Asteroids, Comets and Meteoroids…, who are they?
Asteroids (Left: Galileo image of asteroid Ida and its companion) (Right: Galileo photo of the asteroid Gaspra) As we leave the red planet and its moons behind us, we next encounter a strange collection of small planet-like objects. This is the asteroid belt. These asteroids, also known as planetoids, range in size from several hundred miles to several hundred feet. At least 30,000 of these giant rocks are known to be floating in their own individual orbits between Mars and Jupiter. Scientists are not sure why there are asteroids here instead of a planet. Some believe that a large, rocky planet may have existed here in the past. This planet may have then been blasted to pieces by a cataclysmic impact. Others think that the asteroids are composed of the leftover material from which the solar system was originally formed. The largest of these asteroids, Ceres, is over 630 miles in diameter. It was discovered by Giuseppe Piazzi in 1801. Not all asteroids are confined to the asteroid belt.
