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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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