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Question on Comet 67P tail in Rosetta image

  1. May 1, 2015 #1
    I cam across this picture from the Rosetta mission the other day. You'll notice the sun is illuminating the right hand side of the comet. Additional the tail is coming off the right hand side. This goes against what I've been taught about comets in that the solar wind pushes the tail the opposite direction from the sun. So what's going on here?

    My personal thought: The FOV is small enough that we don't see the larger tail getting pushed away. Just some local effects from the sunlight. Does that seem reasonable?
     
  2. jcsd
  3. May 1, 2015 #2
    Read the description below the picture. It says that heat from the Sun causes the comet's nucleus to expel gas and dust, which is what we see in the picture. You may well be right about the field of view, and also perhaps the larger tail is too dark to see in the comet's shadow, especially next to the bright cloud and comet.
     
  4. May 1, 2015 #3

    davenn

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    that doesn't answer the question .... we all know that that is what happens

    I agree with the OP ... it seems incorrect and Im not sure why

    Dave
     
  5. May 1, 2015 #4

    Bandersnatch

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    I think that's just material expelled from the sunny side where the surface gets heated. Only subsequently the dispersed material floating around the nucleus gets blown away by solar wind to form the tail (which is a huge, diffuse structure only visible from afar).
    It would be odd if it had these jets erupting preferentially on the dark, colder side.
     
  6. May 2, 2015 #5

    Dotini

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    Oddly enough, a dark side jet was captured in the act of erupting the other day.

    http://blogs.esa.int/rosetta/2015/04/20/osiris-catches-activity-in-the-act/
    ESA_Rosetta_OSIRIS_WAC_20150312T071518-350x343.jpg
    The scene at 07:15 CET on 12 March. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

    It happens elsewhere, too.
    http://rpmedia.ask.com/ts?u=/wikipedia/commons/thumb/c/c1/Hartley2jets2_epoxi_big.jpg/220px-Hartley2jets2_epoxi_big.jpg [Broken]
    Gas and snow jets on http://www.ask.com/wiki/Comet_Hartley_2?qsrc=3044 [Broken]
     
    Last edited by a moderator: May 7, 2017
  7. May 2, 2015 #6

    Bandersnatch

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    That's to be expected - the comet is rotating, and the incoming heat gets conducted throughout its bulk. But the energy input comes from the illuminated side only, so the temperature will always be the greatest there (disregarding variations due to reflectivity, material composition, etc) and most of the jets should come off that side.
     
  8. May 2, 2015 #7

    Dotini

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  9. May 15, 2015 #8
    Could this all be the result of some sort of electrically driven erosion? Comet 67P itself was found not to be magnetic yet a magnetic field was detected by both spacecraft. So what could be driving that field?
     
  10. May 15, 2015 #9

    Bandersnatch

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    That's a contradiction. The comet was found not to have a global magnetic field, because the sensors did not detect any.
     
  11. May 15, 2015 #10

    Dotini

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    A magnetic field will be associated with the coma.

    "The ion tail is formed as a result of the ionisation by solar ultra-violet radiation of particles in the coma. Once the particles have been ionized, they attain a net positive electrical charge, which in turn gives rise to an "induced magnetosphere" around the comet."
    http://en.wikipedia.org/wiki/Comet

    Speculation about electrically driven cometary erosion is not well justified at the present time and place; we should allow the Rosetta team time to do their studies and papers. Even so, there are a small clutch of papers published on the interaction between solar wind and various bodies such as the Moon producing interesting effects.

    "Protons in the solar wind can make small amounts of water continuously on the lunar surface by interacting with metal oxides in the rocks. But some of the water is probably deposited on the Moon from other places in the solar system."
    http://science.nasa.gov/science-news/science-at-nasa/2010/18mar_moonwater/

     
  12. May 15, 2015 #11
    From the Rosetta mission site: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_and_Philae_find_comet_not_magnetised

    "ROMAP measured a magnetic field during these sequences, but found that its strength did not depend on the height or location of Philae above the surface. This is not consistent with the nucleus itself being responsible for that field."
     
  13. May 15, 2015 #12

    Bandersnatch

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    Alright, you mean the background readings from the solar wind? Sorry, I completely missed your point earlier.

    From the same page you linked to:
    'Instead, the magnetic field that was measured was consistent with an external one, namely the influence of the solar wind interplanetary magnetic field near the comet nucleus. This conclusion is confirmed by the fact that variations in the field that were measured by Philae closely agree with those seen at the same time by Rosetta.'
     
  14. May 15, 2015 #13
    This "induced magnetosphere" is supposed to deflect the solar wind around the nucleus of the comet so I'm not sure how it could really interact with it to form water. Though I do believe the water is electrically generated.
     
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