[meteorite-list] Vesta, for sure?

[MEM]

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