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

From: MEM <mstreman53_at_meteoritecentral.com>
Date: Sat, 18 Dec 2010 19:39:51 -0800 (PST)
Message-ID: <548773.12846.qm_at_web55205.mail.re4.yahoo.com>

I sit partially corrected: apparently the latest "oldest" is 4.404?.8 and it
wasn't sandstone proper but metamorphosed sandstone which usually equates to
quartzite. The info did express there was some debate about a possible
hydrothermal alteration of the zircons

This tightens the time lines substantially but the other comments
remain valid until I find Where I am wrong again...lol

Elton
<http://en.wikipedia.org/wiki/Oldest_dated_rocks>

Recent research
The zircons from the Western Australian Jack Hills returned an age of 4.404
billion years, interpreted to be the age of crystallization. These zircons also

show another interesting feature; their oxygen isotopic composition has been
interpreted to indicate that more than 4.4 billion years ago there was already
water on the surface of the Earth. The importance and accuracy of these
interpretations is currently the subject of scientific debate. It may be that
the oxygen isotopes, and other compositional features (the rare earth elements),

record more recent hydrothermal alteration of the zircons rather than the
composition of the magma at the time of their original crystallization. In a
paper published in the journal Earth and Planetary Science Letters, a team of
scientists suggest that rocky continents and liquid water existed at least 4.3
billion years ago and were subjected to heavy weathering by an acrid climate.
Using an ion microprobe to analyze isotope ratios of the element lithium in
zircons from the Jack Hills in Western Australia, and comparing these chemical
fingerprints to lithium compositions in zircons from continental crust and
primitive rocks similar to the Earth's mantle, they found evidence that the
young planet already had the beginnings of continents, relatively cool
temperatures and liquid water by the time the Australian zircons formed.



----- Original Message ----
> From: MEM <mstreman53 at yahoo.com>
> To: Greg Catterton <star_wars_collector at yahoo.com>;
>meteorite-list at meteoritecentral.com
> Sent: Sat, December 18, 2010 10:10:39 PM
> Subject: Re: [meteorite-list] Good read about the moon being captured by Earth
>
> ----- 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
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Received on Sat 18 Dec 2010 10:39:51 PM PST