Asteroids and meteors are small bodies of rock that revolve around the sun. Asteroids are concentrated in a belt between Mars and Jupiter. There are millions of asteroids within this belt. Most are less than a kilometer in size. As a result they are too small to be considered planets. Sometimes they are called planetoids.
Photo: Asteroid belt between Jupiter and Mars (© Andreus).
Origin of Asteroids
At one time, the solar system was a large ball of gas and dust. Over time, gravity pulled the tiny gas and dust particles together. They began to condense into larger particles. Over time, large planets were eventually formed by this gravitational process.
However, the tiny particles lying between Mars and Jupiter were disturbed by Jupiter’s gravity. Jupiter’s strong gravity prevented the particles from forming into a planet. As a result, a belt of small planetoids lie between Mars and Jupiter. This belt is known as the asteroid belt.
A small number of planetoids follow a different path around the sun. They may share the orbits of the Earth, Jupiter, Mars, and Neptune. These small objects are known as Trojan asteroids. Some of them may cross the Earth’s orbit.
Rocks that travel through space are known as meteoroids. These are much smaller than your typical asteroid. Meteroids or asteroids that enter the earth’s atmosphere are called meteors. Meteors that reach the earth’s surface are called meteorites.
A smaller meteor that enters the atmosphere is often seen as ‘shooting’ or ‘falling’ stars. Its fiery appearance is the result of burning up in the atmosphere.
From time to time asteroids will collide with planets. The earth collides with smaller meteors on a daily basis. Collisions with large asteroids or meteroids are far less frequent.
Depending on the size of the asteroid, the impact could be minor or destructive. In the worst case, it could trigger the world wide extinction of many life forms.
In earth’s history, large meteors have struck the earth. These meteors have created large impact craters that can still be seen today. These larger meteors (about 1 kilometer in size) strike the earth every two million years or so.
The impact of a large asteroid can be destructive. However the most severe result of a collision is the creation of a large dust cloud. This dust cloud may change the earth’s climate and cause the extinction of lifeforms.
The following is a recommended list of words and their definitions for students.
Improving Your Reading and Thinking Skills
Think for a few moments. Try to recall the major ideas in this article. Try to answer the following questions to improve your reading comprehension.