We have presented and discussed dynamical and spectral properties of 3 dark asteroidal objects. The dynamical behaviors of these bodies are considerably different. (6042) 1990 WW2 has a high-inclination orbit and, during the period in which has been analyzed (821.4 years), it does not show any large variations in semi-major axis, aphelion and perihelion distance.
(6144) 1994 EQ3 shows a very irregular orbital evolution: it undergoes several close encounters with Jupiter and its semi-major axis changes very rapidly. According to its dynamical behavior, this object could be an Edgeworth-Kuiper Belt comet or a fragment of a recent family-forming event in the Trojan cloud. This last possibility is suggested by the fact that 3 clones of its actual orbit, integrated backward in time, are trapped in Jupiter's horseshoe orbits for more than years.
1995 QY2 is a Mars crosser and librates about the 15/7 mean-motion resonance with Jupiter. However, the resonance trapping is not stable and small variations of its orbital parameters can generate different orbital evolutions after the resonance escape: 9 over 15 clones of the original orbit jump on several other resonances with Jupiter and some of them become Earth crossing before the end of the integration. 6 clones end up in Jupiter-crossing orbits on a timescale of the order of yr and, from a dynamical point of view, they become comets.
These dynamical differences do not correspond to strong spectral differences: all spectra show the typical trend of carbon-rich, low albedo, "primitive" objects and are compatible with those of outer-belt asteroids. Results seem to confirm the hypothesis that some low-albedo objects could have cometary origin. In particular, the relatively high redness of (6144) 1994 EQ3 (similar to that of three comet nuclei), coupled with its peculiar dynamical characteristics, support the hypothesis about a possible cometary origin of dark asteroids, which could be exhausted comet nuclei.
© European Southern Observatory (ESO) 1998
Online publication: December 16, 1997