Synthesis in Solar Nebulae

In our own solar system, nearly all volatiles complementary to the inner planets (3 X 10 Mg) were so lost. Earth and Venus contain only about 10 their complement of C, and even lesser amounts of H O, N, and noble gases. Since the retained C appears to show the imprint of the Fischer-Tropsch reaction, it seems likely that the lost C, too, had been involved in this process. 

There exists some circumstantial evidence linking interstellar molecules to protostars. The more complex interstellar molecules tend to occur only in regions of very high density ( 10 H /cm ), e.g. the infrared nebula in Orion. Star formation proceeds at a rapid rate in such clouds, and thus solar nebulae may have formed and dissipated. The lifetime of our solar nebula seems to have been rather short 10 to 10 yr, or 1-2 orders of magnitude less than the age of a typical cloud, e.g. the Orion Nebula, or lifetimes of molecules against UV photolysis (Gammon, 1978). 

If these values are typical, even a young cloud should contain appreciable amounts of carbon cycled through solar nebulae. Abundances of interstellar molecules relative to CO are at least 2 orders of magnitude lower than yields in FTT syntheses (Gammon, 1978). It appears that only a moderate degree of star formation and CO processing would suffice to account for the interstellar molecules. 

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