Perhaps one of the greatest achievements of unmanned space flight has been the wealth of information – not to say stunning images – that resulted from NASA’s programme to send probes to the outer parts of our Solar System. Here we will chart nearly 40 years of exploration, from the Pioneer and Voyager probes in the seventies and eighties to the Galileo spacecraft’s study of Jupiter around the turn of the millennium and, more recently, the Cassini and Huygens probes studying Saturn and Titan.

Pioneer 10

Pioneer 10 was launched from Cape Canaveral on 2 March 1972 and was the first spacecraft to travel through the asteroid belt to reach Jupiter. It entered the asteroid belt on 15 July that year – a region 280 million km wide and 80 million km thick. The material in the belt encompasses sizes from dust particles up to the major asteroids travelling at speeds up to 72,000 km/h, and scientists had feared Pioneer 10 might not be able to negotiate its way through. It was even thought that the debris within the asteroid belt would be so thick that any spacecraft would be destroyed. Happily, these worries proved to be unfounded.