Horizon TV - 95 World and Counting TV - How the Universe Works TV - Torrence Johnson -
Callisto’s surface is covered with impact craters. This is the record of an intense meteorite bombardment. It dates the surface back to the very beginning of the solar system. Horizon: Earth to Miranda, BBC 1990
The most battered body in the solar system. 95 Worlds and Counting
It formed much further out with less debris and less heat. It took longer and cooled faster. Unlike Ganymede, Callisto’s surface is uniform. Rock and ice never separated. How the Universe Works: Moons, Discovery 2010
The basic ingredients for life – what we call ‘pre-biotic chemistry’ – are abundant in many solar system objects, such as comets, asteroids and icy moons. Biologists believe liquid water and energy are then needed to actually support life, so it’s exciting to find another place where we might have liquid water. But, energy is another matter, and currently Callisto’s ocean is only being heated by radioactive elements, whereas Europa has tidal energy as well, from its greater proximity to Jupiter. Torrence Johnson