ASTEROIDS: Scientists have discovered a very large asteroid impact site in Antarctica.

Types of Fossils There are two main types of fossils: body fossils and trace fossils.

A body fossil is the physical remains of an animal. Some very small organisms, called microbacteria, leave behind microscopic particles called filaments.

Footprints, flowers, even droppings; all of these things can be turned into fossils under the right conditions.

A fossil only becomes a fossil when it has reached a certain age.

Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.