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A question of Planetary formation.

  1. Jun 12, 2003 #1
    My question pertains to atmosphere. Forgive me if it sounds stupid, or obvious, but I just don't know how atmospheres come about. I understand how planetoids and planets are formed, but when/how does it get an atmosphere?

    Any help would be appreciated.
  2. jcsd
  3. Jun 12, 2003 #2
    i'm sure there are many others who could answer your question with more insight, but they don't seem to be doing that so i'll give it a go:
    i've always thought that most of the atmosphere that a planet has is created by chemical reactions that take place on the surface. for example, venus has a high *some sort of volital gas that i forgot* which i think is produced by the volcanic reactions. somebody help me out here!!
  4. Jun 13, 2003 #3
    Anybody care to elaborate on maximus' point? Anyone care to present their own idea? Perhaps a site? Anything?
  5. Jun 13, 2003 #4


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    Greetings !

    In a planet the size of the Earth most of the heavy
    ellements sink and the light elements remain close to the
    surface. The energy of the Sun heats these ellements creating
    an atmosphere. If the planet has little gravity then the
    atmosphere - the gas can not remain trapped by the low
    gravity but the Earth, for example, has sufficient mass
    to hold its atmosphere.

    Live long and prosper.
  6. Jun 13, 2003 #5


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    We have only recently come to realise the importance of vulcanism in the formation of an atmosphere. It is this process which puts gasses back into the atmosphere. For example, Mars has a significant gravitational field when compared to Earth's, but its atmosphere is so thin compared to ours as to be virtually non-existant. Both planets slowly lose atmosphere to space, but Earth still has active vulcanoes, which Mars lacks. This, according to current thinking is what makes our two worlds' atmospheres so different.
  7. Jun 13, 2003 #6


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    Contrary to LURCH, I think that has more to do with earth's magnetic field. Earth unlike mars has a strong magnetic field due to rotating currents in the core. This deflects charged particles from the sun, and so protects our atmosphere. Mars being colder does not have a liquid rotating core, and so is unprotected from such radiation, with it's atmosphere more or less "blown away" in the solar wind.
    I may be wrong, though.
  8. Jun 13, 2003 #7
    Couldn't it be all three of those factors (weak gravitation, strong electromagnetism, and active vulcano activity)? I really have no clue, but it seemed like all of these things could be factors in the presence of Earth's atmosphere.
  9. Jun 14, 2003 #8
    I'm not so sure about the magnetic field. Venus has a weak magnetic field with a dense atmosphere.
  10. Jun 14, 2003 #9


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    Staff: Mentor

    Weak gravity means LESS atmosphere, not more. The gravity has to be strong enough to keep the gases from escaping.
  11. Jun 14, 2003 #10
    Part of the reason is vulcanism, another part here on Earth is life forms called blue green algae.
    (Stramatolites if I recall it correctly, funny, cause I just looked at them yesterday in the Queensu geological museum)

    In Australia there are still some of these plant forms existing, they are thought to be one of the primary causes of the oxygen atmosphere that is present on earth, as they took the carbon 'oxides' and converted them, in biological processes, to oxygen.

    Some of the gases would have been a product of the cooling of the rocks, that occured, when the planet formed.
  12. Jun 14, 2003 #11


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    All the factors mentioned do add to forming an atmosphere. Holding on to the atmosphere is mainly a function of gravity, and least important mentioned so far is a magnetic field, or lack of one.

    But, in all planetary sources I see regarding atmospheres, there is one predominant factor I don't see mentioned yet. This would mainly be in the early stages of a solar system's formation, and would be the bombardment of the planets by "cometary material", especially when the forming system had not yet been "swept clean" by the planets, and this material was slamming us on a regular basis. A lot of the experts believe that the predominant portion of platetary atmospheres came from bombardment of gas-rich comets. Our Gas-Giant planets formed from primordial gasses, but have also been enhanced/changed by accumulation of protoplanetary material.
  13. Jun 15, 2003 #12
    Thanks for the responses. I was always really interested in planetary formation, but I never really questioned the origin of atmosphere before.
  14. Jun 17, 2003 #13
    It is a good question, and I went back to the museum and found I have mispelled "Str-O-matolite", pardon.

    Also they mention the gassing that arises from Volcanic activety Carbon Dioxide, Methane, and Amomonia.

    I would agree with the Comet'ary idea as well, makes eminent sense.

    EDIT mislpelled mispelled (SP?)
    Last edited: Jun 17, 2003
  15. Jun 17, 2003 #14
    Actually it's "misspelled" or "misspelt".
  16. Jun 18, 2003 #15
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