Comet activity is on the increase

OSIRIS image of Comet 67P/C-G on 10 September 2014, showing jets of cometary activity along almost the entire body of the comet. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/ INTA/UPM/DASP/IDA

OSIRIS image of Comet 67P/C-G on 10 September 2014, showing jets of cometary activity along almost the entire body of the comet.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/ INTA/UPM/DASP/IDA

Comet 67P/Churyumov-Gerasimenko is showing a gradual, but clear, increase in activity, as can be seen in the latest images provided by the OSIRIS team.

While images obtained a few months ago showed distinct jets of dust leaving the comet, these were limited to the ‘neck’ region. More recently, images obtained by Rosetta’s scientific imaging system, OSIRIS, show that dust is being emitted along almost the whole body of the comet. Jets have also been detected on the smaller lobe of the comet.

“At this point, we believe that a large fraction of the illuminated comet’s surface is displaying some level of activity,” says OSIRIS scientist Jean-Baptiste Vincent from the Max Planck Institute for Solar System Research (MPS) in Germany.

From these images, the team wants to derive a better understanding of the evolution of cometary activity and the physical processes driving it.

“Being able to monitor these emissions from up close for the first time gives us much more detailed insights,” says OSIRIS Principal Investigator Holger Sierks. “But one image alone cannot tell us the whole story; from one image we cannot discern exactly where on the surface a jet arises.”

Instead, the researchers compare images of the same region taken from different angles, in order to reconstruct the three-dimensional structure of the jets. And, since under normal circumstances the comet’s nucleus would outshine the jets, the necessary images must be drastically overexposed to reveal the details of the jets, as shown in the image pair presented here (see below).

While 67P/C-G’s overall activity is clearly increasing, the mission’s designated landing site on the smaller lobe still seems to be rather quiet. However, there is some indication that new active areas are waking up about one kilometre from the landing site. These will allow the lander’s instruments to study the comet’s activity from an even closer distance.

Today, 67P/C-G is about 470 million kilometres from the Sun. Based on a rich history of ground-based observations, scientists expect a comet’s activity to pick-up noticeably once it comes to within 300 million kilometres of the Sun; for 67P/C-G – and Rosetta – this ‘boundary’ will be crossed in late March 2015.

Below: Two views of the same region on the neck of Comet 67P/Churyumov-Gerasimenko (the larger lobe is to the right and the smaller lobe is to the left in this orientation). The first image was taken with an exposure time of less than a second and shows details on the comet’s surface. The second image was overexposed (exposure time of 18.45 seconds) to bring out the details of the jets arising from the comet’s surface. The images were obtained by the OSIRIS wide-angle camera on 20 October 2014 from a distance of 7.2 kilometres from the surface.
Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

ESA_ROSETTA_OSIRIS_WAC_141020bESA_ROSETTA_OSIRIS_WAC_141020a

Comments

85 Comments

  • Bill says:

    "While 67P/C-G’s overall activity is clearly increasing, the mission’s designated landing site on the smaller lobe still seems to be rather quiet. However, there is some indication that new active areas are waking up about one kilometre from the landing site."

    That is good. You want to have a Webcam at Yosemite, but not next to Old Faithful. 😉

    Site J does seem to be less active.

    --Bill

    • Jim says:

      That would be Yellowstone, but good point taken. (I say one when I mean the other all the time!)

      • Frank Cross says:

        Someone has probably spent the weekend downloading the latest operating system on a well known computer and is a little punch drunk. I speak from experience.....

    • Doug Huffman says:

      Old Faithful is in Yellowstone N.P. Yosemite N.P. most famous dynamic site might be Yosemite Falls. Webcams in Yosemite would be nice.

  • Ross says:

    Thanks OSIRIS, we appreciate these images with the resolution of an original Gameboy a month after the data was captured. How about we compare the activity to an OSIRIS image taken at some point in the current month?

