Given that there are thousands of asteroids and probably a
hundred thousand million comets, these small bodies must be
considered essential components of the solar system. Certainly
objects closely similar to the small bodies that remain today
were involved in the agglomeration of the larger planets and
satellites some 4.5 billion years ago, and much of the
importance of the small bodies today derives from the clues that
they may contain about the processes that took place in the
early solar system. This importance is magnified when we realize
that asteroid-like parent bodies are the only solar system
objects (other than Earth and the Moon) of which we have samples
for detailed laboratory studies. Although our understanding of
small bodies is relatively limited, we know enough to realize
that geologically these objects are best studied separately from
the larger bodies, such as Earth and the Moon. For one thing,
gravity is so much smaller on these bodies that it is difficult
to extrapolate our experiences wit