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  1. Standard member sonhouse
    Fast and Curious
    10 Jun '14 12:42
    http://phys.org/news/2014-06-year-dark-side-moon-mystery.html

    More evidence the moon was created by collision with Mars sized planet hitting Earth very early on in the birth of our solar system.
  2. Standard member DeepThought
    Losing the Thread
    10 Jun '14 16:11
    Originally posted by sonhouse
    http://phys.org/news/2014-06-year-dark-side-moon-mystery.html

    More evidence the moon was created by collision with Mars sized planet hitting Earth very early on in the birth of our solar system.
    On a slight note of caution, what it seems to show is that the near side of the moon was molten after the far side had solidified, and that the moon was much closer to earth in the distant past. That means the Earth and the Moon formed near each other, but isn't really conclusive proof of the Theia hypothesis.

    There is more evidence reported on the BBC website [1], based on analysis of rock samples, which seems to show the same thing.

    There is also a theory that the Earth had two moons for a while, which was also reported on the BBC website [2]. It is based on the same Theia collision, the reasoning of the authors is that if one moon could form, why not two? The seas on the moon are a consequence of a second collision between the smaller moon and the one we see now.

    [1] http://www.bbc.co.uk/news/science-environment-27688511
    [2] http://www.bbc.co.uk/news/science-environment-14391929
  3. Standard member sonhouse
    Fast and Curious
    10 Jun '14 17:06
    Originally posted by DeepThought
    On a slight note of caution, what it seems to show is that the near side of the moon was molten after the far side had solidified, and that the moon was much closer to earth in the distant past. That means the Earth and the Moon formed near each other, but isn't really conclusive proof of the Theia hypothesis.

    There is more evidence reported on the B ...[text shortened]... uk/news/science-environment-27688511
    [2] http://www.bbc.co.uk/news/science-environment-14391929
    They said the explanation for the near side more molten was the crust on the near side is thinner so meteor strikes on the far side would find a deeper crust and be more protected against volcanic activity, lava flowing out a thousand miles wide as in the near side, the far side has way less.
  4. Standard member DeepThought
    Losing the Thread
    10 Jun '14 19:43
    Originally posted by sonhouse
    They said the explanation for the near side more molten was the crust on the near side is thinner so meteor strikes on the far side would find a deeper crust and be more protected against volcanic activity, lava flowing out a thousand miles wide as in the near side, the far side has way less.
    Yes, I'm fairly convinced by the theory of how the maria formed. I don't know if this counts as evidence of a collisional origin for the moon though. Entertainingly the second article I quoted was saying that the two moon collision was slow at only 2.4km/s [1] - hardly any speed at all!

    [1] This is slow compared with the speed of sound in rock, apparently.
  5. 10 Jun '14 20:25 / 1 edit
    Originally posted by sonhouse
    They said the explanation for the near side more molten was the crust on the near side is thinner so meteor strikes on the far side would find a deeper crust and be more protected against volcanic activity, lava flowing out a thousand miles wide as in the near side, the far side has way less.
    All this really suggests is that the moon cooled faster on one side than the other. It doesn't on its own tell us anything about the moons origin. It doesn't even rule out multi-moon collision as suggested by DeepThought or even a large asteroid collision heating one side.
    There are other possible explanations such as differences in material on the two sides causing differential cooling or differences in mantle strength.
    The fact that one face always faces the earth is due to it not being a perfectly uniform sphere of uniform density.
  6. Standard member sonhouse
    Fast and Curious
    10 Jun '14 21:17
    Originally posted by DeepThought
    Yes, I'm fairly convinced by the theory of how the maria formed. I don't know if this counts as evidence of a collisional origin for the moon though. Entertainingly the second article I quoted was saying that the two moon collision was slow at only 2.4km/s [1] - hardly any speed at all!

    [1] This is slow compared with the speed of sound in rock, apparently.
    When one planet meets another, I don't think it would matter much if it was going 2.4 METERS per second, there would be a BIG splash! If that was the case though, I imagine there would not have been a moon manufactured from the collision.
  7. 10 Jun '14 22:09
    Originally posted by twhitehead
    All this really suggests is that the moon cooled faster on one side than the other. It doesn't on its own tell us anything about the moons origin. It doesn't even rule out multi-moon collision as suggested by DeepThought or even a large asteroid collision heating one side.
    There are other possible explanations such as differences in material on the two s ...[text shortened]... ace always faces the earth is due to it not being a perfectly uniform sphere of uniform density.
    No, even a perfectly uniform sphere of uniform density will tidally lock.

    What locked the moon was tidal stressing of the moon and not greater
    attraction of one side as compared with the other.
  8. Standard member sonhouse
    Fast and Curious
    10 Jun '14 23:04
    Originally posted by googlefudge
    No, even a perfectly uniform sphere of uniform density will tidally lock.

    What locked the moon was tidal stressing of the moon and not greater
    attraction of one side as compared with the other.
    The energy of stretching and compressing it, both planets actually, like taffy.
  9. 11 Jun '14 06:46
    Originally posted by sonhouse
    "Lunar mystery solved, near side Vs far side:"

    http://phys.org/news/2014-06-year-dark-side-moon-mystery.html
    The first thought when I saw this thread was - No, I don't believe in this. The moon was rotating from the very beginning so when the interesting stuff happened there was no far side.

    When I read the article I realized that I was wrong. When the dust settled to form the moon, then why would it rotate? There was, from the beginning a far side, and that side had different properties than the near side.

    We always learn new things, and that is what's fun with science!
  10. 11 Jun '14 09:03
    Originally posted by googlefudge
    No, even a perfectly uniform sphere of uniform density will tidally lock.

    What locked the moon was tidal stressing of the moon and not greater
    attraction of one side as compared with the other.
    Interesting. I didn't realize that. So I guess it means that the moon is currently not quite spherical but stretched in the Earth - Moon direction.
  11. 11 Jun '14 09:58
    Originally posted by twhitehead
    Interesting. I didn't realize that. So I guess it means that the moon is currently not quite spherical but stretched in the Earth - Moon direction.
    Absolutely.

    It's not just water [and air] that is moved by tidal forces, the rock moves too.

    That effect is what is keeping numerous small moons of Jupiter geologically active
    long after they should have solidified.

    The tidal stretching heats the rocks keeping it warm.

    The amount the moons shape is distorted is very small however.
  12. 11 Jun '14 10:08
    Originally posted by googlefudge
    The tidal stretching heats the rocks keeping it warm.
    Could that deferentially heat the near side more than the far side explaining the phenomena in this thread?
  13. 11 Jun '14 10:12
    Originally posted by twhitehead
    Could that deferentially heat the near side more than the far side explaining the phenomena in this thread?
    Not that I know of.
  14. Standard member DeepThought
    Losing the Thread
    11 Jun '14 11:10
    Originally posted by twhitehead
    Could that deferentially heat the near side more than the far side explaining the phenomena in this thread?
    I agree with googlefudge, but I'll check that, the article indicated that the near side was kept molten radiatively by the Earth's surface still being hot.
  15. 12 Jun '14 05:05
    My intuition suggests the moon didn't come into tidal-locking with earth until long after Earth cooled down from the collision.