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G. Hassel (Rensselaer Polytechnic Institute)
The water ice mantles on interstellar grains trap volatile molecules, such as CO and CH3OH, with an efficiency that depends on the amorphous or crystalline structure of the ice. The ice structure therefore affects the composition of comets formed from the icy grains. I present the results of processing of mantled grains by shock waves in protoplanetary disks. The grains suffer a sudden increase in temperature which can evaporate the mantles. This is followed by an extended cooling time during which the mantles recondense on timescales comparable to the crystallization timescale for hydrodynamic parameters consistent with the Jupiter-Saturn region of the solar nebula. The crystallization of ice and the exclusion of volatiles from the matrix may explain the volatile-depleted composition observed recently in Comet C/1999 S4 (LINEAR), an Oort-cloud comet originating from the Jupiter-Saturn region. This work is supported by the New York Center for Studies on the Origins of Life (NSCORT) at RPI, under NASA Grant NAG5-7598.
The author(s) of this abstract have provided an email address for comments about the abstract: hasseg@rpi.edu
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.