these numbers are even close to correct, we could see at least an eight-fold increase in dust production! Can EU provide any mathematical relationship between electrical discharge, dust production and heliocentric distance? Perhaps it’s a simple linear relationship? Or maybe inverse-squared? If EU/EC is to be recognized as a valid scientific explanation for comet dust production, it MUST provide a coherent model of this behaviour! Full stop! Oh! And while you’re at it, please include a scientific explanation of how electrical discharge removes fluffy dust material from the comet’s surface without leaving a thermal signature (i.e., melting – we’ll get to this momentarily).
On a parallel thread [2], you write – “We have observed enough pictures of the jets and their development now to know that they are extremely important and significant. This should cause the investigation to focus on them as a priority if not exclusively.”
Here’s something to think about … Why is there no evidence to support EU/ES/EC claims? Perhaps because none exists? To date, no scientific data has been published in the journals regarding electrical discharge on 67P, or any other comet for that matter. As one might expect, electrical discharge would leave irrefutable electromagnetic and/or thermal evidence! So far, there is NONE! In the worst case of electrical discharge, we would expect to see damage to the Rosetta spacecraft! Again, nothing reported! And as we all know, Rosetta spends a considerable amount of time flying around and through these jets!
Now, why would you want to waste limited Rosetta science resources investigating something that is not salient to comet evolution? If EU wishes to investigate their nonsense, perhaps they should make an effort to secure funding to build and launch a spacecraft designed to explore the electrical nature of space. Given their propensity for selling t-shirts and books, the folks over at Thunderdolts should be flush with cash. Give them a call.
[1] blog link … /2015/04/14/rosetta-and-philae-find-comet-not-magnetised/#comment-431837
[2] blog link … /2015/04/13/cometwatch-activity-31-january-25-march/#comment-431888
Well Booth why should you be so defensive about my simple observation. In the shaded area of the nucleus there is no sunlight to reflect. Therefore the visibility of the jet ( with camera sensitivity adjusted) is caused by emission of photons in the optical range.
The discharge is a plasma and the intrinsic glow is a visible photon emission. This occurs at comparatively low currents of much less than 1 amp. No visible discharge does not necessarily mean no current. The plasma could still be
discharging in dark mode at even lower current. Zero current means zero discharge.
Neither myself nor anybody else is making claims. We are observing and hypothesising. Perfectly reasonable. You say there is no evidence of electrical discharge activity whereas there is in fact no evidence that any measurement has been made. Quite a different thing.
Incredible that you think the jets are not relevant to the comet mechanism and origin. They are the main visible feature and determine the nature and appearance of the coma and the tail. They appear in hundreds of the ESA published images to date and are a clear indication of degree and origin of nucleus activity. As I have suggested elsewhere analysis and measurement of the jets specifically would end the argument about sublimation versus electrical discharge, In fact temperature measurement alone would do that. So let us see a temperature map of one jet at least, including the nucleus surface.
How much more plausible the sublimation hypothesis you believe in would be if there was the tiniest shred of evidence to support it, or even any positive evidence of the presence of ice, or evidence of huge or numerous holes in
the nucleus surface for the gas to escape from. It is hypothesis presented as fact. Or perhaps you have a good alternative hypothesis.
As far as the dust is concerned Booth that is a complex issue. My hypothesis is that the dust is a product of the reaction at the nucleus surface between oxygen released from the rock by incident high energy solar protons and the
hydrocarbon layer known to coat the surface of the nucleus. Dust emission will therefore be directly proportional to the intensity of that reaction. The dust is a uniform reaction product. This is supported by the very consistent
intensity pattern of the jets carrying the dust. There is no interruption of the illumination intensity profile by spasmodic variable dust emission, as would be expected if the dust was picked up by gas from the surface or carried by
the gas from beneath the surface.
” If EU/EC (whatever that is) is to be recognised as a valid scientific explanation etc etc” Validation is not required Booth. It is a hypothesis and all that is required is a rational criticism of the hypothesis and if available the presentation of an alternative viable hypothesis. And by the way there is no more validity about a mathematical model than one expressed in words. They are both methods of descriptive communication.
The intensity of dust emisson has been found in two previous visits of this comet observed from Earth ( find by search) to have reached a peak weeks after perihelion. The rate of dust emission also varied markedly from day to day both before and after perihelion.
