(Proposal ID) S10B-116

(PI) Watanabe, Junichi

(Proposal Title)
Search for Evolution of Dust Particles in Periodic Comets

(Abstract)
Silicate feature is often observed in comets as a 10- mu m resonant feature, 
and its appearance depends on the size and porosity of dust particles in the 
coma of the comets.Therefore, this feature is thought to be useful to know how 
the small size grains evolved in the surface of the nuclei. Until now, many 
samples of this 10-mu m feature are accumulated by our group, and it has been 
realized that the silicate feature tends to be weak for so-called old short-
period comets. For example, comet 2P/Encke has no silicate feature in the 10 
mu m, although the silicate does exist in the particles of this comet; Taurid 
meteor showers, of which meteoroids are actually larger size and more compact 
than other meteor showers. This may indicate that the evolution of dust 
particles occurs in the surface, and that the particles tend to form larger 
aggregates with time at the surface of cometary nuclei. In order to confirm 
this hypothesis, we would like to observe other sample of short-period comets 
which shows possible meteor showers. Fortunately in S10B semester, comet 
103P/Hartley will have close approach to the Earth (0.12 AU), and it may be 
bright as at least 6-th total magnitude. The display of the related meteor 
shower is expected in the future by our simulation.