[meteorite-list] Questions about accretion. Part 2 UAE, Shock wave distribution proto Solar System

From: Rob McCafferty <rob_mccafferty_at_meteoritecentral.com>
Date: Sat, 11 Apr 2009 16:14:25 -0700 (PDT)
Message-ID: <289388.53982.qm_at_web55207.mail.re4.yahoo.com>

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 <mstreman53 at yahoo.com> wrote:

> From: Mr EMan <mstreman53 at yahoo.com>
> Subject: Re: [meteorite-list] Questions about accretion. Part 2 UAE, Shock wave distribution proto Solar System
> To: "Meteorites USA" <eric at meteoritesusa.com>, meteorite-list at 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 to
> this gradient include the amount of oxygen returned to earth
> via comets in what was known as the great bombardment-- back
> skewing the post shockwave sorting in the early sweep out.
>
> Ok we are at the end almost. O18 being two neutrons
> heavier takes more latent energy to vaporize and results in
> a slight concentration of its ratio in seawater depending on
> how much extra energy is around. The colder the climate the
> more O18 gets left behind in seawater and available for
> building carbonate seashells. The higher the temperature
> trends the more gets evaporated and a portion of that gets
> preserved in paleo-ice cores. Thus ratios differ in
> sequestrations such as in coral reefs and sea shells. This
> characteristic makes O18 content in ancient ice cores and
> fossil shells equivalent to a paleo thermometer.
>
> Long way around answering why some classes of meteorites
> have more iron in them than others.
>
> Elton
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Received on Sat 11 Apr 2009 07:14:25 PM PDT