Why do scientists study comets ?
It is believed that comets may have been the first solids to condense out of the solar nebula 4.5 billion years ago at the birth of the solar system. Matter on the earth and elsewhere in the solar system has continuously evolved since that time, while it may be preserved in the pristine form in a comet nucleus. So they contain clues as to what happened 4.5 billion years ago. Comets may also have played a role in forming the early atmosphere of the earth. They could have been responsible for introducing water and complex molecules necessary for the beginning of life on the earth.
A more urgent reason for studying comets is the very real possibility that a comet may found to be in collision course with the earth. We must catalogue orbits of all earth crossing comets and asteroids , so that we may be forewarned of this eventuality. In addition, to devise strategies and escape the fate of the dinosaurs sixty five million years ago, we must know the physical structure and composition of comets and asteroids thoroughly.