1Mercury: why are its temperatures so extreme? 2Venus: why is it hotter than Mercury? 3Earth: why is our planet different? 4Moon: why does it always show nearly the same face? 5Mars: could people ever live there? 6Asteroid belt: where did all these rocks come from? 7Jupiter: why is it so enormous? 8Saturn: what are the rings made of? 9Uranus: why does it roll on its side? 10Neptune: why are its winds so powerful? 11Pluto: why isn't it one of the eight major planets? 12The Sun: why does it shine? 13Comets and the Kuiper Belt: where do comets come from?