Moon Rocks

Data from the Apollo adventure has kept scientists busy for a generation. After studying the 840 pounds (382 kg) of samples brought back by the astronauts, scientists concluded that the Moon split off from Earth about 4.5 billion years ago, when a very large asteroid collided with Earth. Almost none of the iron from Earth’s core was torn out, which is why the Moon has very little iron and is only 60% as dense as Earth overall. Small quantities of radioactive oxygen in the moon rocks match the amount of radioactive oxygen in Earth rocks.
Mainly because of heat from the collision, the Moon’s surface was almost completely covered by oceans of molten lava for a hundred million years or so. Slightly heavier rocks sank through the molten lava as the less heavy rocks solidified. When the Moon’s surface was almost cooled, the last volcanoes forced some of the slightly heavier rocks back up to the surface. Unlike Earth, the Moon did cool right through and no longer has a molten core. Since the time the lava turned solid, the only thing that has hap
pened on the surface of the Moon has been a hail of various-sized asteroids and meteoroids that came crashing down. That is, until 12 brave men left footprints in the shallow dust.