Avsnitt 1

The four planets closest to the sun, called the rocky planets, were born from the same material in the same era. But they couldn’t be more different: Tiny Mercury is the runt of the litter, almost like a moon. Venus is devilishly hot, and Mars is a frozen desert world. Only on Earth do we find the unique conditions for life as we know it . But why only here? Were Earth's neighbors always so extreme? And is there somewhere else in the solar system life might flourish?