ABSTRACT
This chapter provides a review of the asteroid and cometary populations of the Solar System. It begins by reviewing the growth in our knowledge of the near Earth objects (NEO) population, basic observational properties such as their size distribution and astrophysical theories for their origin. It considers the history of the bombardment of the Earth by comets and asteroids, the effects of impacts by bodies of different sizes and the risk they pose at present. The latter is interpreted in the context of other low-frequency/high-impact risks, together with an insurance or actuarial approach to evaluating the average annual cost of NEO impacts and possible approaches to mitigation. Finally, their long-term implications and the perspective they provide on our place in space are discussed.
