[meteorite-list] Pairing ?-Type Asteroids to OC's (fromArkansas)

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 10 Jul 2008 19:12:08 -0500
Message-ID: <00b601c8e2ea$c28945e0$db5de146_at_ATARIENGINE>

Doug, List,

Here is the another presentation article on the
age and number of asteroid families by David
Nesvorn? and William Bottke of SwRI:
http://www.on.br/acm2005/presentation/R9.2.pdf
Very colorful presentation, despite the fact that
the document code contains the meta-title:
"Design of a Locomotive Engine for Dalian
Locomotive & Rolling Stock Works."

Now, I'm trying to figure out why Salvador Dali
would want SwRI to design a locomotive engine
for him, and just what a Dalian Locomotive would
look like...


Sterling K. Webb
----------------------------------------------------------------
----- Original Message -----
From: <mexicodoug at aim.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, July 10, 2008 5:25 PM
Subject: Re: [meteorite-list] Pairing ?-Type Asteroids to OC's
(fromArkansas)


Hi Listees:

There may be a little more going on here than this quickly published
note with such a glorious title "Discovery of the Source of the Most
Common Meteorites". It seemed a little odd and quickly put together.
Probably is some good work, but ... I see next week at the Asteroids,
Comets and Meteors Meeting,

http://acm2008.jhuapl.edu/

is the following paper:

PHYSICAL CHARACTERIZATION OF VERY YOUNG ASTEROID FAMILIES. P.
Vernazza1, R. P.
Binzel2, A. Rossi3, M. Birlan4, S. Fornasier5, M. Fulchignoni5, S.
Renner6.

http://www.lpi.usra.edu/meetings/acm2008/pdf/8044.pdf

In which the Datura and other families have their spectra taken and
studies.

Hmmm ... sounds like someone may be looking for some extra press a few
days before the ACM meeting. Vernazza, Binzel, et al group has done
the spectra up to 2.5 microns and looks like a much more comprehensive
work.

Also in my original comments, I mentioned S-Type Asteroids. I take
that back until it can be confirmed - from the press release they may
be Q-Type a stony sub-group (with metal), and uncommon subcategory.
Time will shortly expose more of this if it hasn't already.

Best wishes,
Doug





I wrote:

http://www.sciencedaily.com/releases/2008/07/080710103903.htm

The press release was confusing to me at first, highlighting the
Fayetteville H4 (fall, Arkansas) meteorite. Perhaps they did because of
being fresh and closer to the surface (?) in the parent body model. Not
sure why the 1270 Datura family, etc., would be expected to be from the
relatively rarer surface of the original parent body vs more common
heat altered interior).

In any caseit seems they are NOT claiming that (1270) Datura is the
parent body to any of our meteorites (how could it be - don't virtually
all ordinary chondrites have CRE's of floating around as meteoroids
well over 1 million years?)

However, it seems they are pointint out that because it is an S-type
asteroid that has apparently suffered a collision only 450,000 years
ago(which was shown by other researcher a studying the probabilities of
members' orbits couple of years ago), it gives an opportunity to study
fresher material of this most common high silicate asteroid type by
telescopic spectroscopy, and they had an opportunity to take the
spectra. I guess they only look at the 0.5 and 1 um peak because it is
more sensitive to space weathering (?), but this isn't too clear
either. (the authors didn't extend it to the typical 2.5 microns where
some good stuff is visible - at least not in figure in the press
release).

In any case, their proposed contribution seems that they measured
spectra of theyoung Datura family and compared it to ordinary chondrite
spectra and got a better match than ever before helping to solve the
conjecture that the common asteroid class (second only to supposed
carbonaceous chondrites typed asteroids) should be paired to common
meteorites. Hopefully they make a case for a trend in asteroid
reflectance spectra vs. age, vs. a one hit wonder, but there still seem
to be more complexities to be ironed out regarding what meteorite is
appropriate to compare to what asteroid in the clan, IMO. Maybe
Fayetteville was just selected because it is what they had access to...
Article sounds like it will be a good one. Comments?

Best wishes, Doug

PS Interestingly, Wikipedia (at this moment - no doubt it will be fixed
by someone reading this) says the Datura cluster formed 450 MILLION
years ago and a probable source of zodiacal dust.... Maybe Wikipedia
can't be trusted yet again, once the dust has settled :)


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Received on Thu 10 Jul 2008 08:12:08 PM PDT