[meteorite-list] Stardust Sample Return Press Kit

From: Peter Marmet <p.marmet_at_meteoritecentral.com>
Date: Fri Jan 20 14:33:08 2006
Message-ID: <FE6C5973-1E08-4102-83ED-8BBEE16FBADC_at_mysunrise.ch>

Hello All,

this part of the 40-page Stardust Sample Return Press Kit
( http://www.jpl.nasa.gov/news/press_kits/stardust-return.pdf )
might be of special interest for us:

"Science Objectives
The purpose of the Stardust mission is to expand the knowledge of
comets by flying a
spacecraft through the coma of Comet Wild 2, collecting samples from
the comet, and
returning those samples to Earth for laboratory analysis. Additional
objectives include
collecting and returning interstellar particles, imaging the comet
nucleus, and in situ
analysis of comet particles.
The mission?s primary goal was to collect samples of a comet?s
coma and return them
to Earth. In addition, interstellar dust samples were also gathered
en route to the
comet.
Laboratory investigation of the returned samples using instruments
such as electron
microscopes, ion microprobes, atomic force microscopes, synchrotron
microprobes
and laser probe mass spectrometers will allow examination of cometary
matter and
interstellar grains at the highest possible level of detail. Advances
in microanalytical
instruments provide unprecedented capabilities for analysis on the
micron and submi-
cron level, even to the atomic scale for imaging.
These instruments will provide direct information on the nature of
the actual particles
that initiated the formation of the Sun and planets 4.6 billion years
ago. They will pro-
vide a highly intimate view of both pre-solar dust and solar nebula
materials that exist-
ed at the very edge of the solar system at the time of its formation.
Such materials will
be compared with primitive meteorites and interplanetary dust samples
to understand
how solids that built the solar system were formed. One of the most
important aspects
of the mission is that it will provide materials from the edge of the
solar system to be
compared with primitive materials that formed in the inner solar
system and are pre-
served in meteorites from the asteroid belt. The ability to compare
the ancient aster-
oidal materials that formed just beyond the orbit of Mars with the
cometary solids that
accreted near Pluto will provide fundamental insight into the
materials, processes and
environments that existed during the origin and early evolution of
the solar system.
The Stardust mission is also expected to return interstellar grains
formed around other
stars. These will include both grains that assimilated into comets
during their formation
as well as dust from the galaxy that is currently passing the Sun.
Interstellar grains are
generally studied by astronomical techniques capable only of
revealing general physi-
cal properties such as size and shape. The recent discovery and study
of rare interstel-
lar grains preserved in meteorites and interplanetary dust has shown
that they contain
excellent records about the nature of their parent stars, including
details of the complex
nuclear reactions that occur within the stars. Most of the
interstellar grains that have
been identified in meteorites are grains that formed in gas flows
from carbon-rich stars
such as red giants and what are called AGB stars. It is expected
Stardust will collect
grains produced by star types that are major sources of interstellar
dust.
28 Comets are now known to contain large quantities of volatiles,
including organic com-
pounds, as well as a rich variety of microparticles of various types
(pure organic par-
ticles, silicates, sulfides and mixed particles) with sizes ranging
as low as submicron
diameters. Organic particulates actually consist of several sub-
populations, which can
be described based on the elements that they are made up of. These
include particles
containing:
      ? Hydrogen, carbon and nitrogen
      ? Hydrogen, carbon and oxygen
      ? Hydrogen and carbon
      ? Hydrogen, carbon, nitrogen and oxygen, with and without
magnesium
     (termed ?CHON? particles)
Since comets are rich in water and other volatiles, it has been
postulated that they
carried to Earth elements critical to the origin of life. The study
of cometary material is
essential for understanding the formation of the solar system and the
role of organic
matter from interstellar sources. Astronomers have identified some 60
compounds in
interstellar clouds, three-fourths of which are organic.
(?Organic? means that the com-
pound is carbon-based, but not necessarily biological in origin.)
There is compelling
evidence that four of the first five interstellar molecules detected
by astronomers are
present in comets, and the fifth might be also. The volatiles and
silicates that appear
  to be in comets also are found in interstellar
clouds. How the elements necessary for life entered the solar system,
were trans-
formed by solar system processes, were distributed among planetary
bodies, and what
molecular and mineral forms they took during this history are
questions of major impor-
tance for astrobiology. Comparing the composition of the volatiles
from cometary mate-
rial with those found in carbonaceous meteorites and interplanetary
dust will provide a
basis to determine which particles, if any, have common source regions.
Finally, the discovery of an iridium-rich layer in rocks at Earth?s
Cretaceous-Tertiary
geologic boundary marking the end of the age of the dinosaurs about
65 million years
ago has, along with other evidence, shown that that impact of an
asteroid-sized body
with Earth was probably responsible for the demise of the giant
creatures and the
death of many of Earth?s creatures living at the time. Although the
chance of finding a
unique elemental signature in captured cometary coma material might
be slight, such a
discovery would be enormously valuable in distinguishing whether it
was an asteroid or
a comet that made the impact."

Peter
Received on Fri 20 Jan 2006 02:33:42 PM PST