    • Jacob Nielsen says:

      The first image dates back to september, the two below: nov. 20'th legend says

    • Roberto Nesci says:

      The image is 2048x2048. My children played with the Gameboy, and the screen was 160x144 pixels, which is not quite the same!
      If you right-click on the image you can download it at full resolution, which is actually 2048x2048. Don't forget OSIRIS was launched 10 years ago and built several years before launch!

      • Cometstalker says:

        Even if the Osiris was built over a decade ago it is state of the art for an interplanetary functional camera supposed to last in this environment for over a decade. Any cameras on the market today would not last for more then a few weeks in this hard radiation environment bombarded with particles not only from Sun but also from other galaxies. Some of those so energised only to be copied at Cern.

        • Frank Cross says:

          Some of those cosmic rays are 4 - 5 orders of magnitude more energetic than collisions in the LHC with the wick turned up to max

          • Cometstalker says:

            When the LHC is back again in 2015 it is supposed to deliver 15 TeV, that is quite a lot. I suppose that there is quite some uncertainty in those figures as well. Never the less, that the instruments on the mission can take such a beating for so long is quite a bit of excellent engineering.

      • Ross says:

        Well I've been eager to see an OSIRIS image of a detailed surface and when they finally feel we're privileged enough to see some data we get the wide angle camera view of an over-saturated nucleus with jets. I know there's jets but that does nothing for me as far as advancing our knowledge of the mechanisms at work. How about an OSIRIS NAC image of the source of these jets so we can debunk the sublimation model directly.

    • Henk says:

      As explained by ESA the rough imaged over exposure is only used to highlight the comet activity more clearly. Speaking about the Navcam images never before in human history have we seen images this close and in this high resolution of a comet. So lets not get so pessimistic. The comet is also darker than charcoal so it is no easy task to reveal it all.

      And on top of that since this is a European run and funded project the European scientists who developed it also deserve to take the time to develop new papers and make new scientific discoveries before more detailed pictures and data is released including more highly detailed OSIRIS images. This spacecraft will remain at the comet for at least another year as it moves closer and closer towards the sun (relatively speaking). So there is really plenty of time to get more and more superb data for you, me and anyone to see.

      • Robin Sherman says:

        If scientists working on ESA funded projects wish to protect intellectual property in the form of published papers, there should be an official ESA journal in which all contributors and investigators are required to publish their results. Any paper using information from an ESA mission published elsewhere will then clearly not be from legitimate investigators. Who does intellectual property belong to in such huge collaborative endeavours? A planetary geologist does not come up with a paper if the ESA technician doesn't work out how to tighten this bolt here or solder that wire there. Its a simple solution ESA. If ESA wants to be seen as an esteemed scientific organisation this can only help.

        As a publicly funded organisation ESA has already recognised its public outreach obligations, but it is trying to do this with both hands tied behind its back. Short general summaries of results and outlines of theories contained in a regular spot on ESA WebTV, webcast or video podcast like ESO does, would be feasible. The organisation's scientists would already have a guarentee of intellectual primacy. Use the enthusiasm and knowledge of your own teams to present their work. When we occasionally see them in ESA events they are great, real people who do real science and engineering. They will get far more recognition than they will from their name in some obscure journal. First on the web is what counts today.

        • daposter says:

          not to forget that those papers will then also be hidden behind paywalls.
          this is not about protecting IP (science has no IP), but to protect the Springer et all publicators who make $$$ on scientific knowledge that is per se public property.

          all papers should be required to be also published on the Internet scientific publication sites.

    • Matthew Fairtlough says:

      That's exactly what this post does. Haven't you read it?s

    • Robin Sherman says:

      Maybe you shouldn't worry about the resolution of the main image, instead worry about not being able to read the date and source of the two other images. 🙂

    • Steve Kasian says:

      Agreed; However, they've actually included 2 images from October 20 in the article, inexplicably having chosen to use an image from a month and a half ago instead of either of those as the main image. While this mission is absolutely amazing and the imagery is incredible, this team seems to be a bit brain-dead when it comes to the release of data to the public. It brings to light a major part of the reason why European space missions have fallen somewhat short, relative to their foreign counterparts' missions. The people involved seem to simply make bad choices when it comes to the release of data and the PR surrounding it. For that reason, it's really too bad JPL is not playing a larger role in this mission

    • sciencefan says:

      At 10km from the comet OSIRIS cannot image the full body, it would be much larger than the image frame. I find it great that the team is showing us current images of activity in the neck at highest resolution and at the same time a global view from a few weeks ago so that we can understand better the distribution of activity over the whole body. They see many more jets than the navcam, exciting !

