[meteorite-list] Vesta & HED's

From: Benjamin P. Sun <bpsun2009_at_meteoritecentral.com>
Date: Fri, 11 May 2012 19:32:20 -0400
Message-ID: <CAE1PX86PWO0FgPTFcduJv_9OCcRLHjeaU8NtRK2FUhe0=ieXqg_at_mail.gmail.com>

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,?
Received on Fri 11 May 2012 07:32:20 PM PDT