DYNAMICAL AND PHYSICAL-PROPERTIES OF COMET-ASTEROID TRANSITION OBJECTS

In the last few years it has been pointed out that, from both physical and dynamical point of view, it is becoming more and more difficult t o distinguish comets from asteroids and indeed there are some examples of small bodies first designated as comets which had, later, to be re classified as asteroids and vice versa (Hartmann et al., 1990; McFadde n, 1994). In order to investigate the evolutionary path of comets and asteroids in terms of both dynamical and physical properties, we perfo rmed spectroscopic observations of three objects discovered between 19 90 and 1995 - (6042) 1990 WW2, (6144) 1994 EQ(3), and 1995 QY(2) - and analyzed their orbital evolution. Obtained spectra show the typical t rend of low-albedo, ''primitive'' objects, similar to those of outer-b elt asteroids and comet nuclei. The dynamical analysis shows that (604 2) 1990 WW2 is on a stable orbit with a typical asteroidal behavior; ( 6144) 1994 EQ(3) is on a Jupiter-crossing chaotic orbit and in the pas t could have spent some time in a Jupiter's horsehoe orbit; 1995 QY(2) is a Mars crosser and librates about the 15/7 resonance with Jupiter and has a 40% chance to make a transition from asteroid to comet orbit over a timescale of about 3-5 x 10(5) yr.