  • Hans Eekels says:

    Amazing ! But, what is it? Dust or ice ?

    • Ross says:

      Please note that only comet Tempel 1 has been observed with surface ice, and a very small amount of it. The dirty snowball theory is just a theory, no direct observations yet fit the bill. In that case, the answer to your question is dust... as continuous discharges slowly erode the rocky body.

  • Om says:

    just amazing

    • Henk says:

      Thanks. Especially that second image is very impressive. It seems software would be needed to reduce or increase exposure per pixel automatically in each image. To get the most detailed fews possible of this incredible comet. And software to combine all of that including the continues updates and non shaded areas into a full up to date 3D model of 67P in all its glory. Including the option to show or not show activity of the comet.

    • Robin Sherman says:

      Good to have you back with us Bill. Nice montage, very helpful, thanks.

  • logan says:

    "...dust is being emitted along almost the whole body of the comet".

    Thanks for the info, Emily.

    • logan says:

      Passing from dominant tidal to solar energies.

      • Robin Sherman says:

        The close up images might start to get very hazy over the next few weeks. I don't think the comet is even at "simmering point" yet.

  • Bill says:

    Enhanced OSIRIS Wide Angle Camera short exposure image of dust jets showing details on the North Polar Plain and in the jets on 20 Oct 14.

    Image Source: ESA/OSIRIS/Rosetta

    http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets/i-C7zSpFJ/0/L/ESA_ROSETTA_OSIRIS_WAC_141020b--enh3-L.jpg

  • Rebecca Dittman says:

    The most wonderful images yet! Forget about the science, enjoy the beauty. Reminds me of searchlights lighting up the sky. Can't wait until Philae touches down. This is a true 'world' of wonders.

    • Jacob nielsen says:

      Hi Rebecca, searchlights? Itn't it like saying: forget the war, enjoy the beauty of the battle!

    • logan says:

      Hi Rebeca. Following you on this 🙂

  • Cometstalker says:

    Still the streamers are focused to the neck region and the most interesting part of this picture is the angular divergency of the the multiple streamers. The first idea that hits me is that the comets rotation period is the reason to this "twist" the second thing to correlate this information with is the thermal image of this area of concern. With a few essential data it can not be very hard to discriminate the reason to those outbursts if they are due to increasing irradiation or due to tidal effect. The mapping should be accurate enough to be able to measure a position shift of the head relative to the body. If this outburst is increasing, stable or decreasing is also essential. Is this just another picture to get the attention or are there some conclusions being made and soon reported. Please do not make another colorised poster/map issue out of this event.

    • Robin Sherman says:

      A more prosaic reason for the angle of the streamers is that the sources producing these collimated "beams" of particles are not perpendicular to the surface. The crack/vent producing them is firing them at an angle.

      It is unfortunate that these streamers are still so diffuse that we can only see them from a certain orientation against the black background of space. This means the sources always seem to be just over the horizon. If not backlit by the Sun at a certain angle they can't be seen. Makes a spectacular picture though.

      • Cometstalker says:

        Im not sure what the reason of the odd shape of the streamers are, if expelled from barrel like opening in odd directions or any kind of vents. They still stay quite focused for a long time and as they also have a curvature they cant be very fast. Also there seems a bit of self focusing effect present. The real strange thing is that ESA is not prone to give avay any information at all about the streamers other then pictures. Some time a note that it seams to this and that. I can not believe that it is impossible to analyze the properties concerning speed and trend if a full range of pictures are available. The streamer where present from the very beginning of Rosettas arrival to the comet and seams to be sporadic. Its odd that this kind of eye catchers are without further data presented as to me they are one of the real big surprisers and most likely also accompanies the comet when close to jupiter.

