[meteorite-list] Never underestimate or dismiss Spectroscopy

From: Benjamin P. Sun <bpsun2009_at_meteoritecentral.com>
Date: Sat, 12 May 2012 11:07:37 -0400
Message-ID: <CAE1PX86w-RW2qOC2ZwfKQcWXRBsRita2XcewrU4ny-i=C346qQ_at_mail.gmail.com>

Protoplanet in color
May 2012


Recent results of the Dawn mission show that the asteroid Vesta is the
only known remnant from a big early phase of planet formation.

The cameras help NASA's Dawn space probe the mysteries of the asteroid
Vesta. The color images now confirm: Vesta is a relic from the early
solar system. Because of the surprisingly heterogeneous celestial body
is more like a planet than a primitive asteroid. In addition, recent
studies show that most of HED meteorites - a special group of
meteorites - are in fact, fragments of Vesta.

Since the summer of 2011, two cameras on board the spacecraft orbiting
the asteroid Vesta, Dawn - one that is currently in operation, and a
backup camera. With this camera system, the scientists, led by the
Max-Planck-Institute for Solar System Research (MPS) designed and
built, supplied by NASA planetary scientist with the probe image data
of the previously almost unexplored asteroid. The "framing cameras"
are equipped with seven different color filters and a clear filter.
You can do much more than a "normal" camera: The color filters can
decipher the exact composition of the reflected light from Vesta.
Thus, the scientists map the surface of their research subject and
draw conclusions about its mineralogical composition.

After ten months of meticulous observations of the planet, scientists
are now certain that the celestial body is unlike any previously
studied asteroid. Vesta is a kind of living fossil prehistory of
planet formation. Even the diameter stands, with 525 kilometers, as
the third largest asteroid of all. "Vesta is a proto-planet," said the
lead investigator of the camera crews, Nathues Andreas, "and is
therefore in a primitive stage of development, from which have been
once the giant planets such as Earth and Mars formed. Vesta is
probably the last specimen of this species of celestial bodies. The
measurements of the other instruments on-board support this
interpretation."

So far, Vesta was photographed only from a great distance. The
observations with the circular orbit in the framing cameras now
provided are surprising: "No one had expected the large differences in
brightness of Vestas surface," explains researcher Lucille Le Corre
from MPS. "While the brightest spots on Vesta reflect sunlight as much
as some snow, the reflectivity of the dark areas is comparable to that
of coal. The asteroid shows such a brightness variation not yet
observed by a spacecraft."

Striking is the sharp difference between the northern and southern
hemispheres of the asteroid. This is also reflected in the different
colors, which have been identified by scientists at Vestas surface. In
particular, the color differences are interesting, reflecting the
presence of rocks, the planetary scientists know from studying a
particular group of meteorites, the "HED meteorites." The acronym
stands for Howardites, Diogenites an Eucrites. Even before the
mission, these celestial stones were suspected to be fragments of
Vesta, as the reflectance spectra of HED meteorites are very similar
to those of Vesta. An important goal of the Dawn spacecraft was
therefore to find further evidence of the link between Vesta and the
HED meteorites.

Eucrites are rigid crustal rocks similar to terrestrial basalt, but
much brighter, however, diogenites come from greater depths of the
crust. The howardites are mixtures of the two rock types, that come
from impacts. The pictures show our framing cameras now distinct color
differences between regions with rock, which comes from the interior
of Vesta, and those that are more influenced by crustal rocks," says
Andreas Nathues. "We were able to clarify with the observations of
other instruments, the Dawn of origin of the HED meteorites. It is
actually Vesta."

The new data have also revealed that Vesta's color and topography are
not generally correlated . This is the case with the Moon: Dark areas
correspond to valleys on the moon, bright areas indicate the range of
hills. But in this context, not to Vesta.

The Dawn spacecraft is at Vesta until the end of August 2012, and then
on to her second goal of the dwarf planet Ceres. The mission was
launched in September 2007 in the direction of Vesta and arrived July
2011 into an orbit around the asteroid. The dwarf planet Ceres is the
largest asteroid between Mars and Jupiter.


TD/MPG / PH TD / MPG / PH



More info
Original work
CT Russell et al.: Dawn at Vesta: Testing the Protoplanetary Paradigm,
Science 336, 6082, 684-686 (2012), DOI: 10.1126/science.1219381





"2 Pallas has not been visited by spacecraft, but if the Dawn probe is
successful in studying 4 Vesta and 1 Ceres, and if sufficient fuel
remains, it is possible its mission may be extended to include a flyby
of Pallas as Pallas crosses the ecliptic in 2018. However, due to the
high orbital inclination of Pallas, it will not be possible for Dawn
to enter orbit."



yay Pallas 2018! woot! ;D
Received on Sat 12 May 2012 11:07:37 AM PDT