Asteroids, comets, and meteors are forms of interplanetary debris rocky and icy fragments left from the formation of the solar system. They usually travel at a great distance from Earth, but we see them, even with the naked eye, when they near our planet.
Millions of asteroids orbit the sun, usually in a belt between the orbits of Mars and Jupiter. A few brush past the planet Earth. Generally larger than comets and meteors, asteroids are chunks of rock and metal that can range from 100 yards to almost 600 miles in width.
Comets, sometimes likened to big, dirty snowballs, are made of rock, ice, dust, carbon dioxide, methane, and other gases. Asteroids they originate in the Piper belt. As comets journey toward the sun, they begin to defrost.
Solar heat vaporizes ice, which forms a halo of gas and dust, called a coma, around the comet’s nucleus. Approaching Mars, comets may form tails, some hundreds of millions of miles long.