The Asteroid Belt

Between Mars and Jupiter is a region called the asteroid belt. It is filled with millions of space rocks. These rocks are called asteroids. They come in all sizes, from tiny pebbles to huge boulders. The biggest one, Ceres, is so large it is called a dwarf planet.

Rocks in Space

Asteroids are leftover pieces from when the solar system formed. They never became a planet because Jupiter's gravity pulled them apart. Most asteroids are made of rock and metal. Some contain valuable materials like iron and gold. Scientists study them to learn about the early solar system.

A size comparison showing some big asteroids next to Pluto and Charon.
A size comparison showing some big asteroids next to Pluto and Charon. (Ceres image: Justin CowartEros image: NASA/JPLVesta image: NASA/JPL-Caltech/UCAL/MPS/DLR/IDAPluto and Charon images: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker / Wikimedia Commons)

Not So Crowded

In movies, the asteroid belt looks packed with rocks. But in real life, it is mostly empty space. The asteroids are spread very far apart. A spacecraft can fly through the belt without hitting anything. NASA has sent many probes through safely.

Fun Facts

  • Ceres was the first asteroid ever discovered, in 1801.
  • All the asteroids together weigh less than the Moon.
  • Some asteroids even have their own tiny moons.

Did You Know?

The asteroid belt contains more than a million asteroids bigger than half a mile wide.