LIFE
Sometimes something down there thinks
A habitable-zone planet is a place where life is possible. A living world is a place where it is, and a lander tells the two apart: first whether there is life, then whether there is a mind, then who they are.
Life follows from the planet itself: from its star's light, its gravity, water and tides. What grows under a dim star is nothing like what grows under a bright one, and on a light planet the trunks reach higher — the weak gravity holds them up.
The starting system never holds life: you will have to fly to your first living world. Which was rather the point.