Asteroids
Most asteroids, also called minor planets, are found in an asteroid belt between Mars and Jupiter. Jupiter`s intense gravity prevented the rocky matter from forming into a separate planet. Scientists believe that an asteroid struck Earth about 65 million years ago. The impact changed conditions on Earth so dramatically that many creatures, including the dinosaurs, died out. Today, scientists are monitoring many Earth-crossing asteroids that may one day hit our planet. They have also sent a space craft (the NEAR) to study one of these asteroids.

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