Life Sciences in the Space Program 



Carbon-containing minerals of exotic origin have also been isolated from meteor- 

 ites. On the basis of their contents of isotopically anomalous elements, silicon 

 carbide grains appear to have formed as a condensate in the outflows from carbon 

 stars; and diamond grains are thought to have been either similarly derived or 

 produced in the interstellar medium. That these grains have survived the journey 

 through solar system formation to incorporation in the parent bodies of the 

 meteorites establishes another link between astrophysical events that predated the 

 solar system and the accretion of primitive objects that must have occurred early 

 in Earth history. Additional phases linking specific stellar origins to solar system 

 material should be sought in samples of asteroidal or cometarv origin. 



Although great uncertainty continues about how and where the molecular species 

 were formed, the existence of complex mixtures of extraterrestrial amino acids, 

 hydrocarbons, carboxylic acids, and many other classes of organic compounds in 

 carbonaceous meteorites is well established. These same 4.5-billion-year-old 

 meteorites are made up of clays, carbonates, sulfates, and other hydrous materials 

 that were produced by the actions of liquid water on preexisting assemblages of 

 anhydrous minerals, thus recording the earliest history of weathering reactions in 

 the solar system. Together, the organic matter and minerals of carbonaceous 

 meteorites suggest that on certain asteroidal bodies, environments existed of the 

 type that may have occurred on the primitive Earth during prebiotic evolution. 

 How widespread these environments were among the asteroids and what factors 

 were responsible for their occurrence are questions of great interest that can be 

 addressed best by exploration of these small bodies by spacecraft. 



Findings for Cosmic Evolution of Biogenic Compounds 



• Data from astronomical observations of organic matter and water in astro- 

 physical environments and from detailed analyses of samples derived from 

 asteroids and comets are critical to forging the links in the chain of cosmic 

 evolution connecting the origins of biogenic compounds in stars and interstellar 

 clouds to their occurrences in the building blocks of planets. 



• Simulations of processes occurring in astrophysical environments conducted 

 both on the ground and under microgravity conditions on the Space Station 

 are needed to elucidate the mechanisms of synthesis and destruction and the 

 limitations on the development of complexity in the organic matter of inter- 

 stellar clouds, protosolar nebula, comets, and asteroids. 



Recommendations 



• NASA should implement its plans for the following missions and facilities 

 so as to provide new opportunities for direct study of the organic chemistry 

 of comets and asteroids, for infrared observations of organic matter in the 

 cosmos, and for the conduct of astrophysical experiments in space: 



— Comet Rendezvous Asteroid Flyby Mission 



Rosetta Comet Nucleus Sample Return Mission 



Space Infra Red Telescope Facility (SI RTF) 



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