An alien landing might bring up these questions: Does this mean that God have different rules for different planets--or did God send a savior to every planet? (Or perhaps the colonials are not fallen and didn't need a savior).
As it happens, last May "Father Gabriel Funes [director of the Vatican Observatory near Rome], said intelligent beings created by God could exist in outer space. [...] Just as there are multiple forms of life on earth, so there could exist intelligent beings in outer space created by God. And some aliens could even be free from original sin, he speculates."