  • Cometstalker says:

    If the thermal image tells that the streamers are coming from hot spots then it is most likely that its origin is from close to or at the surface. If cold spots are indicated then its most likely that the source is from deep inside. Please make a correlation of your data sets or just file it in the blog and we will make the conclusions ourself.

  • Bill says:

    And a comparison of dust jet/vent (?) activity on the North Polar Plain, 24 Sept, 2 Oct, 20 Oct 14.

    Image source: ESA/Rosetta

    http://univ.smugmug.com/Rosetta-Philae-Mission/Rosetta-Dust-Jets/i-DHNvtXr/0/L/24sept_2oct_20oct-14_vent_activity-L.png

    --Bill

  • TORE SKAAR says:

    After the landing (very demanding!) I hope to be able to watch the gasses streaming off the Comet.
    This will be something out of this World, seen for the very first time up close. Bruce Willis could not have done it any better!

  • C.C. Petersen says:

    This is a fabulous image! Thank you for providing it. By the way, Old Faithful is in Yellowstone, not Yosemite. But, the sentiment is accurate. You want to observe, but from a safe distance. 😉

  • Sovereign Slave says:

    Would like to invite feedback from some of the regulars here on the following article linked below. It's directly related to comet theory and an explanation of what we're seeing in these pictures. More specifically, is there any specific scientific data that completely disproves this theory, and if so, what is that data? Or put another way, why is this explanation scientifically impossible?

    https://www.thunderbolts.info/wp/2014/10/20/will-nasa-rewrite-history/

    • THOMAS says:

      Hyperion provides the strongest evidence yet that the very notion of "impact craters" should be re-examined. Its sponge-like aspect can be much more plausibly attributed to the phenomenon of repeated, violent electric discharge.

  • Vlad says:

    This is by far my favorite ongoing space mission. So incredible! Please keep the posts coming!

  • Sajid Rabbani says:

    At this stage, what could be the speed of the comet at which it is moving?
    And does this speed have anything to do
    with the increased activity of 67P ?

  • PM says:

    Images have full resolution: 2048x2048 and were taken 3 days ago.

  • Cometstalker says:

    So far all forecasts of how comets behave are of the same type an accuracy as weather forecasts. If i say that the wether tomorrow is going to be the same as today then i have in general, where i live an 85% hit probability. If the very best of metrology staff with all their satellites and gears do an estimation of my area they hit it with 95 %. That is a worthless improvement of the information and therefor i always use the wether i get. Now to get back to comet forecasts, it is by historic evidence not worth a lot just refer to Siding Spring or any other comets. Wait and see and use what you get and adapt to that situation.
    Comets are a bit chaotic and not very predictable.

    • THOMAS says:

      "So far all forecasts of how comets behave are of the same type an accuracy as weather forecasts."

      Not true. The EU people PREDICTED the double flash when the Deep Impact projectile hit Comet Tempel 1 in July 2005 and the type of "stardust" brought back from Comet Wild 2 in 2006, amongst other things: http://www.thunderbolts.info/predictions.htm

      And the charcoal-black, totally rocky appearance of 67P/C-G , with the dead-straight "jets" emanating mainly from the neck region are EXPECTATIONS of the EU model.

      • Cometstalker says:

        Sometime the forecast hits the bullseye and so can a wild guess also do. Still there is no 100% hit ratio and that was my point,

        • THOMAS says:

          The EU prediction of the Deep Impact double flash (along with other correct predictions) was not a "wild guess", it was squarely based on the laboratory experiments which underpin the whole of the EU model (unlike the "dirty snowball" model which can call on absolutely no experimental evidence for support and which leaves people floundering around in wilder and wilder speculation).

          The EU model also predicted that the nucleus of Comet 67P/C-G would turn out to be a chunk of rock. Right again. Just another "wild guess" perhaps?

