related objects such as D-asteroids and comets should be obtained. 



2. A comprehensive survey of the strength of the 3-jum water-of-hydration 

 feature in the spectra of dark asteroids should be carried out. 



3. The 3.3- to 3.5-/im region indicative of C-H bonds in organic matter should 

 be searched. 



4. The relationship of meteorite samples to asteroid parent bodies and to 

 contemporary asteroids (especially for the more volatile-rich types) should be 

 determined. 



5. The provenance of Earth-approaching asteroids should be determined. 

 (How can we distinguish between the asteroid-derived population and the come- 

 tary one?) 



6. What clues about the makeup of parent bodies can be inferred from 

 studies of cosmic dust collected in the Earth's upper atmosphere and from 

 meteor investigations? 



These measurements will not of themselves be sufficient to decipher the his- 

 torical connection between asteroids and comets, but they will be helpful 

 adjuncts to the necessarily limited number of flybys that are now being planned 

 by NASA, ESA, and the Soviet Union. 



Suggestions for Further Reading 



Gehrels, T.; and Matthews, M. S., eds.: Asteroids. University of Arizona 

 Press, 1979. 



3.7 The Protosolar Nebula and its Analogs 



The protosolar nebula represents a critical boundary between the local 

 chemistry and processing of the biogenic elements and compounds and the 

 rather ubiquitous organic chemistry that is observed in a large number of inter- 

 stellar and circumstellar regions. The formation of the protosolar nebula was an 

 energetic process, and the fundamental question is how the energetics affected 

 the preexisting complex chemistry. From our studies of primitive solar system 

 bodies we may be able to infer the distribution of the biogenic elements and 

 compounds early in the history of the solar nebula. It is doubtful whether we 

 will discover a timekeeper of sufficient precision to be able to distinguish 

 between the possibility that the deduced distribution of chemical complexity 

 arose ab initio from an elemental mixture within the protosolar nebula, or was 

 imposed upon it by the processing history within the cloud from which it 

 formed. For this reason it is extremely important to search for analogs of the 

 protosolar nebula evolving today within regions of active star formation. The 

 organic chemistry within and without the nebula must be compared in detail to 

 decide whether the material from whence planets might eventually form retains 



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