Asteroid taxonomy types

In recent years several works have been carried out with the aim of understanding some of the physical and compositional properties of asteroid populations. Three recent works are based on statistical analyses of those asteroids for which a complete set of selected parameters were available: namely, a set of 589 asteroids described by seven colors indices /1/, a subset of that one, of 438 asteroids for which IRAS albedo values were available /2/ and a set of 357 asteroids described by three variables: two reflected light color indices and high-quality IRAS albedo /3/. We compare the different methods used and discuss the differences in the results obtained: some differences result from the grouping technique chosen, and some on the quality of the data sets used. We discuss particularly the classifications of some peculiar asteroids: Earth-crossing objects, and asteroids that may be extinct cometary nuclei.