Summary: Melvyn Bragg and his guests discuss comets, the 'dirty snowballs' of the Solar System. Halley's Comet is today the best known example of a comet, a body of ice and dust which orbits the Sun. Since they contain materials from the time when the Solar System was formed, comets are regarded by scientists as frozen time capsules, with the potential to reveal important information about the early history of planets. Melvyn Bragg is joined by Monica Grady, Professor of Planetary and Space Sciences at the Open University; Paul Murdin, Senior Fellow at the Institute of Astronomy at the University of Cambridge and Don Pollacco, Professor of Astronomy at the University of Warwick.
