[meteorite-list] Vesta, for sure?

From: MEM <mstreman53_at_meteoritecentral.com>
Date: Thu, 7 Apr 2011 18:54:55 -0700 (PDT)
Message-ID: <486651.78028.qm_at_web161908.mail.bf1.yahoo.com>

Very good question Richard, which doesn't get explored often enough.

Harry Hap McSween wrote a book titled "Meteorites and their Parent Bodies" where
extensive spectral measurements were taken from meteorites and from asteroids
and an extensive list of possible and probable asteroidal connections were given
for many of the meteorites in our world collection. (BTW He also wrote much
about transport theory to Earth) Several other scientists have followed with
more research in the past decade and there is a conscientious that HEDs do come
from Vesta or its fragmented daughters.

My personal opinion is that the Vesta-HED connection is perhaps taken too
literally at times, but going back far enough-- all HEDs do come from Vesta--
before it lost a part of its mass about 1 billion years ago in a big wack. The
mineralogy we see today was from an intact planetary/differentiated body One
would think for meteorites which are regolyths-- ( e.g. Howardites) we would
have sampled many more asteroid bodies ( Ceres etc) and, it is very likely that
we have sampled (via meteorite) some parent bodies which no longer exist:
collision accretion, ejection etc and would not have any spectral measurements
to compare them to.
 
Here is one of many abstracts regarding 4 Vesta which discuss the probability
HEDs are from Vesta or the 20 small bodies with similar spectra. Chips off of
Asteroid 4 Vesta: Evidence for the Parent Body of Basaltic Achondrite Meteorite
<http://www.sciencemag.org/content/260/5105/186.abstract>
"For more than two decades, asteroid 4 Vesta has been debated as the source for
the eucrite, diogenite, and howardite classes of
basaltic achondrite meteorites. Its basaltic achondrite spectral properties are
unlike those of other large main-belt asteroids.
Telescopic measurements have revealed 20 small (diameters ? 10 kilometers)
main-belt asteroids that have distinctive optical
reflectance spectral features similar to those of Vesta and eucrite and
diogenite meteorites. Twelve have orbits that are
similar to Vesta's and were previously predicted to be dynamically associated
with Vesta. Eight bridge the orbital space between
Vesta and the 3:1 resonance, a proposed source region for meteorites. These
asteroids are most probably multikilometer-sized
fragments excavated from Vesta through one or more impacts. The sizes, ejection
velocities of 500 meters per second, and proximity of
these fragments to the 3:1 resonance establish Vesta as a dynamically viable
source for eucrite, diogenite, and howardite
meteorites.

Perhaps it is simply a matter of the postman's route and Vesta et.al. is the
only candidate with the orbital dynamics to make deliveries to our sector of the
solar system.

To answer your question specifically-- the answer is Vesta is the only
source--unless hypothedical twin was one of those early solar system bodies no
longer with us. The size of Vesta is necessary to produce the variety of
mineralogy we see in the HEDs. It had to be large enough to generate
basalt/differentiation and also possess enough gravity to sort the mineralogy
into layers akin to crust , mantle(s), and (probably) core AND it would also
have to have a huge crater which excavated it down to the deep /lower mantle.
So far as I know there is nothing else that can fill the bill. Safe to say ,all
the larger asteroids in the inner solar system have been identified.

Elton


----- Original Message ----
> From: Richard Montgomery <rickmont at earthlink.net>
> To: lebofsky at lpl.arizona.edu; Michael Gilmer <meteoritemike at gmail.com>
> Cc: meteorite-list at meteoritecentral.com; Shawn Alan <photophlow at yahoo.com>
> Sent: Thu, April 7, 2011 9:09:46 PM
> Subject: [meteorite-list] Vesta, for sure?
>
> Hi List....this is a completely neophyte question, so please accept my
> ignorance in things astronomic....and allow me to ask you experts:
>
> I have always wondered why Vesta is the parent-body-de-jur for our HEDs,
> when so many unfound asteroids are no doubt cruizing around out there.
> Hence my question: Have any asteroids been "paired" yet, and if not, why
> Vesta alone gets the credit; as well, couldn't our HED cousins be cousins
> from a yet-to-be-discovered asteroid pairing?
>
> As you true scientists of course recognize, I'm completely green in this
> area. I guess it's my timeless query (X-factors-we-need-to consider) that
> has me bewildered. Has Vesta somehow distinguished itself as the
> one-and-only parent-body?
>
> I do understand reflection technology has identified our HED meteorites to
> be from Vesta, but why not an undiscovered twin? Or many multiple twins?
>
> With deference to those of you already in the know,
>
> Richard Montgomery
Received on Thu 07 Apr 2011 09:54:55 PM PDT