The primary reason that planetary scientists study asteroids, comets and meteoroids is because it helps them to understand the early formation of the solar system. Additionally, it is important to understand what happens when asteroids or meteoroids collide with the Earth or other planets, as such events have been important factors in the history of the planet.
Asteroids formed at about the same time as the solar system did. Jupiter formed very early in the history of the solar system, and its incredible size and the accompanying gravity this size creates caused the asteroid belt between Jupiter and Mars to form. Without Jupiter’s gravitational influence, these rocks would have eventually coalesced into a planet.
An asteroid is thought to have struck the Earth approximately 65 million years ago, striking the Yucatan Peninsula in present day Mexico. This asteroid impact caused an enormous explosion, which altered the Earth’s climate for years. Many paleontologists suspect that this impact was the primary cause for the extinction of the dinosaurs.
The largest known asteroid is Ceres, with a diameter of approximately 583 miles. Millions of tiny asteroids exist, but most do not have names. The smallest named asteroid, called 1991 BA, is only about 20-feet across.