What Is The Inside Of The Moon Like?
Sensitive instruments placed on the lunar surface by the Apollo astronauts are still recording the tiny vibrations caused by meteorite impacts on the surface of the Moon and by small moonquakes deep within it. These vibrations provide the data from which scientists determine what the inside of the Moon is like. About 3,000 moonquakes are detected each year. All of them are very weak by terrestrial standards. The average moonquake releases about as much energy as a firecracker, and the whole Moon releases less than one-ten-billionth of the earthquake energy of the Earth. The moonquakes occur about 600 to 800 kilometers (370-500 miles) deep inside the Moon, much deeper than almost all the quakes on our own planet. Certain kinds of moonquakes occur at about the same time every month, suggesting that they are triggered by repeated tidal strains as the Moon moves in its orbits around the Earth. A picture of the inside of the Moon has slowly been put together from the records of thousands of
