There are quite a few objects in the universe capable of causing a really, really bad day on planet Earth, including a wayward comet or large asteroid. Most meteors, however, barely rate a 'ho-hum' on an astronomer's scale of scary extraterrestrial events. There are a number of differences between a comet and a meteor, from their general composition to the roles they play in the universe.

A comet is a celestial object believed to be composed primarily of space dust and frozen gases. The birthplace of a comet is thought to be somewhere in the outer parts of the universe, not related to the formation of our solar system at all. A comet follows an orbit that may bring it close to a star, such as our own Sun. As the comet approaches the star, a portion of its ice core may melt and release a trail of dust-sized particles. This cycle can continue for millions of years.

A meteor, on the other hand, does not follow an orbit around the sun. It isn't even called a meteor while it remains floating in outer space – it's called a meteoroid. Only when it enters the Earth's atmosphere is it considered a true meteor.

When the Earth passes through a comet trail or debris field, individual meteoroids hit or skip across the first layers of the atmosphere. Observers on Earth may be fortunate enough to see the last few seconds of a meteor's existence as it streaks across the sky and burns up. Unlike a comet, a meteor will not return a number of years later.

A comet rarely passes within a few million miles of the Earth, while a meteor by its very definition must strike the first layers of the Earth's atmosphere. A comet's arrival can be predicted with some degree of accuracy, but a meteor can enter the Earth's atmosphere at any time of the day or night. A comet can rarely be seen by the naked eye, but during a meteor shower, it is not unusual to see dozens or even hundreds of meteors within a few hours.

A comet also receives an official name for identification, such as Swift-Tuttle, Hale-Bopp or Halley's Comet. A few large asteroids may receive identifying names as well, but meteors do not. Virtually all meteors cease to exist once they've entered the Earth's atmosphere. A rare few make it to the ground, however. Once a meteor has made contact with the Earth's surface, it becomes known as a meteorite. While a comet may be composed of space dust, organic materials and ice, most meteors contain elemental metals, such as iron, along with inorganic minerals such as quartz.