We would clearly learn a lot more about Pluto, its three satellites, the E-K belt, and anything else beyond Pluto, were a spacecraft targeted to investigate this far flung region of the Solar System. As yet no such spacecraft has visited Pluto and beyond, but one is on its way, New Horizons.

THE LONG PATH TO NEW HORIZONS

Table 8.1 lists the spacecraft that have already visited the outer Solar System, and reached their targets. You can see that Pluto is the only one of the original nine planets that has not been visited by a spacecraft. Why? One reason is surely that when each of the missions in Table 8.1 was being selected for development, no other KBOs were known, the first to be discovered was the small body 1992 QB1 in 1992 (Section 6.2), and therefore Pluto and its satellite Charon was regarded as just a small, isolated system. Consequently it was of considerably less interest than it is now, with its numerous companions in the E-K belt. Attention was instead focused on the rich domain of the four terrestrial planets and the four giant planets plus their numerous satellites.

As our knowledge of Pluto grew, so did interest in sending a spacecraft there, such that in the late 1980s a small number of planetary astronomers began to campaign for a mission to Pluto. The campaign was aided by the 1989 flyby of Neptune by Voyager 2.