[meteorite-list] Chondrule formation mechanism (Info Please)

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Tue Oct 24 00:17:07 2006
Message-ID: <20061024041705.44903.qmail_at_web36901.mail.mud.yahoo.com>

Hi Sterling,

I did not post my reply to you to the list, so they
won't know what the extracts you cited came from - if
you have a copy of that message please post it -

The problem still remains what caused sufficient
number of atoms of the same type to be in the same
place at the same time to produce the crystals and
glasses observed.

If you have the gravity of a source proto-planet
differentiating the components in an immiscible melt,
then that problem is solved. I can't see any
differentiating mechanism for an "instellar" melt,
regardless of energy source.

No doubt the dating techniques are accurate. And no
doubt the elements were frozen in time in the
chondrule glasses and crystals. But is what is being
dated, the elements' formation date, or the
chondrule's formation date?

good hunting,
Ed

--- "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>
wrote:

> Hi, Ed,
>
> > ...but does this mean that the
> > formation of the condrules and
> > their matrices date to
> > that time?
>
> The "formation date" is when all the
> various materials can no longer be mixed
> with other material, be wetted, dried, migrate,
> be modified, interact chemically, be altered,
> or otherwise be messed with. The tiny packet
> of the chondrule is melted, fused, sealed --
> ain't nothing going nowhere. From that point,
> the isotopes decay without any material being
> allowed to escape. The uranium turns slowly
> to a peculiar isotope of lead with a long halflife
> (billions of years). You count the uranium atoms;
> you count the odd lead atoms; calculate how
> long it took for some of the original uranium to
> that number of lead atoms. Since nothing can
> enter or leave the chondrule, it's pretty accurate
> (very accurate).
>
> > No doubt the constituent components of our solar
> > system date to that time, but does this mean that
> the
> > formation of the condrules and their matrices date
> to
> > that time?
>
> A solid rock, a melted lump (like a chondrule),
> a piece of glass (like a tektite) are all good
> dating
> candidates because atoms can't go waltzing in
> and out like it was a border bordello... Once a
> rock or any lump shows signs of being altered
> by the environment, partial melting or heating,
> aqueous modification, alarm flags go up.
> Sometimes, it's a good thing: a tektite's K/Ar
> date turns out to be when it either impacted or was
> impacted, but it's Rb/Sr shows (I think) its
> original
> formation date (curiously, about 480 mya). Many
> wouldn't agree with that, but they then have to
> explain
> why its "original" Rb/Sr ratio is radically
> different from
> ANY other rock, on Earth or off. (Mostly that
> detail's
> ignored.) At any rate, it's different from its K/Ar
> date
> (each tektite type has its own K/Ar date).
>
> > If the dates are right, the problem becomes "how
> did
> > that many identical atoms get together in one
> place so
> > that the chondrules could form?"
>
> Not sure what you mean here. The chondrules
> have many elements in many compounds, just like
> the meteorites, many of the same ones. They were
> gas and dust before being flash melted, typical of
> the inner solar nebula -- the usual crap. Lots of
> argument
> about what melted them, and the details, of course,
> solar flare, electric currents in the disc, magnetic
> effects, shock waves?
>
> Your theory of pressure release isn't
> necessarily
> dead. What if a sudden short heating event (solar
> flare for
> example) melts them radiatively and heats the gas
> around
> that region. After the chondrule is flash fried, the
> hot gas
> (no longer being heated) expands rapidly and the
> heat and
> pressure around the chondrule drops as the gas
> expands and
> cools, letting them cool quickly by radiating their
> heat
> away quickly (?). I should shut up; that's
> dangerously
> close to being chemistry...
>
>
> Sterling
>
---------------------------------------------------------------
> My favorite two books on the formation of the solar
> system are John S. Lewis "The Physics and Chemistry
> of
> the Solar System." The 2 Ed. is $75, $35 used. (I
> was
> lucky; I caught it when it was remaindered out of
> print
