<![CDATA[
<BODY bgcolor="#FFFFFF">
<CENTER><H1>Presolar Grains in Meteorites</H1></CENTER>
Presolar grains are tiny dust particles that are literally bits of stars we can
study in the laboratory. They condensed from the gas phase in the cooling
outflows of stars (such as red giants and supernova explosions) billions of
years ago, before the formation of our solar system. These dust grains became
swept up in the interstellar medium and eventually made their way into the
cloud of gas and dust ("molecular cloud") from which the Sun, Earth and planets
formed 4.6 billion years ago. Most of the pre-existing dust in the Sun's parent
molecular cloud (at least the dust that was in what became the inner solar
system where the Earth now sits) was vaporized as the forming solar system
heated up. However, a small fraction of the dust survived solar system
formation, protected inside asteroids. Occasionally, pieces of these asteroids
fall to the Earth and are called "primitive meteorites." By breaking up the
meteorites and dissolving them away in strong acids, we have been able to
isolate some of the presolar stardust. The entire process is illustrated by the cartoon below:
<BR>
<CENTER><IMG SRC="psg.gif" ALT="Presolar Grain Cartoon" WIDTH="404" HEIGHT="522"></CENTER>
<P>
Because the atoms in the grains are the original atoms from the parent stars,
by studying this dust we can probe processes that occur inside stars and in
the interstellar medium. Thus, the discovery of presolar grains has essentially
opened up a new branch of astronomy, where laboratory microanalytical
instrumentation takes the place of telescopes. <P>
Click on the following links for more information about presolar grains:
<H3> <A HREF="psg2.html">How do we identify presolar grains?</A></H3>
<H3> <A HREF="psgtypes.html">What types of presolar grains are known?</A></H3>
<H3> <A HREF="psgmethods.html"> How do we study presolar grains?</A></H3>
<H3> <A HREF="psginfo.html"> What can we learn from presolar grains?</A></H3>
<H3> Other presolar grain links: </H3>
<UL>
<LI><A HREF="http://www.soest.hawaii.edu/PSRdiscoveries/July97/Stardust.html">
D. D> Clayton's article from <I>Planetary Science Research Discoveries</I></A>
<LI><A HREF="http://www.maths.monash.edu.au/~marial/sicgrains.html">
Article from <I>Maria Lugaro's presolar SiC page</I></A>
</UL>
<HR>
<H5>© Larry R. Nittler Last modified February 3, 1999</H5>
<BR><BR><BR>
</body>
</html>
]]>