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Re: Primitive and Evolved Meteorites
Dear List and Frank;
Most things in life are better when simplified, especially when trying to
understand complicated matters. Frank, You are gifted! As I evolve into
meteoritics ever deeper, I struggle at times. Your thoughts on primitive
and evolved allow me to go to the "roots" and regrasp parts that I may not
have learned so well or needed to refresh upon. Thank You for a regrasping
handle as I plunge deeper. Well put!
Best Regards, David Freeman
Frank Stroik wrote:
> 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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