THE DUST PROPERTIES OF A SHORT-PERIOD COMET - COMET-P BORRELLY

We have calculated the thermal emission spectrum of the dust of comet P/Borrelly (19941), a short-period comet (Jupiter family), from 3 mu m to 14 mu m as well as the 10 mu m silicate feature in terms of the co met dust model as porous aggregates of interstellar grains. Compared t o comet P/Halley dust, the dust grains of P/Borrelly appear to be rela tively more processed (more carbonized), less fluffy, and richer in sm aller particles. The fluffy aggregate model of silicate core-amorphous carbon mantle grains with a porosity P = 0.85 can match the observati onal data. To generalize the dust properties of short-period comets, s ystematic observations of the thermal emission spectra and the silicat e features for a large set of samples are needed.