          • Cometstalker says:

            No comets are rock as no high pressure sediments and/or melting processes are present, asteroids are rock comets are dust. Some dust might be very hard mineral but still is no rock. If ice or not is present is of no concern. Alchemy is only wild guessing and so far no comets are created in laboratories by experiments. This comet has an average density of about 0,4kg/l and no matter of ist contents it is no rock. If a wild guess prediction has an 85% hit ration then that is not bad at all.
            http://planetary.brown.edu/pdfs/4621.pdf

          • Marco says:

            EU =Electric Universe, not European Union.
            I think it is early and presumptuous to claim that 67P is a "chunk of rock".
            Also, the "predictions" of deep impact of the EU model appear to me to have been vague enough that a range of plausible data could easily be made to fit into the vague predictions to justify the model.
            I think there is merit to thinking outside the box when the default model is dubious, but the EU has set up a false dichotomy here. it doesn't matter how wrong the Whipple model is, it doesn't make the EU model any more correct.

  • Texas says:

    It seems more than coincidental that a larger percentage of matter loss (the jets) seems to be emanating from the thin "neck" of the comet. Perhaps that's how the neck became thinner in the first place? Is the neck located around the comet's center of mass or center of gravity? Can we postulate anything about cause and effect of the jet activity? If there's any kind of relationship there, shouldn't most active comets be at least slightly dual-lobed?

    • Cometstalker says:

      To your questions there are a lot of answers from people in this and related blogs. If you await an answer from anyone at NASA or ESA then be very patient because this will take about 20 +/- 19 years to get 70+/-25 % of your questions answered.
      Better to scan the blogs and take your pick, this takes only a few hours and so far the ESA alchemist are anyway too occupied to argue with each other who found out what and when and who is going to order the pizza this time.

    • Robin Sherman says:

      I think that might depend on whether there is some disparity in densities at the ends. Possibly caused by the spin direction of the comet, longitudinal or latitudinal and whether the comets material is so loosely bound internally that migration of different density materials within the body of the comet occurs. That is something the CONSERT instrument hopes to determine.

  • slappy says:

    Whoa !! I can't believe it! It's OSIRIS images taken on monday 🙂 Astonishing! Thank you OSIRIS team and whole Rosetta crew!
    How fast this jets emanating from surface? Would it blow me off if i step right on it? Its more like gusts of gases or streams of dust?

  • slappy says:

    In which direction points the jets relatively to rotation axis of comet? If there is just small inclination angle, they should provide measurable thrust and change comet's orbit a bit over long period of time (as like ion propulsion)..

    • Cometstalker says:

      This is possible to estimate and to do some calculations but a guess is also good enough.
      The comet has a mass of 1E13 kg and the so called jet is not a jet at all as i se it, its rather a moderate speed stream at the most 10 m/s. If it looses 10 kg mass per second and this is directed in the worst case direction then the power of about 1000 Nm/s is trying to accelerate this lump out of orbit. The altered trajectory this gives is not possibly to measure as those figures drowns in the the rest of things that influence the orbit of this comet. You can play around with those figures and to get a measurable deviation, the outburst is becoming ridiculous in size. The Siding Spring comet was measured and its trajectory forecasted several times and not until it passed Mars the figures did fit the bill. With the trajectory the comets mass was calculated and this figure canged a few magnitudes from the first observation until the Mars passage. If the scientist would play fair and not always tried to get the publics attention with specularity the presented figures should also have a note of the accuracy of the estimation. Something like " we are aiming for the keyhole but almost certain will miss the barn-door" or "we did a calculation and the result is 34+/- 567 units" . On the opposite they say; hey guys we created a few neutrinos at Cern and guess what, they are flying faster then the speed of light, and by the way we are out of beer again!

  • JSintheStates says:

    Comet observation may be on the incease. I sincerely doubt that comet activity has changed. Pure unfounded speculation on the internet!

