1. The partially molten layer of the moon's interior.

2. The study of the moon's physical features.

3. The period between two successive new moons, approximately 29.5 days long.

4. A small difference between high and low tides that occurs twice a month.

5. An instrument used to observe celestial objects like the moon.

6. Having an orbital period equal to the rotational period of the moon.

7. When the full moon or new moon coincides with the moon's farthest approach to Earth.

8. The layer of loose material covering the solid bedrock on the moon.

9. A type of mineral that emits a soft glow like the moon.

10. A small celestial body that burns up upon entering the moon's atmosphere.

11. The rise and fall of the ocean caused by the moon's gravitational pull.

12. A large, dark plain on the moon's surface formed by ancient volcanic eruptions.

13. A dark, volcanic rock found on the moon's surface.

14. More than half, but not fully illuminated moon.

15. When the moon moves into the shadow of the Earth or vice versa.