The collected dust samples can play a unique and important role in the future 

 study of primitive solar system materials. Probably the most significant aspect 

 of this effort would be the collection of materials from a variety of specific 

 comets and the capture of interstellar dust in transit through the solar system. 

 The laboratory analysis of both cometary and interstellar particles would 

 provide the first direct information on cometary and interstellar grains. It is par- 

 ticularly intriguing that it might be possible to examine the abundances and pos- 

 sible forms of the biogenic elements and compounds in materials that existed 

 before and just after the formation of the solar system. In addition, elements 

 heavier than oxygen in the interstellar medium occur primarily in the form of 

 interstellar grains, and contemporary grains are probably very similar to those 

 that contained most of the condensable elements in the solar nebula during its 

 collapse stage. Dust particles in comets are believed to be well preserved grains 

 that may have been typical of the materials that existed at the outer fringes of 

 the solar nebula. The collection of dust may then provide direct information on 

 the composition of some of the original material from which the solar system 

 formed, and the composition of collected grains can then provide useful data for 

 modeling solar nebula processes and environments. 



Among the important scientific questions pertinent to exobiology that 

 could be addressed by detailed laboratory studies of cosmic dust are the 

 following: 



1. What similarities exist in the relative abundances of the biogenic elements 

 and compounds in interstellar, cometary, and meteoritic samples? Can these 

 similarities be traced to common sources and histories in the interstellar 

 medium, the solar nebula, or the parent objects? 



2. What connections exist between the gas-phase chemistry observed in inter- 

 stellar clouds and the organic chemistry of cometary and interstellar dust? 



3. What evidence of grain-mediated organic chemistry in interstellar clouds 

 can be found in interstellar or cometary dust? 



4. What role has water played in the chemistry and mineralogy of interstellar 

 dust particles? Do they contain hydrous silicates? 



5. What evidence is there for the influence of liquid water on the chemistry 

 and mineralogy of cometary samples? 



6. What materials in interstellar and cometary dust can be attributed to dis- 

 crete nucleosynthetic sources? Are they the same as can be inferred from some 

 components of meteorites? 



7. What correlations can be drawn between astronomical observations of 

 interstellar clouds and the structure and compositions of collected cometary and 

 interstellar dust? 



8. Did radiation-induced polymerization of organics occur in presolar or early 

 solar system environments? 



A special attraction of the dust-collection approach is the abundance of dust 

 particles, providing the capability to collect samples from a variety of comets 

 and thus address the possible diversity among comets. The properties of come- 



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