“Specifically, the Rosetta NAVCAM employs, as media, an Active Pixel Sensor (APS) Charge-Coupled Device (CCD)”
I’m informed that this statement is an oxymoron as APS sensors are CMOS devices. Can you clarify, or do you know which device type? I’d thought it was a Star1000 APS, the only info available says a CCD47-20. Thanks.
Why would electrically machined dust be fluffy? Should it not be high density, solid spherical nodules?
I’ve heard EU/EC proponents talk about electrical discharge machining (EDM) as a mechanism for dust liberation on 67P. I’ll wager no member of the EU/EC community has ever taken the time to research EDM? Here’s a really brief overview of some EDM plasma physics …
Natural and artificially produced plasmas are classified by their temperature and density. These two parameters are used to determine the Coulomb or plasma coupling parameter, which determines whether a plasma is ideal or not. In an “ideal” plasma, the mean kinetic energy of particles is significantly higher than the mean Coulomb potential energy between them. By definition, the plasma coupling parameter,
Gamma is proportional to n^(1/3) / T.
Hence, a plasma is deemed to be ideal if Gamma < 1. This relationship indicates that ideal plasmas are characterized by low particle densities and high temperatures. The following is a short sample of plasmas with their associated densities (particles/cm^3) and temperatures (K) (from Descoeudres, 2006)
Solar Wind (at 1 AU) : ~10^01 : ~10^5 an ideal plasma
Earth’s Ionosphere : ~10^05 : ~10^2
Glow Discharge : ~10^08 : ~10^5 a non-erosional plasma
Z-Pinch Plasma : ~10^18 : ~10^7
EDM Plasma : ~10^18 : ~10^4 a weakly non-ideal plasma
Specific to our discussion, EDM is a microscale manufacturing process employed to machine complex parts from *electrically conductive workpieces* using a pulsed current discharge that thermally erodes thin layers of material. The method is primarily used on hard metals or parts that would be very difficult to manufacture with traditional techniques. Density and temperature measurements obtained during characterization research indicate EDM plasmas typically exhibit very high electron densities, on the order of 1E24 e/m^3, and cold plasma temperatures between 3000 and 8000 K, making them weakly non-ideal. It is worth noting that under EDM conditions, the Debye length is ~6 nm, which implies the Debye sphere contains roughly one particle per.
As a manufacturing method, electrical discharge machining can be corrupted or terminated by what is called gap pollution (i.e., machined debris trapped between the anode and cathode). To avoid this problem, EDM uses short duration electrical pulses, typically on the order of microseconds, followed by a material removal phase. While techniques like dielectric flushing and workpiece movement are used in industrial applications, the vacuum of space would represent an efficient removal method for comets. Unfortunately, material removal would not generate collimated jets, but an expanding hemispherical debris field centered on the discharge point. To restate, collimated jets would impair the discharge machining process. Perhaps sublimation represents a better explanation for these observed jets?
Another claim made by EU/EC dogmatists is that electrical phenomena is scalable from the lab to the IPM. Again, I would ask for some guidance on this secret scaling relationship. In the mean time, however, while waiting for modeling information directly from the EU brain trust, let us assume a simple linear scaling relationship versus an inverse-square or exponential curve, for example. Now, refering to Figure 7.6 in Descoeudres (2006), we find the following EDM dimensions and values,
Electrode gap = ~100 micron
Plasma sheaths = ~10 nm (the approximate Debye length)
Crater diameter = ~10 micron
Plasma current = ~10^10 A/m^2
Electric field = ~10^8 V/m
According to EU “science” the Sun and 67P are our two electrodes. Thus, we get
Electrode gap = 3 AU = 4.5E11 m (i.e., earlist claims of electrical discharge)
Plasma sheaths = 4.5E7 m (three orders of magnitude larger than 67P’s diameter)
Crater diameter = 4.5E10 m (Obliteration! Note Earth’s diameter = 1.3E7 m)
Question for the EU crowd – Is it possible that the electric potential between the Sun and 67P is really 45000000000000000000 Volts? So, what is that scaling factor again?
It would appear that EDM is NOT a viable mechanism to explain dust erosion on comets. As a matter of fact, every aspect of the EU/EC model seems rather preposterous at this point. Still, there is a possibilty that I made some mistakes with my calculations when scaling from MEASURED lab data to the IPM and 67P. If someone from the EU community could correct my math with math I would really appreciate that. Remember, don’t tell me I’m wrong! PROVE IT, with reference to real data and scientific principles! Go!
