			15min:

ISOTOPE FRACTIONATION IN PROTOPLANETARY DISKS AND COMETS.

A. J. MARKWICK, Space Science Division, NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035, USA. ajm@ajmarkwick.com.

New models of the chemistry occurring in protoplanetary disks similar to the protosolar nebula will be described. These models determine the spatial distribution of molecules in the inner 100~AU of the disk, thereby including the 5-40~AU comet-forming region. The chemistry and abundances of isotopically fractionated species, including multiply deuterated species like D₂CO and D₂O, will be discussed in the light of future observations of comets. Any significant chemical variations between the long and short-period comet families will also be reported.