[meteorite-list] Good read about the moon being captured by Earth

[almitt2 at localnet.com]

Greetings,

The Earth capture theory creates a lot of problems due to the size of 
the Earth/Moon system. I believe it is physically impossible. It has 
long been discarded as a viable theory.

More likely an impact occured with the Earth during formation. At least 
that is the most logical idea put forth so far.

I guess that bad ideas are defended until the death of the person that 
generated the idea. Tektites also come to mind.

--AL Mitterling


Quoting MEM <mstreman53 at yahoo.com>:

> ----- Original Message ----
>> From: Greg Catterton
>> Subject: [meteorite-list] Good read about the moon being captured by Earth
>> about a year  old but a good read and something to consider. I think this
>> theory is more  plausible also.
>> Maybe the moon was hit and knocked towards Earth and was  captured.
>
> Yeah...BUT.....Capture theory doesn't address the identical oxygen isotope
> ratios shared by Terra and Luna. Nor our 23° axis tilt. Nor the migration
> dynamics to move .88 AU in 100 million years to be in place for the capture.
> According to the article, Malcuit has been working on this for 
> several decades.
> While Malcuit wasn't looking up from his desk, he may have missed the little
> isotope-ratio "thingy".
>
> While some rocks in Australia were dated to 4.0±.03 billion, the 
> claim for the
> oldest earth rocks dated were in the range of 3.8-4.3 billion( a one half
> billion error margin) leaving 400-500million years for the surface to
> re-congeal--which the author doesn't think is adequate.  The wack obviously
> would have excavated some of the mantle but not necessarily the core. 
>  I haven't
> seen the math, so I don't know if the envelope of possibilities allow 
> for some
> deep-crust plutons to have avoided being disrupted.  Maybe we need to 
> be looking
> for plutons with giant shattercones rather than micrometer-sized zircon
> crystals.  Another caveat in this "dating" is it isn't the rocks themselves
> which are that old-- its the un-remelted zircons within them and a giant wack
> would not necessarily have melted every last reservoir of zircon.  
> The zircons
> in Australia were in much younger sandstone.
>
> I'd like to know more about the mechanism of capture to convert a highly
> elliptical orbit (which would be likely be passing inside the Roche radius of
> the earth 16 times per year) into an almost circular one. ( I'd like to hear
> more about the wack from the orbit from inside Mercury and how the Moon would
> have retained so much silicate content which should have been boiled away).
> While we know there is a small, permanent, tidal bulge, on the 
> backside of the
> moon, the moon is far far less ellipsoid then predicted given the 
> perturbations
> of the Roche limit would have exerted over part of the 3 billion years of
> stabilizing--AND the moon would have to have been largely plastic-- if not
> molten , for the ellipsoid to become spherical.  BUT the moon is missing
> compression ridges that would have been left by the tectonics a solid crust
> floating on a plastic lunar mantel. I do agree that the churning would have
> heated both earth and the moon if the moon had survived the capture for any
> length of time--according to this theory. And we have calculated the rate the
> moon is moving away from us such that 400mybp we had 20 hour days. So 
> where is
> the orbital mechanics that got the moon so close and only to let it assume a
> different orbital radius?  The mechanism should have been a single vector not
> first one than another.
>
> I would also like to know what these "geologically impossibilities" are the
> author did not elaborate on other than his argument on cooling rates and the
> inferred "earliest age" the zircons could have formed that we use to date the
> oldest rocks.   This is the first I've heard that the" Big Wack" was 
> estimated
> to have occurred after the earth had formed oceans.
>
>
> Finally, some do believe there were a dozen or more bodies in the very early
> solar system that were ejected out of the solar system else were 
> absorbed into a
> body that yet remains. Calculations show that there are resonances and that
> bodies have moved into orbits other than the ones they were formed in 
> but IIRC
> these were largely inward migrations(?).  What wacker "knocked" the 
> moon into a
> radical orbit and where is the wacker today?
>
>
> Seems someone has too much of their life invested in a theory 
> overcome by events
> to accept that it is only a matter of time before the memorial 
> service.  Thanks,
> however, was a good read and I think we are open minded enough to weigh the
> facts.  Now if I can just get someone to agree with me about cold vs hot
> meteorites...
>
> Elton
> ______________________________________________
> Visit the Archives at 
> http://www.meteoritecentral.com/mailing-list-archives.html
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>