Oh! There’s one more thing. I would really like someone from the EU camp to explain that measured density difference. Recall that RSI and OSIRIS gave us a density of 3400 kg/m^3 for the rocky asteroid Lutetia, and 470 kg/m^3 for the icy comet 67P. Without an answer, I think it is time for the EU folks to give up on 67P being rock!
The curse of special characters.
Following the plasma coupling equation above, the paragraph should have read …
Hence, a plasma is deemed to be ideal if Gamma is much, much less than 1, and non-ideal if Gamma is greater than 1. This relationship indicates that ideal plasmas are characterized by low particle densities and high temperatures. The following is a short sample of plasmas with their associated densities (particles/cm^3) and temperatures (K) (from Descoeudres, 2006)
Apologies for the oversight, my poor grammar, and the occasional speling mistake.
Booth, thanks for taking up the ‘rational’ batton 🙂
I’ve made many of these points before, but of course the EU community never responds. It is ludicrous to make comparisons between features tens of microns across formed under oil and those km across formed in vacuum.
One additional point is that EDM is normally done *under oil* (it happens that I bought a CNC EDM for our workshop a while back and use it a fair bit.) it doesn’t actually work in air.
However you can’t scale the breakdown voltage like that. You can’t really scale at all from liquid phase to such low pressures.
But in low pressure gas, it scales with the pressure-path product according to the Paschen curve. So actually a longer path can have a *lower* breakdown voltage than a shorter path. This actually happens in vacuum systems, you can sometimes see a discharge ‘ignore’ the shortest route and choose a far longer one, which looks very odd and can catch people out.
However I don’t think it safe to apply the scaling to interplanetary pressures and distances!
This is ABSOLUTELY NOT intended to be any sort of support for EU nonsense, but for the sake of accuracy.
See
https://en.m.wikipedia.org/wiki/Paschen%27s_law
Booth,
You have taken a lot of effort to prove no discharge activity.
However, It would be good if you could explain in the same detail how exactly sublimation is produces the jets.
We probably all accept that sublimation will happen where there is exposed ice, but there is little evidence of this.
Even the boulders, like Cheops or the the 3 rocking stones recently, show no sign of reducing in size that would surely happen if they were made of ice and exposed to sublimation from all sides.
The only model we have seen for producing jets on the comet by sublimation needs the surface not to be ice, it needs a large amount of ice below the surface and some heap to conduct through the surface to start sublimation. It also needs a hole in the surface for the jet to escape and the hole has to have specific ratio of diameter to the diameter of the developing cavity underneath it.
I have not seen any other model on the blog.
It would be great if you could put the same amount of detail and maths into describing how the sublimation of jets on illuminated parts of the comet and the non illuminated parts.
This would enable people to come to some sort of reasoned conclusion as to what is happening. Trashing someone elses model does nothing to to explain how the Jets are formed and maintained.
There are plenty of people who can trash, but very few who are willing to try to explain. So Far trashing is not helping anybody to understand what is happening.
regards
Dave: It is unfortunately true that arguing against a theory is easier than constructing a model which works.
The dirty snowball model was constructed based on spectral information about the molecules seen in a comet’s head. It is clear that we can’t find free-floating ice on the surface of a comet nucleus since there is nothing to prevent it having sublimated away. So far we have seen no more than half a dozen comet nuclei close enough to make out some details, and 67p is the first one we are seeing for an extended period of time. If we don’t find ice on its surface do we immediately throw out all the spectral data we know of comets from earlier and start thinking in terms of a new theory? Again on the basis of spectral infromation we have colour images showing that Hapi has a presence of H2O. I find spectral information most telling, and am hoping that we will be able to see proportion changes in the composition of dusts and gases surrounding the nucleus over the few months that Rosetta can observe the comet.
Already we find other gases in the spectra like carbon monoxide, carbon dioxide, sulphur dioxide. Do people even know the details of how sulphur dioxide sublimates? (I believe it reacts in ways which are not understood.) Why should all the evidence be in a form visible for you to be convinced? Why should there be holes, why can’t vapours escape through narrow fissures which are not visible to Rosetta? Why should Cheops be so full of ice that it reduces in size by meters?
