Vesta and the Vestoids: A new rock group?

Moderate spectral resolution observations of the 505-nm Fe2+ pyroxene absor ption feature were obtained for 13 asteroids dynamically linked to 4 Vesta, or located between Vesta and the 3:1 resonance gap. Eleven showed spectra with deep 0.9-mu m mafic silicate absorptions suggesting a pyroxene composi tion (Binzel and Xu 1993). Spectra of only six of these asteroids show the absorption feature centered at 506.5 nm, suggestive of an augite (high-calc ium) component to the surface pyroxenes consistent with previous spectral o bservations across the surface of Vesta (Cochran and Vilas 1998). Five of t he six asteroids include all objects observed at heliocentric distances bet ween Vesta and the 3:1 resonance gap. The spectrum of only one asteroid int erior to Vesta's orbit showed this feature. No correlation between the pres ence or absence of this feature and the strength of the 1-mu m mafic silica te feature was found. (C) 2000 Academic Press.