What New Horizons found exceeded almost everyone's expectations. Pluto was not the geologically dead, featureless ball that many scientists had expected of a small, cold, distant body. It had mountains of water ice rising 3,500 metres above the plains — as tall as the Rocky Mountains. It had a vast, heart-shaped basin of nitrogen ice the size of Texas and Oklahoma combined, called Tombaugh Regio in honour of its discoverer. It had complex atmospheric chemistry producing layers of blue haze. It had possible ancient cryovolcanoes. It had a surface with regions of completely different ages, some ancient and cratered, some young and essentially uncratered. It was a world.
And it had five moons. Charon — discovered in 1978 and half the size of Pluto itself, so large that the two bodies are sometimes called a binary dwarf planet — was revealed in unprecedented detail. Four smaller moons — Nix, Hydra, Kerberos, and Styx — were imaged for the first time, showing themselves to be small, bright, tumbling worlds with their own surprising characteristics. This book tells the complete story of Pluto and its five moons: their discovery, their geology, their mythology, and what New Horizons taught us about the most famous dwarf planet in the solar system.
