Even before the exciting new data came flooding back from the pioneering missions to various comets (see Chapter 2), scientists on both sides of the Atlantic were starting to consider their next steps. This process of crystal-ball gazing came at a time when knowledge of the origin, physical properties and composition of these ‘cosmic icebergs’ was distinctly sketchy. Innumerable comets had been studied by ground-based observatories, but, as yet, none had been visited by spacecraft and inspected at close quarters.