> and bought it for $8. The other is Stuart Ross
> Taylor,
> "Solar System Evolution" (1992) also very expensive.
>
> I bought a copy when 1st ed. was remaindered out of
> print for $4. However, the 2nd Ed. (1999), much
> bigger,
> is available used for $20:
>
http://www.bookcloseouts.com/default.asp?R=0521641306B
>
---------------------------------------------------------------
> ----- Original Message -----
> From: "E.P. Grondine" <epgrondine_at_yahoo.com>
> To: "Sterling K. Webb"
> <sterling_k_webb_at_sbcglobal.net>
> Sent: Monday, October 23, 2006 3:25 PM
> Subject: Re: [meteorite-list] Chondrule formation
> mechanism (Info Please)
>
>
> > Hi Sterling,
> >
> > If the dates are right, the problem becomes "how
> did
> > that many identical atoms get together in one
> place so
> > that the chondrules could form?"
> >
> > Since this question has no good answer, one is
> forced
> > to look at the dating and exactly what it is that
> that
> > dating measured.
> >
> > No doubt the constituent components of our solar
> > system date to that time, but does this mean that
> the
> > formation of the condrules and their matrices date
> to
> > that time?
> >
> > I still want to look at that Krasnojarsk - the
> > mechanism for the olivine inclusions has to be
> > interesting, whatever it was - its the best excuse
> I
> > can come up with - what do you think about that
> one?
> >
> > Thanks,
> > Ed
> >
> >
> >
> > --- "Sterling K. Webb"
> <sterling_k_webb_at_sbcglobal.net>
> > wrote:
> >
> >> Hi, Ed,
> >>
> >> Those dates are from all those isotopic
> >> dating methods that will reach that far back:
> >> uranium/lead (U/Pb), ratios of lead isotopes
> >> (Pb/Pb), rubidium/strontium (Rb/Sr),
> >> samarium/neodymium (Sm/Nd), potassium/argon
> >> (K/Ar) sometimes (hard reach). Some methods
> >> are very precise, others have bigger uncertainty,
> >> but they all land inside each other's error
> range.
> >>
> >> I could put the isotope numbers in there, but
> >> I'd have to go look'em up to be sure... Will if
> you
> >> need'em.
> >>
> >> A lot of chondrules have been tested along
> >> with the chondrite matrix they're from, to get a
> >> line on the time order of the two and the age of
> >> earliest objects to form. If anyone found an
> >> oddball, like I said, it would be an occasion
> >> for hollering and hooting!
> >>
> >> The picture is that the chondrites we have
> >> are all very old, older than the planets, formed
> >> in a hurry at the beginning of the solar system.
> >> We are just barely able to see slight age
> >> differences
> >> in different types of meteorites, but that can't
> >> cover more than a few dozen million years.
> >>
> >> The place those meteorites mostly come from,
> >> the "asteroid zone," which we used to think
> >> of as the remainder of the planetesimals
> originally
> >> in that zone, seems instead to contain a lot of
> >> junk cars from all over. Some things, like Ceres,
> >> obviously belong there (could have formed there)
> >> but others (like Vesta and all those hundreds of
> >> big iron cores) are out of place and have come
> >> there from further "south." Refugee Rocks.
> >>
> >> The chondrules test (right on the ragged edge
> >> of accuracy) just a teeny bit older than the
> rocks
> >> they're in, maybe 2-3 my. It's almost too close
> >> to make out. They seem to have formed very
> >> fast (in a flash) and all at once. Rob's idea of
> a
> >> vibration-free environment for their formation
> >> seems doubtful to me. I think that early phase of
> >> the solar system was violent and quick, with,
> >> as Elvis put it, a whole lot of shakin' going
> on...
> >>
> >>
> >> Sterling
> >> -----------------------------------
> >> PS: Larry Lebofsky, editor of Meteorite, told
> >> me that they have an article on this very subject
> >> being worked on, possibly done by next issue
> >> (or the next...)
> >> ------------------------------------
> >> ----- Original Message -----
> >> From: "E.P. Grondine" <epgrondine_at_yahoo.com>
> >> To: "Sterling K. Webb"
> >> <sterling_k_webb_at_sbcglobal.net>
> >> Sent: Monday, October 23, 2006 1:38 AM
> >> Subject: Re: [meteorite-list] Chondrule formation
> >> mechanism (Info Please)
> >>
> >>
> >> > Hi Sterling -
> >> >
> >> > Do you happen to know what dating technique
> they
> >> used?
> >> >
> >> > Ed
> >> >
> >> > --- "Sterling K. Webb"
> >> <sterling_k_webb_at_sbcglobal.net>
> >> > wrote:
