Great postings Elton. They take the whole discussion to a far greater level and
I fo one applaud you for it.
I like to think there are others that appreciate it and thin this is what this
list should be about.
As an addition to what you say I will say the following.
The short half life of Al26 (yes, I believe it is 720 thousand years) is a
really good indication that differentiation took place very quickly.
Al26 would have been present in large quantities (1 part in 10^5 of aluminium
atoms) and would provide a large source of energy. Info from encyc of
meteorites).
It's short half life limits the differentiation period to less than 10Ma, borne
out by the majority meteorite samples we have).
There is, of course the issue of homogeneity amongst the pre/proto solar nebula.
Even distribution of isotopes around the nebula used for dating the solar
system is assumed rather than confirmed.
Personally, I don't think it makes much difference.
The sphericity of the Oort cloud versus the disk of the solar system is likely
a density of matter issue. Beyond 60AU, the material is likely to be too thinly
spread in the early solar system to form into a proper disk (a factor that
would also induce heating in the inner region thoug I don't know how much and
it'd be more significant closer in).
There is also the issue of the E-M effect produced during the T-Tauri phase.
I adored the idea you made (I've never heard it before) of it resisting
differentiation. I think you're right and it may be a contributing factor to
the size of planetary bodies. Only when gravity can overcome such an effect can
differentiation occur.
We know that T-Tauri stars eject material out through their poles. Maybe as
much as 0.0001 solar masses may re-accrrete to the disk (+/- an order of
magnitude). As it does so, huge EM effects will take place.
We know it happens but we don't know how or why or the effect it has.
Personally, I think it's great that we have found out so much but still have so
much to know and I love being able to chew it over here.
Rob
--- On Wed, 4/8/09, Mr EMan mstrema...@yahoo.com wrote:
From: Mr EMan mstrema...@yahoo.com
Subject: Re: [meteorite-list] Questions about accretion. Part 2 UAE, Shock
wave distribution proto Solar System
To: Meteorites USA e...@meteoritesusa.com,
meteorite-list@meteoritecentral.com
Date: Wednesday, April 8, 2009, 3:33 AM
There was a question regarding the sorting of elements and
why for example common chondrules had more iron than did
Carbonaceous chondrites. The reason for the difference also
includes why we use isotope ratios to determine from where a
parent body probably formed within the solar system.
Sometime in early solar system development there was a
sustained and or repeated strong solar wind or mini-nova, or
perhaps our own ancestral sun's predecessor nearby
supernova, or other cosmic water hose(?) that sweep through
the swirling matter in the proto-solar disk, significantly
sorting it out by elemental and molecular weights. Heavier
particles weren't pushed out as far as the lighter ones.
Thus we have heavy to light sorting of particles/ elements/
molecules/ solids/ gases etc from the inner rocky planets at
one end to the giant gas planets beyond the asteroid belt
and all way out to the Ort cloud. The sorting was not
perfect but did rearrange the mixtures of elements locally.
Conservation of angular momentum must have broken down at
some level such that the Oort Cloud is theorized to be more
or less spherical while planetary masses tend to lie close
to the plane of the ecliptic. (This glitch influences
measured elemental ratios of our known
solar system and just mentioned for those paying
attention)
Thus before significant planetary accretion(first 3-5
million years?) we experienced a cycle of sorting that left
zones of like particles to be accreted. This sorting also
locally affected the ratios of the individual isotopes of
elements from a concept we know as the Universal Abundance
of the Elements.(UAE) (The UAE says that based on human
measurements the mass of the universe is concentrated in the
first 20 elements which incidentally were the main elements
associated with living processes).
When the local Solar system abundance of the UAE was
disturbed, distribution of isotope ratios were also skewed
in the local solar system. Ergo oxygen isotope studies in
meteorites tell us what relative distance/radius a parent
body formed away from the sun.
On Earth the ratios for Oxygen:
O18(Tritium)-O17(Deuterium)-O16 is something like 18O / 16O
= 2005.20 ±0.43 ppm (a ratio of 1 part per approximately
498.7 parts) 17O / 16O = 379.9 ±1.6 ppm (a ratio of 1 part
per approximately 2632 parts) This ratio signature is
specific to an origin in the Earth Moon distance and there
is a different one for Mars, the asteroid belt, Jupiter,
Saturn and carbonaceous chondrites etc. Complications
