Related Clues:
- Mars or Mercury
- Not natural
- Xenophobe's fear
- With 27-Down, sci-fi phenomena that help explain this puzzle's theme
- Border crosser
- It has solar heating
- Mercury or Saturn
- 1979 sci-fi thriller
- Heavenly body
- Nonnative
- From another planet
- Krypton, for one
- One with a big head?
- Mercury, for one
- Out of this world?