54 



Solvent-extractable organic matter in CII meteorites (i.e., 

 the Murchison meteorite) is distributed among a variety of com- 

 pound classes: alcohols, aldehydes, amines, amino acids, carboxylic 

 acids, hydrocarbons (aromatic and aliphatic), ketones, purines, 

 pyrimidines, etc. Carbon species found in the Murchison meteorite 

 include the following: 



1 . A carbonaceous phase not affected by solvent 



2. Carbonate 



3. Hydrocarbons (aliphatic and aromatic) 



4. Carboxylic acids 



5. Amino acids 



6. Ketones and aldehydes 



7. Urea and amides 



8. Alcohols 



9. Amines 



10. Nitrogen-containing heterocycles 



More detailed information on these chemical compounds will be pre- 

 sented in the next chapter. At most, these compounds constitute 

 30% of the total carbon, and less than 0.5% of the total mass of the 

 meteorite samples in which they are found. Some of these com- 

 pounds have been sought and found in other carbonaceous meteo- 

 rites, but only the Murchison meteorite has been studied in great 

 detail because of the availability of samples and its relative freedom 

 from terrestrial contamination. 



The variety of types of compounds found and their molecular 

 structures point to origins in nonbiological processes. However, the 

 nature of the processes and where they occurred remain to be clearly 

 established. Electric discharges and other gas-phase processes and gas- 

 solid reactions requiring catalytic grain surfaces could have taken 

 place both in the nebula and on parent bodies. An interstellar origin 

 for some of these compounds should also be considered. 



Recent isotopic studies of organic matter in carbonaceous 

 meteorites have revealed that large differences exist in the 

 deuterium/hydrogen, carbon- 13/carbon- 12, and nitrogen-15/ 

 nitrogen-14 ratios associated with different organic components 

 within the same meteorite. Although the full implications of these 

 findings remain to be elucidated, the magnitudes of the isotopic 



