Asteroid and Comet Encounters with the Earth

Abstract

While progressing in its orbit about the Sun, planet Earth encounters large numbers of small solar system bodies—asteroids, comets, and meteoroids. In the course of time, some of these small bodies collide with the Earth and are destroyed in the atmosphere, while some prevail until a catastrophic impact on the surface. There is vast agreement among scientists that the interplay between the Earth and the small bodies poses a significant, natural hazard for the humankind. The near—Earth asteroids and comets have affected the evolution of life on the Earth in the past. It is relevant to work toward preventing the asteroids and comets from colliding with the Earth and, at the same time, toward protecting the humankind from the cosmic impacts. Here the populations of near—Earth asteroids and comets and their impact hazard are reviewed. The review is succeeded by Gaussian and rigorous methods for the calculation of the collision probability of a large and a small body, and for the derivation of upper bounds. Finally, the close approach to the Earth in year 2028 by the small body 1997 XF11 is analysed in detail starting from its discovery in 1997 Dec. 6.