> >> >
> >> >> Hi, Ed, Rob,
> >> >>
> >> >> This scenario (Ed's) would require that we
> >> would
> >> >> find a chondrule with a formation age of 3.9
> Gya,
> >> I
> >> >> think. As far as I know, that has never
> happened.
> >> >>
> >> >> All chondrites (so called because they
> >> contain
> >> >> chondrules) are the same age: "about" 4.555
> Gya.
> >> >> Chondrules are the same age (2 to 5 million
> years
> >>
> >> >> variation among chondrules) as the chondrites
> >> they
> >> >> occur in. The "about" is because the dating
> >> methods
> >> >> have a limit to how precisely they can resolve
>
> >> >> small age differences.
> >> >>
> >> >> Dating by lead isotopes says the solar
> system
> >> >> is 4.560 +/- 0.005 Gya old. Other systems of
> >> isotope
> >> >>
> >> >> measurements (like 147Sm/143Nd) give 4.553 +/-
> >> >> 0.003,
> >> >> and so forth. Within the limits of
> measurement,
> >> all
> >> >> chondrites are the same age, a hair younger
> than
> >> the
> >> >> solar system itself, the Class of Zero, and so
> >> are
> >> >> their
> >> >> chondrules.
> >> >>
> >> >> Meteorites that do not (never did) contain
> >> >> chondrules
> >> >> have varying ages. Lunaites are the age of
> that
> >> >> portion
> >> >> of the lunar crust they came from, generally
> >> quite
> >> >> old
> >> >> compared to Martians which have the "formation
> >> age"
> >> >> of the basalt flow they were chipped off of
> for
> >> the
> >> >> long
> >> >> haul to Earth. Irons, which formed inside a
> >> >> differentiating
> >> >> body, have younger ages; some very much
> younger
> >> if
> >> >> the differentiation took a long time (Weekeroo
> >> >> Station IIe
> >> >> is 4.340 Gya, Kodaikanal IIe 3.800 Gya, many
> IAB
> >> >> irons
> >> >> the same).
> >> >>
> >> >> I'm thinking that before you need to
> develop
> >> a
> >> >> theory
> >> >> to explain a 3.9 Gya chondrule, you'd have to
> >> >> actually
> >> >> have a 3.9 Gya chondrule. As far as I know,
> none
> >> >> with
> >> >> discordant ages have ever been found. In
> certain
> >> >> solar
> >> >> circles it would be Big News.
> >> >>
> >> >> Oddly, if you Google for "oldest
> chondrule,"
> >> you
> >> >> get
> >> >> the oldest chondrules, and if you Google for
> >> >> "youngest
> >> >> chondrule," you get the oldest chondrules...
> on
> >> the
> >> >> grounds
> >> >> that it is "young" as the solar system. If you
> >> >> Google for
> >> >> "discordant chondrule age," you get arguments
> >> over 2
> >> >> or 3
> >> >> million years in the age of something 4-1/2
> >> billion
> >> >> years old.
> >> >>
> >> >>
> >> >> Sterling K. Webb
> >> >>
> >> >
> >>
> >
>
--------------------------------------------------------------------
> >> >> ----- Original Message -----
> >> >> From: "E.P. Grondine" <epgrondine_at_yahoo.com>
> >> >> To: <meteorite-list_at_meteoritecentral.com>
> >> >> Sent: Sunday, October 22, 2006 10:24 AM
> >> >> Subject: Re: [meteorite-list] Chondrule
> formation
> >> >> mechanism (Info Please)
> >> >>
> >> >>
> >> >> > Hi Rob -
> >> >> >
> >> >> > You noticed the contradiction in cooling
> >> periods
> >> >> as
> >> >> > well.
> >> >> >
> >> >> > What I am thinking is that there was at
> least
> >> one
> >> >> > larger parent body which was "disrupted"
> about
> >> 3.9
> >> >> Gya
> >> >> > (at time of LPBE). When this larger parent
> >> body
> >> >> was
> >> >> > disrupted, then the "effervescent" "foaming"
> >> that
> >> >> led
> >> >> > to some chondrules occured - sudden cooling,
> as
> >> >> > gravitation pressure had been released, and
> >> much
> >> >> lower
> >> >> > local gravity. Local processes suddenly take
> >> over
> >> >> - a
> >> >> > sharp gravitational and pressure transition,
> >> and a
> >> >> > sudden cooling. Gross processes - perhaps
> >> >> sufficiently
> >> >> > gross to overwhelm other small forces.
> >> >> >
> >> >> > Through collisions of the resulting
> fragments,
> >> we
> >> >> see
> >> >> > some of the meteorite types we see today.
> >> >> >
> >> >> > good hunting,
> >> >> > Ed
> >> >> >
> >> >>
> >> >>
> >> >> ______________________________________________
> >> >> Meteorite-list mailing list
> >> >> Meteorite-list_at_meteoritecentral.com
> >> >>
> >> >
> >>
> >
>
http://six.pairlist.net/mailman/listinfo/meteorite-list
> >> >>
> >> >
> >> >
> >> >
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Received on Tue 24 Oct 2006 12:17:05 AM PDT