1. he has been trying to find a new planet that humans can live on.
= he has been trying to find a new planet which humans can live on.
= he has been trying to find a new planet on which humans can live.
= he has been trying to find a new planet where humans can live.

맞나요??

2. they were moving in a totally different direction, away from the planet that eric had wanted to visit so badly.
= // which //
where(x)
맞나요?