It is not a question of putting in the math and seeing the answers staring you in the face. Math makes a model more precise and checkable, it doesn’t build a model for you. We are now building a model of what happens on a comet surface, and our ideas are evolving as more images come in. No one expected to see the sudden jet on 12 March, but now that we have seen it the model has to work so that such phenomena are allowed. I think you are expecting answers to big questions faster than they are coming in. Lots of science is a slow process of model building. With Rosetta it is actually quite fast, in less than a year we have learnt so many new things.
Booth, why would the product of electric discharge removal of material not be fine dust, or fluff if agglomerated. The process is one of ion impingement and ions are smaller than atoms. No possibility therefore of removal in big lumps, spherical or otherwise.
You talk at length about the parameters and ideal conditions for lab or industrial EDM but these are optimised conditions. They are by no means the only conditions under which material removal will occur. And whether the discharge is a collimated jet or a hemisphere in shape would depend on the conditions. Material removal would not be exclusive to one or the other. And you list examples of plasma coupling parameters but you do not include the plasma in the coma at the surface of a comet nucleus, because as yet we do not know the properties of that plasma, nor the relationship between coupling parameter and material removal. If the plasma conducts (all plasmas) and there is a discharge at a surface, material will be removed ( or deposited, under other conditions ie MIG welding).
The reason for the very high particle densities in EDM plasma is specifically to maintain a short as possible Debye length so that the working distance can be very short from electrode to surface, which promotes precision of material removal. The conducting plasma must be maintained at very short distances, beyond the Debye length.
In the comet nucleus discharge situation the anode is a virtual one established by the surrounding environment. There is therefore no electrode gap and the concept of gap pollution is irrelevant, and no need for pulsing, although pulsing may still occur. And the vacuum of space is an obsolete concept. We know that space is occupied by plasma, including the interplanetary medium. You quote an ion density figure for the solar wind yourself.
So your conclusion that EDM is not viable for material removal from comet nuclei is unfounded. Your data and examples are irrelevant to the comet nucleus situation. No huge electrode gap as you assumed and no huge voltage or current required. So no need to correct the maths. It is not applicable.
The scaling aspect that escapes you is in fact self evident. No mystery. No secret relationship. We know the universe is predominantly plasma. We see numerous plasma structures and shapes in astronomy, light years across that can be reproduced on a laboratory scale. Look at the work of Anthony Perratt. This cannot be done with gravity because the forces are too minute at a lab scale. The gravitational force is a billion billion billion times weaker than the electrical force
As far as the measured density of the 67P nucleus is concerned I am sure it is approximately correct. To understand why this is so and yet it could still be solid rock all the way through you have to think outside the box about how mass might change but quantity of material might remain the same. Go!
Booth, why would the product of electric discharge removal of material not be fine dust, or fluff if agglomerated. The process is one of ion impingement and ions are smaller than atoms. No likelihood therefore of removal in big lumps, spherical or otherwise.
You talk at length about the parameters and ideal conditions for lab or industrial EDM but these are optimised conditions. They are by no means the only conditions under which material removal will occur. And whether the discharge is a collimated jet or a hemisphere in shape would depend on the conditions. Material removal would not be exclusive to one or the other. And you list examples of plasma coupling parameters but you do not include the plasma in the coma near the surface of a comet nucleus, because as yet we do not know the properties of that plasma, nor the relationship between coupling parameter and material removal. If the plasma conducts (all plasmas) and there is a discharge at a surface, material will be removed ( or under some conditions deposited ie MIG welding).
The reason for the very high particle densities in EDM plasma is specifically to maintain a short as possible Debye length so that the working distance can be very short from electrode to surface, which promotes precision of material removal. The conducting plasma must be maintained at very short distances but greater than the Debye length.
In the comet nucleus discharge situation the anode is a virtual one established by the surrounding environment. There is therefore no electrode gap and the concept of gap pollution is irrelevant, and no need for pulsing, although pulsing may still occur. And the vacuum of space is an obsolete concept. We know that space is occupied by plasma, including the interplanetary medium. You quote an ion density figure for the solar wind yourself.
So your conclusion that EDM is not viable for material removal from comet nuclei is unfounded. Your data and examples are irrelevant to the comet nucleus situation. No huge electrode gap as you assumed and no huge voltage or current required. So no need to correct the maths. It is not applicable.
