Present-day Classifications
The present-day classification was initiated by Clark R. Chapman, David Morrison, and Ben Zellner in 1975 with three categories: C for dark carbonaceous objects, S for stony (silicaceous) objects, and U for those that did not fit into either C or S. This classification has since been expanded and clarified.
A number of classification schemes are currently in existence, and while they strive to retain some mutual consistency, quite a few asteroids are sorted into different classes depending on the particular scheme. This is due to the use of different criteria for each approach. The two most widely used classifications are described below:
Read more about this topic: Asteroid Spectral Types
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