To see a planet in your dream signifies creativity, exploration, and new adventures. You are trying to align yourself with untapped energies that you never knew you had. Alternatively, to dream of planets suggests that you are trying to escape from your own waking reality.
To dream that you discover life on a new planet refers to your desire to escape from a current situation. Alternatively, the dream represents your own self-discovery. You have uncovered a part of yourself that you did not realize existed within yourself.
Look up the specific planet for additional significance.