The scaling aspect that escapes you is in fact self evident. No mystery. No secret relationship. We know the universe is predominantly plasma. We see numerous plasma structures and shapes in astronomy, light years across that can be reproduced on a laboratory scale. Look at the work of Anthony Perratt. This scaling effect cannot be tested with gravity because the
forces are too minute at a lab scale. The gravitational force is a billion billion billion times weaker than the electrical force
As far as the measured density of the 67P nucleus is concerned I am sure it is approximately correct. To understand why this is so and yet it could still be solid rock all the way through you have to think outside the box about how mass might change but quantity of material might remain the same. Go!
Booth: Even if one does not accept the electric theory, the question of how a dark side jet is illuminated is interesting. It does not seem from the picture (although it is easy to be mistaken) that what we are seeing is beyond the shadow of the Imhotep region. So if it is only dust grains, how do they shine, even faintly and requiring processing to bring out? I do not agree with the suggestion that because of this question all the jets have to be intrinsically illuminated. Day and night are so different on the comet that there can be more than one mechanism at work.
Looking at the shadows elsewhere on the comet, it seems that the shadow of Imhotep would perhaps be only a couple of hundred metres or so. So if there are several jets and we don’t see their bottom 200 metres, one can get the cloudy effect seen in the picture. Harvey mentions something like this in his post below.
It will be very interesting to see whether the jets cause any net change in its rotational period and/or axis.
Jim: Accomazzo said this is happening.
https://www.bbc.com/news/science-environment-31965458
Thanks Claudia, H. NAVCAM Team and ESA.
Using ‘Posterize’ transform at 3/8 [from any photo editor] so to admire the luminosity map of the environment immediate to the core.
If the photo editor support ’rounded’ posterization Then it’s a joy to play with it.
Also helpful to turn the monitor toward dark reflection zones.
Also helpful to turn off lights while browsing ESAC’s photo archives.
Since this is the second consecutive post focussing on the characteristics of Bastet and Aker, it’s promoted me to write up the matches between the two regions. These are presented in the link below. It’s in the form of photos that are annotated in the finest possible detail. They show that Bastet and Aker were once joined firmly together and that the two lobes were once one single body.
https://scute1133site.wordpress.com/2015/05/10/67pchuryumov-gerasimenko-a-single-body-thats-been-stretched-part-21/
A. Cooper,
Yes! Great view for this. Would like to rquest you link features with double ended arrows or lines (try Adobe Illustrator?l instead of the usual multitude of colored dots in your blog. Thinking this may be more intuitive to follow for laymen (like me), and others!
Thanks anyway for all your contributions!
Ramcomet
Thanks for the ideas. I don’t think I’ll ever get an award for graphic artistry 🙂 There may be a new photo added soon BTW with a close-up in high relief.
A. Cooper,
Great, looking forward to it. I’m a graphic artist. Would love to help anytime! Will pm you on your blog contact info.
As an avid follower of A.Cooper’s blog, and a co-enthusiast for stretch theory, there is not much that more sophisticated marking techniques can do without obscuring the very features that relate to the match in question. The real issue is working with navcam quality images with thousands of surface features, none of which are officially named.
Thus when one is looking at two different photos with randomly different lighting conditions, it is time consuming just to work out whether you are looking at the same feature. This just wouldn’t be a problem with 3D models generated from OSIRIS resolution images, with prominent peaks and monoliths named officially.
One can work out what a feature looks like in 3D with multiple NAVCAM pictures with shadows etc. helping. But then remembering and explaining that in a way that others can see it is hard and tedious. Over time, the 3D models will be available, but in the meantime other evidence showing ongoing changes may make that a moot point…..
Amazing the width of the jet columns. Have any of the scientists proposed what is creating the columns yet? And based on the size of P67, most of the columns shown in this picture must be several hundred meters across from their base on up. Of course, this is a 2 dimensional picture, so if the column bases are at least several hundred meters across, I’d assume they’d have a similar surface “depth” from this perspective, similar to a very large flood light who’s face is actually round, though the light from the side view isn’t. This would be a LOT of surface area. Even if a column was only 100 meters across, if it has a similar breadth, that’s a 10,000 square meter total surface area more of less, as well as thickness as they rise. And many of those columns look much bigger across than 100 meters. Also, many of the jets in the columns appear to be perfectly parallel to each other, which doesn’t seem likely if they are coming from different openings. That means that they’re pointing in the exact same direction not just 2 dimensionally (side to side), but 3 dimensionally (forwards and backwards and everything in between) as well. Last I heard from the article posted some time ago about the columns, there wasn’t any accounting for them. Has this changed?
