Peter,
No one disputes science is messy, but Jim's point is valid. Drs. Rubin
and
Grossman have forgotten more than I will likely know in regards to
meteoritics, but I also feel a bit frustrated. I expect papers in a
journal
like "Meteoritics and Planetary Science" to be thoroughly reviewed before
being published. It's not an issue of a few esoteric differences, it's
about
the paper as a whole being rejected by esteemed and respected
meteoriticists.
Again, Jim's question is valid. Was this paper peer reviewed? I'm sure it
was, which leads to the next question. How was it allowed to be published
if
it is so far off?
The answer is important to me because I do not have the time to read
everything. I have time to read selected books and articles and want to
make
sure I am properly furthering my education.
Best,
Mendy Ouzillou
On Mar 13, 2013, at 10:05 PM, "Peter Scherff" <[email protected]>
wrote:
Hi Jim,
I find this all delightful. Science is messy. Theories compete for
acceptance. The one that best fits the facts and is able to predict
future
discoveries wins!
If I wanted absolute truths I would read books that the religions of
the world are based on.
Thanks,
Peter
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Jim
Wooddell
Sent: Wednesday, March 13, 2013 9:46 AM
To: Meteorite List
Subject: Re: [meteorite-list] Origin of chondrules
Hello Alan, Jeff, Mendy,
I find this response somewhat bothersome.
I recently read a paper that little old me, not being anyone close to
being
a scientist, can shoot dozens of holes through because of the use of
outdated obsolete information and now I read this from Alan and Jeff, who
I
look up to and consider piers in this field.
The fact is, people read these papers, therefore they must be true!!!
It's like the TV commericial where the girl read something on the
interenet,
so it must be true because no one can put stuff on the interent that
isn't
true!
So, what is going on with these papers? People are creating papers that
are
supposed to be pier reviewed and here we have two piers shooting them
down
in a public forum? What happen to the process of pier review and if this
particular paper is completely wrong! Who were the piers?
I am not going to appologise for being a little critical about this but
come
on guys, has it just become a paper mill? It sure beginning to seem that
way. I am completely missing the point of publishing papers with
outdated
and obsolete information (when the new data is in
hand) and papers that we are reading completely wrong!
I honestly do read these papers and try to ingest as much as I can, but
here
of late, it seems I am completely wasting my time reading them and then I
read your responses! Arrrrrgh.
Jim Wooddell
On Wed, Mar 13, 2013 at 3:28 AM, Jeff Grossman <[email protected]>
wrote:
I second what Alan wrote, at the 90% level. With my remaining finger,
I'll add that the worst problem may be that these molten planetesimals
must magically keep metallic and silicate melts mixed together in
order to make chondrules, many of which have abundant metal. I think
this would be physically difficult, to say the least.
I think the ideas in this paper are philosophically quite attractive,
joining modern research on cosmochronology with dynamical models of
the disk. But despite this new way of thinking, the basic tenets are
quite retro. Many people up through the 1960s hypothesized that
chondrules were fragments of igneous rock. Then modern research on
them began. Study after study found problems with these models, many of
which Alan outlined.
Although the new model is a twist on the old ones, it still is subject
to the same tests... and it cannot pass most of them.
Jeff
On 3/13/2013 2:03 AM, Alan Rubin wrote:
I'll be happy to give my opinion on the paper. I think it is
completely wrong. Here is my reasoning:
1. Many chondrules are surrounded by secondary igneous shells, still
others by igneous rims. These shells and rims indicate that the
chondrules haev experienced more than one melting event.
2. Many FeO-rich (i.e., Type-II) porphyritic olivine chondrules
contain relict grains of different FeO contents and different
O-isotopic compositions, again indicating multiple melting. This is
very hard in a collision model.
3. One might expect molten planetesimals to have well-mixed melts.
If the chondrules are mainly from the larger planetesimal (the
target) as one would expect, the O isotopic compositions of the
chondrules would probably be mass-fractionated and lie on a slope-1/2
line on the standard three-isotope diagram. We don't see this.
4. One might also expect that as the planestimal melted and began to
crystallize, it would become chemically fractionated, unlike the
unfractionated, solar, compositions of chondrules in primitive
chondrites.
5. The occurrence of microchondrules in the fine-grained rims around
some normal-size chondrules and the apparent melting of pyroxene at
the outer surface of the chondrule to form the microchondrules
indicates chondrule melting by a mechanism capable of melting only
the outer surface of the chondrule. This is totally inconsistent
with the formation by splashing by the collision of molten
planetesimals.
6. There are correlations between chondrule size, the proportion of
different chondrule types, the proportion of those with igneous rims
and secondary shells that are difficult to explain by splashing but
come naturally to a model invoking multiple melting in dusty nebular
regions.
7. The non-spherical shapes of most CO chondrules indicates very
rapid cooling or else they would have collapsed into spheres. This
might be okay except for the fact that the large size of their
phenocrysts require a growth period thousands of times longer than
the time it would take a molten droplet to collapse into a sphere.
This again indicates a flash heating mechanism.
8. The fairly rare occurrence of chondrule-CAI mixtures are difficult
to explain by colliding molten planetesimals, but are sinple to
explain by melting of a mafic dustball that had and old CAI fragment
inside.
9. Each chondrite group has its own distinctive narrow range of
chondrule sizes. In fact, about 90% of the chondrules in any group
have diameters within a factor of 2 of the mean size. One would
expect molten planetesimals to produce a similar size of chondrules
range
for each group.
Furthermore, chondrule size is correlated with lots of other
chondrule properties (proportions of textural types, numbers with
rims and secondary shells, etc.) that are hard to explain by molten
planetesimals.
10. And, I just don't see how we get the different chondrule textural
types by that model. Some chondrules lack olivine, others lack
pyroxene, some are coarse grained, some are fine-grained, some have a
mixture of different size grains, some include relict grains. This
seems impossible to produce by the molten planetesimal model.
Since I only have 10 fingers, I'll stop there.
Alan Rubin
Institute of Geophysics and Planetary Physics University of
California
3845 Slichter Hall
603 Charles Young Dr. E
Los Angeles, CA 90095-1567
phone: 310-825-3202
e-mail: [email protected]
website: http://cosmochemists.igpp.ucla.edu/Rubin.html
----- Original Message ----- From: "Mendy Ouzillou"
<[email protected]>
To: "met-list" <[email protected]>
Sent: Tuesday, March 12, 2013 7:06 PM
Subject: [meteorite-list] Origin of chondrules
And now for something completely different ... Meteorite talk.
I am in the process of reading through a fascinating article in
latest issue of "Meteoritics and Planetary Science" called "The
Origin of Chondrules and Chondrites: Debris from Low Velocity Impacts
Between Molten Planetisimals."
This paper is very well written and readable even by a novice such as
myself. What I find interesting is the proposal for a (somewhat) new
theory that chondrules did not instantly form from clumps of heated
nebular dust but instead formed 1.5 to 2.5MY after the formation of
CAIs. the paper states that chondrules formed from splashing when two
differentiated planetisimals collided at a relatively slow speed of
between 10 to 100m/s.
Without being able to review the previous papers, I have to say that
to me this makes a great deal of sense and appears to solve many of
the inconsistencies that have been raised in some of the older books
that I have read.
Note: there is a typo in the paer on page 2177. Is states "A strength
of the splashing model is that it can explain why chondrules are
mostly between
1.5 and 2.5MYr younger than CAI ...". The sentence should read
"older", no "younger".
Dr. Jeff Grossman, would love to hear your thoughts on this paper.
Mendy Ouzillou
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Jim Wooddell
[email protected]
928-247-2675
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