[meteorite-list] Vesta & HED's

From: barrat at univ-brest.fr <barrat_at_meteoritecentral.com>
Date: Sun, 13 May 2012 17:44:53 +0200
Message-ID: <1336923893.4fafd6f5cac84_at_webmail-sdt.univ-brest.fr>

It is true that a few eucritic rocks are ungrouped. Ibitira is one example. It
is not surprising that basalts were erupted on a few distinct small bodies, 4.5
Ga ago...

But all the diogenites display the same D17O as the (regular) eucrites, and no
ungrouped diogenite has been identified at present. The fact that Vesta exhibits
diogenites AND eucrites is a strong argument for a link between HED and Vesta.

Jean-Alix Barrat


Selon "Benjamin P. Sun" <bpsun2009 at gmail.com>:

> Yes, but aren't the relatively few non-Vesta eucrites classified as
> ungrouped achondrites or anomalous eucrites?(if not then they should
> be)
> So I would like to think that there is already the notion that there
> may be a few rare exceptions.
>
> On 5/13/12, MstrEman <mstreman at gmail.com> wrote:
> > Keep in mind that there are now some non-Vesta originating eucrites
> > identified. So the pass state of knowledge holding that all HEDs were
> > from Vesta should be qualified with a caveat that "Most all eucrites
> > are from Vesta" or "with rare exception..." or "all most all..."
> >
> > Elton
> >
> > On 5/11/12, Benjamin P. Sun <bpsun2009 at gmail.com> wrote:
> >> This is not a surprise to me... or to most of us. But it may be "news"
> >> to some of you out there..
> >>
> >>
> >> http://www.jpl.nasa.gov/news/news.cfm?release=2012-132
> >>
> >> https://asunews.asu.edu/20120510_Vesta
> >>
> >> "Data also confirm a distinct group of meteorites found on Earth did,
> >> as theorized, originate from Vesta. The signatures of pyroxene, an
> >> iron- and magnesium-rich mineral, in those meteorites match those of
> >> rocks on Vesta's surface. These objects account for about 6 percent of
> >> all meteorites seen falling on Earth.
> >>
> >> This makes the asteroid one of the largest single sources for Earth's
> >> meteorites. The finding also marks the first time a spacecraft has
> >> been able to visit the source of samples after they were identified on
> >> Earth."
> >>
> >> ?Dawn observations enabled us to recognize that there are actually TWO
> >> large basins at the south pole, an older one named ?Veneneia? and a
> >> younger one named ?Rheasilvia?,? explains Williams.
> >>
> >> The Rheasilvia basin dominates the geology of Vesta, as the basin
> >> itself and its impact ejecta cover most of the southern hemisphere.
> >> The center of Rheasilvia has a central peak taller than Mt. Everest or
> >> Mauna Loa on Earth, similar in height to Olympus Mons on Mars. This
> >> basin appears to have excavated into the mantle of Vesta, exposing
> >> material spectrally similar to diogenite meteorites; Vesta?s crust is
> >> spectrally similar to eucrite and howardite meteorites, thus
> >> confirming that Vesta and its family of asteroids are the source of
> >> the howardite-eucrite-diogenite (HED) family of basaltic achondrite
> >> meteorites.
> >>
> >> ?For most planets and moons we see the pictures first, then have
> >> samples collected later to confirm our geologic interpretations. In
> >> the case of Vesta, thanks to the HED meteorites, we have the samples
> >> first, and must try to relate them to our emerging geologic picture of
> >> Vesta from the Dawn mission,?
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Received on Sun 13 May 2012 11:44:53 AM PDT