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S. D. Rodgers, S. B. Charnley (NASA Ames Research Center)
An important issue for the ISM-comet connection is to determine under what conditions largely unmodified interstellar matter could first arrive in the protosolar nebula. The results of recent chemical collapse calculations will be presented. These calculations indicate that, soon after the collapse has started in Shu's dynamics, infall time-scales become shorter than most chemical time-scales. This results in material from the cool envelope collapsing onto the central protostar without significant chemical alteration. New detailed calculations will be presented of the chemistry that occurs in a rotating collapse. This allows the composition of accreted interstellar material to be studied as a function of entry position on the nebular disk. In this case, the effects of UV photolysis from the disk surface and the accretion shock are also considered. The preshock and postshock chemistry of volatile material is then followed as it is heated and allowed to cool and recondense onto dust grains. This is the first study to compute in detail how ISM gas and ices are processed as they collapse down onto the disk and through the accretion shock, and to quantify its relationship to the volatile inventory of comets.
This work was supported by NASA's Origins of Solar Systems, Long-Term Space Astrophysics, and Planetary Atmospheres Programs.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.