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RE: Primitive and Evolved Meteorites
Dear Frank,
Well stated.
Thanks,
Larry
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From: Frank Stroik[SMTP:autumnbreeze71@hotmail.com]
Sent: Saturday, October 24, 1998 8:30 PM
To: meteorite-list@meteoritecentral.com
Subject: Primitive and Evolved Meteorites
The concept of primitive and evolved products of nature have been the
crux of most scientific research. The primitivness of any object is
necessary to determine. With out that distinction, our knowledge of
natural systems would not be built on any firm foundations.
Meteorites have long been recognized as being remnants of the early
solar system. With out being overly redundant here, meteorites tell us
a story of where we came from and our relation to the universe. But what
is a primitive meteorite in relation to other meteorites?
Chondrites are the most primitive meteorites. This may be common
knowledge to some, less evident to others. Chondrites are considered
primitive by virtue of their lack of secondary heating. They have
remained in stasis since the cooling of the nebula, held in their
sarcophogus of sorts, known as asteroids. Unchanged from the moment they
cooled to today, they record events which occurred before, during, and
immediately after nebular accretion, which provides us with a series
of(hopefully)unaltered epitaphs to events long since forgotten on the
entity we are all to familiar, time.
Achondrites are meteorites that have been altered in some way. A better
way to state this is, achondrites are a result of secondary processes on
asteroidal bodies, or any planetary body that has differentiated. This
means that, chondritic material(presumably, as this is considered to be
primitive) has undergone heating due to accumulation of material through
gravitational attractions, pressure, and most importantly, radioactive
decay of unstable elements. These meteorites are our window into how
planets are composed, and how they may have undergone the process of
creating a core, mantle, and crust. Lest I forget to say, iron
meteorites, and pallasites( but not in all cases) also allow for
inspection of the internal anatomy of a planet.
There is one distinction that needs to be made with in the achondrite.
Relative to the members in the group, some are more primitive than
others. In some cases an asteroidal body failed to fully differentiate,
and what ever heating was occurring did not obliterate the chondritic
signature of the asteroid. meteorites that exhibit these traits can be
considered primitive achondrites. Acapulcoites, and lodrandites would be
examples of primitive achondrites.
I wanted merely to point out this to those on this list who have not
been exposed to the above concept. This view of meteorites, admittedly
simplified, can bring an individual closer to grasping the true meaning
of meteoritics.
Frank
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