I don’t think there is any doubt that there really are ‘jet’ type phenomena is some pictures.
But this one, and something I saw a couple of days ago (and have seen before) made be wonder if another effect matters.
I’m an amateur pilot, and I have the UK IMC rating, which means I can legally fly in and above cloud in restricted circumstances. I was flying back across the channel above rather worsening cloud, but not in fully clear air as we approached the UK coast. At one point I had a dense, opaque sharp edged cloud in front of me with light behind it but much thinner ‘transparent’ cloud round it, possibly a bit behind.
And what I saw looked somewhat similar to this picture of 67P; the dense cloud taking the place of the comet, and the thin cloud the ejected dust. The ‘columns’ one clearly saw were associated with structured shadowing from the scalloped 3D shape of the dense cloud. I wish I could have got a photograph, but it didnt last long and I had other things on my mind! (Like safely getting down through it and whether I was going to need radar vectors!)
Anyway, I wonder if structured shadows from the irregular edge of 67P may cause *some* of these effects.
I can’t resist however noting, that at 1mA/cm^2, a very low intensity ‘discharge’ indeed, 100x100m would be 100kA.
Glad I was sitting down when I read your last paragraph there, Harvey. Of course I don’t know how significant a 100kA discharge is, and Google seemed as ignorant as I. But perhaps significant. And most of the columns seem much much larger than 100m wide, so no telling how big the surface area of a large column is. But as you say, perhaps they are just visual effects, could certainly be. But, they’re very persistent and consistent effects if so, and the scientists seem to think the columns actually exist.
Harvey’s note just means, that even a very low intensity discharge of 1mA/cm² on a 100×100 m area is ruled out by magnetometer measurements.
100kA is a very large current; firstly you need a source for it; secondly it would produce easily detectable magnetic fields even km away.
But spread over 100X100m, it is a low *current density*, far lower than is used in say sputtering etc. It would be a very weak discharge indeed. Even 1A/cm^2 is pretty low. EDM (under oil!) uses vastly bigger current densities – but pulsed.
Just going back in time and saying:
This is not just dust and gas!
https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2011/03/comet_halley_s_nucleus_as_seen_by_giotto/9632510-3-eng-GB/Comet_Halley_s_nucleus_as_seen_by_Giotto.jpg
If 67P following Halley’s behavior Then we are going to have a few [even a single] super-jet, or a super-jet aura.
Logan: What illuminates the aura in the region in the shadow of the Sun?
Halley’s Perihelion 0.6 AU!
Perhaps its source is electrical.
Claudia!
I note a lose of 11 (out of 22) comments since this morning. Is this a case of judicious editing after a post has passed moderation, or signs of a technical problem with the Rosetta weblog servers? As an aside, I have also noted additional loses on other threads that point towards editing.
If this is not a technical problem, moderator feedback and clarification of policy would be greatly appreciated!
Thanks in advance!
Hi Booth,
We’ve been looking in the back-end in case of a technical problem but there is nothing obvious – but we certainly would not be deliberately deleting comments that have already been approved. We’ll keep an eye on it, but apologies for any frustration in the meantime.
Emily & Claudia
Hi Emily,
To characterise the glitch, I copy my comment to my clipboard before verifying and submitting. About half the time, the comment disappears rather than going into the queue for moderation. But here is the kicker – if I repost the precise comment using paste from clipboard, and re submit, the comment is detected as a duplicate. If I add a dot at the end before resubmitting, it gets a chance at being properly put in the queue. It appears the disappeared comments are logged as submitted before they disappear.
Hi Marco,
Thanks for clarifying the glitch you have been experiencing. Indeed there have been occasions of duplicate posts in the system where I have deleted the second post if it has been submitted on the same thread.
I see you have also posted this comment twice, albeit on two separate threads, so probably not related to this specific glitch, and I’ll approve both anyway.
In the meantime, maybe you can try to avoid copy/pasting in and out of the blog environment and see if that solves the problem in this case?
Thanks for letting us know if you have further problems.
Emily
Kamal, 28/05/15
I agree with you kamal, the model you describe is logical as are others. All of the models people have are currently waiting information that can prove the case.
My point is that spending a huge amount of time to trash some ones model is counter productive. Generally it adds nothing to the whole knowledge.
Ofcourse people who put their models on the blog generally would enjoy some feed back even if negative.
However there is a point where you begin wish people would do more to support their own theory than just trash others. It would I think do more to draw different view points together.