3. The moon was once part of the earth. Due to the rapid rotation of the primitive earth, the moon broke away from it. The moon formed from the outer layers of the earth depleted of iron. This explains why there is a lack of iron on the moon.

4. The moon formed in orbit about the earth but not out of the material drawn from the earth. According to this theory, both bodies formed at about the same time out of the same swarm or cloud of material.

5. Also called the Double Planet Theory.

6. Explains that the moon formed elsewhere in the inner solar system and was captured by the earth during a close encounters.

9. The only extraterrestrial body to have been visited by humans. The only world, other than the earth where people have been. The first celestial body from which materials have been selected and brought back to earth for analysis. Study of the moon began with earth-based observations when the telescope was invented.

10. Examined the moon through a telescope in 1609.

11. Spacecraft began to supply new lunar data.

12. United States astronauts Neil Armstrong, Edwin E. Aldrin Jr. of the spaceflight Apollo 11 landed in the Mare Tranquillitatis, or Sea of Tranquility.

13. Edwin E. Aldrin Jr.Neil Armstrong

15. Astronomers mounted cameras on telescopes and took pictures of the moon.

16. The successful landings of unmanned spacecraft of the surveyor series by the US and the Luna series by the USSR.

17. Finally, the manned landings on the lunar surface as part of the US Apollo program made direct measurement of the physical and chemical properties of the moon a reality.

18. The moon is about 4.6 million years old, or about the same as the age of the earth and probably the rest of the solar system by measuring the lunar rocks.

19. Rocks from the lunar maria were formed when molten rock solidified between 3.16 to 3.960 M years ago.

21. Used to determine the distance from the earth to the moon.

22. It recorded several events interpreted to be moonquakes, landslides or meteor impacts

23. Was placed on the moon’s surface so that it faced the sun. It was brought back to earth and analyzed for rare gases. The results showed that it had trapped gases such as helium, neon and argon.

24. Was launched after Apollo 11, which carried another instrument, the magnetometer.

25. Used to record a magnetic field some ten times stronger than scientist had expected.