  • Turbo says:

    At the photos I've seen the dust seems to be raised in the white side of the comet (the part I understand is in front of the Sun) why? When we see a comet from earth the dust tail seem to be at the opposite side.

    • sciencefan says:

      Dust is emitted from where gas sublimates, which is mainly the illuminated regions. It is the same for all comets. After the dust is released it will be pushed away from the Sun by the radiation pressure. So it's a matter of resolution. The OSIRIS images show only dust very close to the nucleus, not yet affected by radiation pressure.

    • Cometstalker says:

      It takes a few thousand kilometers to alter the direction of the stream to be aligned with the solar wind. Those thousands and more kilometer tails you see from earth or other observation points is not the close about 10 km streams you see from Rosetta. This comet also has a large and growing coma behaving just as it should. The streamers you see on some images close to the comet is not this coma, its streamers or outbursts or jets or whatever the preference.

      • Jacob Nielsen says:

        ...This also means: First stuff is blasted towards the sun at some speed, then it is accelerated in the opposite direction, the opposite direction being back towards the nucleus. Now gasses have no means to settle again on the nucleus, unless by chemical bonding, because the gravity is too low. Particles, however, will strike the nucleus if their summed trajectories so demand. Larger particles should be more likely to enter orbits around the nucleus for some time before impacting more or less at random across the entire surface. Once impacted, the particles, or 'objects' may bounce, break, bury, roll or tumble, or a mix of these, and this way settle primarily where gravity and obstacles so dictate.
        Yeah! I do what i can to keep my 'monster hailstone' / 'comet baby' hypothesis alive...I mean it might be dead and gone in year, so i nurse it while I still have it.

  • dave says:

    soverign slave,

    Yes its certainly possible, and the effects of electrical machining tearing at the surfaces of comets & the moon has been tested in the lab in the early 70s by NASA of all people.
    The 6 million doolar question though, is this whats happening on this comet.
    The instruments esa have should be able to measure magnetic field due to current flow if there is some. Also they should be able to measure the electric field if there is one.
    No information from these instruments yet though. I not sure if that means, nothing detected or nothing released.
    There are plenty of other theories to consider though , just look through the blogs. Despite wonderful pictures recently, other data is a bit scant.

    • Cometstalker says:

      To my understanding all instruments back packed on this mission work just fine. This only means that essential data is not released due to a lot of reasons. The major reason is that the persons working with this data sets have nothing yet to present because they are still very far away from the finish line. This again is due to the amount of work load does not match the capacity of the workshop. So if management would increase the capacity the work would be finished of a lot faster. This again would result in the disadvantage to the management not being needed any more for this project. No you can extrapolate the main reason of not getting a presentation of essentials from this mission in a hurry.

  • Robin Sherman says:

    The "Solar Wind" that is bowing away from the Sun pushes all the plasma, gas and dust away and behind the comet to create the tail.

  • Robin Sherman says:

    The last report from ESA concerning the presence of Water was given after readings taken from well before Rosetta reached 100Km away. That report said that there appears to be almost no Water ice on the surface, adding, if there is some, it is at an amount below the level of the resolution available at that time.

    Now that Rosetta is only 10Km or less away, that assessment may have changed. If it has changed significantly, that would be one of those closely guarded secrets we are not allowed to know. So either way the presence of Water ice or otherwise and its amount is still a mystery. We do know there is Water in the coma, just not how much and where it has come from or how it got there. Not much help to anybodies pet theories.

  • Sovereign Slave says:

    Hi Emily, posted a comment yesterday, hasn't shown up, was wondering if it was censored for some reason. Please let me know if this was an oversight, or if censored, the reasons so I'll know how to post in the future as I would like to participate on occasion. I had linked to the following and asked for comments. Thanks.

    https://www.thunderbolts.info/wp/2014/10/20/will-nasa-rewrite-history/

  • Sovereign Slave says:

    Oops, my mistake, just found it posted, so please disregard.

  • Sajid Rabbani says:

    Cometstalker, wonderful site. Thanks

  • Giuseppe Spinella says:

    Che meraviglia... vorrei essere su Rosetta per guardare questo spettacolo!

