[meteorite-list] A Look Into Vesta's Interior

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 7 Jan 2011 13:07:15 -0800 (PST)
Message-ID: <201101072107.p07L7FUO011653_at_zagami.jpl.nasa.gov>

6 January 2011

Media Contact:
Dr. Birgit Krummheuer
+49 5556 979-462, cell: +49 173 395-8625
krummheuer at mps.mpg.de

Science Contact:
Dr. Andreas Nathues
+49 5556 979-433
nathues at mps.mpg.de

Text & Images:
http://www.mpg.de/english/portal/index.html

A LOOK INTO VESTA'S INTERIOR

--
Scientists from the Max Planck Institute for Solar System Research
discover a cosmic chunk in space that originated from deep inside the
third-largest asteroid.
--
Researchers from the University of North Dakota and from the Max
Planck Institute for Solar System Research in Germany have discovered
a new kind of asteroid using NASA's Infrared Telescope Facility on
Mauna Kea, Hawaii. The mineralogical composition of 1999 TA10 suggests
that unlike many other asteroids it did not originate from the outer
rocky crust of its parent asteroid Vesta, but from deeper layers.
Until now, no asteroid with this composition was known. With the help
of this new discovery it is now possible to determine the thickness of
Vesta's crust and study its internal structure. This summer Vesta will
be the first destination of NASA's mission DAWN. In addition, the body
with a diameter of approximately 525 kilometers is believed to be the
only remaining protoplanet from the early phase of our solar system.
The asteroid Vesta is unique: Unlike all other minor planets that
orbit the Sun within the main belt between the orbits of Mars and
Jupiter, Vesta has a differentiated inner structure: A crust of cooled
lava covers a rocky mantle and a core made of iron and nickel -- quite
similar to the terrestrial planets Mercury, Venus, Earth, and Mars.
Scientists therefore believe this onion-like built asteroid to be a
protoplanet, a relict from an early phase of planet formation more
than four and half billion years ago. All other protoplanets either
accumulated to form planets or broke apart due to violent collisions.
Vesta seems to have witnessed a huge impact, as can be seen from a
large crater on its southern hemisphere. The so-called Vestoids -- a
group of asteroids with a composition similar to that of Vesta -- were
most probably created due to this impact. Since some meteorites that
were found on Earth consist of similar rock as does Vesta's mantle,
scientists believe that this collision also hurled material from deep
within the asteroid into space. But till now there was no source in
the form of near-Earth Vestoids for these meteorites with Vesta's
mantle composition.
Near-Earth asteroid 1999 AT10 fills this gap. Using the NASA IRTF, the
scientists were now able to analyze the infrared radiation that 1999
AT10 reflected into space and compared its characteristic spectral
fingerprints with those of Vesta. Apart from calcium-rich
wollastonite, the measurements mainly point to iron-rich ferrosillite.
''These materials can be found in Vesta's mantle and crust," explains
Dr. Andreas Nathues from MPS. ''However, the ratio is decisive." In
the case of 1999 AT10 the concentration of iron is clearly lower than
in any known Vestoids. "This all points to 1999 TA10 having originated
from the interior of Vesta," says Nathues.
The newly discovered body now allows important inferences about its
parent asteroid. Models of Vesta's surface based on observations made
by the Hubble Space Telescope render a depth of the South Pole crater
of ~25 kilometers at the most. The new discovery now suggests that
this would be the maximum possible thickness of the outer crust.
In order to reconstruct the processes that led to the formation of
planets more than 4.5 billion years ago, scientists need to determine
the thickness of Vesta's layers as precisely as possible. Only this
makes it possible to calculate from which material mixture the
protoplanet was made -- and thus which materials were present when the
solar system formed and in what ratio.
The scientists now hope for more information about Vesta's structure
from NASA's mission Dawn. In August 2011 the probe, which has been
traveling through space since 2007, will rendezvous with Vesta and
orbit the asteroid for a year. On board Dawn there are two cameras
that were designed and built under the leadership of the Max Planck
Institute for Solar System Research in cooperation with the German
Space Agency (DLR) and the Institut fuer Datentechnik und
Kommunikationsnetze of the Technical University of Braunschweig.
Original publication: Vishnu Reddy, Andreas Nathues, Michael J.
Gaffey: "First fragment of Asteroid 4 Vesta's mantle detected,"
Icarus, in press, published online on December 5, 2010.

Received on Fri 07 Jan 2011 04:07:15 PM PST