ROCKS FROM SPACE
When a meteoroid reaches the groand as meteorite, it can help complete our picture of the universe. Many meteorites are pieces of matter unchanged since the earliest days of the Solar System, while others are bits of Mars or the Moon blasted into orbit by comet or asteroid impacts.
Meteorites are divided into three main types according to their composition: stony meteorites; iron meteorites; and stony iron meteorites.
Stony meteorites are angular gray or brown stones, made up of stony minerals. They tend to be fairly smooth and often have a glassy black fusion crust, formed as the rock ablated in the atmosphere.
Iron meteorites contain 90 percent iron and 10 percent nickel, making them heavy for their size. Their surfaces can be black or rusty brown and are often pitted with thumbprint-shape depressions.
Stony iron meteorites bridge the stony and iron classification. They have the coarsest sufrace, with crystals of olivine in a network of nickel-iron.