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

From: lebofsky_at_lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Tue Oct 24 14:40:49 2006
Message-ID: <2505.128.196.250.86.1161714955.squirrel_at_timber.lpl.arizona.edu>

Hi Sterling:

Derek's book is "only" $107.50 on Amazon.com.

I hope that Derek will be writing an article for the February issue of
Meteorite magazine.

Larry

On Tue, October 24, 2006 11:28 am, Sterling K. Webb wrote:
> Hi,
>
>
> For those interested in follow-up to Sears'
> theories but reluctant to pop for the new book:
>
> Here's a nice (free) piece by Sears (cheaper than buying the $110
> book...) http://www.lpi.usra.edu/meetings/lpsc97/pdf/1179.PDF
>
>
> A summary of some of Sears' views (by Bernd Pauli):
> http://www7.pair.com/arthur/meteor/archive/archive4/Feb98/temp/msg00213.ht
> ml
>
>
> The best tests are experimental:
>
>
> Chondrules can be made in the laboratory:
> http://www.space.com/scienceastronomy/solarsystem/fiery_rain_000809.html
>
>
>
> Sterling K. Webb
> -----------------------------------------
> ----- Original Message -----
> From: Warin Roger
> To: Sterling K. Webb ; meteorite-list_at_meteoritecentral.com
> Cc: E.P. Grondine
> Sent: Tuesday, October 24, 2006 11:15 AM
> Subject: Re : [meteorite-list] Chondrule formation mechanism (Info Please)
>
>
>
> Hi, all,
>
>
> I am surprised that nobody evoked the theory following which chondrules
> were formed in relatively very few privileged zones of space. They would
> then form through one or more impacts of relatively large asteroids, onto
> the parent body covered with regoliths (and even with megaregoliths). The
> excellent book of Derek Sears, entitled ?The origin of chondrules and
> chondrites? (Cambridge Planetary Science, 2004) supports this hypothesis.
> In
> corollary, ordinary chondrites (85% on Earth) would be quite rare in
> cosmos, and only few parent bodies would produce chondrites.
>
> Glad to hear some comments on the above assumptions.
>
>
> Thanks,
>
>
> Roger Warin
>
>
>
>
> ----- Message d'origine ----
> De : Sterling K. Webb <sterling_k_webb_at_sbcglobal.net>
> ? : meteorite-list_at_meteoritecentral.com
> Cc : E.P. Grondine <epgrondine_at_yahoo.com>
> Envoy? le : Dimanche, 22 Octobre 2006, 20h38mn 55s
> Objet : Re: [meteorite-list] Chondrule formation mechanism (Info Please)
>
>
>
> 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
>>
>>
>
>
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Received on Tue 24 Oct 2006 02:35:55 PM PDT