SIZE AND ORBIT DEPENDENT TRENDS IN THE REFLECTANCE COLORS OF EARTH-APPROACHING ASTEROIDS

New observations show that reflectance colors of Earth-approaching ast eroids depend on their sizes and orbits. Most bodies larger than simil ar to 2 lan have reddish colors similar to common main-belt asteroids of spectral type S. Smaller bodies, and those that may have recently m igrated from the main belt, have relatively neutral spectra in the 0.5 - to 0.8-mu m wavelength range, These trends may result from the actio n of ''space-weathering,'' recently proposed to explain similar spectr al variations on the surfaces of S-type asteroids and the disparity be tween the colors of ordinary chondrite meteorites and their probable m ain-belt parents. (C) 1998 Academic Press.