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Elements of mother earth

  1. Jul 31, 2005 #1
    All elements are/ were made in stars, correct?

    Why is earth predominated by certain elements and not by others?

    Does the composition of elements of other planets in our system differ from earth?
    If so, why?
  2. jcsd
  3. Jul 31, 2005 #2


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    Pretty much everything started out as Hydrogen, and over a very long time, was fused into heavier and heavier elements and then dispersed throughout the galaxy/universe to form other planets/stars.

    I think it has to do with density as to why the inner planets (Mecury through Mars are predominatly rocky, when the solar system was just being formed, the denser stuff was pulled more toward the center.

    Yes, the elemental composition of other planets differs from Earth to a degreel. The most obvious differences would be the gas giants such as Jupiter and Saturn which are mostly Hydrogen. also, Mars in red due to its high concentration of Iron Oxide in the soil, not to say that Earth doesnt have just as much if not more Iron, it is just that mars has it so prominantly displayed.
  4. Aug 1, 2005 #3
    more posts, please
  5. Aug 1, 2005 #4


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    I think you'll get more answers here in GA&C! :smile:
  6. Aug 1, 2005 #5
    It possible that it requires a certain mix of elements to allow a form of life to view it. (If we had a similar composition to Saturn, for example, life as we know it wouldn't exist and the question would never arise)
    Last edited: Aug 2, 2005
  7. Aug 2, 2005 #6


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    Consider the temperature at which various elements 'freeze'. Inner planets tend to be rock [high melting point], outer planets tend to be gas [low melting point].
  8. Aug 2, 2005 #7
    I found this:

    Earth formed as the Sun itself was being born in a great disk of hot gas that came together when a nearby star exploded in a supernova. Earth was created hot, from the energy of many smaller bodies falling into it and adding to its mass. As the Sun ignited, it blew away almost all of the light gases hydrogen and helium from around Earth (these gases became part of Jupiter and Saturn). The same story applies to Mercury, Venus, and Mars, the other terrestrial (rocky) planets.
  9. Aug 2, 2005 #8
    The elements we have here on good 'ol planet Earth come from one of three sources:

    nucleosynthysis during the big bang
    ---produced H and He (75% by weight of H)
    ---a trace of D and Li
    nucleosynthysis in stars
    ---this makes elements up to Fe
    nucleosynthysis in supernovas
    ---this makes any element, and all heavier than Fe

    So that's where elements come from. To get to Earth, they go through fractionation, which is the process of sorting out some elements from others. For instance, there is lots of Si, O, N, C in and on Earth because they are chemically reactive and form non-volatile substances, like rocks. Other elements, like He, Ne, Xe etc are very very rare on Earth because they don't form chemical compounds that will stick around. They are volatile gases that go away during planetary accretion.

    So it's two steps: elements are formed in the BB, in stars, and in supernovas, then they are sorted depending on their chemical reactivity and stability.

    That's a brief writeup on a long, and fascinating, topic. Hope that helps!
  10. Aug 2, 2005 #9
    It does. Thanks Tropo and a very welcome to Physics Forums.
  11. Aug 2, 2005 #10


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    As you have found, the era when a star ignites has important effects on the environs in which its planets are forming. Very energetic stars exert a pressure that clears light elements and even dust from their environs. The elemental profiles of the planets that are forming in these voids are highly dependent on when and how strongly the "stellar winds" from the nascent star developed. This is likely to be a very rich field of study in the future as we discover more about planets orbiting other stars.
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