WELCOME TO THE PLANET THAT WAS

摘要

Four and a half light-hours from Earth, a small planet is about to get a small visitor. On 14 July, NASA's New Horizons craft will skim within just 13,000 kilometres of Pluto, entering a hitherto-unexplored zone of the solar system. When this probe was launched in January 2006, its destination was still the solar system's ninth planet. Pluto was controversially demoted to a dwarf planet later that year, but its allure is undiminished. Above its surface, frosted with exotic ices, is a strange atmosphere that seeps constantly into space, and a complex system of moons, including the giant Charon. Pluto will be a dazzling destination in itself, and this first visit could also give us clues to how our own planet formed, and to the ancient upheavals that shaped the solar system. With the blobs of Pluto and Charon already swelling in New Horizons's sights, these are exciting times at the solar system's new frontier.