Meteorites, asteroids and comets

Episode number 25 of Series “Universe: the infinite frontier: an introductory astronomy telecourse”.
Meteorites have crashed to the Earth since time began with massive craters proving this, although scientists initially found it difficult to believe. Once it was determined that the rocks were “out of this world”, serious study was given to the phenomena. The location of the asteriod belt between Mars and Jupiter implies the existence of a now disintegrated planet. These asteriods are composed of three types: silicate, metal and carbon based. Comets have always been seen as “emissaries of chaos”. Halley’s Comet has offered scientists a chance to study this celestial body, which is largely an ice ball on an orbit through space. Comets have been known to cause destruction upon impact, and scientists believe that such a collision, which would result in mass devastation, may have explained the sudden extinction of dinosaurs on Earth. The likelihood of such an event re-occuring is also discussed.