  • Andrew says:

    Why no mention of electrical processes likely as the basis for the jetting? This is not off gassing, this is particulate matter getting 'machined' off the surface. The comet, like all astral bodies has an electrical charge. The comet exists within the heliopause of the sun, so naturally the comet and the sun sense each other to a high enough degree, that a charge equalization is occurring. You can show this simple process in a lab, with the evident connection between an anode and cathode. There does not have to be an arc for machining to occur on surfaces. Why is astrophysics choosing to live in the dark ages when the evidence is so obvious?

    • Phil Stooke says:

      Of course! It's so obvious now you have mentioned it. How could every scientist for the last 200 years have been so wrong? We are so lucky to have you to set us straight. This is Nobel material for sure.

      • John says:

        Ah, Phil Stooke, resorting to sarcasm. But you will have to stop believing everything you are told by the experts and start understanding how the big science world works. There are many historical examples of scientists being collectively wrong for long periods and with regard to astrophysics and planetary science it looks as though we are in one of those periods now. Hopefully the pioneering Rosetta mission will start to correct that.

    • John says:

      Well said Andrew. The widely repeated dirty snowball and ice sublimation theory is a sad example of a possibility turned into a certainty by decree and consensus. One way of preserving this here seems to be to endlessly discuss trivial aspects and ignore the main issue. There is apparently instrumentation on both the Rosetta craft and the lander capable of measuring plasma and electrical properties, as well as other physical properties. The outcome of that should be obvious ultimately.and then perhaps the language will change, if we are looking at true science.

    • Robin Sherman says:

      @ Andrew, I think you will find some very dedicated advocates for this theory have posted regularly on this blog.

  • armchair explorer says:

    Is the increase in comet activity reflected in the GIADA data?

  • Robin Sherman says:

    Its a great theory Jacob, not sure about the "giant" hailstones, but some of what goes up must come down again. Plenty of it is Water and dust, ideal recipe for little balls of ice to form in a chaotic environment. Hailstones get bigger as they fall through clouds saturated with Water vapour. Even at its greatest outflow I don't think the coma could ever be said to be "saturated" with Water. I think it more likely bigger chunks of material could be blasted off the surface of the comet when the venting really gets going.

    • Jacob nielsen says:

      ...exactly: comet Hartley-2 probably behaves like that: http://satellitesnews.blogspot.dk/2011/05/at-heart-of-hartley-2-new-breed-of.html
      different substances mix less than would generally be expected, leading to chunks of (water) ice beeing ejected (like cannonballs) by the evaporation of more volatile gasses, thus no accretion has to take place in the coma, which I agree would be.. Exotic. The chunks of water might get covered in 'soot' though, this way camouflaging they are actually.. Hailstone 😉

  • Dave says:

    Andrew you have it dead right, it's virtually possible to see the process in front of us. it will get ever more obvious. Please ESA release the data, no water ice and the electrical machining of the surface is putting water and other volatiles in to the atmosphere, also the composition of the dust you are collecting will also speak volumes. Give us some data please. Strange you can give us science fiction but not real data.

  • Robin Sherman says:

    My first thought was searchlights too, Rebecca. A unique and wonderful image thats for sure.

  • Kamal Lodaya says:

    Emily: This image was posted on Diwali, the festival of lamps/fireworks in India. One of them, anaar (literally means pomegranate), has similar jet-like activity.

  • Funny that no one have noticed that the two OSIRIS wac images are mirror flipped.

    They are actually looking from almost the same direction as the navcam mosaic in this post:

    http://blogs.esa.int/rosetta/2014/10/08/cometwatch-focus-on-the-neck/

    Look at the D image...

    • emily says:

      Hi Mattias, we checked with the OSIRIS team who confirm that all WAC images come down flipped (left-right) due to the mirror system and the orientation of the CCD. Usually these are 'corrected' before being provided for release, so well-spotted that these were in their original format!

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